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Über dieses Buch

This book addresses the latest research advances, innovations, and applications in the field of urban drainage and water management as presented by leading researchers, scientists and practitioners from around the world at the 11th International Conference on Urban Drainage Modelling (UDM), held in Palermo, Italy from 23 to 26 September, 2018. The conference was promoted and organized by the University of Palermo, Italy and the International Working Group on Data and Models, with the support of four of the world’s leading organizations in the water sector: the International Water Association (IWA), International Association for Hydro-Environment Engineering and Research (IAHR), Environmental & Water Resources Institute (EWRI) - ASCE, and the International Environmental Modelling and Software Society (iEMSs). The topics covered are highly diverse and include drainage and impact mitigation, water quality, rainfall in urban areas, urban hydrologic and hydraulic processes, tools, techniques and analysis in urban drainage modelling, modelling interactions and integrated systems, transport and sewer processes (incl. micropollutants and pathogens), and water management and climate change. The conference’s primary goal is to offer a forum for promoting discussions amongst scientists and professionals on the interrelationships between the entire water cycle, environment and society.

Inhaltsverzeichnis

Frontmatter

Drainage and Impact Mitigation (BMP, LID, CSO quality and quantity, etc.)

Frontmatter

From Rainwater Harvesting to Rainwater Management Systems

This keynote extended abstract investigates the recent shift in the drivers, objectives and application of rainwater harvesting. A review of historical rainwater harvesting technologies was undertaken and the context set for rainwater to be valued as an alternative water resource in specific circumstances. Recent research and exemplars were reviewed which suggest that the widespread use of the term rainwater harvesting, no longer captures the nuanced applications of rainwater capture and control technologies. A conceptual model was presented which sees rainwater management systems used as a term to cover installations and associated technologies and practices where rainwater harvesting features are also used to manage stormwater discharges. Global exemplars were identified where active/smart rainwater management systems have been successfully deployed to achieve wide ranging benefits. To evidence the broader benefits of rainwater management systems, a supply-demand analysis was used to investigate three different rainwater management types for a household in Palermo, Sicily. The abstract concludes with reflections on the future of rainwater management systems and the opportunities they could pose to increase urban resilience to threats such as water shortages, extreme hot weather, stormwater flooding, sewerage overflows, and a changing climate.

David Butler

Modelling to Support the Planning of Sustainable Urban Water Systems

Water Sensitive Urban Design (WSUD) is commonly employed to restore urban water systems back to pre-developed conditions and can provide multiple benefits. However, WSUD planning is a challenging task that involves multidisciplinary effort to deal with highly complex and uncertain futures. Hence, an integrated approach is required to address this task with a high level of scientific rigour. This paper introduces an integrated modelling tool – UrbanBEATS (Urban Biophysical Environments And Technologies Simulator) which supports the planning and development of sustainable urban water strategies. Initially developed to plan WSUD stormwater infrastructure for management of runoff, pollution and stormwater harvesting, UrbanBEATS’ ecosystem is currently being extended and includes, among others, three new modules, which are introduced in this paper: (1) uptake, needs and suitability assessment module for simulating the behaviour of the main actors in urban stormwater management to assess uptake, suitability and needs for WSUD technologies; (2) mapping of water pollution emissions, linking detailed information of the urban form and land use with stormwater pollution algorithms (allowing identification of pollution hotspots within the catchment to guide pollution management strategies); and (3) a novel cellular automata fast flood evaluation model known as CA-ffé for the rapid prediction of inundation extent, depths and flood risks in urban areas (including assessment of the WSUD benefits for reducing flood damages).

Ana Deletic, Kefeng Zhang, Behzad Jamali, Adam Charette-Castonguay, Martijn Kuller, Veljko Prodanovic, Peter M. Bach

Model-Based Sewer Network Control - Practical Experiences

A model-based flow control system was installed at an existing sewer network. On-line radar data and radar forecasting are used to model the inflow to the sewer system. Based upon these data the model evaluates optimised flow control set-points at twelve storm-water-retention-basins in the sewer network. Flow rates of adjacent pumps and throttles are thus controlled by a central unit. The use of radar-data in discharge control systems is new and provides proper and reliable results. The overall system is now operative since more than two years. During this time, high operational stability could be achieved. The modular design also allows the addition of further elements of sewer network control. Practical experiences with the flow control system from early design to implementation in the field and ongoing operations are presented. The operation of the system significantly reduces storm-water overflows to rivers and water bodies an more storm-water is treated at the central wastewater treatment plant and retention soil filter.

Christoph Brepols, Heinrich Dahmen, Maja Lange, Annelie Sohr, Reinhold Kiesewski, Richard Rohlfing

Use of Shrimp-Shell for Adsorption of Metals Present Surface Runoff

This research analyzes the use of in nature shrimp shells for biosorption of metallic ions in surface runoff. Tests were carried out with different amounts of shrimp shells (5 g and 10 g) for 200 mL of runoff, with shaking of 100 rpm for 24 h. The results evidenced the high presence of metal ions in the shrimp shells and that it directly influenced the results of the tests with the different amounts of biosorbent. The shrimp shells in nature had high concentrations of metal ions (Pb, Ni and Cu), which have high toxicity to the environment, however there had been specific metal ions (Fe, Mn, Zn and Cr) removing. According to the results, a pretreatment is required for biosorbents prior to full scale use.

Aline Schuck Rech, Julio Cesar Rech, Jakcemara Caprario, Fabiane Andressa Tasca, María Ángeles Lobo Recio, Alexandra Rodrigues Finotti

Nitrogen in Infiltrated Water from Pervious Pavements Under Different Rainfall Regimes and Pollution Build-up Levels

Sustainable urban drainage systems (SUDS) are a nature based solution for best management of rainwater in urban areas. Pervious pavements are one of the SUDS typologies. This study evaluates the water quality filtered by a type of pervious pavement and the influence of the rainfall regime (Atlantic and Mediterranean) and the pollution build-up degree. Total nitrogen (TN) infiltrate concentrations have increased over the study due to the increasing of sediment build-up levels on the pavement surface, with maximum concentrations between 2.7 and 5.0 mg N/l depending on the rainfall regime and the pavement configuration; temperature also influences significantly the leachability of nitrogen. In fact, linear regression models for TN as dependent variable and accumulated mass and temperature have been obtained with a high goodness-of-fit. TN leached over the study represents between 22% and 31% of the total nitrogen present in the sediments accumulated on the pavement surface so the total load is much lower than what would have occurred in an impervious pavement under the same build-up conditions.

Carmen Hernández-Crespo, Miriam Fernández-Gonzalvo, Miguel Martín, Ignacio Andrés-Doménech

Where Does Infiltrated Stormwater Go? Interactions with Vegetation and Sub-surface Anthropogenic Features

The practice of stormwater infiltration is widely used to reduce the amount of urban stormwater runoff delivered to drainage systems and receiving waters. In theory, the practice recharges groundwater, leading to increased urban stream baseflows. However, little is known about the fate of infiltrated stormwater. We tracked the fate of infiltrated stormwater from an infiltration basin using a network of piezometers for three years. We found that groundwater levels downslope of the basin were increased while water levels in an array of reference piezometers lateral to the basin showed no change. In summer, most of the infiltrated stormwater was evapo-transpired by the vegetation downslope of the basin, and thus did not reach the receiving stream. The reverse was true in the colder months, where some infiltrated stormwater did reach the stream as plant water use declined. Particularly during these Summer-Autumn months, anthropogenic disturbances interacted with the plume of infiltrated stormwater: infiltrated stormwater seeped into nearby sewer infrastructure. The study provides evidence that the fate of infiltrated stormwater largely depends on surrounding land use and that urban groundwater pathways are susceptible to disturbance by anthropogenic features. Infiltrated stormwater may not always reach receiving streams as baseflow as often assumed, which has implications for the design and placement of infiltration structures. This experimental data can be used to refine conceptual models of urban catchments and stormwater models.

Jeremie Bonneau, Tim D. Fletcher, Justin F. Costelloe, Peter J. Poelsma, Robert B. James, Matthew J. Burns

Shifts of Resilience and Recovery of Aquatic Metabolism in Stormwater Green Infrastructure

This research showed the effectiveness of aquatic metabolism as a proxy indicator of urban stormwater green infrastructure (SGI) performance, and how resilience and recovery of metabolism shift during storm events. Sensor-based dissolved oxygen (DO) data from an SGI in Western Australia during fourteen storm events over two years period were used to develop metabolism metric. The SGI showed positive and negative metabolism depending on stormwater flow, DO level and time of the events. Water level, water volume, hydraulic retention time, inflow rate, antecedent dry days, etc. were some major factors to determine the recovery and resilience of metabolism during the storm perturbation. The system showed metabolism resistivity during small events or event that took place during the frequent rainfall time that made SGI lotic. The SGI recovered metabolism quickly during the less frequent rainfall event, particularly during the summer when SGI became lentic. The strong correlation between positive metabolism and nutrient attenuation indicating metabolism’s applicability to assess SGI performance in absence of routine water sampling.

Tanveer Adyel, Carolyn Oldham, Matthew Hipsey

The Rainfall Interception Performance of Urban Tree Canopy in Beijing, China

Green spaces play an important role in low impact development and runoff mitigation, but rain loss intercepted by tree canopies affiliated to green spaces are always overlooked. In this research, common garden trees in urban area were selected to explore the rainfall interception performance and the relationship between tree feathers and rainfall characteristics by monitoring variabilities including precipitation, interception, tree features, etc. for 24 rainfall events. The results show that ranging from less than 40.8 mm rainfall, interception increases and hasn’t saturated among most species, while rainfall rate declines. Interception of conifers declines when rainfall intensity increases but it not obvious in the deciduous. Interceptions show a positive correlation with crown density which means lusher trees may intercept more rain, but the interception effect would be damaged by garden pruning. Some species of deciduous trees such as lilytree, purple-leaf plum and maple have a better interception performance than conifers. Smaller branch angles may facilitate intercepting. Good performed species and appropriate managements are suggested to apply to LID to mitigate runoff.

Xiaowen Liu, Qing Chang

Flood Risk Management in an Urban Area Applying LID Techniques

We analyze the benefits of a practical application of Low Impact Development (LID) structures in an urbanized area in terms of reduced flooding volumes and peak flow. LID techniques are fairly economic and easy to implement solutions for the hydraulic restoration and improvement of the efficiency of existing urban drainage networks. The case study is the New Rome Fair, a recent urban development where flooding problems have been observed in the last few years. The study illustrates the potential of LID structures together with a dual system, and their impact on flooding occurrences, for two different Return Periods, highlighting the need for attentive and feasible applications of such structures in a heavily urbanized environment, harmoniously with the related architectural aspects.

Hamed Ghafghazi, Beatrice Dionisi, Antonio Zarlenga

Enhancing the Retention Performance of a Small Urban Catchment by Green Roofs

In existing urban areas the drainage systems can be retrofitted in order to address flooding and water quality problems. In this study, the installation of green roofs is assumed as hypothetic retrofitting scenario according to a sustainable storm water mitigation strategy for a selected urban catchment. The modelling is undertaken using EPA SWMM; the simulations are performed over a continuous simulation of 26-years of rainfall records. The modelling results point out that the retrofitting scenario contributes to the storm water runoff mitigation mainly in terms of volume and peak reduction.

Anna Palla, Ilaria Gnecco, Paolo La Barbera

A Method to Identify Key Sub-catchments for LID Placement Based on Monte Carlo Sampling

Low impact development (LID) can treat excess urban runoff and improve the performance of urban drainage system. LID located in different sub-catchments has quite different effect. However, using optimization algorithm to find the key sub-catchments will cost much computing resources and time. This research proposed a method to rapidly identify key sub-catchments for LID placement by a new index called Rank Score. A case study area in Kunming, China is adopted to test the validity of the method. The application of Rank Score is found to be effective and key sub-catchments are recognized to generate optimized solutions. It is discovered that compared to the average of Monte Carlo samples, optimized performance indices are 41.7%, 26.8% and 42.4% less in terms of the amount of flooding, CSO and shock to WWTP respectively. The numeric features and spatial characteristics of Rank Score distribution are discussed as well.

Hao Guo, Siyu Zeng, Xin Dong

Effects of LID-Based Urban Designs on Water Balance

Low impact development (LID) has received significant attention in supplementing urban drainage designs. This study demonstrates the effects of LID-based urban designs on water balance components for an urban catchment. Two LID-based urban designs (A, B) are simulated for short term (E1) and long term (E2) periods and the effects of the various designs on different water balance components are assessed. The goal of the study is to demonstrate the performance of the designs to realize the sponge city concept. For the intensive short event, scenario A with 15% LID is not effective whereas scenario B with 49% LID is highly effective. For the longer period, both scenarios are highly effective in replicating sponge city concept. In addition, the A scenario possesses a potential for producing sponge city concept for rain events for return periods lower than 100 years.

Ambika Khadka, Teemu Kokkonen, Elisa Lähde, Tero Niemi, Nora Sillanpää, Harri Koivusalo

Developing a Stochastic Sewer Input Model to Support Sewer Design Under Water Conservation Measures

Population growth and climate change place a strain on water resources. There is growing motivation to reduce household water use. UKWIR (2016) have stated the aim to halve water abstraction by 2050. This will significantly reduce inflow to the sewer and drive up wastewater concentration. How will our sewers respond to this and could changes in design lead to a more efficient system in the future? This work presents the development and calibration of a stochastic sewer input model that will predict both hydraulic and pollutant loading for various water saving scenarios. For the first time the stochastic water demand model SIMDEUM® will be integrated with InfoWorks ICM (Sewer Edition), software for hydraulic sewer modelling. This enables accurate time dependent predictions of water, BOD and nitrogen loads from household discharges to the sewer under dry weather conditions. Calibration has been carried out using two sets of sewerage data from small residential catchments in the Wessex Water region of the UK. The model gives an accurate prediction of the diurnal patterns of sewage discharge at a household level. This will be used as an input to future sewer simulation models to accurately predict changes to flow velocity and pollutant concentration as a consequence of water conservation.

O. Bailey, J. A. M. H. Hofman, T. C. Arnot, Z. Kapelan, M. Blokker, J. Vreeburg

Impact of Biochar on Treatment Performance of Roadside Sand Filters – Field Monitoring and Geochemical Modelling

Roadside filters can be used to treat polluted stormwater. In this study, sand and sand-biochar filters were investigated in full-scale field conditions during three rain events. Stormwater influent and effluent of the filters were sampled with high frequency and up to 29 water quality parameters were determined. The obtained field data was analyzed and used as an input for geochemical modelling. The study showed promising results for both filter types with respect to retention of metals, total suspended solids and total phosphorus. Biochar amendment had clear improvement only for nitrogen removal; some release of organic carbon from biochar filter material was observed. Concentrations of most measured parameters varied considerably during and between the studied events. Geochemical modelling showed that precipitation is one possible removal mechanisms for many pollutants along with sorption and physical filtration.

Eero Assmuth, Nora Sillanpää, Laura Wendling, Harri Koivusalo

Measurement and Planning–Level Modelling of Retention of Trace Metals (Cu, Pb, Zn) in Soils of Three Urban Drainage Grass Swales

Grass swales are important elements of urban green infrastructure that convey, attenuate and improve the quality of urban runoff mostly through stormwater infiltration into and retention of conveyed pollutants by swale soils. Such processes were addressed in this study, investigating the enrichment of swale soils by ubiquitous urban trace metals, Cu, Pb and Zn. Three swales were selected for study in the City of Lulea (Northern Sweden) and their soils were sampled by coring. Sample cores covered soil depths up to 30 cm, but only the results from the top 5 cm layer characterized by 9–15 samples in each swale are discussed here. After estimating metal mass in this layer in individual swales, such burdens were compared to those modelled by the proprietary StormTac Web model, which estimates annual loads of specific constituents for given land uses and is supported by an extensive database referenced to Swedish environmental conditions. The annual loads modelled for individual swales were multiplied by the swale age to obtain long–term inputs of the trace metals. A good agreement between the measured and modelled loads in soils was obtained and characterized by the ratio Lmod/Lmeas, with an average value of 0.96 and standard deviation of 0.55. Such results suggest the feasibility of assessing the long–term performance of grass swales by modelling trace metal (Cu, Pb, Zn) inputs into swales, estimating the metal loads retained in soils by sampling and analyses, and taking the difference (Lin − Lret) as the exported load.

Snežana Gavrić, Thomas Larm, Heléne Österlund, Jiri Marsalek, Anna Wahlsten, Maria Viklander

Adaptation of SuDS Modelling Complexity to End-Use Application

Sustainable urban Drainage Systems (SuDS) have gained popularity over the last two decades as an effective and optimal solution to continuous population growth and urban creep. SuDS do not only provide resilience towards pluvial flooding but they also provide multiple benefits ranging from amenity improvement to ecological and social well-being amelioration. To understand these complex interactions SuDS modelling is the tool to inform decision makers. Major developments in SuDS modelling techniques have been observed in the last decade, from simple lumped or conceptual models to very complex models. Several software packages have been developed to aid planning and implementation of SuDS. These often require extensive amount of data and calibration to reach acceptable level of accuracy. However, in many cases simple models may fulfill the aims of a particular stakeholder. Thus, it is very important to understand stakeholders’ priorities and aims and optimize the selection of modelling techniques according to the end-use application.

Mohamad H. El Hattab, Ana Mijic

Modelling Stormwater Pollutant Reduction with LID Scenarios in SWMM

Simple and automatic optimization approaches were used to create Low Impact Development (LID) scenarios for a residential catchment in Espoo, Finland. Ten LID scenarios were simulated with the Storm Water Management Model (SWMM) to evaluate their impact on urban runoff and pollutant load on a catchment scale. Permeable pavements and bioretention cells were located at the asphalted areas in the catchment. A large variability was observed in the simulated load reduction depending on the LID type, location and pollutant. Scenarios with permeable pavements reduced pollutants effectively, but require knowledge about the pollutant sources and pathways. Scenarios with bioretention cells benefitted the most from location optimization due to their smaller spatial footprint and storage capacity compared with permeable pavements.

Camilla Tuomela, Daniel Jato-Espino, Nora Sillanpää, Harri Koivusalo

Resilience and Its Relation to System Structure of Combined Sewer Systems: Virtual Case Study Based on Stochastic Generation

Resilience is a system’s ability to minimize failure consequences when faced with exceptional conditions. This paper studies the relation between resilience and system structure of combined sewer systems. Stochastic generation model is used to obtain systems with various structures and their performance is tested in Storm Water Management Model (SWMM). Results show that resilience is mostly affected by the total count of combined sewer overflow (CSO) outfalls. The count of wastewater treatment plants (WWTP) also influences resilience but not remarkably. The cost-effectiveness of each system structure is also discussed. This study provides insight into the structural characteristics of combined sewer systems and can provide guidance for their planning and design.

Dazhen Zhang, Xin Dong, Siyu Zeng

Developing a New Modelling Tool to Allocate Low Impact Development Practices in a Cost Optimized Method

Nowadays there is a need to overcome the effects caused by rapid urbanisation with more innovative methods. Recently, source control approaches, known as Low Impact Development (LID), are being used by urban planners to cope with water related problems and any other environmental issues due to their cost-effectiveness and reliability. To meet the needs of decision makers, the effects of these practices should be analysed at catchment scale. To do this, allocation of LID techniques in most suitable locations is essential. In this research a new modelling tool called LID locator is added to the WetSpa-Urban software package for more accurate placement of these techniques. The maximum area that can be covered by different types of LIDs are defined by finding the potential areas prone to generate runoff in combination with suitability maps calculated based on size limitation and implementation restriction for each LID measures. Then, the new cost-optimization tool is added through new procedure. This study is testified in the Watermaelbeek catchment situated in Brussels capital region.

Nahad Rezazadeh Helmi, Boud Verbeiren, Mohamad El Hattab, Ana Mijic, Willy Bauwens

Modelling of Green Permeable Car Park Water Retention

Permeable car parks, as part of SuDS (Sustainable Drainage Systems), are developed for better management practice of urban stormwater. Even if lots of researches studied permeable pavements, none specifically studied green permeable pavement impact on urban water quantity and quality, or modelled its behaviour. In this study three types of experimental parking places (1 with gravels and 2 with vegetation) are monitored. The data obtained from a simulated rain event and a natural rain event, served to test and adapt a reservoir model, initially developed for green roofs. First calibration tests showed that permeable car parks (vegetalized or not) behaviour can be simulated with the reservoir model with a calculated water mass balance around ±15% for different conditions. However, the model needs to be improved to have better water mass balance results, and to be better adapted to green permeable car park.

Varnède Lucie, Ramier David, Georgel Pierre, Gromaire Marie-Christine

Modelling Study on the Impacts of BMPs at Riacho Fundo (Brasília, Brazil)

High urbanization affects significantly on cities, intensifying runoff and impairing old urban drainage systems, which may cause floods. Solutions analyzed in this study include management of rainwaters in cities by means of mitigation measures. Riacho Fundo drainage network simulation was carried out using PCSWMM software to evaluate the system behaviour. The simulations evidenced the observed high flows and other problems such as system overloading. BMPs were tested in the model to indicate do the stakeholders which measures can lead to better improvements.

Vítor Tomaz Mineiro Camuzi, Maria Elisa Leite Costa, Arthur Tavares Schleicher, Jeferson da Costa, Sérgio Koide

Use of Retention Basin for Flood Mitigation and Urban Requalification in Mesquita, Brazil

Unplanned urbanization is one of the main factors responsible for worsening flood-related problems in cities, increasing the frequency and flooding depths and degrading the environment. Considering this, the use of engineering techniques that reduce runoff and promote the urban requalification are efficient for the management of rainwaters. This paper presents a case study of flood control project using a storm water retention pond, designed to allow multiple use of an urban space. The operation of the system is evaluated by a Cell Model, developed in the Computational Hydraulic Laboratory of the Federal University of Rio de Janeiro (LHC-COPPE/UFRJ), known as MODCEL. The results showed the best configuration of the layout of “Celso Peçanha” Retention Basin, considering the area restrictions imposed by the City of Mesquita - Brazil, optimized to damp rainfall flows resulting from rainfall with return periods up to 50 years. The solution proposed is concerned about social urban space use, revitalising degraded areas and giving it different possibilities of use.

Osvaldo Moura Rezende, Matheus Martins de Sousa, Ana Caroline Pitzer Jacob, Luiza Batista de França Ribeiro, Antonio Krishnamurti Beleño de Oliveira, Cícero Matos Arrais, Marcelo Gomes Miguez

Quantifying Long-Term Benefits of Multi-purpose Rainwater Management Systems

This paper investigates the performance in terms of yield, peak stormwater discharges and annual stormwater reductions for a set of four rainwater management scenarios tested against a hypothetical household in England. The work builds on recent progress in modelling of rainwater management systems (RMS) using a mass balance approach. The novelty lies in the ability to investigate both; local water provision; and the reduction in stormwater discharges associated with the RMS strategies. Recent research studies and case study exemplars demonstrate a shift away from single objective rainwater harvesting systems. Projects are now being delivered using dual-purpose RMS to control discharges as well as augment water supply. The study illustrates for the first time, how a long time series rainfall record (85 years) can be used to drive mass balance simulations and enable key metrics to be calculated. The results illustrate how well-designed RMS can reduce stormwater discharges whilst also meeting design needs for water resource augmentation. The length of rainfall dataset analysed enables long performance evaluation including during low probability events that exceed the UK’s current stormwater drainage design standards (e.g. 1 in 30 year rainfall event). The study also investigates the potential for climate change to affect performance. It concludes that an actively controlled RMS with a 3000 l tank can potentially reduce the largest rainfall event in the 85 year dataset by 72%, up from just 6% for a traditional RWH configuration with the same tank storage capacity.

Peter Melville-Shreeve, David Butler

Swinging Self-cleaning Screen Bars the Tube Hobas CSO Chamber, Their Physical Properties and Design

This paper deals with the design of the suitable shape of the swinging rods in the Tube overflow chamber (CSO HOBAS CHAMBER), in order to support the self-cleaning effect of the screen bars. The self-cleaning effect is caused by the free ends of the rods, which are swinging in the 45° range and freely vibrating in the stream. By oscillation, the settled dirt is released into the lower part of the CSO, from where it is subsequently discharged to the WWTP. The main objective of the research was to find suitable shapes of swinging rods so that the self-cleaning effect of the screen bars could be supported at different rod lengths. The measurement was carried out on a physical model made in 1:1 scale and was captured on a high-speed camera. The design criteria for swinging screens on CSO HOBAS CHAMBER of different sizes was established after analysis of created slow footage. It is a commercial product manufactured by HOBAS. Information about the standards of this technology can be found on the HOBAS website.

Jiri Prochazka, Jaroslav Pollert, Ondrej Svanda

A Prioritization Tool for SUDS Planning in Large Cities by Coupling an Urban Drainage Model with Mixed Integer Linear Programming

Decision making regarding Sustainable Urban Drainage Systems (SUDS) sitting is an analytical complex process, as it involves the evaluation of a high number of environmental, physical and technical considerations. Additionally, as the resources are always limited (e.g. budget and land availability), the prioritization of sub-catchments for SUDS placement would help decision makers to determine where is most beneficial to locate these infrastructures. This study proposes a methodology that couples an urban drainage model and Mixed Integer Linear Programming (MILP) to determine where is more beneficial to locate SUDS to reduce both runoff volumes and combined sewer overflows (CSOs). To achieve this goal, the City Drain model is used to model the runoff generation and the flows among sub-catchments. Three indexes are proposed to quantify the reduction on both CSO and runoff volumes, and a lexicographic multi-objective model is used to find the prioritized sub-catchments within a city. The methodology was applied to sub-catchments of Bogotá (Colombia), comprising an area of 38 km2. Preliminary results showed that the prioritized sub-catchments were highly dependent on land availability and the optimal solution did not necessarily involve the selection of the sub-catchments that yield most runoff. This study demonstrates the importance and usefulness of the prioritization tool for SUDS planning, which can be used by other large cities like Bogotá.

María Narine Torres, Zhenduo Zhu, Juan Pablo Rodríguez

Modelling Bioretention Systems

Bioretention systems are of great importance LID structures for acting in runoff control and pollutant removal. Modelling bioretention systems are defying because many process and functions are involved. There are many efforts in modelling such systems. In this paper, we reviewed literature in order to stablish what are the functions and process involved in the systems modeling and the most important gaps. Bioretention performance in controlling flood and in pollutant removal are of great variability. Process considered in models and their mathematical representation are very diverse. Clogging, evapotranspiration, chemical removal were the most defying process to be modelled.

Alexandra Finotti, Marie Christine Gromaire

Surface Runoff in Urban Area – Case Study

The world’s population nowadays is concentrated in urban areas. This change in demography has brought land-use and land-cover changes that have a number of documented effects on stream flow. The most consistent effect is an increase in impervious surfaces within urban catchments, which alters the hydrology and geomorphology of streams. In addition to imperviousness, runoff from urbanized surfaces as well as municipal and industrial discharges results in increasing floods in urbanized areas as it decreasing river bed capacity for flow. Rainwater management should be considered as a sustainable strategy for reconstruction of rural and urban settlements from the aspects of environmental management and social criteria. The paper presents the current state of runoff condition in the study area taking into account the urban development in the last 30 years, mainly newly built hypermarkets. The goal of the study was an evaluation of surface condition, calculation of the runoff coefficient and design of potential measures to stabilize conditions in the drainage basin of Myslavský creek in eastern part of Slovakia.

Martina Zeleňáková, Zuzana Vranayová, Adam Repel, Daniela Kaposztasová

Modelling Different Types of Stormwater Treatment Facilities Considering Irreducible Concentrations

To design Stormwater Treatment Facilities (STFs) properly, we recommend the use of an urban drainage model that should include the calculation of runoff quality, to be based on a detailed land use specification, include site-specific design parameters, calculated outflow concentrations and loads of specified pollutants of relevance for the receiving water. This study compiles minimum outflow concentrations from stormwater databases of different types of STFs (wet ponds, wetlands, biofilters and underground retention basins with filters). These concentration data are used for the suggested values of specific “irreducible concentrations” (Cirr). Suggested Cirr for phosphorus (P) varies from 20–40 μg/l depending on facility type, for copper (Cu) 1.8–4.0 µg/l, for zinc (Zn) 2.0–15 μg/l and for total suspended solids (TSS) 2 900–5 000 μg/l. Corresponding data for 70 substances are compiled in the StormTac database and employed in the urban drainage model StormTac Web. Cirr have significant impact regarding the choice of facility type and its calculated dimensions. This design parameter and the calculated outflow concentrations can be used to investigate the need for combined serial facilities or complemented design elements with more planted vegetation or installed filters. Such elements can be required to decrease Cirr and thereby reach project specific limit outflow concentrations and loads. The suggested data will be further evaluated and updated with respect to more data from different facility types and more substances.

Thomas Larm, Anna Wahlsten

Metals Potential Removal Efficiency of Permeable Pavement

Permeable Pavement (PP) represents a good solution to solve stormwater management problems both in quantitative and qualitative way. In this way, the potential removal efficiency of a permeable pavement in treating metals was assessed by performing a monitoring campaign at a lab-scale system constructed for the purpose. Based on literature experiences, different relatively high-level concentrations of Copper and Zinc were applied during 8 different synthetic rainfall events. Results shown that the removal rates of Cu and Zn of the lab-scale pavements range from 85% to 92% and from 65% to 82%, respectively. Results also shown that the Cu removal rates of the lab-scale pavement are higher than Zn removal rate.

Michele Turco, Giuseppe Brunetti, Michele Porti, Giovanna Grossi, Mario Maiolo, Patrizia Piro

Comparison of Cost Benefits of New Installation and Retrofitted Rainwater Harvesting Systems for Commercial Buildings

This paper aims to evaluate cost benefits of new installation and retrofitted rainwater harvesting system (RWHS) for commercial building. The selected commercial building is AEON Taman Universiti, Johor, Malaysia. Daily rainfall data were obtained from the Senai International Airport station. The mass balance model was adopted for the simulation approach. Several economic parameters, namely, net present value (NPV), return on investment (ROI), and benefit-cost ratio (BCR) are used for the evaluation. Maximum NPV, BCR, and ROI of the new installation RWHS are 1.9, 1.5, and 5.5 times higher, respectively, than those of the retrofitted RWHS. It is concluded that new installation RWHS provides more economic benefits compared to the retrofitted RWHS.

Nor Hafizi Md Lani, Achmad Syafiuddin, Zulkifli Yusop

Rainwater Reuse in Urban Areas: A Mathematical Model and a Long-Term Modelling Approach

Natural water resources are becoming increasingly limited due to global-scale climate change and water availability issues have become so severe that they must be addressed. Given these issues, reuse of wastewater and rainwater provides a promising way to cope with water shortages. This paper describes an investigation into the efficiency of rainwater usage systems. A conceptual model was built to assess the behaviour of rainwater tanks and their effectiveness in coping with water shortages. The study is based on a long-term simulation (12 years) of different rainwater reuse tank schemes. The associated reductions in residential freshwater demand (water reuse efficiency) and wet-weather runoff delivered to the sewer system (sewer discharge efficiency) were surveyed. The results clearly show that rainwater usage systems can significantly reduce drinking water consumption. The specific volumes required for the reuse of rainwater are high; however, for local scale application, the specific volumes necessary are comparable to the reservoir volumes already used to store freshwater resources during potable water shortage.

Gabriele Freni, Giorgio Mannina, Michele Torregrossa, Gaspare Viviani

Long Term Efficiency Analysis of Infiltration Trenches Subjected to Clogging

In recent years, limitations linked to traditional urban drainage schemes have been pointed out and new approaches were developed introducing more natural methods for retaining and/or disposing of stormwater. Such practices include infiltration and storage tanks in order to reduce the peak flow and retain part of the polluting components. The impact of such practices on stormwater quantity and quality is not easily assessable because of the complexity of physical and chemical processes involved. In such cases, integrated urban drainage models may play a relevant role providing tools for long term analysis. In this study, the effect of the clogging phenomenon has been assessed by means of a simplified conceptual modelling approach developed in previous studies has been employed and different soils as well as different design criteria have been considered. On the basis of a long-term simulation of 6 years rain data, the performance as well as the effectiveness of an infiltration trench measure are assessed. The study confirmed the important role played by the clogging phenomenon on such infiltration structures.

Gabriele Freni, Giorgio Mannina

Frontiers in Urban Drainage

Frontmatter

Controlling Urban Drainage Systems

The key issue in urban drainage (UD) systems, looking from a control engineering perspective, is operation. Measurements, feedback, control and automation are tools to address the challenges. Measurement technology combined with analysis and parameter estimation are used to obtain relevant information for decision and control. The UD control problem is truly multivariable with many sensors and actuators. A major concern is how to define performance indices that reflect requirements from the natural and urban environment and how to translate this into operational variables. This makes the UD system operation a multi-objective control problem.

Gustaf Olsson

Development of a Smart System for the Operation of a Complex Sanitation System

The urban runoff contains a significant amount of pollutants. Due to CSO limitations and WWTP’s biological processes, wastewater discharge must be regulated not only in quantity but also in quality. In this regard, Canal de Isabel II is working on the Manzanares Sanitation System project to characterise pollution in different rainfall scenarios by profiling the collected rainwater pollutants. The results will be used to develop an integrated management protocol for the stormwater tanks during rain events focused on minimising not only the discharged volume, but mainly the environmental impact produced by the discharge into the receiving water bodies. After a storage period, the effluent pollution is noticeably reduced for the mere reason to be stored into the stormwater tank. As a conclusion, the sewer system’s dimensioning idea based on characterisation of sewage is gaining straight over first flush or dilution concept. The project, headed by Canal de Isabel II, takes place in the city of Madrid and studies the CSS that belongs to Manzanares river’s catchment.

Antonio Lastra, Joaquín Suárez, Jerónimo Puertas, José Anta, Xavier Falcó, Mónica Ortega, Alejandro Pinilla

Holistic Water Cycle Management in Priority Growth Area in Sydney’s West by Managing the Water Cycle Strategies of Individual Precincts

The most significant development in Sydney is taking place in Priority Growth Areas (PGA) along the South Creek corridor, Sydney’s West. The Water Cycle Management (WCM) Strategy is a key component in the development of PGA. WCM strategies for PGA precincts development carried out in isolation were reviewed. Their shortcomings were addressed through a regional 2D TUFLOW hydraulic model. This 2D regional model was used to control the cumulative impacts of Leppington precinct development. The Urban Site Detention (USD) guidelines were prepared to maintain pre-developed hydrological behaviour. USD guideline for 50% Annual Exceedance Probability (AEP) was used to mitigate waterways stability impacts reducing erosion and Total Suspended Solids (TSS), while 1% AEP USD guideline was used to mitigate flooding. The adoption of the USD guidelines enhanced the stability of bed and bank, biotic habitats and ecosystem health of creeks. Water quality requirements were addressed by Water Sensitive Urban Design (WSUD). WSUD and the reuse of stormwater planning were based on MUSIC modelling. Climate change impacts were considered. The precinct planning integrates stormwater management with liveability by reducing flood risks to properties and infrastructure and increases the safety and security of residents. This paper will discuss the application of updated strategies in WCM for Leppington precinct and its achievements in holistic WCM strategy in PGA development.

Maria Pinto

Interaction Between City Subsurface Infrastructure and Groundwater

The interaction between the underground infrastructure and groundwater generates hydrogeological problems in Bucharest city (1.9 million people/228 km2 surface). One is the barrier effect produced by an extensively channelized river, increasing consequently the groundwater hydraulic heads in the surrounding areas. A second one is due to the strong hydraulic interaction between sewerage and the groundwater. As result, the seepage into the sewer network increases the influent flowrate received by the waste water treatment plant. Restoration of the sewer conduits triggers consequently the groundwater hydraulic heads increase. Answers to these problems have been foreseen by developing the Bucharest city hydrogeological model with the support of several institutions, companies, and experts. As a first step the 3D geological model, for the first 50 m below ground level, has been developed. The spatial intersection between the urban infrastructure elements (subway, parking lots, etc.) and the geological model, provided the geometrical parameters needed to quantify their groundwater flow barrier effect. It also enabled to identify the location of the sewer conduits and their potential hydraulic connection with the aquifer strata. The hydrogeological model englobes the following datasets: hydraulic heads, surface water, groundwater recharge from precipitation and from the water supply system losses, drainage systems and seepage into tunnels. The resulted hydrological water balance identified that about 0.92 m3/s wastewater surplus originates from seepage. It has been determined that more than 20% (96.7 km) of the sewer network is completely or partially immersed into groundwater. Scenarios to neutralize the groundwater sink impact have been simulated.

Constantin Radu Gogu, Mohamed Amine Boukhemacha, Dragos Gaitanaru, Irina Moraru

Assessment of Separation Efficiency of Reconstructed Combined Sewer Overflow in Debr (Czech Republic)

This paper is aimed to assess the function of renovated combined sewer overflow (CSO) in Debr nad Jizerou. The former lateral CSO, which did not meet the requirements, was replaced with a modified type of tube CSO in 2012. The main goal of this study was to determine separation efficiency of the new CSO and to compare it to the previous situation. Monitoring itself included online observation of hydrological indicators in the sewer system, then continuous sampling during precipitation events and its assessment, moreover the chemical quality water judgment in recipient body in both immediate and long-term view. Comparing of current and older results, it is clear that the new CSO works better than the former CSO. The newly installed CSO decreases the pollution into the receiving body about 30–50% on average. Separation efficiency is improved and also values of the basic chemicals indicators in the recipient are better. Measuring on CSO showed the relevant correspondence of actual separation efficiency of suspended solids with the mathematical model.

Kristyna Soukupova, Jana Nabelkova, Jaroslav Pollert, Petr Chmatal

Frontiers in Urban Drainage - An Analysis of a Preliminary Water Quality Recovery Program Plan in a Developing Country

Rapid growth and high population density concentrated in small areas became inadequate urban water resources, especially in the developing countries. The pollution of rivers and degradation of ecosystems are the result. Rivers restoration appears as a solution to improve this panorama. In this way, this paper analysed one of these projects. It was developed by a Brazilian university in response to a Public Civil Action. The actions described in the program are still insufficient and they can be summarized as monitoring of the current situation. These streams are degraded due to sewage and wastewater pollution from external and internal sources of the university, which has been proven by studies on water quality. Despite of this, the program actions contemplate only interventions within the territory of the university. From a holistic view it is believed that these actions are insufficient to recover the water quality of the rivers.

Fabiane Andressa Tasca, Camila Ely Januário Silva, Maria Vitart de Abreu Lima, Alexandra Rodrigues Finotti

Modelling for Integrated Stormwater Management of the Renfrew Neighbourhood: A Pilot Study

The Renfrew Neighbourhood within the City of Calgary is about 1.3 km2 and is undergoing infill redevelopment with effective lot imperviousness increasing three-fold, straining the existing storm sewer system. Combined with existing localized flooding, the City of Calgary is challenged with providing adequate flood storage and improving downstream water quality. These challenges are not unique to the Renfrew Neighbourhood, but permit the project and location to be used as a pilot study to compare the cost effectiveness of different retrofit options using a novel benefit optimization approach. Four potential retrofit options were identified for integrated stormwater management: pipe replacement (size) inlet flow controls, distributed management (LID/SUDS/WSUDS), regional or community storage, and a combination of controls. Hydrologic and hydraulic analyses conducted using EPA SWMM was coupled with an extension software package (OptimizerTM) to determine the placement and sizing of improvements for each scenario that most cost-effectively managed runoff for future redevelopment conditions. Optimization can often result in significant cost savings over more traditional infrastructure planning approaches. By using optimization software, planning can minimise costs and maximize flood control and water quality benefits. Runoff conditions from small storm events through a 50-yr, 4-hr design event for the 2076 redevelopment conditions were considered in scenario optimization. Results from the analyses demonstrate the value of using an optimization approach for long-term integrated stormwater planning which can serve as a template for future capital improvements.

Scott Struck, Marc Leisenring, Lucas Nguyen, David Seeliger, Bert van Duin, Pablo Lopez Hernandez, Joshua Cantone

Development of Screening Methods for Secondary Settling Tanks Monitoring and Optimization

Lately, the environmental awareness that leads to legislation changes has been pushing the waste water treatment plant (WWTP) operators to increase the secondary settling tanks’ (SST) efficiency in order to meet the new requirements. The SST efficiency is commonly understood as the ability to separate suspended solids from the effluent water. The internal SST dynamics depends strongly on both physical and biochemical properties of the activated sludge and thus the sludge properties are specific for every tank. Also, the geometry of the influent and effluent objects determine the sludge behaviour and are therefore often a subject to research and modification through the use of numerical models. The aim of this paper is to describe an innovative screening method that enables for better capturing of the current state SST sludge behaviour and with the cooperation of the numerical model provides a tool for SST geometry optimization. The benefit of this method compared to traditionally used models lays in utilizing both the experimental measuring data and numerical model data together to provide for a good calibrated model that can be used for efficient SST optimization.

Ondřej Švanda, Jaroslav Pollert, Iva Johanidesová

Assessing Uncertainty of a Biofilter Micropollutant Transport Model MPiRe

MPiRe (Micro-Pollutants In RaingardEns) model was developed to predict both flows and removal of micropollutants by stormwater biofilters. It is a conceptual 1D model that includes sorption/desorption, biodegradation and volatilization processes. This paper presents an uncertainty evaluation of MPiRe using the GLUE methodology with atrazine as a representative pollutant. The uncertainty analysis shows that the soil-water partitioning coefficient (normalized to organic carbon content) is the most sensitive model parameter, while there is some correlation between sorption parameters and high uncertainty in the degradation rate estimation. It is hypothesized that the correlation between sorption parameters can be diminished by choosing two different combinations of calibration parameters (e.g. variations of their mutual products), and this hypothesis will be further tested. The practical implication of this analysis is that particular care should be given to measurements of initial outflow concentrations of events (to decrease the uncertainty in the degradation rate estimation). Additionally, if it is necessary to prioritize between monitoring procedures, the most attention should be given to sorption kinetics.

Anja Randelovic, Kefeng Zhang, David McCarthy, Ana Deletic

Study for the Proper Management of Rainwater Withing the Mexican Water Technology Institute

The Mexican Water Technology Institute (IMTA) is located at the meeting point of two streams that tend to saturate and overflow during the rainy season. Several flooding incidents have taken place throughout past decades resulting in complications for the IMTA and surrounding zones. This article presents the results of the analysis of basins-of-contribution drainage, the behavior of the streams and the flood zones for different return periods. A proposal to modify the pluvial-drainage network was developed with the results of the analysis in order to mitigate flood impacts. The efficiency of the proposed infrastructure was evaluated under the same conditions of the original scenario. All of this was carried out with the aid of a digital elevation model (DEM), of the basins of contribution, a hydrological study performed with the help of software developed at the IMTA. Several drainage coefficients were taken into account for the distinct uses of land in the zone, primarily urban, and mathematical simulation models were created in two dimensions that included current pluvial infrastructure, the digital elevation model, and the sub-basins with their particular characteristics.

Rodrigo Santos-Tellez, Oscar Llaguno Guilberto, Manuel Rodriguez Varela, Manuel Figueroa Mendiola

Exploring the Use of Low Impact Development Strategies in a Low-Income Settlement in São Carlos, Brazil

The challenges of applying integrated stormwater management strategies in developing countries such as Brazil are particularly complex due to economic, environmental, and wider social issues in these localities. Factors like housing deficits, real estate speculation, urban land costs, massive demand for affordable housing, and the attempt to associate economic development with environmental preservation have led researchers in the drainage field to seek different models of urbanization. In this context, the present work aims to explore the possibilities of using low impact development (LID) strategies in a low-income settlement in the city of São Carlos, Brazil for the runoff management (two-year return period). To evaluate the feasibility and hydrological performance of the proposals, three scenarios were simulated in Storm Water Management Model (SWMM): Scen.CONV, a conventional urbanization and storm sewer drainage system; Scen.WELL, a conventional urbanization associated with the use of an infiltration well to disconnect the lots; and Scen.LID, which uses vegetative swales and infiltration trenches associated with urbanistic changes such as land use/imperviousness coefficients and roads typologies. Comparing Scen.CONV with Scen.WELL, the results indicated a potential 18% reduction in the linear length of buried conduits and a 40% reduction in the number of curb inlets. In the Scen.LID, the use of combined LID strategies allowed for the source control of all of the surface runoff, excluding the need for conventional drainage systems. The results also indicated a decrease of 60% in the peak flows of Scen.CONV in comparison with Scen.WELL and of 100% in relation to Scen.LID.

Maria Fernanda Nóbrega dos Santos, Anaí Floriano Vasconcelos, Ademir Paceli Barbassa

Controlling Stormwater Runoff from Impermeable Areas by Using Smart Inlets

Climate change and rapid urbanization are driving the need for improved urban stormwater runoff strategies. Urban stormwater drainage systems are severely affected by the changing climate bringing along inter alia more intense rainfall events. The pipeline system, usually having limited capacity, is unable to cope with these excessive flows and becomes surcharged. This may trigger overland flow from the drainage manholes and activate combined sewer overflows. Both events have negative consequences and therefore should be avoided. There are available effective solutions, like low impact development techniques for the catchments under development. However, options for retrofitting the existing drainage facilities are much more limited. Enlarging the pipelines, which has been a traditional response for rising demands is often financially unrealistic due to the large scope of the work. Therefore, recent advances in “smart” water system technologies are considered as an opportunity to meet the future challenges. In this study the concept for controlling stormwater outflow from impervious catchment areas, i.e. parking lots is developed. The target is to find a solution that is affordable and can be implemented with minor disturbances in the area. For that, a novel approach of controlling water flow by regulating the inflow to the manholes is analysed. The adjustable gullies are real time controlled by coupling rule-based algorithms with distributed model predictive control. The concept is successfully tested in a 12 ha impervious catchment area in Tallinn.

Nils Kändler, Ivar Annus, Anatoli Vassiljev, Raido Puust, Katrin Kaur

Multi-criteria Evaluation of Sustainable Urban Drainage Systems

This paper evaluates the use of Sustainable Urban Drainage Systems (SUDS) measures with hydrological-hydraulic modelling and multi-criteria analysis on a case study of Girona, Spain. To assess their effectiveness for rainwater runoff reduction and consequently the reduction of combined sewer overflow (CSO) the software Giswater was employed for development of the urban catchment model. This software couples spatial data from QGIS with EPA Storm water management model (SWMM). In accordance with the conditions in the urban catchment, five scenarios were developed consisting of following SUDS measures: infiltration basins, infiltration trenches, green roofs and their combinations. These scenarios were evaluated with multi-criteria analysis based on CSO reduction, CAPEX, OPEX, amenity, biodiversity, and feasibility regarding ownership. According to the results, the scenario that included only infiltration basins was most favourable (average grade: 4.1/5), followed by the scenario which combined infiltration basins and tranches (average grade: 3.5/5).

Matej Radinja, Joaquim Comas, Lluis Corominas, Nataša Atanasova

Exploring Uncertainty in Uncalibrated Bioretention Models

Using SWMM 5.0.016, a case study of a street right-of-way bioretention system (ROWB) configured as a storage node is compared against SWMM’s “LID Controls”. Through a series of 1-yr continuous simulations, the uncalibrated models indicate that a storage node representation of a media-filled system substantially underestimates stormwater retention and detention compared to the LID Control. This is because the latter explicitly accounts for dynamic flow through porous media. Lined/underdrained ROWB may provide significant stormwater mitigation because the majority of storms are small, thus fully captured by the media without the need for exfiltration. As the storage node approach is typical of the current (USA) industry for green infrastructure or low impact development modeling, outcomes raise concern around over-design (and misspent resources). Sensitivity analysis of the LID Control parameterization indicates that the relative difference between the engineered media’s porosity and field capacity have the most significant influence on performance. This may be an artefact of the calculation procedure rather than actual physical phenomenon. Future work should prioritize calibration with observed data sets from multiple sites (i.e. multiple media), and actual measurement of field capacity and porosity for multiple examples of bioretention.

Elizabeth Fassman-Beck, Firas Saleh

Promoting Successful Urban Watershed Restoration Through Enhanced Bioretention Cell Modelling

Urban runoff and stormwater is one of the top ten leading causes of water quality impairment in lakes, estuaries and streams in the United States (USEPA 2009). Over the last decade, bioretention systems have become a leading stormwater control measure (SCM) that contributes to the restoration of urban streams and watersheds. Bioretention cells increase infiltration of stormwater thereby reducing urban runoff volumes and peak flows which alter the hydrology of local waterways. Although these systems have proven to perform well in many site-scale field studies, less is known about how well these systems work when implemented en masse. Modelling of bioretention allows designers to scale local impacts to the larger watershed. However, current hydrologic models with bioretention capabilities consist of lumped parameters and simplifications that do not fully account for fundamental hydrologic processes. DRAINMOD is an agricultural drainage model that has shown promise when applied to bioretention systems. However, because DRAINMOD was designed for agricultural purposes, it cannot currently accommodate the rapid response time of an urban runoff hydrograph, instead aggregating data to a daily timeframe. For this study, DRAINMOD has been recoded to allow high temporal resolution inputs and outputs, more closely matching the travel times of urban systems. DRAINMOD simulations were conducted both with and without the time scale modifications (original vs. bioretention-specific model) to determine if improvements in site-scale modelling were realized. Future work will compare these results to those of simplistic, lumped-parameter bioretention modelling.

Whitney Lisenbee, Jon Hathaway, Ryan Winston

Wastewater Modification Processes in a Stabilization Reservoir: A New Mathematical Model

The paper presents a mathematical model for the simulation of the ecology of a wastewater stabilization reservoir (WSR). WSRs are hypertrophic aquatic systems devoted to water storage in warm countries where shortage conditions are often encountered. Several factors that affect the stabilization reservoir’s effluent quality were taken into account: hydraulics and hydrology, solar radiation, reaeration, algae, zooplankton, organic matter, pathogens, and sediment-water interactions. The model quantifies the specific influence of each factor on effluent quality, and evaluating the correlation between the different factors. State variables included in the model were: algae, dissolved oxygen, organic matter, zooplankton and indicator bacteria. The model was applied to an Italian stabilization reservoir located in the south part of Sardinia: Simbirizzi lake. The model generated satisfactory results and can be employed as a useful tool for environmental water quality management of stabilization reservoirs.

Giorgio Mannina, Gaspare Viviani, Steven C. Chapra

Receiving Water Quality

Frontmatter

Advances in River Water Quality Modelling and Management: Where We Come from, Where We Are, and Where We’re Going?

The historical roots of environmental engineering and water-quality management are traced to mid-19th century London when engineers and public health workers worked to control and manage the major water-quality problems derived from urbanization. This is followed by a brief review of the field’s subsequent century-plus evolution. The talk then turns to the current state of the art and a delineation of key research issues and frontiers. These include the modelling of “black water”, scum formation, the nepheloid layer, floatables (plastics & weeds), macrophytes, zooplankton, and uncertainty analysis of large model frameworks. Beyond specific research needs, global warming and mega-urbanization mean that, in the future, water-quality management must be expanded beyond the traditional reduction of pollutant inputs with novel approaches essential to maintain acceptable water quality in a sustainable fashion. Several case studies are used to illustrate possible approaches including dissolved oxygen bubblers, pure oxygen injection, lake hypolimnetic electron acceptor injection, boom deployment to capture floatables, flushing flows for oxygen and pathogen control, and deep lake siphons. Many of these schemes will be facilitated by coupling improved observational technology such as drones, robots, and sensors with water quantity and quality models. Real time, model-based distributed control could allow the development of “smart waters” where in situ interventions could be implemented in a sustainable fashion.

Steven C. Chapra

Analysis of the Po River Environmental Compatibility

The aim of this paper is to examine water quality of the Po River in a small stretch in Piedmont region (northern Italy). In this stretch a large pollution load, derived from Turin’s metropolitan area (about 2 million population equivalent) is mainly treated in the wastewater treatment plant (WWTP) located in Castiglione Torinese, and discharged in the Po River. The study quantified and modelled (using the tool of the mass balance) this load (in particular for the two parameters Total Nitrogen and Total Phosphorous) in order to understand the sources, destinations and effects of the emitted pollutants.The objective was to define the environmental impact produced by the Castiglione Torinese Wastewater Treatment Plant on the water quality of the river, based on various hydrological conditions and the possible interventions on the point and diffuse loads. The obtained results show that the environmental status of the Po River is only minimally influenced by the Castiglione Torinese WWTP discharge and so an intervention on the diffuse load is necessary.

Deborah Panepinto, Mariachiara Zanetti, Eugenio Lorenzi, Margherita Deceglia

Parametric Inference in Large Water Quality River Systems

Environmental models often contain parameters, which are not measurable, yet conceptual descriptions of some physical process. The value of such parameters is often derived by measuring internal state model variables in the system and indirectly tuning/calibrating the value of the parameters so some degree of match is achieved. Bayesian inference is a widely used tool in which the modeller can transfer some prior beliefs about the parameter space, which is updated when additional knowledge on the system is acquired (e.g. more measurements are available). However, the amount of simulations required to perform a formal inference becomes prohibitive when using computationally expensive models. In this work the inference of the hydraulic and dissolved oxygen processes is presented for a large scale integrated catchment model. Two emulator structures were used to accelerate the sampling of the river flow and dissolved oxygen dynamics. Posterior parameter probability distributions were computed using one year of measured data in the river.

Antonio Moreno-Rodenas, Jeroen Langeveld, Francois Clemens

Interfacing Stakeholder Involvement into a Surface Water-Quality Modelling System for Water Management and Policy Development

Water quality has been under unprecedented pressure over the past few decades due, in part, to increasing nutrient pollution from cities, industrial zones and agricultural areas entering river systems. The dynamics of these impacts on water quality are complex and stem from decisions and activities of different groups of stakeholders, who can have different business plans, values and attitudes towards water quality. This means that, improving the quality of water requires incorporating stakeholders’ viewpoints and decisions into water quality management processes. This study proposes a modelling framework to engage stakeholders in selecting practices and policies that can improve riverine and lacustrine water quality.

Karl-Erich Lindenschmidt, Eric Akomeah, Helen Baulch, Lisa Boyer, John-Mark Davies, Elmira Hassanzadeh, Luis Morales Marin, Graham Strickert, Michelle Wauchope

Transport of Traffic-Related Microplastic Particles in Receiving Water

A majority of microplastic particles (MPs) in marine waters are transported with rivers from land-based sources. Traffic is estimated to be one of the largest sources of MPs, hence stormwater and subsequently urban waterways are expected to be important transportation routes of MPs to marine waters. However, there is currently little knowledge of MP fate from land sources to marine waters. The aim of this study is to investigate the transport of traffic-related microplastic particles in a receiving freshwater body using hydrodynamic modelling. A 16 km stretch of the Göta River, Sweden’s largest river, was set up using MIKE 3 FM software. The model builds on data on water flows in the river and its tributaries, water levels and salinity stratification in the Kattegat strait, and meteorological conditions. Concentrations of MPs in stormwater and MP characteristics data, including prevalent particle sizes and density of commonly occurring polymers, were found in the literature. The simulations show that peak concentrations of MPs have a short duration; however, elevated concentrations of MPs may be present for hours after rainfall. If the MPs do not settle, as is the case for low density MPs including tyre rubber, a high load of MPs from the city of Gothenburg will reach the marine environment. Biofouling and MPs adhering to mineral particles, as has been shown in marine waters, may considerably change the characteristics of MPs and should be considered in future studies.

Mia Bondelind, Ailinh Nguyen, Ekaterina Sokolova, Karin Björklund

Hybrid Filtration System for Treatment of Stormwater Runoff

Hydrocyclone is widely used in industry, for its simple design, high capacity, low maintenance and low operational cost. The objective of this study is to develop ballasted hydrocyclone flocculation and filtration systems (BHFF) system. The BHFF system is consisted of hydrocyclone ballasted coagulation with polyaluminium chloride silicate (PACS) and upflow filter to treat micro particles in urban storm runoff. Roadside sediment particles (<100 μm) was mixed with tap water to make various turbid suspensions to determine the optimum PACS dosage. The experiment of Jar test was applied with rapid mixing at 200 rpm for 1 min, slow mixing at 50 rpm for 3 min, and settling period for 5 min. The results of Jar test showed that PACS optimum dosage was 7.0 mg/L, which these conditions left residual turbidity to less than 2.0NTU. The synthesized turbidity was made with roadside sediment particles to evaluate performance of BHFF system. There are two modes (without PACS use and with PACS use) of operation for BHFF system. In case of without coagulant use, the range of SS, turbidity removal efficiency were 42.9–95.8% (mean 80.8%), 20.2–88.2% (mean 61.7%), respectively. And, the recovery rate of filter was 72.8–85.9% (mean 80.9%) the rate of remained solid loading in filter media was 16.6–27.2%(mean 19.1%) after backwashing. The results of Jar test showed that PACS optimum dosage was 7.0 mg/L, which these conditions left residual turbidity to less than 2.0NTU. In case of BHFF run with coagulant use, the range of SS, turbidity removal efficiency were 62.2–100.0 (mean 88.8%), 64.5–99.8% (mean 88.7%), respectively. Based on SS loading mass balance analysis, the recovery rate of filter was 87.5–90.1% (mean 89.2%). It was found that removal efficiency was enhanced with PACS dosage. In case of coagulant use, the particle size of effluent is bigger than influent particle size. The BHFF system, which came out to solve the problems of low efficiency of removing micro particles of upflow filtration type stormwater treatment devices, therefore HBFF is considered as an alternative system.

J. H. Lee, S. H. Yang, D. H. Song

Flow Features of an Unstable Tangential Vortex Intake

Tangential vortex intakes are compact hydraulic structures commonly used in water supply, drainage and sewerage systems to convey water from high to low elevations efficiently. For certain design of tangential vortex intakes, flow instability can occur in the approach channel and the vortex dropshaft, resulting in undesirable hydraulic jump and shock waves. Due to the complex three-dimensional (3D) flow in the tangential vortex intake, current theoretical models are not sufficiently complete to interpret the flow process reliably. This paper presents an experimental and 3D Computational Fluid Dynamics (CFD) modeling study of an unstable tangential vortex intake flow. The CFD predictions are in good agreement with detailed point velocity and air core size measurements. Despite of the hydraulic jump at the tapering channel, the swirling flow at the vortex drop shaft is similar to that of a stable vortex intake with Rankine vortex behaviour.

S. N. Chan, Q. S. Qiao, J. H. W. Lee

An Integrated Approach for Assessing the Impact of Urban Stormwater Discharge on the Fecal Contamination in a Recreational Lake Near Paris

Urban stormwater discharges contribute to the fecal contamination of recreational lakes. It is essential to assess the spatial and temporal distribution of fecal bacterial indicators in the receiving waterbodies, to prevent public health risks. This study develops for the first time in continental waters an integrated monitoring and modelling approach, linking the SWMM and Delft-3D models and including a detailed monitoring of the stormwater discharge and at different points of the lake, for assessing Escherichia coli (E.coli) dynamics in stormwater discharges and the receiving urban lake. This integrated approach is applied to a recreational shallow lake and its adjacent urban catchment, with a single stormwater outlet which discharges into the lake. The SWMM model parameters are calibrated and validated with continuous measurements of the flow rate and mean concentration of E. coli in the stormwater discharge measured during each rainfall event. Using the simulated flow rate and E. coli concentration at the sewer outlet, the Delft3D-FLOW-WAQ model simulates E. coli transport in the urban lake with previously calibrated hydrodynamic parameters and default values of E. coli parameters. Comparing simulations with E. coli concentrations measured at different points in the lake, this integrated modelling approach yields promising results. Further studies will focus on the development of automatic model coupling and parameter optimisation, as well as on the evaluation of long-term impacts and management scenarios.

Yi Hong, Chenlu Li, Bruno J. Lemaire, Frédéric Soulignac, José R. Scarati Martins, Adélaïde Roguet, Françoise Lucas, Brigitte Vinçon-Leite

Flood Risk Mitigation in a Mediterranean Urban Area: The Case Study of Rossano Scalo (CS – Calabria, Italy)

Urban flooding is recently affecting several towns in the Italian Mediterranean region. The study focuses on the interconnection between the sewer network of the town (Rossano Scalo) and the main water course (the Citrea Creek) flowing through it. An integrated approach considering both town planning and hydraulic aspects lead the search for potential flood risk mitigation solutions. Through the use of GIS and field surveys a highly urbanized sub-basin was selected and analysed. The hydrologic- hydraulic system was simulated through SWMM software, paying attention to interactions between the minor and the major system. Critical nodes (urban flooding points) were finally considered for planning potential mitigation solutions.

Patrizia Piro, Mario Maiolo, Vito Cataldo Talarico, Salvatore Falco, Gennaro Nigro, Michèle Pezzagno, Filippo Carlo Pavesi, Francesca Berteni, Giovanna Grossi

Dissolved Phosphorus Treatment in Stormwater Biofilters Enhanced with Media Amendments

Biofiltration systems are one type of vegetated sustainable drainage systems particularly suited for diffuse pollution control and with a relatively compact footprint that make them an ideal choice for retrofit in urban areas. Existing knowledge on dissolved pollutant fate in biofilters, the influence of their design and configuration on hydrological, pollutant removal and long term performance is limited. This paper focuses on investigating the influence of amended media on the removal performance of dissolved pollutants through a laboratory study using batch test and mesocosms under controlled condition. Duplicate control and three amended configurations comprising of Zeolite, Granular Activated Carbon, and a mix of both, were dosed with synthetic stormwater runoff simulating typical pollutants concentration of urban runoff areas. In this paper the results for phosphate removal are reported. Preliminary results suggested that there is significant difference between inlet and outlet phosphate concentration (P < 0.001) with the configurations with both the amendments and the zeolite resulting in highest average removal performance. Mean phosphate removal performance for the four configurations were lower than 27%. Batch test highlighted the occurrence of leaching from topsoil and woodchips used in the biofilters. Higher phosphate removal was observed after longer dry periods between runs.

Andrea Aiello, Christian Berretta, Martin Tillotson

Measuring and Modelling the Nutrients Residual Load from the Combined Sewer of the Eastern Shore of Lake Iseo

The research is motivated by the need to understand the nutrient pollution dynamics in combined sewer overflows (CSOs) contributing to the eutrophication of Lake Iseo, the fifth largest Italian lake in terms of volume. To this end, the effectiveness of the combined sewer system along the lake’s eastern shore is assessed. The sewer’s efficiency is quantified with regard to the residual nutrients load from CSOs, which was originally reckoned at no more than 3% of the overall sewer load. A hydrodynamic model of the sewer system was developed by SWMM and calibrated by a long time series of measurements collected at two selected CSOs. This data allowed to investigate in detail the occurrence of first flush and to estimate the pollutant loads discharged during wet weather periods. The calibrated model then allowed to extrapolate the results of the year-long campaign to a 10-year simulation period providing, for the first time, quantitative information on the total residual loads to the lake. Such loads are at least 5 times larger than the design value. This research provides important insight into the potential impact of CSOs on the other deep lakes of the pre-alpine chain (e.g., lakes Como, Maggiore, and Garda in Italy), that are struggling with growing environmental stressors, opening the way to important technical and management considerations regarding remedial actions.

Laura Barone, Marco Pilotti, Manuel Murgioni, Giulia Valerio, Steven C. Chapra, Matteo Balistrocchi, Luca Milanesi

Multiregression Analysis of the Kinetic Constants in Ephemeral Rivers: The Case Study of the Oreto River

Profuse efforts have been committed to develop efficient tools to measure the ecological status of the receiving water body quality state. The recurrence to mathematical models as support tools for the receiving water body quality assessment can be an optimal choice. Indeed, mathematical models can allow to build-up the cause effect relationship between polluting sources and receiving water quality. Regarding the river water quality modelling, two different kinds of river can be single out: large and small rivers. In the modelling approach, the main differences between the two types of rivers are reflected in the model kinetic constants. Indeed, the main quality processes which control and govern the quality state play a differ rule. As a results, the application of model approaches as well as kinetic constants derived for large river, can lead to wide biases thus misevaluating the river quality state. The paper presents a study where a multiregression analysis was carried out for assessing relationships to be employed for the evaluation of the kinetics constants for small rivers. To accomplish such a goal, the kinetic constants derived by a previous application of a river water quality model applied to a real case study were used. Such kinetics constants were employed for deriving new multiregression equations for the assessment of the kinetics constants for small rivers.

Angela Candela, Giorgio Mannina, Gaspare Viviani

Rainfall in Urban Areas

Frontmatter

A Generator-Disaggregation Approach for Evaluating Climate Change Impact on Urban Drainage

Climate change on a global scale results in more intensive and frequent extreme rainfall events, which would likely increase the vulnerability of the urban drainage systems. Combing techniques of weather generator, Gumbel distribution, rainfall disaggregation and urban drainage modelling, this study examined impact of climate change on urban drainage flow based on the output from a number of global climate models (GCMs) for the timeline of the second half of this century. The proposed methods were employed on a small catchment in the tropical area for demonstration. The results showed that the selection of different GCMs (i.e., future climate conditions) exerted a remarkable effect on prediction of future maximum daily rainfall and the flooding condition of the drainage system. The impact of climate-induced extreme events is of significant concern and deserves more thorough investigation in the future.

Wei Lu, Xiaosheng Qin

The Influence of Household Rainwater Harvesting System Design on Water Supply and Stormwater Management Efficiency

Rainwater harvesting is increasingly being recognised as a sustainable option for both urban water and stormwater management. This study explores the potential impact of household rainwater harvesting on water supply augmentation and stormwater management in a typical three-bedroom house in Newcastle-upon Tyne, NE England. The continuous simulation of historical rainfall events at 15-min resolution over a 30-year period (1984–2013) is carried out to evaluate the system’s water saving and stormwater control efficiencies. Current and future rainfall projections are also incorporated in the analysis. The British Code of practice (BS 8515) is adopted to design the rainwater harvesting system. Results indicate that a rainwater harvesting system which is primarily designed for water supply augmentation with the size of 2.4 m3 contributes 64% of non-potable water demand (toilet flushing) and an 86% reduction of stormwater runoff volume into the sewer system. A larger system (6.5 m3) which is sized for both water supply augmentation and flood management provides 70% non-potable water supply and 96% reduction of stormwater runoff volume, indicating that a system which is designed for water supply only may be sufficient to achieve dual benefits. The relationship between storage and system efficiencies are explored for commercially available tanks for historical and future rainfall events. The influence of storage volume on flood peak attenuation is also explored for the historical flood events.

Sangaralingam Ahilan, Peter Melville-Shreeve, Zoran Kapelan, David Butler

Anomalous Extreme Rainfall Variability Over Europe ― Interaction Between Climate Variability and Climate Change

Climate variability and change are expected to alter the frequency, intensity and duration of extreme rainfall and urban flooding, which in turn will pose challenges to the urban drainage systems and management. This study analyses the decadal variability of daily extreme rainfall at 263 European stations and its connection with North Atlantic Oscillation (NAO), Western Mediterranean Oscillation (WeMO) and Southern Oscillation Index (SOI) over a roughly centennial period (1925–2015). The impact of climate change on the linkage between the anomalies of extreme rainfall and atmospheric circulations is also investigated. The results show a strong imprint of winter NAO and summer WeMO on extreme rainfall variability in Europe, with significant relationships (α = 0.05) at 70% and 45% of the stations, respectively. About 10–15% of the significant relationships is because of the underlying trend in the anomaly series due to climate change. Further investigation of climate change impact on the linkage reveals that the significant positive trend (α = 0.05) in winter NAO and summer WeMO anomaly series is accompanied by the same trend in extreme rainfall anomaly series at 67% and 37% of the stations for winter and summer, respectively. These results provide new insights into the climate variability versus trends and corresponding changes in extreme rainfall.

Hossein Tabari, Patrick Willems

Temporal Pattern Analysis of Rainstorm Events for Supporting Rainfall Design in a Tropical City

Synthetic rainfall distributions of the design storm have been commonly used for the hydrological design of urban stormwater infrastructures in many regions of the world. However, there are still limited studies in a tropical city dealing with design storm hyetographs for flood estimation even though rainfall intensity/depth-duration-frequency (IDF/DDF) relationships have been derived to estimate rainfall depths for a specific rainfall duration and return period. This study presents a storm-event based rainfall analysis method to determine a representative quartile of the design storm in which, both inter-event time definition (IETD) and depth/duration/intensity thresholds are considered. Similar to Huff’s method, 5-min rainfall data during three years at two rain gauge stations in Singapore were used to obtain the percentage frequency of the four types of quartile storms depending on the location where the heaviest rainfall occurred in each storm duration. It was found that the proposed approach could give the shape and magnitude of the design storm hyetograph from the location of peak rainfall corresponding to the largest portion of quartile storms. As a result, the second quartile design storm was suggested to be applied for flood estimation in order to better address the temporal characteristic of actual rainstorm events in the study area. It offers an alternative way of describing the temporal distribution of rainfall within a design storm period, which is helpful in improving the design of urban stormwater infrastructures in a tropical region.

Changhyun Jun, Xiaosheng Qin, Wei Lu

Modelling of Green and Grey Roofs in Cold Climates Using EPA’s Storm Water Management Model

Rooftops retrofitting, typically extensive green roofs, is a favoured sustainable drainage system technology in densely developed urban areas. They provide multiple benefits in terms of stormwater retention and runoff detention. The latest version of Storm Water Management Model (SWMM) 5.1.012 with Low Impact Development (LID) Controls was used to model hydrological the performance of a green and grey (non-vegetated) roof by defining the physical parameters of individual layers in LID Control editor. In this study, high-resolution 1-min data from a previously monitored green and grey roof were used to calibrate the SWMM LID Green Roof module. Results from the un-calibrated model were unsatisfactory considering the hydrological response of the green and grey roof. After calibration, the observed and simulated runoff had Nash-Sutcliffe model efficiency (NSME) of 0.88 (green roof) 0.68 (grey roof). This indicates that better fit between observed and modelled runoff could be achieved with calibration, primarily of the grey roof. Ideally the calibrated parameter set of the LID modules should be transferable between watersheds given the same LID structural build up. This should be investigated through further research finding the optimal parameter set, and data validation of proposed parameters across catchments.

Vladimír Hamouz, Tone Merete Muthanna

Coordinated Precipitation Evaluation of Damage-Producing Events: First Steps

Damage after rainfall events requires detailed analysis of causes and rainfall extremity for the determination of liability: the question who has to pay for what. Recent years have shown that damage has increased, but also the insight that extreme events call for the whole municipal community and not only the single citizen or sewer agency. The determination which rainfall category occurred requires thorough inspection of all available data. This includes weather radar, station data, flow data and damage data. It is important to be able to rely on quality controlled high resolution data for detailed analyses in mainly urban areas. This contribution presents important corner stones on the road towards a more harmonized way of evaluating damage producing precipitation events.

Thomas Einfalt, Sascha Hinsken, Marc Scheibel

Influence of Flood Water Contribution from Multiple Sources in Extreme Event Statistics of Urban Flooding

For pluvial flood risk assessment in urban areas it is important to be able to calculate how often a specific area is at risk of flooding. This is especially evident in urban areas subject to contribution from multiple sources, e.g. surcharging drainage system, surface runoff, overflowing rivers, etc. In this study extreme event statistics are assessed by simulation of rainfall impact and consecutive statistics of flood response in order to estimate return periods of flooding. The model applied is an integrated hydraulic model which includes relevant hydrological processes that contribute to urban flooding. The setup is analysed based on a small urban catchment in Aalborg Denmark. Results show that it is possible to estimate return periods of flood volume, flood extent and local water levels based on simulation and that rainfall and hydrological conditions critical to flooding can be identified.

Søren Thorndahl, Damian Murla-Tuyls, Rasmus Vest Nielsen, Marc Schleiss, Jonas Olsson

Investigation of Impacts of Spatial Variability and Motion of Rainfall in Urban Drainage Modelling

The topic of this paper is to investigate which knowledge can be acquired from weather radar systems on the case of spatial variability of storm events. Furthermore, it is investigated how this variation affects the results of an urban drainage model. The main focus of the study is to determine if the motion of a storm event has any impact on the runoff response in the drainage system. To do this a novel method is developed to rotate and relocate existing radar images and use the result as input to a selected model. At the moment the results show that the dominant direction of the storm has little to none effect on the outcome, but further research is being conducted to confirm this.

Christoffer B. Andersen, Søren Thorndahl

Urban Stormwater Monitoring and Modelling at the Riacho Fundo Sub-basin, Brasília – DF

This research is aimed to evaluate the application of the PCSWMM model to an urban watershed in Paranoá Lake basin to verify if the hydraulic model correctly simulates the flow discharge, an important step to estimate the loads conveyed to the Lake. This study was carried out to evaluate the use of the SWMM model on small urban basins in central Brazil, based on rainfall and runoff monitoring during events. The modelling was carried out using observed rainfall as input to PCSWMM model with SCS method generation. It was confirmed that this model fits well to this type of watershed, however it can be improved by calibration to single events.

Thays Mitsuko Tsuji, Maria Elisa Leite Costa, Sergio Koide

Rain Gauge vs. Radar Measurements - Modelling an Extreme Rain Event with High Spatial Variability

This work investigates the usage of both rain gauge measurements and radar data of a 500-year event that happened in Innsbruck in July 2016. The occurring intensities varied strongly, e.g. they could be classified into a return period of 500 and 25 years within a distance of 2 km. The underlying research question is, whether a change of model performance can be expected due to a better representation of the spatial variability of this specific rain event. This further leads to the question, whether a spatially accurate representation of rain events is still decisive for model performance when modelling such intense rainfalls. For high return periods, other impacts may gain importance instead. Performance assessment is done by comparing simulated water levels to in-sewer measurements. Results show, that measured peak intensities and runoff volumes are significantly higher for radar measurements than for gauged precipitation which leads to a significant overestimation of water levels. Consequently, radar rainfall input did not improve the model performance. A reason could be found in the missing radar image at peak time, different temporal resolutions of the data sets, in the accuracy of the measuring methods during such heavy rainfall intensities or even in the underlying ideas of the initial model establishment.

Tanja Vonach, Thomas Einfalt, Wolfgang Rauch, Manfred Kleidorfer

Influence of Dynamic Properties of Rainfall on Urban Drainage Infrastructure

Temporal and spatial variability of rainfalls have a significant impact on the operation of urban drainage systems. Stormwater storage reservoirs are particularly sensitive to these variations. This paper presents the results of research on the impact of the direction and speed of rainfall movement over an urban catchment of total area 560 ha on required volume of the storage tank. Simulations (using SWMM5 software) showed that movement of rainfall cells has a moderate impact on the peak-flows (around 20% increase in comparison to static variant), however, significantly affect the volume of stormwater accumulated in storage tanks. The most unfavorable variant is the rainfall moving in the direction and with velocity close to the general direction and average velocity of stormwater flow in the drainage system. The estimated increase of the unit volume of stored stormwater resulting from the dynamic properties of rainfall is about 6.5 to 8.0 m3 per hectare of impervious surface in comparison to static scenario.

M. Mrowiec, E. Ociepa, R. Malmur

Modeling Infiltration Wells in SWMM and Comparing Its Performance with a Real-Scale Well

The low impact development (LID) controls are increasingly encouraged to control the urbanization drainage impacts. A particularly interesting LID control for densely urbanized areas is an infiltration well (IW), as it occupies a small area and is efficient in recharging groundwater. The Storm Water Management Model (SWMM) is a hydraulic-hydrological modeling software program for urban areas that has been widely used and accepted. Its most recent versions already allow the modeling of some LID controls. However, despite their importance, IWs have not been studied yet. In this context, the goal of this article is to present a way to model the IW in SWMM using the available tools. For this purpose, infiltration trench (IT) input parameters were used. They were adapted to represent the IW stored volume and outflow. The water levels (WLs) calculated by the proposed model were compared to the WLs from a real-scale IW in the city of São Carlos, Brazil. The WLs were measured in the field by six controlled tests. The results showed a good fit between the WLs obtained by SWMM and the monitoring data, with an R2 between 0.96 and 0.97 and a Nash-Sutcliffe efficiency coefficient (NS) between 0.79 and 0.84. These results validate the procedures adopted, which allows the IW modeling in the current version of SWMM.

Anaí Floriano Vasconcelos, Thays Santos Ferreira, Maria Fernanda Nóbrega dos Santos, Ademir Paceli Barbassa

Efficient Calibration and Validation of Physical Stormwater Quality Modelling by Meta-model Based Approach

Model calibration and validation is still challenging for applications of physical stormwater quality model in the field of urban drainage modelling. In this context, this study aims to develop a new meta-model based framework for efficient calibration of complex and computationally intensive physically-based models. The proposed approach is applied to the physical FullSWOF-HR model for optimizing the washoff parameters. According to the average rainfall intensity, eight rainfall events are categorized into three groups for parameter optimisation, such as three light rains, three moderate rains and two heavy rains. After upscaling the original model, 77 parameter sampling experiments can be defined by a convergence analysis. Applying these 77 parameters series in FullSWOF-HR simulation runs, the interpolating polynomial of the original model is then generated by using the adaptive stochastic collocation method, which adopts sparse grid algorithm and selects the important parameters adaptively and automatically. Calibration process of the meta-model is based on the Markov chain Monte Carlo (MCMC) method. The optimized parameters are verified with the original model and then validated for different rainfall events. These promising results show that the proposed meta-model based approach can efficiently calibrate parameters for complex physical stormwater quality models. Our ongoing work focuses on the sensitivity/uncertainty analysis with this new meta-model based approach.

Yi Hong, Qinzhuo Liao, Celine Bonhomme, Ghassan Chebbo

Automatic Calibration Approach for Multiple Rain Events in SWMM Using Latin Hypercube Sampling

The present study aimed for the development and application of an automated calibration approach based on Latin Hypercube Sampling (LHS). The proposed methodology was used for calibrating an urban drainage model of a small sewer network of Dresden, implemented in EPA Stormwater Management Model (SWMM). Based on predefined ranges, LHS was applied to generate 1000 calibration parameter sets, which were used to simulate 24 different rain events. Nash-Sutcliffe Efficiency (NSE) was used to assess the goodness-of-fit of the results. NSE values were stored in an m-by-n matrix, where m corresponds to the number of parameter sets and n is the number of rain events and converted into 0 if they were below a defined threshold and 1 otherwise. For each row the sum of columns was calculated. The resulting number, referred to as degree, represents the amount of rain events for which the specific configuration yields a good NSE. Then, higher degrees imply a more robust set of parameters. By selecting a threshold of NSE = 0.75 it was possible to determine 11 different configurations, for which 6 out of the 24 events fulfilled the threshold. Analysis of these positive solutions revealed that one of them, parameter set 18 (S18), consistently reported the best NSE values for all analyzed events, and therefore was selected as the best solution. Although, adequate validation results were obtained, additional improvements are needed. Moreover, this approach can also be used to perform sensitivity analyses and evaluate the influence of rain events on calibration efficiency.

Benjamin Wagner, Julian David Reyes-Silva, Christian Förster, Jakob Benisch, Björn Helm, Peter Krebs

Flash Floods in Urban Areas: Case Studies in Reggio Calabria (Italy)

Flash flood is a precipitation of short duration and strong intensity which, generally, takes place in small portions of territory. Italy, due to climate, morphology and anthropization, is particularly subject to these phenomena. The major consequences of the flash floods occur in small basins, characterized by modest times of concentration and low storage capacity, especially if located close to urban areas. From this point of view, the development of alert systems can mitigate the impact of the phenomenon on the population. The paper will analyze the problems related to flash flood through two case studies near Reggio Calabria. It is a site of interest because it is located at the southern end of Calabria region, in the South of Italy, and is particularly prone to flash floods and environmental risks due to the morphological and climatic characteristics of its territory.

Marcello De Franco, Marianna Minniti, Rosa Versaci, Giandomenico Foti, Caterina Canale, Pierfabrizio Puntorieri

Urban Hydrologic and Hydraulic Processes

Frontmatter

Automatic Discretization and Parameterization of Watersheds Using a Digital Elevation Model

Characterization of overland and channelized flow is crucial for understanding runoff. This paper examines the SWMM setup and parameterization of an existing model and one highly discretized using a watershed delineation/parameterization tool.

Karen Finney, Rob James, Nandana Perera, Tiehong Xiao

Determination of Pluvial Flood Hazards for Critical Infrastructures and Buildings Taking in Account Impacts of Grid Resolution in Grid-Based Flood Models

The identification of flood hazards and flood risks (spatial overlay of flood hazards and potential damage) are basic tasks of flood risk management. Due to a lack of data for a comprehensive assessment of potential damage in urban areas, flood risks are often only determined for buildings (based on the building use from real estate cadastres). Therefore, building-related statements about flood hazards are required to assess flood risks. In practice, flood hazards for buildings are usually determined from results of hydrodynamic 2D surface runoff models using simple methods. These methods do not take into account the fact that building structures in the model may differ from the data of the underlying cadastre. This is particularly relevant for grid-based models, where the structure of a building in the model depends on the resolution of the calculation grid. To avoid inaccuracies inherent to these methods, we introduce a new algorithm. It first evaluates the results of a grid-based model on the basis of the calculation grid and then links them to the underlying building structures from the cadastre. Thus, differences between the rasterized buildings and their structure in the cadastre are taken into account. In addition we investigate the dependence of the results of the algorithm on the resolution of the calculation grid.

Michael Jeskulke, André Liebscher, Holger Hoppe, Theo G. Schmitt

Analysing the Cause of Urban Pluvial Flooding in a Hillside Settlement

Pluvial flood risk is increasing in urban and rural areas due to changes in precipitation patterns and urbanization. Pluvial flooding is often associated with insufficient capacities of the sewer system or low drainage efficiency of urban areas. In hilly areas hillside runoff additionally affects the risk of pluvial flooding. In the presented case study the cause of pluvial flooding at two selected sites in a settlement is investigated. To investigate all effects of pluvial flooding a coupled 1D-2D model of the whole catchment of the settlement is necessary. The results show that even though bottlenecks in the sewer system are important the effect of low drainage efficiency and hillside runoff greatly influence pluvial flooding. The knowledge of different causes of flooding can be further used for selecting and positioning appropriate adaption measures.

Lena Simperler, Florian Kretschmer, Thomas Ertl

Implementation of GIS and Hydrologic/Hydraulic Modelling for Integrated Floodplain/Stormwater Management

A very unique stormwater and flooding issue presented itself in Carlisle Borough, Pennsylvania, USA. The Letort Spring Run traversed the town and its watershed had become substantially developed causing excessive runoff, and a series of low capacity bridges caused subsequent flooding. An existing storm sewer conveyance system became submerged during significant rain events, causing a surcharge of the system, which overflowed inlets and flooded local streets, residences and businesses. The Borough also needed to address water quality from stormwater runoff to meet their National Pollutant Discharge Elimination System (NPDES) permit requirements. The analysis was complex due to flat surfaces and storm sewer system profiles, a complex system of multiple open channels with low banks, culverts, bridges, ditches, little documentation of the existing storm sewer system, backwater, and the timing of peak flows that create backwater. The problem required a unique GIS and modelling analysis through development of detailed GIS data, field survey and hydrologic and hydraulic modelling using WMS, HEC-RAS, SWMM, PeakFQ and StreamStats. Data developed in the GIS was exported into the HEC-RAS and SWMM input file formats. Various scenarios were modelled to determine storm frequency and durations that caused the most damage so that various alternative solutions could be determined. The low impact development options were also run in SWMM to evaluate alternative solutions.

Paul A. DeBarry, Gerald W. Longenecker, Ryan Burrows

Uncertainty Quantification of Flood Damage Estimation for Urban Drainage Risk Management

The study presents an inundation damage estimation method which quantifies the uncertainty in inundation damage statistical data for urban drainage management. The flood damage is usually estimated by multiplying inundated asset value by damage rate determined by the inundation depth. The dispersions of the asset values and the damage rates related to the uncertainty were expressed quantitatively using probability distributions for the actual flood damage data surveyed by the national government. Monte Carlo simulation was utilized to calculate the damage from the two parameters with probability distributions. Thus the simulations brought about the monetary flood damage not in deterministic but in probabilistic form.

Masaru Morita, Yeou Koung Tung

Hydrological Modelling of a Road-Side Vegetated Filter Strip: Validation of a Coupled 2D Subsurface Flow and 1D Overland Flow Model

Vegetated filter strips (VFS) are commonly employed as a best management practice to treat road runoff. In order to understand the long-term hydrologic behaviour of a road-side VFS, a coupled HYDRUS 2-D subsurface and 1D overland flow model was used. This model was validated over an 8 months period based on five soil moisture sensors readings. Results show good agreement between simulations and measurements for some sensors. Conversely, a discrepancy was identified for other sensors at particular periods. This outcome leads to a better understanding of the actual hydrological performance, such as a probable occurrence of preferential flow.

Tala Kanso, Marie-Christine Gromaire, David Ramier, Ghassan Chebbo

Hydrologic Performance Simulation of Green Infrastructures: Why Data-Driven Modelling Can Be Useful?

Green infrastructures are decentralized semi-natural solutions for managing stormwater runoff. To assess their effectiveness in urban drainage, many process-based hydrological models have been developed. However, these models sometimes fail to deliver satisfactory results due to inadequate representations of the involved hydrological processes or due to limited field measurements for model setup. Data-driven modelling simulates directly the connections between the state variables of the system (such as the input variable and the output variable), and thus reduces the need for hydrological process characterization. Yet the usefulness of this modelling approach in green infrastructure related studies has not been fully explored. To demonstrate its effectiveness, two bioretention systems in the U.S. are studied. The designs of these two systems are unique, making them difficult to be modelled directly using the standard process-based models. In one site, the observations are also censored, i.e., only the overflow/no overflow binary outcomes are being monitored, with which the model calibration is inhibited. We showed that using the state-of-the-art data-driven modelling framework (e.g., CARET and MXNET), the occurrence or the outflow discharge rate of the bioretention systems at a given time can be accurately simulated only using the rainfall, evapotranspiration and the inflow time series. We conclude that data-driven modelling can be useful for simulating the hydrologic performance of green infrastructures, especially when the existing process-based models are inadequate in representing the design variabilities or the data for model setup is limited.

Yang Yang, Ting Fong May Chui

Assessing Cost-Effectiveness of Different System Structural Characteristics in Enhancing Resilience of Urban Drainage Systems

Different urban drainage system structural characteristics such as topological structure, return period of pipe-sizing, green infrastructures and grey infrastructures are both significant in designing and managing urban drainage systems. These characteristics can somehow influence the resilience of systems and research is required to determine their cost-effectiveness. This study uses 1000 virtual drainage systems to evaluate the effect of each system structural characteristic on enhancing resilience. The results show that it is more cost-effective to enhance resilience in planning stage especially by finding better topological structure. In operational stage, building storage tanks is more cost-effective than building LID, but considering the feasible site for storage tanks, it has limited effect on enhancing resilience.

Zhiwei Xu, Yinan Zhao, Xin Dong, Pengfei Du

Multilayer Modelling as a Supporting Tool for Flood Diagnosis and Drainage System Design

The use of dual drainage models have increased significantly in the past decades, mostly because of advances in mathematical and GIS tools methods. This type of modelling provides precise diagnosis and can be applied to evaluate storm water infrastructure and diverse drainage alternatives. This study aimed to analyse minor and major drainage relations in Dona Eugênia River Basin, located in the metropolitan area of Rio de Janeiro, Brazil. Two alternatives were simulated using MODCEL. The first one considered only the terrain surface layer, while in the second the layer containing a designed storm sewer was introduced. The results provided information on where minor drainage gaps were located and on the effects of the storm sewer network discharges in the major drainage system.

Marcelo Gomes Miguez, Fernanda Dias Radesca, Aline Pires Veról, Matheus Martins de Sousa, Laurent Feu Grancer Silva Oliveira

A Data Analysis and Modelling Approach to Understand the Role of Urbanization Features on the Hydrological Regime

The impact of urbanization on the hydrological regime is complex and depends on different urban features. Increased imperviousness is the most studied one, but the reduction of buffers (river bed, ponds), increased drainage efficiency, or underground infrastructure interacting with subsurface flows can also be relevant. Classical assessment methods use data analysis on coupled catchments: they are limited by case-studies availability and cannot discriminate between different urban features. We associate here data analysis on 6 catchments in Brussels to detailed modelling, allowing to assess separately the role of different features of urbanization, i.e. imperviousness and ponds filling.

Guido Petrucci, Kevin De Bondt, Philippe Claeys

Transport Capability of Intake Vortices at Horizontal Intake Structures

Transport capability of intake vortices at horizontal intake structures was investigated by small-scale physical model tests on a scale of 1:5. The intention was to develop a prediction model which allows an evaluation of the transport capability of intake vortices on the basis of a calculated probability for various floating solids for a given geometry of intake structure. It could be demonstrated that the transport capability of intake vortices under constant geometrical boundary conditions can be determined on the basis of (i) the present hydraulic boundary conditions and (ii) the characteristics of the floating solids (density and diameter). A prediction model developed on this basis allows an estimation of the transport of floating solids for the present boundary conditions.

Nina Voßwinkel, Jörg Steinhardt, Andreas Schlenkhoff, Rainer Mohn

Uncertainty Analysis of Pollutant-Hydrograph Model in Assessing Inflow and Infiltration of Sanitary Sewer System

Infiltration and inflow is a very severe problem in the sanitary sewer system. There are many method to evaluate the RDII, of which a novel conductivity-based method for estimating RDII was proposed. However, the reliability such as uncertainty and accuracy are seldom evaluated. In this paper, the uncertainties of model parameters were estimated using the generalized likelihood uncertainty estimation (GLUE) method. The parameter uncertainty was considered in three types of rainfall events and two different system characteristic. The proposed method exhibits distinct advantages, compared to the traditional flow-based methods, in estimating RDII and overflow particularly when the two processes happen simultaneously.

Moran Wang, Mingkai Zhang, Yanchen Liu

Integration of Green Areas into a Suburban Flood Model

As a result of urbanization, suburban areas are growing. The catchment of this areas is characterized by different land use and sealing types. Due to climate change, there is a tendency towards more intense precipitation events, which causes a respectable increase of overland flow on permeable surfaces (green area). For a detailed flood management a coupled model of runoff, sewer transport and overland flow which also integrate green areas is much more powerful. Available software is usually built as semi-distributed (SD) models whereof the 2D surface module can only convey but not generate grid cell runoff. Fully distributed (FD) models solve this problem but are often not applicable due the required detailed object data. This paper describes a method to integrate green areas into an existing sewer (SD) model by virtual networks. The runoff module is founded on the kinematic wave computation, which includes a module for the infiltration capacity based on the Horton equation. Therefore the additional runoff of the green areas is predictable and the results shows more representative expression of the flood situation. Otherwise, the natural retention effect of green areas is directly implemented and is therefore also quantifiable.

Boris Richter, Christine Stapel, Jens Tränckner

Modelling Road Transport Congestion Due to Flooding

Transportation is essential for the normal flow of the economy because it is responsible for the movement of people and goods to planned locations. Therefore, traffic disruptions can have detrimental effects on multiple services. Road transportation is vulnerable to many threads, but flooding has the potential to lead to significant road network capacity reductions for a prolonged period of time. To assess the potential impacts of flooding on road transport, a detailed microscopic traffic model (SUMO) is integrated with an InfoWorks 1D–2D flood model. The traffic model simulates individually each vehicle in the network and has an adequate description of congestion, which makes it suitable for representing knock-on effects in transport systems. As both flooding and transport systems exhibit dynamic characteristics in space and time, dynamic model integration is carried out. Depending on the flood characteristics, a flooded road can undergo either a speed limit reduction or a complete closure. Once a road has been closed for traffic, vehicles that originally pass through it are forced to choose alternatives route to reach their unique destinations. That reroute will put an additional strain on a system already suffering reduced network capacity. The most congested roads in the network are identified after a comparison of the traffic conditions under normal conditions and flood conditions. The results suggest that the traffic delays in a dysfunctional network are more significant flood impact than the increased travel distance.

Katya Pyatkova, Albert S. Chen, David Butler, Slobodan Djordjević

How Important Is the Physical Interpretation and the Role of the Model User in Urban Flooding Simulation?

Computational models for flood simulation were consolidated in recent years as a design tool. Due to technological evolution, the use of 2D mathematical models has become more frequent. However, the choice of 2D models is not always accompanied by an actual physical based demand that justifies this process, and often the problem that is solved does not need a 2D approximation or even does not actually configure a 2D solution surface. This study aims to present an alternative modelling in order to bring back the physical interpretation and highlight the modeller role as key elements in the interpretation and representation of the real systems. We used a Quasi-2D flow-cell model that solves 1D equations, constructed in a conceptual and interpretive way, as an alternative to the use of 2D models, showing the possibility of maintaining the same degree of representativeness. The Quasi-2D model was subjected to a test proposed by the British Environmental Agency. The results have demonstrated the importance of the modeller, emphasizing that the knowledge of the physical reality, of the hypotheses and simplifications adopted in the model construction, guarantees an optimized simulation and the quality of the results.

Matheus Martins de Sousa, Antonio Krishnamurti Beleño de Oliveira, Bianca Maria Gomes da Silva, Marcelo Gomes Miguez

Numerical and CFD-Based Modelling of Concentrated Domestic Slurry in Turbulent Flow Through Circular Pipes

The concentration of domestic slurry has two advantages, it promotes resource recovery (nutrients and biomass) and saves water. But the design of a relevant sewerage requires a clear understanding of the frictional losses incurred during the transport of the slurry. This abstracts describes numerical & CFD-based methods to estimate losses while the concentrated slurry flows through circular pipes in a fully-turbulent flow. To model turbulent flows through circular pipes, one can rely on either the Newtonian Moody Charts appropriate for engineering applications or a computational fluid dynamics (CFD)-based analysis, made possible through the Newtonian universal law of the wall. However, our studies reveal that concentrated domestic slurry behaves like a non-Newtonian fluid, of the Herschel-Bulkley type. Therefore, the analysis of such a slurry would require modifications to both, existing engineering models and CFD methods. This abstract summarises a modified law of the wall suitable for Herschel-Bulkley fluids, which has been validated against experiments on concentrated domestic slurry. It further details possible non-Newtonian numerical engineering models that could be modified to assess frictional losses incurred by Herschel-Bulkley fluids. The latter will be a quicker and perhaps reliable alternative to computationally expensive CFD-analyses.

Dhruv Mehta, Adithya Krishnan Thota Radhakrishnan, Jules van Lier, Francois Clemens

A Framework to Assess Urban Floods Resilience

Urban flooding is still often treated as a straight consequence of excess rainfall, without considering the watershed as an interdependent system connected with the development of its territory. The traditional approach implies continuous corrective interventions, usually of local character and resulting from post-events responses. This process requires increasingly large investments to implement structures capable to accommodate the runoff generated by urbanization. These efforts have not prevented floods from continuing to cause major damage worldwide, indicating the need for a change in storm water management strategy, shifting from a simple cost-benefit analysis to a risk management approach, with residual risk internalization, regarding inherent uncertainties, such as climate change and fast and uncontrolled urban growth. This paper proposes a multi-criteria index, the Urban Flood Resilience index-UFRI, to quantitatively measure resilience to floods, supported by a hydrodynamic mathematical model and socio-economic indicators, resulting in spatialized maps. A case study for an urban watershed in Rio de Janeiro is used to demonstrate UFRI potential.

Osvaldo Moura Rezende, Anna Beatriz Ribeiro da Cruz de Franco, Antonio Krishnamurti Beleño de Oliveira, Ana Caroline Pitzer Jacob, Marcelo Gomes Miguez

Impact of Urbanization (Trends) on Hydrological Behaviour of Belo Horizonte Watersheds (Brazil)

The paper presents an analysis of runoff behaviour of four, small urban catchments between the city of Belo Horizonte and Contagem in Brazil, linked to their land-use. Two year of on- line measurements of hydrological and basic water quality data, combined with spatial analysis, made it possible to compare urban catchment with different land use and urbanization and support the generally admitted hypothesis that more dense urbanization generate faster and bigger discharges, accompanied by stronger solid fluxes. These findings contribute to better understanding of the urbanization trends of Pampulha watershed and to predict measures of mitigation if actual trends go on.

Martin Seidl, Luiz Palmier, Guido Petrucci, Nilo Nascimento

Modelling Runoff in Watershed Without Calibration Using PCSWMM

Urbanization process changes the runoff generation, essential factor for drainage systems design. Unfortunately, it is very common in Brazil and in underdeveloped countries the lack of rainfall and field data, being frequently adopted the rational method for runoff estimation. To improve runoff estimation, it is growing the use of hydrodynamics models performed with computer programs, such as PCSWMM™ (SWMM with GIS integrated), but, most of the times model parameter values have to be assumed based on default values or developers´ recommendations. In this study, PCSWMM was used for calculation of drainage system of Riacho Fundo’s urban area in Federal District in Brazil, in preparation for future analysis of LID implementation. The main objective is to analyze the PCSWMM use in a watershed without data for calibration using the SCS method, implementing PCSWMM recommendations and comparing them with the rational method in terms of peak flow results. The results showed that adopting PCSWMM recommendation only for the Imperv (%) parameter for subcatchments characteristics is the simulated scenario which is closest to rational method, while other modifications from the default values alter substantially the peak flow value.

Daniela Junqueira Carvalho, Maria Elisa Leite Costa, Jeferson da Costa, Sérgio Koide

Modelling Urban Drainage in Taquari – Federal District in Brazil

Taquari is a recent neighbourhood in Brasília, Federal District in Brazil, that started be occupied in 2002, with prevision more three phases to total occupation, however many impacts can be caused in water body receptor because the changes in land use. Therefore, this study investigated these variations in hydrology parameters, such as peak flow, with the objective of analysing in other to avoid possibilities impacts in Paranoá Lake, the new reservoir to water supply in the city. It was been used the PCSWMM software to analyse the differences before the urban system network implementation and after it. The results showed that the peak flow increased more than 300% mainly because all the discharged were concentred in two principal outfalls while, in the natural scenario were more distributed with more than 40 outfalls. It was possible to conclude that the new projects have to be design to natural scenario about hydrologic parameter because of several impacts in runoff volume, water quality and erosion process caused to hydric resources. This objective can be achieve though using LIDs, storing the excess runoff in the lot itself.

Tamara J. Brandão, Maria Elisa Leite Costa, Conceição de Maria Albuquerque

Tools, Techniques and Analysis in Urban Drainage Modelling including Real-Time Control

Frontmatter

Uncertainty in Environmental Water Quality Modelling: Where Do We Stand?

The physical and biochemical processes that underpin the generation and transport of water quality constituents are extremely complex, as are the social and institutional processes that determine how human activities impact the landscape. Any models attempting to represent these processes will therefore be fraught with huge overall uncertainty. It is incumbent on developers and users of water quality models to manage the sources of uncertainties and reduce the critical ones that affect the clarification of decisions. This paper documents ten sources of uncertainties and suggests nine ways in which uncertainty in a model might be handled. Model conceptualisation is a major source of uncertainty that is all too often not reported nor justified. Commonly used process-based models are often non-identifiable, thus issues concerning the selection of scales and detail of model representation need more rigorous treatment. While parameter fixing is often undertaken to address over-parameterisation, seldom do we see the increasing use of sensitivity and uncertainty analyses leading to model structure improvements. Formal methods of uncertainty analysis are hindered by the many required assumptions. One way around this is to utilise exploratory modelling to identify conditions and assumptions under which certain objectives are met and not met. Methods of robust decision and risk analysis also have much to offer in this respect. Another known source of uncertainty is errors in the data. The paper advocates more attention to understanding one’s data and the signals therein before embarking on any modelling. It also proposes complementary uses of empirical modelling when warranted by the problem context.

Anthony Jakeman, Barry Croke, Baihua Fu

Integrated 1D/2D Urban Inundation Modelling with Refined Grid and OpenMP Parallelization

Urban area consists of artificial structures such as buildings, roads, walls, parking lots etc. Therefore, the generation of fine meshes is a crucial component in depicting the complex urban features. However it accompanies huge amount of computational load with impractical calculation time. In this study, computational load reduction methods are tested using integrated 1D/2D urban inundation model based on refined grid with OpenMP parallelization technique. Refined grid (10 m with 5 m resolution) was able to reduce surface grid 2.47 times compared with regular grid (10 m resolution) and OpenMP parallelization shows 3.67 times running time reduction compared with serial code.

Seungsoo Lee

Multiple Regression Analysis as a Comprehensive Tool to Model Flood Hazard in Sewersheds

Flood modelling in urban areas is usually undertaken using stormwater tools, which are complex and time-consuming in terms of parametrization. To replace them, this research developed a methodology for predicting flooding probability in urban watersheds (sewersheds) through the modelling of peak flow rates from a set of watershed and sewer network-related factors relevant for the occurrence of floods. This was addressed through the stepped integration of Multiple Linear Regression (MLR), Multiple Nonlinear Regression (MNR) and Multiple Binary Logistic Regression (MBLR). A case study of a sewershed in Espoo (Finland) was used to validate the proposed approach and test it for future estimates, enabling the prediction of flooding probabilities under different Climate Change scenarios.

Daniel Jato-Espino, Nora Sillanpää, Ignacio Andrés-Doménech, Jorge Rodriguez-Hernandez

Generation of Stormwater Drainage Networks Using Spatial Data

In this paper a tool to automatically design drainage systems for urban districts is provided. Since pipe networks typically follow public streets, the drainage network is placed below the existing streets. The presented approach supplies a complete workflow in R, including an interface to hydraulic solvers implemented in the simulation software Stormwater Management Model. Algorithms to compute (1) subcatchments from land use data and (2) stormwater drainage networks from street polylines and topography are implemented. A test case, focussing on the stormwater drainage network on district scale, is setup. The stormwater network generator performs well for the small test case, however, some improvements on deriving the percentage of impervious surface cover have to be implemented. Further work includes the application to a more complex urban area, with pumps, combined sewer systems and multiple outfalls.

Anneke Döring, Insa Neuweiler

A New Saint-Venant Solver for SWMM

The next generation of the public domain Storm Water Management Model (SWMM) code needs to be able to effectively use parallelization of 1000+ threads for high-resolution simulation of large urban drainage systems. We propose a new explicit solution technique using a “no-neighbour” finite-volume algorithm. A no-neighbour algorithm is strictly limited in the design of its time/space discretization stencil to limit the communication bandwidth issues that typically cause codes to lose efficiency when applied over large numbers of parallel threads. Returning SWMM to an explicit solver creates a number of challenges for implementing the solution technique, but also raises some new possibilities for how the model can be used. In this work, we briefly describe the proposed algorithm and examine its performance in simulating a steep urban stream.

Ben R. Hodges, Frank Liu, A. Charles Rowney

Benefits of Real Time Control for Catchment Scale Stormwater Harvesting in Cape Town, South Africa

South Africa is a water stressed country with average annual rainfall of about 450 mm (well below 860 mm world average) and low stream flow. In Cape Town, limits of conventional water resources i.e. from reservoirs, have effectively been reached and in 2018, the city faced the prospect of taps running dry because of the prolonged exceptional drought that commenced in 2015. With no additional major dam sites available near Cape Town, the city is exploring alternative sources e.g. groundwater, wastewater treatment and reuse, and desalination of seawater. This study assessed the potential of harvesting stormwater from the existing, largely dry, ponds situated in the 100 km2 Zeekoe catchment. Storage is critical as Cape Town has a Mediterranean-type climate with short, wet winters and long dry summers. Since the potential storage capacity of the existing ponds is somewhat limited and their physical increase not practical due to land limitations in urban areas, an investigation was carried out into storage enhancement using Real-Time-Control (RTC) techniques that would safeguard the original purpose of the ponds which was largely flood-control. The envisaged RTC would dynamically manage pond outlets based on water levels and the expected inflow volume from rainfall so that ponds are pre-emptively drained just sufficiently to maintain their flood-control function before a storm event and end up full afterwards. An assessment was undertaken to compare demand met with and without RTC. It was determined that application of RTC on ponds and vleis would increase their effective yield by 113–290%.

John Okedi, Neil Philip Armitage

Emulation of a Detailed Urban Drainage Simulator to Be Applied for Short-Term Predictions

The challenge of this study is to investigate on applicability of a data-driven Gaussian Process Emulator (GPE) technique to develop a surrogate model for a computationally expensive and detailed urban drainage simulator. The novelty is the consideration of (short) time series for the simulation inputs and outputs. Such simulation setup is interesting in applications such as Model Predictive Control (MPC) in which numerous, fast and frequent simulation results are required. Here, an emulator is developed to predict a storage tank’s volume in a small case study in Luxembourg. Three main inputs are considered as the GPE’s parameters: initial volume in the tank, the level in which the outlet pump of the tank must start to work, and the time series of expected rainfall in the upcoming 2 h. The output of interest is the total volume of the storage tank for the next 24 h. A dataset of 2000 input-output scenarios were produced using different possible combinations of the inputs and running the detailed simulator (InfoWorks® ICM). 80% of the dataset were applied to train the emulator and 20% to validate the results. Distributions of Nash-Sutcliffe efficiency and Volumetric Efficiency are presented as indicators for quantification of the emulation error. Based on the preliminary results, it can be concluded that the introduced technique is able to reduce the simulations runtime significantly while imposing some inevitable accuracy cost. More investigation is required to validate the more generic applicability of this technique for multiple outputs and interactions between different urban drainage components.

Mahmood Mahmoodian, J. A. Torres-Matallana, Ulrich Leopold, Georges Schutz, Francois Clemens

Automated Approach for Rainfall-Runoff Model Generation

Manually constructing hydrological model descriptions for urban areas tends to be laborious due to the detailed mosaic land cover and the required high-resolution model setup. Here, the performance of a novel automated subcatchment generator with a detailed DEM-based surface flow routing is assessed against observations and manually constructed models. In general, the auto-generated models perform well against observations and comparably to manually constructed models regardless of the detail of land cover information input. The introduced inter-subcatchment connections may require previously acquired model parameters to be re-calibrated. This is due to the calibrated parameters in manually constructed models, even with high-resolution landuse, partly compensating for missing flow routes due to the larger scale used in subcatchment description.

Tero J. Niemi, Gerald Krebs, Teemu Kokkonen

Real-Time Water Level Prediction Based on Artificial Neural Networks

Urban flooding is often characterised by short lead times. In combination with the uncertainty in precipitation forecasting, the real-time forecasting of urban flooding is still challenging. Fast physically based models are still too slow for the usage in real-time forecasting. Data driven models are suitable to face this problem. The present study deals with testing an artificial neural network based model for the prediction of water levels with two dimensional spatial distributions at the catchment surface. The model was tested for synthetic rain events in a prior study. In the present study the model is successfully tested for spatially uniform distributed natural rain events.

Berkhahn Simon, Neuweiler Insa, Fuchs Lothar

Selection of Calibration Events for Modelling Green Urban Drainage

Urban drainage models are often calibrated using a limited number of rainfall-runoff events, which may be selected in different ways from a longer observation series. This paper compares 13 different single- and two-stage strategies for selecting events used to calibrate a SWMM model of a predominantly green urban area. Most led to successful calibration, but performance varied for various validation events. Most selection strategies were insensitive to the choice of Nash-Sutcliffe Model Efficiency or Root Mean Squared Error as the objective function. Calibrating impervious and green area parameters separately in two-stage strategies can help improve prediction of low-flow events in validation.

Ico Broekhuizen, Günther Leonhardt, Jiri Marsalek, Maria Viklander

Conceptual Framework for Integrating Real-Time Control and Source Control Solutions for CSO Frequency Control

Combined sewer overflows (CSO) are associated with water quality degradation and health risks, but limited knowledge exists on the optimal solutions applicable to reach maximal overflow frequency targets as specified by some regulatory agencies. This study assesses the potential benefit of integrating source control with real-time control solutions based on hydrological/hydraulic modelling of urban catchments of the Province of Québec (Canada). Firstly, modelling procedures for volume sizing of CSO solutions are improved by determining the proper rainfall input among the three most common types of rainfall data (continuous simulation, historical rainstorms and IDF-derived storms) excluding winter months in the analysis to be aligned with Quebec legislation. Secondly, a methodological framework is developed to integrate source control and optimal real-time control solutions based on a cost-efficiency performance objective. Thirdly, two optimization software are coupled to iteratively solve for the best flow management strategy according to physical and operating constraints; iPOP for source control design and CSoft for dynamic control. Preliminary results showed that simulation of continuous rainfall series results in the most accurate volume estimations for sizing CSO solutions and IDF-derived design storms could serve as input data for initial optimization runs. Based on the determined appropriate rainfall data, source control optimization showed considerable solutions implementation cost reduction for acceptable runoff reduction. Future work includes refining the integrated solution framework and comparative analysis of modelling results under optimal implementation of source control and real-time control solutions.

Marie-Ève Jean, Sophie Duchesne, Geneviève Pelletier, Martin Pleau

Active Control of Combined Sewer Systems Based on Flow and Water Quality

Discharges from urban wastewater systems are the main source of pollution for inland and coastal waters, and intermittent unsatisfactory discharges from combined sewer systems have been recognized as a major environmental concern. The aim of the research was to investigate active system control of an interceptor sewer system. The dynamic multiobjective optimization approach developed considered the unsteady flow and pollution load in the sewers and wastewater treatment costs. Contrary to previous approaches in the literature, the combined effect of the various primary contaminants was addressed by means of the effluent quality index.

Tiku T. Tanyimboh

Experimental Design to Support Water Quality Modelling of Sewer Systems

The paper proposes a model-based experimental design to calibrate a sewer water quality model for the Clos de Hilde catchment in Bordeaux, France. In order to carry out an experimental design, a preliminary calibrated model is developed and the influential parameters are identified. Subsequently the model is used to select the most information-rich experiment for calibration of the final model. This is done by simulating proposed experiments and evaluating the Fisher Information Matrix that quantifies the experiment’s information content. The selected experiment will be carried out during the upcoming measurement campaign in summer 2018.

Julia M. Ledergerber, Thibaud Maruéjouls, Peter A. Vanrolleghem

A Graph-Theory Based Algorithm to Generate Decentralized Urban Drainage Layouts

Recently, the implementation of centralized urban drainage networks, has increasingly been questioned. The main reasons are the lack of capital especially in developing countries, environmental-ecological concerns, the risk of failure, rapid change and high uncertainty in a developing country context. Latest investigations suggest a transition from centralized urban water management to decentralized or hybrid schemes. Therefore, there is a need for methodologies to evaluate the difference in performance of all feasible systems, from purely centralized to purely decentralized. For this purpose, the current study introduces the hanging gardens algorithm based on graph theory to generate all possible layouts for optimization purposes. The focus of this study is to find the optimum configuration of the pipe networks (grey infrastructures) considering different number and location of outlets. The algorithm starts with generating a centralized layout using an arbitrarily selected outlet, than another randomly nominated outlet among all candidates is added to the current layout. In the next step, the only path between new and old outlet is systematically found. Employing a randomly generated variable a pipe in the path is chosen to cut and decentralize the layout. A real case study, the stormwater collection network of a part of Ahvaz city in Iran is designed using the proposed approach. The number and location of the outlets, the layout configuration of each part and the size of the pipes are used as optimization variables. A single-objective optimization for the cost is done and obtained results are discussed.

Amin E. Bakhshipour, Milad Bakhshizadeh, Ulrich Dittmer, Wolfgang Nowak, Ali Haghighi

Electro-Magnetic Velocity Meters: Assessment of the (Missing) Technical Parameters

Flow measurements in Urban Drainage Systems are essential for the pollution control. Since the accuracy of the Acoustic Doppler Velocimeters is impeded by several factors, this research is focused on the alternative or a supplemental Electro-Magnetic Velocity (EMV) meters. EMV meters are more robust and reliable and can provide accurate measurements of low flows or even under a porous sediment cover. However, the downside of their usage is the small control volume (CV) where the flow velocities are integrated in a non-linear manner to obtain a single one-dimensional velocity measurement. To provide accurate mean flow velocity it is necessary to determine the size of the CV and to understand the non-linear integration principle within the CV. These valuable data are typically not provided by the manufacturer. In this paper, an experimental methodology is proposed for defining the size of the CV and the one-dimensional (1D) weighting function, used to describe the sensor’s integration principle. In the experiments, bed-mounted flat DC2 EMV probe was used. The size of the CV and 1D weighting function were determined based on the results of the EMV operation under sand cover of varying depth. It was shown that the reach of the CV for the used device is 6 cm from the electrodes of the sensor.

Damjan Ivetic, Dusan Prodanovic, Luka Stojadinovic

Urban Flooding and Adaptation to Climate Change in Sukhumvit Area, Bangkok, Thailand

Flooding in urban areas is an inevitable problem for many cities in the world. In Thailand, Bangkok has serious problems related to urban flooding. The situation was highlighted in May 2017, when residences experienced ankle to knee-deep flood water on the streets. Daily activities in parts of the city were nearly paralyzed and heavy traffic jams occurred due to stagnant water on the streets. The study has depended on a combined approach of physically based modeling and GIS. The urban drainage is structured by iRIC software for the basis of two networks, one simulating the two-dimension free-surface flow over the streets and one for the pumping/canal/pipe system. The interaction between street and pumping/canal/pipe system is modeled in a simple way. In 2017, ADAP-T project carried out a pilot study about urban flooding and adaptation modeling for Sukhumvit area, Bangkok Metropolitan. This study is performed as an extension and improvement of pilot study in terms of analyzing drainage system on effect of flood hazard, vulnerability, risk map and adaptation under the issue of climate change in Sukhumvit area, Bangkok, together with suggestion of alleviation scenarios to relieve flood problems.

Sanit Wongsa, Varameth Vichiensan, Napaporn Piamsa-nga, Shinichiro Nakamura

Hydrological Modelling and Detention Ponds Evaluation at Paranoa Lake - Brazil

Paranoá Lake is an urban lake and since last year Brasilia started to use its waters for human consumption. Until the 1990’s algae and cyanobacteria blooms occurred and improvements on wastewater treatment plants brought the water quality to very good conditions in the 2000’s. Recently water quality is starting to deteriorate mainly due to diffuse pollution. Thus, the evaluation of urban drainage waters entering the lake and the proposition of technological alternatives to minimize impacts are important for the analysis of diffuse urban pollution flowing into the lake. Quantitative and qualitative behaviour of the urban drainage waters were analysed by means of monitoring the precipitation amount and runoff flow and quality. Mathematical modelling using the SWMM and PCSWMM programs was carried out, and good results were obtained for flow modelling. However, in water quality simulations, poorer response was obtained. It was also evaluated the implementation of 13 alternatives of detention ponds to study the effects of their location on the removal of pollutants, as well as influences on the network flow support. It was observed that ponds allocated in the downstream part of the network are more efficient, but requireconstruction in environmentally and urbanistically problematic areas and high commercial value. Alternatives with smaller volumes in areas areas near the center ofthe basin can meet flood-damping needs of the presently constructed drainage network.

Fernanda Pereira de Souza, Maria Elisa Leite Costa, Sergio Koide

Using Precipitation and Combined Sewer Overflow Data for Predicting Hygienic Contaminations in Bathing Waters – A Data Analysis

Rivers and lakes in urbanised areas are increasingly appreciated for their high ecological and recreational value. The demand for bathing sites is growing. However, in many German rivers as the Ruhr River, bathing has been prohibited for decades. At Lake Baldeney, an impounded lake of the Ruhr River, located in a densely populated area in North-Rhine-Westphalia, the first bathing place was opened in 2017. Receiving water from combined sewer overflows during heavy rain events, the hygienic quality of the water body could be affected. Due to that an extensive monitoring programme of quality parameters along the Ruhr River has been carried out during the last years and an early warning system has been established to assure a safe bathing environment at all times in a previous research project. In this article highly resolved precipitation data from six rain gauges, overflow data from four combined sewer overflow (CSO) tanks and one storage sewer as well as flow data from the River Ruhr was analysed together with daily measurements of Escherichia coli (E. coli) and intestinal enterococci (Int. E.) to assess the prediction capacity of hygienic contaminations at the bathing site during three swimming seasons. Data evaluation showed a good predictive capability of precipitation data. Overflow data showed less predictive performance when using overflow information from one tank only, indicating that single overflow events not necessarily lead to hygienic contaminations above critical thresholds.

Anna Bachmann-Machnik, Ulrich Dittmer, Annika Schönfeld

FloodCitiSense: Early Warning Service for Urban Pluvial Floods for and by Citizens and City Authorities

FloodCitiSense aims at developing an urban pluvial flood early warning service for, but also by citizens and city authorities, building upon the state-of-the-art knowledge, methodologies and smart technologies provided by research units and private companies. FloodCitiSense targets the co-creation of this innovative public service in an urban living lab context with all local actors. This service will reduce the vulnerability of urban areas and citizens to pluvial floods, which occur when heavy rainfall exceeds the capacity of the urban drainage system. Due to their fast onset and localized nature, they cause significant damage to the urban environment and are challenging to manage. Monitoring and management of peak events in cities is typically in the hands of local governmental agencies. Citizens most often just play a passive role as people negatively affected by the flooding, despite the fact that they are often the ‘first responders’ and should therefore be actively involved. The FloodCitiSense project aims at integrating crowdsourced hydrological data, collaboratively monitored by local stakeholders, including citizens, making use of low-cost sensors and web-based technologies, into a flood early warning system. This will enable ‘citizens and cities’ to be better prepared for and better respond to urban pluvial floods. Three European pilot cities are targeted: Brussels – Belgium, Rotterdam – The Netherlands and Birmingham – UK.

Boud Verbeiren, Solomon Dagnachew Seyoum, Ihab Lubbad, Tian Xin, Marie-Claire ten Veldhuis, Christian Onof, Li-Pen Wang, Susana Ochoa-Rodriguez, Carina Veeckman, Michelle Boonen, Linda See, Dominique Nalpas, Barry O’Brien, Andy Johnston, Patrick Willems

Mitigation of Urban Surface Runoff Through LID Solutions: Case Study in Mediterranean Area

Here we investigate the influence of Low Impact Development (LID) practices implementation at urban catchment scale, by applying SWMM model to a densely urbanized area of the city of Cosenza, using monthly storms events. Among the source-control measures, Green Roofs and Permeable Pavements were chosen, being particularly suitable for highly urbanised areas already equipped with an underground drainage system. The main objective of this study is to assess how the implementation of LID techniques in urban areas can be an effective solution to improve stormwater management and restore the natural flow regime. With this aim, different conversion scenarios have been simulated and compared to the existing condition of the catchment, before LIDs implementation at catchment scale. Results reveal that combined LID techniques perform better than single LID practices in terms of both runoff reduction and increase in total infiltration.

Francesca Principato, Aldo Pedro Ferrante, Ferdinando Frega, Manuela Bartolo, Patrizia Piro

Urban Flood Area Delimitation Using Reverse Water Local Flow Paths

South America is vulnerable to flood disasters, which must be prevented and managed, especially in the urban area close to the rivers. Different terrain descriptors (e.g. hydrographic network, altimetry) are taken into consideration to identify area with potential risk of flooding. INPE has developed tools to process and manage hydrological information. This paper aims to improve such tools proposing a method to study urban flood area delimitation starting from a raster elevation representation of the urban area with high resolution and water level information. In particular, the proposed method considers the water behaviour assuming that water flood happens in the part of the river having altimetry higher than the surrounding surface. The use of such water behaviour information results in the improvement of the accuracy of the study of urban area with risk of flooding.

Sergio Rosim, João Ricardo de Freitas Oliveira, Monica De Martino, Alfonso Quarati, Alexandre Copertino Jardim

Numerical Unsaturated Flow Model of Railway Drainage Systems

Substandard drainage assets are considered to be a major cause of flooding, earthwork failures, and deficient track geometry. Considering the deterioration of track materials due to cyclic loads and tamping forces, the impact of more frequent extreme rainfall events is likely to lead towards higher rates of hydraulic overloads in the drainage system, earthwork failures, and service disruptions. Therefore, the development of a numerical model could be able to describe the ageing track bed materials and provide an alternative tool for the simulation of the flow through the porous media used in the construction of railway tracks. In this paper the model HYDRUS is tested to simulate the drainage of trackbed materials under laboratory controlled conditions prior its application on actual railway drainage case studies.

Legaire Pinedo Ortiz de Mendivil, Christian Berretta, Andrew Sleigh

Characterization of the Dynamics of Microbiological and Chemical Contaminants in an Urban Catchment in South of France: From Field Data Collection to Modelling

Densely urbanized areas generate a wide range of contaminants exerting pressures on the quality of downstream rivers. As urban areas are in permanent extension, assessing the potential evolution of water quality and the effects of mitigation measures is a real challenge. Modelling tools could be helpful in decision making but require sound field data for calibration steps. The present study focuses on the urban river Lez that crosses the area of Montpellier city. Due to the Mediterranean climate, extreme precipitations intensify the transfer of contaminants by generating land runoff and significant sewer overflow. The spatiotemporal variability in microbiological and chemical contamination of the Lez river and its tributaries is characterized through field campaigns. Three low flow campaigns and a flood event are presented here, with a focus on the most urbanized sub-catchment: Verdanson. Hydrological conditions are shown to have a strong impact on the water quality in terms of concentrations of fecal indicator bacteria, organotins, trace metals and polycyclic aromatic hydrocarbons. As a first step towards the modelling of the water quality during a flood event, a sensitivity analysis was performed to test how land cover could be properly be taken into account in the modelling process. The analysis reveals that discretizing the catchment into land cover-homogeneous subcatchments enhances the suitability of water quality model outputs, keeping good outputs of the hydrological model. Consequently, a rigorous description of land cover is required to properly assess the impacts of territorial dynamics on water quality.

Marlène Rio, Marie-George Tournoud, Christian Salles, Chrystelle Bancon-Montigny, Patrick Monfort, Claire Rodier, Mylène Toubiana, Pierre Marchand

A Water Quality-Quantity Model for Avcilar Campus of Istanbul University Incorporating LID Implementation

Rainwater management practices are implementations for improvement of storm water quality and quantity. Implementation of these practices in urban areas is vital because urbanization results in low percentage of permeable soil and cuts off the ground water recharge. Over impermeable surfaces, rain quickly turns into surface runoff and causes flooding. With urbanization, contaminants, which accumulate over the surface, increase and therefore, the contamination of the surface runoff also increases. A number of precautions and control mechanisms are needed to remove these contaminants from the surface runoff which are called as Low Impact Development (LID) Best Management Practices (BMP). LID-BMPs serve for protection of the hydrologic cycle, ecological balance, reduction of the flood risk and improvement of surface water quality. In this study, first, a hydrological model for Avcılar Campus of Istanbul University is developed by using Environmental Protection Agency Storm Water Management Model (EPA SWMM). Then, the water quality model is integrated into the hydrological model by defining various land use types such as low-density residential, high-density residential, highway commercial and highway, and pollution parameters such as total suspended solid (TSS) and lead (Pb). Finally, several LID implementations such as green roof, permeable pavement, bioretention, rain garden, and rain barrel, are defined into the model according to the settlement type on the campus. The impact of the LID implementations on the water quality and quantity are observed. Model results show that the LID implementations greatly reduce the peak discharge. Moreover, LID implementations also decrease pollutant concentrations in surface runoff.

Sezar Gülbaz, Abdulsamed Yıldırım, Cevza Melek Kazezyılmaz-Alhan

Combined Sewer Flow Prediction Using Hybrid Wavelet Artificial Neural Network Model

This study presents a hybrid model for the prediction of dry and wet-weather flows in a combined sewer system. For this aim, a model based on wavelet transformation and artificial neural network (WANN) is developed. A high-resolution data set of rainfall and combined sewer flow from a catchment in Germany is used in the hybrid model. To simulate the combined sewer flow, the dry-weather flow is firstly modelled employing Artificial Neural Network (ANN). Subsequently, another ANN is applied and fed with rainfall time series, dry-weather flow simulated in the previous step and lagged combined sewer flow time series as the main input variables to simulate the combined sewer flow. In modeling both the dry-weather flow and the combined sewer flow, the wavelet transformation is firstly applied to extract the temporal and the spectral features of the measured sewer flow time series before using them in the ANN. To improve the WANN hybrid model result, different mother wavelet functions and decomposition levels, various lagged values for input variables, several training functions and network structures are implemented in the model and their influence on the hybrid model is investigated. According to this study, the proposed hybrid model can identify the complicated and dynamic nature of the combined sewer systems and thus provide accurate results.

Zolal Ayazpour, Amin E. Bakhshipour, Ulrich Dittmer

Modelling Interactions and Integrated Systems

Frontmatter

Forecasting Pollution Transport in Drainage Water

The EVUS project ( www.pluvialfloods.uni-hannover.de ) has developed a concept for a real time forecasting system for urban flood damages. During heavy rainfall events the capacity of urban drainage systems can be exceeded, resulting in complex flow interactions between surface and pipe system via manholes and street inlets. The flow patterns of accidently spilled hazardous substances can be quite complex. In this study, we implemented a particle based transport model for fast prediction of travel paths of contaminants after a spill during a flash flood. The model calculates mixing and dispersion in the pipe system and on the surface by using a random-walk approach. It is applied to an urban catchment of 5 km2. Influence of pipe to surface coupling due to the additional transport paths is demonstrated. The model is based on pre-calculated flow fields and can forecast potential contaminated areas within less than one minute.

Robert Sämann, Insa Neuweiler, Thomas Graf

Impact Evaluation of Wet-Weather Events on Influent Flow and Loadings of a Water Resource Recovery Facility

Since the introduction of environmental legislation and directives in Europe, the impact of combined sewer overflows (CSO) on receiving water bodies has become a priority concern in water and wastewater treatment industry. Time-consuming and expensive local sampling and monitoring campaigns have been carried out to estimate the characteristic flow and pollutant concentrations of CSO water. This study focused on estimating the frequency and duration of wet-weather events and their impacts on influent flow and wastewater characteristics of the largest Italian water resource recovery facility (WRRF) in Castiglione Torinese. Eight years (viz. 2009–2016) of routinely collected influent data in addition to the arithmetic mean daily precipitation rates (PI) of the plant catchment area, were elaborated. Relationships between PI and volumetric influent flow rate (Qin), chemical oxygen demand (COD), ammonium concentration (N-NH4) and total suspended solids (TSS) are investigated. Time series data mining (TSDM) method is implemented for segmentation of time series by use of sliding window algorithm to partition the available records associated with wet and dry weather events based on the daily variation of PI time series. Appling the methodology in conjunction with results obtained from data reduction techniques, a wet-weather definition is proposed for the plant. The results confirm that applied methodology on routinely collected plant data can be considered as a good substitute for time-consuming and expensive sampling campaigns and plant monitoring programs usually conducted for accurate emergency response and long-term preparedness for extreme climate conditions.

Sina Borzooei, Ramesh Teegavarapu, Soroush Abolfathi, Youri Amerlinck, Ingmar Nopens, Maria Chiara Zanetti

Wastewater System Ventilation – A Friend or Adversary?

Wastewater systems and their designs have been documented for thousands of years. However, little written evidence exists of the potential unpleasant odours that can be associated with drainage systems until the mid-nineteenth century. This paper presents a holistic overview of historic ventilation systems and wastewater network designs. Modelling the ventilation and potential fugitive emissions from urban drainage systems is a significant challenge. Yet using a revised approach, in association with calibrated and verified case study data, reliable holistic modelling may be achieved. Modern fugitive emissions are discussed and opportunities are further examined with the ventilation and gas in headspace model. This key predictive information may potentially extend asset life and therefore enable cost benefit analysis if the correct corrosion abatements solutions are applied.

Steve Adkins, Slobodan Djordjević, Dragan A. Savić

Influence of Drainage Network and Compensatory Techniques on Urban Flooding Susceptibility

The occurrence of urban flooding due to the accelerated urbanization process and resulting drainage problems has become a worldwide issue and has been the subject of several studies in recent decades. In this sense, the goal of this study is to assess the influence of the drainage network associated with compensatory techniques on susceptibility of the urban flooding occurrence in Campeche District (Florianópolis – Brazil). To achieve this goal, the following methodological steps were used: (1) data collection and preparation; (2) application of the AHP method and consistency analysis; and (3) overlapping influence parameters considering two scenarios. The results show that the introduction of a drainage system decrease the degree of susceptibility of the urban flooding occurrence in approximately 27% of the areas of the Campeche District. It should be noted that, although costly, interventions for implementation of a drainage infrastructure associated with compensatory techniques make is extremely important for sustainable development.

Jakcemara Caprario, Aline Schuck Rech, Fabiane Andressa Tasca, Alexandra Rodrigues Finotti

Sensitivity Analysis of an Integrated Urban Flood Model

In this paper, the model parameter sensitivity of an integrated urban flood model, including groundwater system, overland flow, sewer network, and river network, is investigated. The sensitivity analysis quantifies how influential the individual and correlated model parameters are to the simulated flood depth and area for an urban catchment in Aalborg, Denmark. The key parametric contributors to output sensitivity are analyzed by: (i) identify the most sensitive model parameters using a Morris screening; (ii) using the generalized Sobol’ method to investigate the sensitivity of the individual input parameters and the interaction between each parameter. The results indicate that the groundwater system, overland flow, and river network contribute most to the flood depth and as such, they need to be considered in urban flood modelling.

Rasmus Nielsen, Søren Thorndahl

Quantifying Benefits of Permeable Pavement on Surface Runoff, An Agent-Based-Model with NetLogo

Permeable pavements benefits are large and well-studied all over the world by the scientific community however they are still not yet frequently used in urban projects. In order to explore permeable pavement benefits an Agent-Based-Model (ABM) was built. The model addresses the impact of the soil occupation of an urban catchment on its hydrological response. Specifically, it aims at quantifying the impacts of permeable pavement on runoff. ABM allows for exploring global phenomena by the integration of local processes. In this model, a simple micro-scale rule (move to the adjacent cell with the lowest piezometric level) performed by all the agents Drops gives a very relevant flow simulation at catchment-scale. This conceptual model is GIS-based and does not require important hydraulic data. Results show that turning 2.5% of the impervious cover into permeable pavements can reduce the runoff by 8.3%. Model exploration highlights where and in which proportion permeable pavements should be used to be the most efficient.

O. Cortier, M. Boutouil, O. Maquaire

Coupling Urban Water and Energy Budgets with TEB-Hydro: Case Study on the French Catchment Pin Sec

In view of climate change and demographic pressure in cities, Sustainable Urban Drainage Systems (SUDs) have become essential to urban planners. Understanding their influence on the urban microclimate (energy and water budgets) at city scale is essential for developing adaptation strategies to global change. The hydro-microclimate model TEB-Hydro enables treating the water and energy budgets with the same level of detail. Its hydrological component has been improved recently and the hydrological processes have been evaluated. However, it has not yet been investigated how those changes affect the energy component of the model. Therefore, the model is applied to a long-term instrumented urban catchment in Western France, allowing its evaluation on water and energy fluxes. The comparison of the simulated total sewer discharge to observations shows a correct KGE criterion of 0.79, with a tendency of overestimation of the model. The maximal daily observed latent heat fluxes, on the contrary, are mostly underestimated. However, taking into account a source area analysis of the observed turbulent heat fluxes achieves better results while comparing them to simulation.

Stavropulos-Laffaille Xenia, Chancibault Katia, Andrieu Hervé, Lemonsu Aude, Masson Valéry

Calculation of the Hydraulic Capacity of Grate Inlets with Supercritical Surface Flow and Unsurcharged Drainage Flow Conditions

According to an increasing number of heavy rainfall events, the managing of urban flooding requires new design approaches in urban drainage engineering. With bidirectional coupled numerical models the surface runoff, the underground sewer flow and the interaction processes between both systems can be calculated. Most of the numerical models use a weir equation to calculate the surface to sewer flow with unsurcharged flow conditions, but uncertainties still exist in the representation of the real flow conditions. Street inlets, existing in different types, are the connecting elements between the surface and the underground system. In the present study, an empirical formula was developed based on physical model test runs to estimate the hydraulic capacity of grate inlets with supercritical surface flow. The influencing hydraulic parameters are the water depth and flow velocity upstream of the grate and in addition different geometrical parameters are taken into account such as the grate dimensions or the orientation of the bars (transverse, longitudinal or diagonal).

Svenja Kemper, Andreas Schlenkhoff

An Alternative Model Calibration Strategy for Watersheds Lacking Proper Data Records: Case Study of Riohacha, Colombia

The city of Riohacha presents a disorganized development model that added to recurrent events of intense rains, cause increasingly flood disasters. Due to the complexity and the hydrographic density of the region and the need to propose systemic solutions to flood problems, it was used mathematical modelling tools. Within the modelling process, calibration and validation are two fundamental actions that must precede the use of the hydrodynamic model. However, most of the river basins around the world lack hydrometeorological information, indispensable for calibration process. The present work develops a new approach for the calibration process, based on interviews and retrieval of historical information by flood marks. This new approach enables calibration in a scenario where there is a lack of information for the calibration process. Thus, the result of this work can be used as a conceptual basis of support in the calibration process for future hydrodynamic models in places where there is little or no information to support the process.

Antonio Krishnamurti Beleño de Oliveira, Osvaldo Moura Rezende, Matheus Martins de Sousa, Marcelo Gomes Miguez

Model Based Assessment of Sanitation Systems for the Integrated Management of Industrial Discharges

This work presents a global model of sanitation system that integrates different simulation tools. The main objective of this work is to manage, in a controlled way, high salinity industrial discharges to ensure the stability of the sewer network and the municipally wastewater treatment plant.

Luis M. García, Jesús A. Pelegino, Luis Sancho, Alberto Ciriza, Mónica Gutiérrez, Tamara Fernández-Arévalo

Implementing Sustainable Sanitation in an Integrated Model - A Straightforward Approach for Long-Term Simulation

At present, increasingly requirements aiming resource efficiency and environmental sustainability demand more knowledge about the feasibility of implementation of such technologies in a large-scale as well as in the long-term. Even at modified sewage flows and compositions, water infrastructures must always remain reliable in order to guarantee a sustainable urban water management. Dimensioning methods and assessment variables must be adapted in order to achieve systems that are more flexible in the long-term. This paper aims to assess the actual impact of the implementation of sustainable sanitation systems in an existing sewage disposal system with means of a dynamic simulation. Various scenario simulations showed that the implementation of the module for BW/GW separation represents the investigated sustainable sanitation measures reliably with means of dynamic simulation. Moreover, the impact of the implementation of these measures and the consideration of population decline demand a more dynamical operational flexibility within the WWTP. To sum up, implementing this simplified approach for a stepwise integration of resource-oriented sanitation technologies allows a sewage system evaluation not only for dry weather conditions but also for stormwater conditions.

Claudia Campusano Garcia, Inka Kaufmann Alves

Cellular Automata Approach for 2D Pollution Transport Modelling in Urban Groundwater

Integrated modelling requires many simplifications in order to speed up long time calculations and simulations. Therefore, many non-traditional methods are being widely used. Cellular automata (CA) represents one of these methods. The paper presents the application of the CA approach in modelling of the contaminant transport in unsteady groundwater conditions. It compares the results obtained using the two CA models modified for groundwater problems. Results obtained in this paper show that CA approach can be successfully used for simulations of unsteady groundwater conditions, caused by surface-groundwater interaction, and pollution transport.

Miloš Milašinović, Anja Ranđelović, Nenad Jaćimović, Dušan Prodanović

Sewer-Groundwater Interaction in Urban Coastal Areas

Fecal Indicator Bacteria (FIB) are the primary tools recommended by the U.S. EPA to monitor sewage contamination in waterways. Their concentration along one of the most populated area in the U.S. can exceed the EPA guidelines for water quality after a minor rain event or even in dry weather conditions. Here, we present a study to investigate the role of groundwater infiltration into damaged sewer pipes on combined sewer overflow (CSOs) after a minor rain event or even in dry weather. Groundwater and sewer modelling were combined with a statistical model accounting for weighted risk factors, such as, e.g., pipe material and size, and type of soil, for a coastal city (Hoboken, NJ) located in one of the most populated areas of the U.S. A risk map of groundwater infiltration was then determined. Preliminary simulations of the groundwater accounting for the tide show that the large parts of the sewer network of the city may be submerged always by groundwater. Parts of the network present also high risk of failure, suggesting that they may be affected significantly by infiltration and may require, therefore, renovation or upgrading.

Ting Liu, Maryam Beheshti, Xin Su, Valentina Prigiobbe

Smart Rain Barrels: Advanced LID Management Through Measurement and Control

Rain barrels are micro-scale applications which are used as temporary storage and for rainwater harvesting. They can be easily implemented into existing stormwater infrastructure. Recent advances in the field of Internet of Things (IoT) have opened up new possibilities for real-time monitoring and control of such structures, that enable the reduction of urban flooding or combined sewer overflows. The special feature of our smart rain barrel is its integration into a pilot project for smart cities, where every water inflow and outflow of the university campus in Innsbruck (Austria) is measured. Weather forecasts and time-controlled filling levels of different Low Impact Developments (LID) structures and the connected sewer system are used for real-time control (RTC). In a first step, the smart rain barrels are implemented into a SWMM-model with the objective of reducing the peak runoff rate by using the filling level in the main conduit as the control variable for real-time control. Results show that depending on the installation site and the storage volume of the rain barrel, a flood volume reduction of 18–40% can be achieved although only a simplified automatic control system has been implemented.

Martin Oberascher, Jonatan Zischg, Stefania Anna Palermo, Carolina Kinzel, Wolfgang Rauch, Robert Sitzenfrei

Visual Risk Communication of Urban Flooding in 3D Environments Based on Terrestrial Laser Scanning

In this paper, attention is focused on the extension of the urban flood-mapping concept from an eminently cartographic context to a three-dimensional one, by applying techniques for the representations of urban flood inundation in a virtual environment for hazard communication purposes. In particular, visual risk communication of urban flooding in 3D environments, based on terrestrial laser scanning, has been analyzed here. Moreover, a web-based rendering of point clouds for the visualization of urban flooding has been explored in order to highlight its benefits in urban flood risk communication.

Rosa De Santis, Francesco Macchione, Pierfranco Costabile, Carmelina Costanzo

Water Quality Characterization of Irrigation and Storm Runoff for a Nursery

Commercial nurseries grow plants in containers on semi-permeable production areas. Fertilizer is added to the substrate or applied via irrigation to facilitate plant growth, the resulting runoff has increased levels of sediment, nitrogen and phosphorus compared to background. This runoff is often collected and recycled, but, if discharged, could negatively impact water bodies downstream. Several storm and irrigation runoff samples were collected from a mid-Atlantic nursery and analysed for pH, electrical conductivity (EC), total suspended solid (TSS), total nitrogen (TN), and total phosphorus (TP). Samples were collected downstream of 5.2 hectare production area, which consisted of 1.82 ha in gravel roads and 3.38 ha in 26 pads, draining to a central ditch. The nursery was modelled using the Storm Water Management Model (SWMM), an urban drainage model, since runoff hydrographs behave similar to urban areas (i.e., flashy). A preliminary hydrologic and water quality calibration was performed with the limited dataset to assess the potential of using SWMM to characterize runoff. During irrigation, there was a direct relationship between runoff and TSS peaks, i.e., TSS peaks follow peak runoff, with a defined lag. In contrast, there was an inverse relationship between runoff peaks and concentrations of TN and TP. During irrigation, simulated event mean concentrations (EMCs) of TP, TN and TSS were 0.42, 2.77 and 36.0 mg/L, respectively. SWMM was able to characterize the runoff well from the 5.2 ha area and can be potentially used to assess water quality treatment options if further calibrated data become available.

Mohammad Nayeb Yazdi, David J. Sample, Durelle Scott, James S. Owen

Sewer Flow Prediction at a Large Urban Scale: Influence of Radar Rainfall Spatial Resolution

There is a growing interest in using radar rainfall data to evaluate the performance of urban drainage systems in near real time. This paper describes a study based on a large (55 km2) urban catchment in northern Italy. Different spatial resolutions of radar data have been compared and used as input to a numerical hydrological-hydraulic model of the drainage system, constructed by means of Infoworks CS software. The results show that the spatial resolution of weather radar data plays a significant role when modelling the hydrological behaviour of the drainage system and using different resolutions may result in significant differences in peak flows and runoff volumes.

Sara Simona Cipolla, Giulia Paola Di Ventura, Marco Maglionico, Pier Paolo Alberoni, Attilio Castellarin

Uncertainty Propagation in Integrated Urban Water Quality Modelling

Sensitivity and uncertainty assessment of integrated urban drainage water quality models are crucial steps in the evaluation of the reliability of model results. Indeed, the assessment of the reliability of the results of complex water quality models is crucial in understanding their significance. In the case of integrated urban drainage water quality models, due to the fact that integrated approaches are basically a cascade of sub-models (simulating the sewer system, wastewater treatment plant and receiving water body), uncertainty produced in one sub-model propagates to the following ones in a manner dependent on the model structure, the estimation of parameters and the availability and uncertainty of measurements in the different parts of the system. Uncertainty basically propagates throughout a chain of models in which the simulation output from upstream models is transferred to the downstream ones as input. The paper presents the uncertainty assessment of an integrated urban drainage model developed in previous studies by means of the Generalized Likelihood Uncertainty Estimation (GLUE) methodology. A straightforward approach based on the analysis of the coefficient of variation (Rxy). Rxy is defined as the ratio between the standard deviation (α) and the average (μ) value of the model output of reference taken into account. The analysis has been applied to an experimental catchment in Bologna (Italy) which consists of a part of the Bologna sewer network and a reach of the Savena river. The results showed that the method can be a useful tool for uncertainty analysis and for guiding the operator in the choice of the modelling approach.

Giorgio Mannina

Transport and Sewer Processes including Micropollutants and Pathogens

Frontmatter

Percolation of Water from Surface Runoff – Case Studies

At present great emphasis is placed on draining rainwater from town and village lands through percolation facilities, which represent a sustainable method of handling precipitation water from surface runoff. Therefore, the work is focused on experimental insitu analysis for resolving the percolation of rainwater from surface runoff. The study focused on determining the filtration coefficient, for which existing percolation facilities were used, so-called percolation shafts in two study areas, on the basis of confrontation of theoretical and practical analyses. The use of percolation facilities is demonstrated in the work; this represents an effective method of draining precipitation water from surface runoff for a specific project design.

Martina Zeleňáková, Petr Hluštík, Gabriel Markovič, Gabriela Hudáková, Ladislav Tometz

Mathematical Modelling of In-Sewer Processes as a Tool for Sewer System Design

The objective of this paper is to evaluate the potential impact of in-sewer processes (COD components transformation and hydrogen sulphide production) on the design of sewer systems. The tool used for such analysis is a mathematical model derived from the WATS model (Wastewater Aerobic/anaerobic Transformation in Sewers) able to describe the processes occurring in the sewer system both under aerobic and anaerobic conditions. The model is applied to three catchments with, respectively, 10,000, 50,000 and 250,000 inhabitants connected to gravity sewer systems different in terms of type (separate or combined), slope, length, travel time, wastewater temperature. The simulation results enable to assess the effect of the in sewer transformations in terms of hydrogen sulphide formation and transformation of the biodegradable organic matter that is necessary for biological nutrients removal at the WWTP.

Giorgio Mannina, Paolo S. Calabrò, Gaspare Viviani

Detection of Exfiltration in Sewer Systems with Tracers

Due to the ageing of our underground wastewater infrastructure, leakage of sewers and pressure mains and subsequent infiltration or exfiltration are becoming an increasingly important issue. Herein, we present a novel method to detect and potentially quantify exfiltration from sewer systems under variable flow conditions; the DEST method. The DEST method is based on the principle of setting up a mass balance of a tracer substance. At an upstream point a tracer is injected in a sewer with a constant rate for a certain period, subsequently downstream high frequent time discrete grab samples are combined with discharge measurements to complete the mass balance. The method is applied on a sewer section in Loenen (NL) to investigate its feasibility. Two different tracers are used; Lithium chloride and Deuterium. Preliminary results indicate that both tracers show similar behaviour at the downstream measurement point. Final lab results are expected at the end of March, allowing in depth analysis of the experimental results with a focus on the measurement uncertainty.

Bram Stegeman, Jeroen Langeveld, Thom Bogaard, François Clemens

Improving the Hydraulic Integrity to Separate the Sewer System in Hilly Regions Using a New Manhole Design

The design of the sewer system in hilly regions has a different concept from other areas due to the high flow velocity generated in the system that characterises a sloped system. The flow velocity of sewage or stormwater in the sewer system is limited by design criteria, using minimum velocity to avoid settlement of suspended solids in the pipes and maximum velocity to keep the solute homogeneous (fluid and suspended solids) and avoid pipe erosion. Maintaining these limits of the velocity within hilly regions is challenging and designers usually use steep cascade manholes to dissipate the fluid flow energy. This paper presents a new manhole design to mitigate stormwater flow energy, which is more critical than sewage flow in such areas, and using the traditional normal steps manhole for the sewage chamber. The new manhole design includes two chambers, an inner chamber used as in the traditional manhole for sewage and an outer chamber used for stormwater flow. The hydraulic properties of the new manhole have been explored using a physical model in laboratory conditions and compared with traditional manhole performance. The laboratory results are used for validation and are compared with computational fluid dynamic model outputs of the new design. The hydraulic performance of the new design reveals improvement in decrease in the flow energy of stormwater and increase in the capacity of storage for the stormwater network.

Alaa Abbas, Iacopo Carnacina, Felicite Ruddock, Rafid Alkhaddar, Glynn Rothwell, Robert Andoh

Estimation of Faecal Indicator Bacteria in Stormwater by Multiple Regression Modelling and Microbial Partitioning to Solids

Concerns about the contamination of sources of drinking water by stormwater motivated a sanitary survey of several urban catchments in the City of Östersund (Northern Sweden). A data subset from these surveys, comprising of faecal indicator bacteria (FIB) concentrations (E. coli and enterococci), measured for six storm events in three catchments, was used for investigating the feasibility of developing a FIB estimation procedure for the studied catchments by two approaches: (a) Multiple regression models, and (b) microbial partitioning to solids. In regressions, five explanatory variables (associated constituents) were derived from the literature and measured data: stormwater temperature and flow rate, and measurements of total suspended solids (TSS), total phosphorus (TP) and electric conductivity (EC). The obtained regression models were satisfactory for enterococci (regression of modelled FIBs on measured FIB was described by R2 = 0.7), but less acceptable for E. coli (R2 = 0.2). Microbial partitioning to stormwater solids from gully pots was found infeasible; the sediment sampled contained very low FIB counts. Hence, the former method is recommended for further refinement and applications.

Helen Galfi, Heléne Österlund, Jiri Marsalek, Maria Viklander

Developing and Validating a Model to Assess Sewer Sediment Issues from Changing Wastewater Inflows and Concentration

Sewers are critical for the maintenance of both public and environmental health in urban areas through their transport of wastewater for treatment. Despite significant costs associated with excess sewer solids deposition causing blockages and reduced hydraulic capacity, there are still gaps in our knowledge of sewer solids processes. This is particularly a concern with the implementation of Decentralised Water Recycling (DWR) and further reductions in per capita water consumption. This will reduce wastewater inflow to and increase the concentration of solids in sewers, leading to increased blockages and reduced hydraulic capacities in sewers. Sewer solids can be divided into two main groups based on their size: gross solids and sewer sediments. This paper details the development, initial calibration, and validation of a comprehensive sewer sediment transport model to assist in quantifying the impacts of changing wastewater inflows and concentration. This model aims to facilitate the transition to more sustainable cities by reducing the uncertainties in the implementation of sustainable water measures, such as DWR and water use reduction. OpenFOAM, an open-source computational fluid dynamics package, was used to develop the sewer sediment model. This model has components that model flow, suspended sediment transport, bedload transport, and deposited bed development. Model calibration, using a square hydraulic flume, shows model results for flow and sediment transport are promising. Model validation experiments in a pilot-scale sewer system show that reducing sewer inflows are going to be a concern for sewer solids, especially in non-ideal or ageing sewers.

Madhu K. Murali, Matthew R. Hipsey, Anas Ghadouani, Zhiguo Yuan

Conceptualizing the Sewage Collection System for Integrated Sewer-WWTP Modelling and Optimization

In this paper, a new conceptual modelling approach and calibration method is proposed for integrating sewage collection system and wastewater treatment plant (WWTP) operations. The method consists of simplifying a complex sewer network into a computationally efficient (conceptual) model able to capture the sewer dynamics, both in terms of flow rate and water quality, entering the wastewater treatment plant. Biochemical process modelling was carried out on this conceptual model and compared with a whole-network biochemical model which covered all pipes of a sewer system. The conceptual biochemical model can achieve similar results as the whole-network model in terms of water qualities, but provides fast simulation speed and easy calibration. Those advantages mean that the conceptual biochemical model of a collection system can be used in an integrated model with which sewer and WWTP can be simulated simultaneously for long-term evaluation of optimization scenarios.

Lisha Guo, Sovanna Tik, Julia M. Ledergerber, Domenico Santoro, Elsayed Elbeshbishy, Peter A. Vanrolleghem

Multiphase CFD-Simulation of Transport Phenomena in Sewer Systems

This paper presents different computational fluid dynamics applications using the multiphase solver interFoam which is implemented in the open source software OpenFOAM. The solver uses the volume of fluid approach. When modelling tracer transport in the proximity of the interface between two phases, the problem of non-physical tracer spreading across the interface has to be overcome. In this paper, two ways are presented to model such systems successfully. First, tracer transport around concrete probes in the headspace of a sewer pilot plant is considered. In this case a two-phase (water-air) system is assumed by describing an idealized water surface as a boundary condition and a passive tracer is applied. Second, flow in a complex sewer stretch containing a hydraulic jump is simulated and a tracer is applied in the water phase. A multiphase transport approach based on the Henry coefficient is used in this case and plausible results are obtained.

Katharina Teuber, Tabea Broecker, Shibashish D. Jaydev, Gebregziabher M. Goitom, Maria Sielaff, Daneish Despot, Dietmar Stephan, Matthias Barjenbruch, Reinhard Hinkelmann

The Efficiency of Storm Water Sedimentation Tanks for Fine Particles in Urban Run-off

The sedimentation process seemed to be a well-known process to treat the urban runoff before discharging it into a water body. The flow mechanisms in real-life sedimentation tanks have now been investigated closer to optimize them for finer particle fractions and interesting findings occurred. The aim of the study was to investigate the sedimentation efficiency of finer mineral particle fractions, which are suspected carriers of heavy metal loads, with the help of an induced flow characteristic. Preparatory studies showed that recirculation zones could have a positive effect on the settlement of finer particles, especially if the axis of the recirculation is horizontal and perpendicular to the flow direction. Therefore the ratio of inlet-height (HInlet) to the height of the sedimentation tank (HTank) was varied systematically to maximize the sedimentation efficiency (η (-)) of fine mineral particles. It was found that the particle behaviour is influenced by the shear-layer between the main flow and the various sizes of the circulation zone, which depends on the height-ratio at the inlet.

Wietbüscher Maike, Voßwinkel Nina, Mohn Rainer

Relevance of Different CSO Outlets for Bathing Water Quality in a River System

Combined sewer systems are one of the major sources of microbiological contamination in urban water bodies. However, identification of hotspots for pathogen emissions is not straightforward, especially in large and complex drainage systems. To determine the relevance of different CSO outlets for bathing water quality a simple tracer approach which uses wastewater volume as a proxy for pathogen emissions has been developed and tested for the city of Berlin, Germany. The approach reveals that the average wastewater ratio in CSO varies largely between different river outlets (0 to 15%). Hence, the outlets with the largest CSO volumes are not automatically the greatest wastewater emitters and assumed hotspots for pathogen contamination do not coincide with hydraulic hotspots. This is verified with own measurements that show enormous differences in pathogen concentrations between waste and stormwater of 4 orders of magnitude. As a result, wastewater which represents only 5% of the CSO volume contributes >99% of the pathogen loadings to the river. The study highlights the relevance of wastewater volumes for the identification of point sources for the hygienic impairment of water bodies.

Mathias Riechel, Wolfgang Seis, Andreas Matzinger, Erika Pawlowsky-Reusing, Pascale Rouault

Pollutant Loading of Different Particle Size Fractions Compared to the Pollutant Loads of Urban Stormwater Runoff Events

A stormwater monitoring campaign at a treatment facility is undertaken to further investigate the relationship of TSS removal and the reduction of micropollutant loads. Therefore the particle characteristics are investigated as well as the associated pollutants within different particle size fractions. First results in terms of pollutant loadings are used to calculate the respective PAH loads of the sampled rain events. Furthermore on the basis of the current monitoring campaign, TSS data of a preliminary investigation is used to also calculate the pollutant loads of this time period. The comparison reveals, that a difference between the two monitoring campaigns can be seen. In a next step, the loadings of different substances (flame retardants, plasticisers, pesticides) will be evaluated in the same way.

Baum Philipp, Dittmer Ulrich

Spatiotemporal Modelling of Sediment-Related Blockages in the Sewer System of Bogotá (Colombia)

The planning and scheduling of maintenance operations of large sewer systems generate a complex decision-making environment due to the difficulty in the collection of spatiotemporal information about the operational and structural condition of their components (e.g. pipes, gully pots and manholes). Thus, water utilities generally carry out these operations following a corrective approach. This paper studies the spatiotemporal distribution of failure events, considering the stochastic process involved using a Log-Gaussian Cox process model. In addition, association of failure occurrences to environmental and sewer system covariates was assessed. The proposed method was applied to analyze sediment-related blockages in the sewer system of an operative zone of Bogotá (Colombia).

Eliana Soriano Pulido, Carlos Valencia Arboleda, Juan Pablo Rodríguez Sánchez

Modeling Storm Water Pipe Leakage: Transient vs. Steady-State Groundwater Flow

Storm water pipe leakage in an urban environment may lead to severe problems such as a reduced pipe system capacity. Detailed physically-based numerical models are necessary to understand leakage and mitigate risks. In the present study, we present the application of a physically-based pipe flow-groundwater flow model (full model) for storm water leakage in an urban catchment. We further present the application of a simplified model, in which the transient groundwater model is neglected and the soil domain is represented by a steady-state pressure distribution. We compare both models based on a series of simulations in the same urban catchment. We conclude that the simplified model is as accurate as the full model for the given setup. Comparing both models, the computation time could be reduced from several hours to one minute.

Peche Aaron, Graf Thomas, Kidmose Jacob, Christiansen Barlebo Heidi, Fuchs Lothar, Neuweiler Insa

Just Suspended Speed for Solid Particle Transport in TorusReactor

The deposing velocity is an important parameter in the designing of solid transportation in pipe; it represents the lowest speed at which transportation can operate corresponding to no solid particles remains in the reactor or pipe bottom. This minimal velocity has been investigated in several types of reactors in water treatment and solid transport. A Little importance has been given to loop reactors in liquid solid mixtures especially torus reactor which has significant advantages in chemical and biochemical process and mixing. In the present work solid-liquid suspension in torus reactor is investigated by the experimental determination of the just suspended speed Njs at which all the solid particles are completely suspended. For this purpose a modified method based on visual assessment have been used. The effect of solid loading (1–7%) and particle size (80–500 µm) and different solid density was carried out. The Njs is largely depending on concentration and density of solid particles, it presents a weak dependence on particles size. The determination of Njs seems necessary in solid transport and operations involving solid-liquid mixtures where the mass transfer is a limiting factor.

Alouache Ali, Selatnia Ammar, Halet Farid, Abdelouhab Lefkir, Houssem Eddine Sayah, Nadjemi Boubekeur

Stormwater Runoff Treatment Filtration System and Backwashing System

This study has been carried out to evaluate the applicability of the pilot scale the hybrid type of stormwater runoff treatment systems (SFS) for treatment of combined sewer overflow. And, to determine the optimum operation parameter such as coagulation dosage concentration, effectiveness of coagulant usage, surface loading rate and backwashing conditions. The SFS system is consisted of hydrocyclone coagulation/flocculation with polyaluminium chloride silicate (PACS) and upflow filter to treat combined sewer overflows. There are two modes (without PACS use and with PACS use) of operation for STS system. In case of without coagulant use, the range of SS, turbidity removal efficiency were 72.0–86.6% (mean 80.0%), 30.9–71.1% (mean 49.3%), respectively. And, the recovery rate of filter was 79.2–83.6% (mean 81.2%) the rate of remained solid loading in filter media was 16.4–20.8% (mean 18.8%) after backwashing. In case of SFS run with coagulant use, The range of influent flowrate and surface overflow rate were 6.8–8.0 m3/day (mean 7.2 m3/day), 163.2–191.8 m3/m2/day (mean 172.4 m3/m2/day), respectively. The influent turbidity, SS concentrations were 59.0–90.7 NTU (mean 72.0 NTU), 194.0–320.0 mg/L (mean 246.7 mg/L), respectively. The range of PACS dosage concentration was 6.0–7.1 mg/L (mean 6.7 mg/L). The range of SS, turbidity removal efficiency were 84.9–98.2 (mean 91.4%), 70.7–96.3 (mean 84.0%), respectively. It was found that removal efficiency was enhanced with PACS dosage. The recovery rate of filter was 92.0–92.5% (mean 92.3%) the rate of remained solid loading in filter media was 6.1–8.2% (mean 7.2%) after backwashing. In case of coagulant use, the particle size of effluent is bigger than influent particle size. The results showed that STS with PACS use more effective than without PACS use in SS and turbidity removal efficiency and recovery rate of filter.

J. H. Lee, M. J. Lee, S. H. Yang

Microalgae Cultivation Using Various Sources of Organic Substrate for High Lipid Content

The ingredients of photosynthetic reactions can be exploited to increase algal culture productivity to effectively treat wastewater by significantly reducing the presence of organic and inorganic compounds. In this study, we introduced microalgae Chlorella pyrenoidosa (C. pyrenoidosa) into four different wastewater samples, including Palm Oil Mill Effluent (POME), piggery, domestic, and mixed-kitchen wastes. The C. pyrenoidosa growth efficacy of POME and subsequent drop in nutrients were demonstrated. It was clearly seen that POME had the highest Chemical Oxygen Demand (COD) values at 700 mg L−1. The Total Nitrogen (TN) ratio for the piggery sample was the highest at 590 mg L−1. Productivity was evaluated in terms of chlorophyll content, growth rate, biomass, and lipid content. POME and domestic wastes had the first and second highest chlorophyll a content of 3 mg L−1 and 2.5 mg L−1, respectively. The optimum growth rate for C. pyrenoidosa was observed when using POME as a substrate. This study confirmed that Cell Dry Weight (CDW) in POME was the highest with 500 mg L−1 after 20 days cultivation of C. pyrenoidosa, when compared to other substrates. Maximum lipid content was recorded for POME, domestic sample, piggery, and mixed-kitchen waste, at 182, 148, 0.99, and 117 mg L−1, respectively. The above results revealed that POME was the best substrate choice for alga C. pyrenoidosa with the highest lipid production rate of the four substrates. It was established that POME (as a nutrient enriched media) assisted C. pyrenoidosa growth and considerably reduced the presence of organic and inorganic compounds.

Hesam Kamyab, Shreeshivadasan Chelliapan, Chew Tin Lee, Shahabaldin Rezania, Amirreza Talaiekhozani, Tayebeh Khademi, Ashok Kumar

Partitioning of Metals in Urban Drainage from Paved Source Area Catchments

Representation of metal partitioning in urban drainage is required when determining loadings, treatment, maintenance and regulatory compliance. This is particularly the case for paved urban source areas where, if a first-flush exists, the design volumetric capture and treatment will be based on such regulatory requirements. However, such treatment for metals requires partitioning information if metals are to be effectively separated from flows from paved source areas. This study examined partitioning and transport of metals from paved surfaces of four differing land uses: highway, airside and landside within aviation site, commercial/tourism terminals within port area. Equilibrium concentrations of metals and particulate matter (PM) using a non-parametric analysis for a series of six paved surface area catchments were compared. In particular two American highway sites, and four Italian sites located in the Liguria Region (two port terminal sites and two aviation sites) were examined and compared with event based concentrations collected from catchments with similar land uses. The role of hydrology on mass transport and partitioning of aqueous and particulate-bound metal fractions was evaluated. Finally transport of metal phases on an event basis, thus relating hydrology and PM mass delivery impacting metal partitioning were examined. Partitioning, indexed through a partitioning coefficient, Kd (L/kg) accounts for hydrologic transport, PM transport and interactions with and between metals. Kd can vary by orders of magnitude across a runoff event for the source area catchments of this study. Highway sites were more heavily loaded with PM and metals than airport sites. The metals results from the six sites of this study were compared to similar sites around the world. Based on the variability of partitioning, whether intra- or inter-event, results indicate that paved source area treatment requires a combination of sedimentation, filtration and adsorption mechanisms for in-situ unit operations and processes (UOP).

Ilaria Gnecco, Anna Palla, John Sansalone

Water Management, Society and Climate Change

Frontmatter

Advances in Modelling Particle Transport in Urban Storm- and Wastewater Systems

Suspended solids in sewers not only carry organic and inorganic pollution but are also the preferred vector for heavy metals, hydrocarbons, many hydrophobic micropollutants and pathogens that are preferentially attached to them. Their behaviour in sewer systems has thus been object of many studies, but, unfortunately the predictive power of the available models remains limited due to the complexity of the processes that determine their transport, sampling and measurement. This contribution summarizes 10 years of research at Université Laval that took advantage of the ViCAs measurement set-up that allows for characterizing the wastewater particles’ settling velocity distribution (PSVD) to come up with a conceptual modelling framework of storm and wastewater transport systems in which mass balances are made of particle classes, each with a characteristic settling velocity. The models have been calibrated and validated for stormwater basins, combined sewer retention tanks, primary clarifiers and complete combined sewer systems, from sewer catchment to stormwater basins outlets, sewer overflows and primary clarifier effluents. The ViCAs experimental set-up is simple to build and work with, and has intrinsic quality control indicators that allow evaluating the quality of the obtained PSVD’s.

Peter A. Vanrolleghem, Sovanna Tik, Paul Lessard

Redesign of Water Quality Network for the Urban Rivers in Salitre in Bogotá, Colombia, Using an Artificial Neural Network

Bogotá is the biggest urban center in Colombia, and has the largest population in the country, with about eight million inhabitants. This has led to an impact on different natural resources, principally the water resource. This is why the city currently has a water quality network that allows measuring of the quality conditions of Bogotá’s rivers. This network has been operating since the nineties, but has not been optimized, despite the dynamics of the city and the sanitation infrastructure. For this reason, a redesign of the network over the Torca and Salitre rivers was planned using an artificial neural network, which allowed us to optimize the measurement frequency (month and day) and the number of measurement points on each river.

Carlos Peña-Guzmán, Paula Balaguera, Nathalia Hernandez, Ronal Sierra

Evaluating City Scale Surface Water Management Using a Rapid Assessment Framework in Melbourne, Australia

This research develops application of a strategic surface water management screening framework to enhance decision support in cities. Decision support in cities is typically constrained by resource costs of detailed analysis, this new methodology overcomes this through applying a simplified option screening process to evidence strategy and direct future detailed modelling of promising options. This study advanced on previous research by developing the methodology through option evaluation using a real world case study in collaboration with key catchment stakeholders. Research included stakeholder engagement workshops to identify catchment flood hazards and design potential management strategies, followed by application of the fast flood assessment framework to assess the flood reduction potential of each strategy. Theoretical implications indicate that city scale interventions demonstrate effective performance at managing design standard flood events. Practical findings indicate the framework to be an effective stakeholder engagement tool due to fast analysis of collaborative strategies. The key benefit to readers is understanding that fast, simplified urban drainage modelling can provide an opportunity to collaboratively screen flood hazards and generate evidence for prioritising detailed modelling in urban catchments.

James L. Webber, Matthew J. Burns, Guangtao Fu, David Butler, Tim D. Fletcher

Optimizing SVM Model as Predicting Model for Sewer Pipes in the Two Main Cities in Colombia

As in most of the cities around the world, in the last 30 years Latin-American ones have focused on investing in building infrastructure to provide sewer and water services to the communities. However, these infrastructures are going aging day to day. The municipalities need to extend management activities by the development of support tools such as deterioration models to face the aging problem. In the literature of sewer asset management, SVM has been a useful tool to predict and forecast the structural condition of pipes. In this work, the use of differential evolution method as optimization tool was implemented to find the optimal hyper-parameters for SVM models. The SVM models were applied in the main cities of Colombia (Bogota and Medellin) given as a result that the optimized SVM model provides less than 5% of deviation in the prediction of structural conditions in both cities.

Nathalie Hernández, Nicolas Caradot, Hauke Sonnenberg, Pascale Rouault, Andrés Torres

Climate Change Impact on Water Supply Demands: Case Study of the City of Skopje

The aim of the paper is to present climate chance impact on drinking water supply and assess availability of current water resources to meet the increasing demands in climate change conditions for the city of Skopje. Series of monthly precipitation and temperature data are generated up to 2050, using recorded data and data for predicted changes of air temperature and precipitation according to climate change scenarios developed for the Republic of Macedonia within the Third National Communication. Climate change impact on drinking water supply is assessed using statistical models for dependence of the water supply data to the main climate parameters: temperature and precipitation. Forecast of future water quantities includes implementation of multi regression models defined with a set of independent variables: number of population for time sets (t, t − 1, t − 2, t − 3), precipitation and air temperature including predicted changes of the data under climate change conditions for the same time sets. Two scenarios are analysed: first – predicts the number of population until 2050 remains nearly the same as nowadays, second – predicts increase of number of population on average annual rate of increase of 0,58%. Results are indicating shortage of available water resources for population and industry in climate change scenarios (increasing of temperatures and decreasing of precipitations) and increase of population. Understanding the vulnerability of both water resources and variability of drinking water demands for the city of Skopje results in identifying the most dominant factors that influence vulnerability. It is vital to ensuring sustainable water management in the region.

Katerina Donevska, Angelco Panov

Combined Sewer Overflow Management: Proof-of-Concept of a Screening Level Model for Regional Scale Appraisal of Measures

Combined sewer overflows (CSO) represent a potentially important source of pollution in several river basins. Yet, the quantification of CSO loads is still problematic, and their management may be consequently hampered. In this contribution we present a proof of concept for a simplified, screening level model to quantify CSO loads, for regional scale applications. The model has two parameters, a runoff coefficient of the drainage catchment and the effective dilution ratio at which CSO begins. These two parameters enable appraising the potentials associated with reduction of runoff (e.g. urban greening) and retrofitting of the sewer network. We present and discuss a preliminary calculation for the functional urban areas (FUA) of the European Union, highlighting the possibility to use the model in the screening of management options.

Alberto Pistocchi, Chiara Dorati

Selection of the Best Water Supply Scenario for Urban Demand Based on the Risk Analysis in Decision-Making Model

In recent years, inefficient water resources management has caused to serious crisis in supplying water for urban demand within the watersheds. Therefore, one of the most important challenges for urban decision-makers (DMs) is selecting the most desirable water supply scenario, satisfying the several sustainable development criteria. Accordingly, this paper has developed a risk-based multiple criteria decision-making (MCDM) model for selecting the best scenario based on the modified ordered weighted averaging (MOWA) operator. This operator considers the risk-taking degree of DMs, the criteria importance degree and the DMs’ power weight, simultaneously. By use of this operator, the scenario scores have been calculated in several risk cases of decision-making, depending on the satisfaction of the number of criteria. This approach has been developed for Mashhad watershed in north-eastern Iran, to select the best water supply scenario for urban demand in 2040. The evaluation of scenarios has been performed with respect to the sustainable development criteria based on the urban watershed modelling. Finally, depending on each case of risk-taking degree, the most preferable scenario has been determined for satisfying the important criteria within the watershed. Development of this model is recommended for any watershed management modelling to supply urban demand.

Reza Javidi Sabbaghian, Amir Pouyan Nejadhashemi

Rainwater Harvesting System Efficiency and Economic Assessment for Different Residential Building Typologies

The focus of the paper is the evaluation of the water saving efficiency and the payback period of domestic rainwater harvesting (DRWH) systems. The study was carried out with reference to different residential building typologies (flat and condominium) in sub-coastal Italian climate regime. The buildings are characterized by different rooftop area, number of building floors and inhabitant number. The economical assessment is provided by comparing, along the design life span of the building, the capital costs and the savings due to the replacement of the water supply with the rainwater. In the present analysis the rainwater is used for both indoor and outdoor non-potable consumption.

Sara Corvaro

Model Based Estimation of a Natural Water Balance as Reference for Planning in Urban Areas

The water balance of urban areas differs considerably from the landscape water balance. Increased surface runoff, reduced groundwater recharge and evaporation change the hydrological regime, the morphology and ecology of water bodies close to the cities, the groundwater in the urban area and the urban climate. Today’s urban drainage systems are designed to prevent, reduce, drain, seep away, evaporate or discharge precipitation into nearby surface waters with considerable delays. In doing so, it follows the principles of the German Water Resources Act (WHG) and the objectives of the relevant technical regulations DWA-A 102 to keep changes in the natural water balance by settlement activities as low as ecologically, technically and economically acceptable. A reference for the “natural” water balance has to be defined as a planning objective in order to quantify the hydrological changes in settlements. As a suitable reference, we propose to use the water balance of the landscape of the associated ecoregion with today’s cultural land use without urban developments. This approach is more suitable to define local conditions than the water balance of the enclosed catchment. The presented calculation approach to define reference values of the water balance, uses soil and geological properties, precipitation and climate data and can be implemented and applied uniformly throughout Germany. The water balances in this study are simulated with the water balance model RoGeR. In this study, the developed approach is applied for five locations in Germany.

Malte Henrichs, Andreas Steinbrich, Hannes Leistert, Isabel Scherer, Tobias Schuetz, Mathias Uhl, Markus Weiler

Preliminary Analysis About the Effects on the SPI Values Computed from Different Best-Fit Probability Models in Two Italian Regions

Droughts are one of the most challenging issues in water resource management in urban areas due to their major socio-economic impacts. The identification and evaluation of droughts are commonly based on the Standardized Precipitation Index (SPI), which is estimated through easily accessible information (i.e., monthly rainfall). In this work, we show a preliminary analysis on the role played by the nature of the probability distribution in the calculation of the one-month SPI. Long-term rainfall time series from two Italian regions are investigated.

Claudio Mineo, Benedetta Moccia, Federico Lombardo, Fabio Russo, Francesco Napolitano

Energy Assessment of Seawater Toilet Flushing in Qatar

Seawater toilet flushing (SWTF) is an alternative water source that has been utilised in Hong Kong for economical water supply and demonstrated using other Asian case studies. Yet how the impact of SWTF translates to other regions with different water supply sources and wastewater discharge requirements remains unexplored. In this study, we look at SWTF for the water-scarce Middle East using Doha, Qatar as a case study. We demonstrate the importance of wastewater discharge conditions on the effectiveness of this technology and the role that corresponding water conservation efforts may play. Where water reuse is a baseline condition the effectiveness of SWTF is limited.

Hamish R. Mackey, Saad Hafiz, Sami G. Al Ghamdi

An Assessment of Per Capita Water Consumption in Sirte, Libya

Worldwide, where freshwater resources are limited, a major water scarcity problem occurs. Population growth, which leads to increased water consumption with high inefficiencies of household water use behaviour especially in developing countries, makes the problem worse. In this situation, a sustainable urban water management approach which considers household water consumption patterns is required. However, country specific water consumption data particularly for the developing countries is limited. This paper investigates per capita water consumption in Sirte city by evaluating the indoor and outdoor domestic water uses using a survey. The survey contains information about demographic, socio-economic and household water end use behavioural characteristics. The preliminary results suggest that water consumption varies with the type of dwelling and females tends to consume considerable more water in comparison to males. Household income does not seem to affect water consumption.

Iman Alharsha, Fayyaz Memon, Raziyeh Farmani

Applying Socioeconomic Optimisation on Blue-Green Climate Adaptation Projects in an Urban Catchment

Climate adaptation projects are often conducted without assessing the socioeconomic losses or benefits associated with the project. Methods for conducting socioeconomic assessments and optimisations have been proposed in various articles, but these methods often include more simulations than what is feasible for the common climate adaptation project. Identifying the optimum service or protection level for climate adaptation is important to avoid over or under investments, to understand the residual risks, and for informed decision-making and communication. This study develops a methodology for socioeconomic optimisation and applies it to the Kildeskovsrenden catchment in Gentofte, Denmark. The methodology requires many simulations to optimise the return period for climate adaptation. This study aims to reduce the number of simulations by defining the acceptable water level on terrain in collaboration with stakeholders. The return period combined with an acceptable water level on terrain constitutes the dimensioning criteria for the climate adaptation projects. Three return periods of 20, 50 and 100 years in year 2100 make up the optimisation exercise of identifying the optimum service level. Following its application, a set of recommendations are developed to accompany the optimisation and strengthen the methodology, including the use of the risk density curve during initial assessment of the catchment. Although the optimisation is built on a reduced amount of simulations, the methodology still requires large resources for modelling and assessments of investment and damage costs.

Steffen Davidsen, Thomas Kruse, Trine Stausgaard Munk, Karsten Arnbjerg-Nielsen

Parameter Sensitivity of a Microscale Hydrodynamic Model

Here we present the results of a global sensitivity analysis (GSA) applied for a microscale hydrodynamic model, which combines pipe infrastructure and small scale source treatments in terms of raingardens (RGs). The aim is to identify the most influential model parameters to support the decision for future measurement installation sites and smart water control. For the model creation and simulation, the Storm Water Management Model (SWMM) is used. For the GSA method the Elementary Effect Test (EET) is applied, were uncertainties to 18 model input parameters, comprising 10 subcatchment and 8 Low Impact Development (LID) parameters, are assigned and analysed by 1,900 simulations. The model’s responses are evaluated at four main RGs and for two model outputs: Inflow and Surface runoff at the RGs. First results show that the most sensitive factors are the Depression Storage Impervious and the Soil Hydraulic Conductivity for the Inflow and Surface Runoff at RGs, respectively.

Stefania Anna Palermo, Jonatan Zischg, Robert Sitzenfrei, Wolfgang Rauch, Patrizia Piro

Leveraging Open Source Software and Parallel Computing for Model Predictive Control Simulation of Urban Drainage Systems Using EPA-SWMM5 and Python

The active control of stormwater systems is a potential solution to increased street flooding in low-lying, low-relief coastal cities due to climate change and accompanying sea level rise. Model predictive control (MPC) has been shown to be a successful control strategy generally and as well as for managing urban drainage specifically. This research describes and demonstrates the implementation of MPC for urban drainage systems using open source software (Python and The United States Environmental Protection Agency (EPA) Storm Water Management Model (SWMM5). The system was demonstrated using a simplified use case in which an actively-controlled outlet of a detention pond is simulated. The control of the pond’s outlet influences the flood risk of a downstream node. For each step in the SWMM5 model, a series of policies for controlling the outlet are evaluated. The best policy is then selected using an evolutionary algorithm. The policies are evaluated against an objective function that penalizes primarily flooding and secondarily deviation of the detention pond level from a target level. Freely available Python libraries provide the key functionality for the MPC workflow: step-by-step running of the SWMM5 simulation, evolutionary algorithm implementation, and leveraging parallel computing. For perspective, the MPC results were compared to results from a rule-based approach and a scenario with no active control. The MPC approach produced a control policy that largely eliminated flooding (unlike the scenario with no active control) and maintained the detention pond’s water level closer to a target level (unlike the rule-based approach).

Jeffrey M. Sadler, Jonathan L. Goodall, Madhur Behl, Mohamed M. Morsy

Remobilization of Sediments in Gully Pots During High Intensity Precipitation Events

The urban drainage system experiences increasing challenges due to limited capacity, increased precipitation amount, and intensity cause a higher risk of urban flooding and frequent combined sewer overflows (CSOs). This is a common problem in Norwegian cities, and around the world. The gully pots in the urban drainage system should trap sediments that is transported with stormwater and function as a pollutant trap for low flow events. However, this is dependent on regular maintenance for proper function. If poorly maintained the gully pots in the drainage systems can become a source of resuspension of accumulated sediments during high intensity rain events that. This can be a significant source of polluted sediment transported to receiving waters. This study investigates the pathways and occurrence of remobilization of sediments through the use of a SWMM model and a case study area in Damsgaard, Bergen. Steep slopes characterize the research catchment, with elevation ranges from sea level to 468 m above mean sea level. Built-up areas (i.e. buildings and roads) cover about 48.3% of the area while about 44.5% of the catchment is forested. The case study illustrates how poorly maintained gully pots can be a net source of pollutants to receiving waters, in this case the Puddefjord fjord, where the City of Bergen wishes to establish swimmable water quality in the inner harbor areas.

Tone Merete Muthanna, Maria Viklander

Distributed Sewer System RTC in Öhringen – On the Way to the Internet of Things

The assessment of real time control (RTC) potential and the development of RTC systems is supported by a number of guidelines and evaluation tools. For the city of Öhringen in the South of Germany such a simulation-based evaluation has been carried out in preparation of implementation of an RTC system. RTC represents a good example of the application of concepts of “Internet of Things” (IoT), in particular if decentralised controllers are applied. On the way to the IoT world, open platforms that enable web-based simulation without having to install a simulation engine on a local computer can support and simplify the planning and implementation process of RTC systems. This might be of particular benefit for smaller municipalities and consultancies who do not have the necessary simulators available, but need them only on a case-to-case basis. The paper illustrates these concepts for the Öhringen example.

Manfred Schütze, Nico Suchold, Horst Geiger

Backmatter

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