Flood Forecasting and Hydraulic Structures

Floodplains are the natural pathways that accommodate the excess water overtopping the riverbanks during high flow times. However, they have become a zone that causes enormous damage and losses during a flood event, primarily due to floodplain-oriented uncontrolled and unplanned urbanization and developments altering the natural linkage and layout of these regions. The fertile soil, proximity to abundant surface and groundwater sources, and higher land value make them more appealing for human settlements. However, their frequent flooding nature is often overlooked. Earlier studies reveal that a large part of the world’s floodplains has disappeared due to haphazard developments, industrialization, and urbanization, this being more prominent in developing nations like India. Most floodplains in the country have been devastated, floodplains of the rivers Adyar, Cooum, Kosathalayar, Yamuna, and Periyar being a few to list. This study assesses the impact of encroachment of floodplains of the Adyar River of the Chennai basin, in India, on the flood flow pattern using Landsat images and hydrologic–hydraulic modeling of the 2015 flood event. The study puts forth a concise idea of the possible flood flow pattern that would have developed during the 2015 flood event if the floodplains were as in 1991 or prior years, unaltered by unnecessary human interventions, depicting the impact of encroachments. The study reveals that the area has undergone rapid urbanization and haphazard encroachments along the Adyar River floodplains resulting in a 188% increase in flood peak and a 48-h reduction in the time to peak of flow. Better late than never—proper floodplain management and strict implementation and execution of floodplain development regulations and guidelines can still be a solution for these impacts and thus reduce the havoc situation and losses created by a flood.

Flood models can be a valuable source of information for flood risk assessments because they predict inundation extents. Due to the impact of climate change, the semi-arid zone of Gujarat is experiencing an increase in annual rainfall. Bhavnagar and the surrounding district received around 521 mm of rain in August 2020, compared to Bhavnagar district’s average annual rainfall of 658 mm. The Kalubhar and Ranghola dams in the Bhavnagar district were filled with water, causing high flows in the Kalubhar, Rangholi, Keri, and Ghelo rivers. The flows from these four rivers merge before meeting the Gulf of Khambhat. Despite the lack of data, an attempt has been made in this study to develop a two-dimensional flood model for this region using HEC-RAS v6.0. The study shows that the flood in the region was caused by a high amount of rainfall combined with unplanned development along the coastal line. Based on the simulated results and the difficulties encountered during model development, recommendations and guidelines for resolving the waterlogging problem and reducing the extent of flood inundation for the Bhavnagar coastal region were provided. The study will aid government officials and stakeholders in determining flood prevention measures.

Hydrologic–hydrodynamic modelling has been considered to be an important tool to understand and quantify hydrological processes of the river basins. The scarcity of the in-situ gauging network has made it a challenging task, as these with recent advancement in satellite altimetry, it may play a vital role in establishing the virtual gauges (VG) along the river stretch. In this study, HEC-RAS-based 1D/2D coupled hydrodynamic (HD) model has been set up for the stretch of around 170 km from Boudh to Naraj in the lower Mahanadi River along with two flood-prone tributaries, Kusumi and Rana. Based on the extreme flood events, the model was calibrated for the monsoon season of 2018 and, however, validated for monsoon of 2015 at daily time step. The Nash–Sutcliffe Efficiency (NSE) of 0.83 and root mean square error (RMSE) of 46 cm was estimated between simulated and observed water level (WL) for the calibration and NSE of 0.76 and RMSE of 45 cm during validation. The 04 ground tracks of Jason-2/3 satellite altimeters were identified, which cross the river. The virtual gauging stations were established at these locations to generate the rating curves (RCs) using HD model. The comparison of HD model and altimetry-based water level depicted the NSE and RMSE ranging from 0.76–0.84 to 42–88 cm, respectively. The high agreement between the two showed the potential of satellite altimetry data for the multi-site validation of HD model and constructed RCs at VG stations. This study showed the advantages of the combined use of HD model and satellite altimetry data enabling WL and RCs at multiple virtual locations in addition to existing physical ones. The proposed framework may open new perspectives for enhancing flow dynamic studies at a large scale even in remote and poorly gauged basins. Further, upcoming satellite missions like SWOT ensures detailed observations in future as well.

A two-dimensional (2D) hydrodynamic (HD) model is developed for densely populated Surat city, India, located on the bank of the lower Tapi River. Surat city has experienced flooding in the past during the monsoon period due to heavy releases from the Ukai Dam situated 100 km upstream of the city. In the current study, the 2D HD model is developed for the lower Tapi basin (LTB), focusing on Surat city for the past flood that occurred in August 2006. The hourly discharge from the Ukai Dam and tidal levels at the Arabian Sea was used as upstream and downstream boundary conditions, respectively. The distributed floodplain roughness coefficient based on the existing land use land cover (LULC) of the study area is considered across the flood plain. The performance of the model is evaluated against observed water levels along the channel, including maximum flood depth across the flood plain of Surat city and found satisfactory. The developed model will be useful for the local administration in predicting maximum water depth, velocity, and flood duration for various return periods floods of high magnitude and help prioritize the mitigation strategies.

Abnormal heavy rainfall in July–August months of 2018 resulted in severe flooding that led to the loss of many lives and damages to properties. Hydraulic simulation models play a vital role in the flood risk management and aid in estimating the flood extent over the flood plain. This paper presents the application of HEC-GeoRAS and HEC-RAS to determine the flood hazard and flood vulnerability of Chaliyar River basin from Kuniyil to Beypore along the 32 km study stretch. The SRTM digital elevation model (DEM) is used to extract the river geometry. Water surface profiles are generated for the unsteady flow simulation and are calibrated using different Manning’s values. The result of the analysis indicates the coefficient of determination (R2) value as 0.99 and 0.76 which indicates a good correlation between the observed and simulated water levels and discharges. Flood inundation maps are developed which identifies the areas at high risk of flooding.

Massive property damage and loss of life have resulted from flooding, which is a common occurrence in many regions of the world, particularly in the developing world. A flood occurs when water from a stream or river overflows its banks and submerges normally dry terrain. Future development and flood mitigation methods rely heavily on understanding flooding behavior and hydraulic features of rivers. The main objective of the research is to simulate the flood event for Lower Narmada River Basin and develop inundation maps. A hydraulic model was utilized in this research to examine a variety of physical variables that are critical to water movement in the river. A digital elevation model (DEM) was used for geometry data generation in ArcGIS, a Geographical Information System (GIS) program, is used to segment the research region for the hydraulic model. Because of this, it makes use of a hydraulic model developed by Hydrologic Engineering Center (HEC-RAS). HEC-GeoRAS is an intermediary module that allows data to be migrated between ArcGIS and HEC-RAS. Flood inundation maps are generated by adding flow data into a model once the necessary geometrical and hydraulic structural data have been gathered and compiled as needed. As a result of hydraulic modeling, flood depth and velocity are also determined. It is necessary to consider flood inundation, depth, and velocity statistics in order to identify flood-prone regions. By using the information from this study, we may better prepare for floods by building an embankment, a flood wall, and other flood mitigation measures. Hydrologists and water resources engineers may utilize the results and findings to plan and develop using the HEC-RAS model, which has excellent performance.

Big data has recently become popular all around the world. Data generation in each discipline has substantially improved due to the usage of computer systems. Flooding appears to be the most frequently calamity in a tropical country like India. Flooding in urban coastal areas is caused by heavy rainfall, industrialisation, high population density and urbanisation. The Navsari City, Gujarat, India, located near the Arabian Sea coast affected by a disastrous flood in 2004. In this study, the use of big data is implemented to assess the flood using HEC-RAS 2D hydrodynamic modelling. The big data of past floods would be a foundation for the enlargement of the HEC-RAS 2D flood assessment model. Calibration and validation have been performed to ensure the consistency and adequacy of the model. The outcomes of the model depicted that the R2 of the model was 0.9679 indicating that the observed values are in good agreement with the simulated value. Comparable to most developed and advanced cities in countries such as the Europe, USA, Japan and China who are exploiting the advantages of big data for assessment of flood, monitoring and mitigation, where as in India, the use of big data for assessing flood is very limited. In the said context, this research work is focussed on the use of big data for flood assessment in Navsari. In this study, we have discussed the needs and applicability of flood assessment through HEC-RAS 2D model across the world’s urban coastal areas including Navsari City, accompanied by the important benefits of big data approach.

The Krishna River basin in Western Maharashtra, India, has been facing acute flood problems since 2005. The Krishna River, which originates at Mahabaleshwar in Maharashtra, has a steeper gradient in the initial reach. When the river enters a flatter region after Karad in the Satara District, it travels in a zigzag pattern with many bends and turns with 17 meanders on it. With these meanders with flatter gradients, the river becomes saucer-shaped, which in turn increases flooding and inundation. Straightening and removing the meanders at some places may reduce the channel length and improve the bed gradient, increasing the discharge carrying capacity, which in turn will help to reduce the flood inundation. In this paper, a hydrodynamic analysis with HEC RAS is done with natural river conditions and by removing a meander on the Krishna River, which is just upstream of its confluence with a tributary called Panchganga. The study reveals that removing this meander helps in flood mitigation. The flood level reduction is 1.29 m at Miraj and 0.45 m at Sangli which are the two majorly affected cities along the banks of the Krishna River in the state of Maharashtra.

In the current study, a two-dimensional (2D) hydrodynamic (HD) model is developed to investigate the effect of proposed Bhadbhut Barrage on the hydraulics of lower Narmada River, India. The model has been developed for the river stretch of 63 km from Shuklatirth to the Arabian Sea at Gulf of Khambhat. The flood flow, routed from Garudeshwar gauging site to Shuklatirth (ungauged site) using the Muskingum channel (hydrological) routing method, is used as upstream boundary condition, whereas a constant (observed) high tide of 4.69 m above mean sea level is used as a downstream boundary condition in the model. The model is developed for the existing condition, for the flood of year 2006 by considering distributed floodplain roughness coefficient based on land use land cover (LULC) pattern. The performance of the developed model is found satisfactory, against the water level at Golden Bridge, Bharuch, with RMSE of 0.49 m. The calibrated model can be useful to simulate the different scenarios regarding the construction of barrage across lower Narmada River as well as the embankment along the channel and its effect of water level at different locations.

Flood assessment in the data scare region is the most challenging task for decision-makers and scientists to estimate the flood catastrophe and flood vulnerability in a flood-prone area. In addition, future preparedness and flood mitigation plan solely depend on the accuracy of the flood assessment after the catastrophic flood. The present case shows state of the art for flood assessment using UAV (drone) techniques. Nowadays, flood assessment is performed using hydrodynamic modeling, where DEM/DTM is the basic input for flood simulation. Dhanera city, Rel River catchment of Banaskantha district, which was affected by the flood in 2015 and 2017, is considered for preparing high-resolution DEM. Phantom 4 Pro RTK and Pix4D software are applied to process the 9222 images across the study reach. The point cloud and high-resolution DEM (3.6 × 3.6 cm) have been extracted from Dhanera city for flood assessment using advanced software techniques. Prepared high-resolution DEM will be utilized for pluvial and fluvial flood assessment through hydrodynamic modeling under unsteady flow conditions. UAV-based high-resolution DEM/DTM has been described, and a significant achievement for preparing high-resolution DEM/DTM for flood modeling to improve the decision-making system has been discussed.

The Surat city located alongside the banks of the lower Tapi River and at the inference of Arabian Sea. The densely populated Surat city is vulnerable to multiple hazards including extreme rainfall, urban (pluvial) and riverine flooding, tide surge, sea level rise, cyclones as well as human-induced hazard of industrial accidents. The current study focuses on the computation of socio-economic vulnerability of the Surat city area coming under the jurisdiction of the Surat Municipal Corporation (SMC) (area = 326.5 km2), by considering the risk to the population and asset in the area. The census-based indicators representing socio-economic status are identified for each ward of Surat city; the ward is considered as decision-making unit (DMU). The principal component analysis (PCA) is applied on the indicators for the dimensional reduction as well as to remove the possible co-relation amongst the indicators. Further, the decorrelated data (nearly 75% variability) used as input in the data envelopment analysis (DEA) model to evaluate the vulnerability for each ward. The analysis performed on total 89 wards of the Surat city indicates that the major area within the city is under high to very high vulnerable category specifically densely populated areas. The low to medium vulnerable areas are mostly concentrated over the tail portion South-west zone. The developed socio-economic vulnerability maps will be useful to identify the susceptibility of flood prone Surat city against upcoming (flood) hazard, planning of mitigation strategies during flood risk assessment and to improve the flood resiliency of the society in near future.

In this study, a hypothetical dam break analysis is carried out at Umrar Dam, Madhya Pradesh, India to map the extent of flood and sensitivity analysis is conducted to find out the impact of dam break parameters on water depth and water velocity at four locations on the downstream side of the dam. An overtopping failure mode is selected based on the type of dam and historical failures of the dam. Different regression equations are used to estimate dam break parameters. The Hydrological Engineering Centre's River Analysis System 2D (HEC-RAS 2D) model was used to model and analyze the dam break flood based on the parameters of the dam break. To determine the effect of terrain resolution on the extent of flood inundation, the differential global positioning system (DGPS) was used to generate the following three different resolution terrains: SRTM-30 m, ALOS PALSAR 12.5 m, and 8 m resolution DEM. The terrain with high resolution (8 m) gave the maximum inundation area of 4.383 km2 which is 13.84% higher when compared with the low-resolution DEM of 30 m cell size. The effect of this dam failure is very high inundating 9 villages on the downstream fully or partially within 1.5 h of dam break failure with a maximum inundation depth of 16 m. The sensitivity analysis conducted by varying the dam break parameters (dam break bottom width, side slopes, break formation time) by ± 25%, + 50%, + 75% showed that their impact on water depth and water velocity is minimal on downstream side and limiting to only immediate downstream area, concluding that the dam break parameters estimated using the regression equations developed by Froehlich DC (2008) are optimum. However, the results at 0.4 km downstream of dam site shows that the water depth and water velocity values increase with the dam break bottom width.

Flood inundation mapping can assist with municipal and urban growth planning, disaster management, flood insurance rates, and ecological studies. Both the ability to forecast the behavior of the stream in question for various recurrence interval storm events and the ability to interpret the forecasted results into a plan-view extent of flooding are required for mapping a flood plain. Dam break was modeled and analyzed using the HEC-RAS model based on the dam breach parameters. The Hydrologic Engineering Center River Analysis System (HEC-RAS) can simulate flood events and generate water surface profiles along the length of a stream model. Using the companion GIS tool, HEC-GeoRAS, those water surface profiles can be easily converted to flood inundation maps. The type of dam and the dam’s historical failures is used to select an overtopping failure mode. Different regression equations were used to estimate breach parameters, and the final breach parameters for the dam were chosen, which were derived by Froehlich. In this study, two different types of DEMs were used: first, an Advanced Land Observing Satellite (ALOS) The Phased Array Type L-band Synthetic Aperture Radar (PALSAR) DEM with a resolution of 12.5 m, and second, an Shuttle Radar Topography Mission (SRTM) DEM with a resolution of 30 m. Both DEMs were compared, and it was discovered that the inundation area is larger for higher resolution. Finally, the downstream inundation area is calculated, and outflow hydrographs at key sites are exported to ArcGIS from the RAS mapper in HEC-RAS for analysis. The maximum depth map, maximum velocity map, maximum water surface elevation map, and minimum flood wave arrival time map were created for various bridges along the river on the downstream side of the dam.

Flood is the disastrous phenomenon of the nature, especially, when it is associated with large dams. The large dam is constructed for multipurpose use, however the major objective to operate to reduce the flood threat at downstream. In recent climatic uncertainty and extremity, dam operation is the challenging part for flood resilience. In addition, old dams have chances to break under extreme condition. To strengthen the resilience condition and improve the decision-making system, recent state-of-art to utilize a dam break analysis for prior threat detection. This is the case of dam break analysis, it has been developed for Madhuban large dam in Gujarat. The Hydrologic Engineering Center's River Analysis System (HEC-RAS) 5.0.7 version of hydrodynamic model in 2D environment is developed for studies. The digital elevation model, flood hydrograph and elevation capacity curve of dam has been utilized for building the model. The entire approach is simulated under the unsteady flow condition. The water surface elevation, water depth, velocity, arrival time, and inundation maps have been prepared under the guideline of Dam Rehabilitation and Improvement Project (DRIP). Probable future catastrophe has been identified and addressed for future resilience. The case will help to produce the flood mitigation strategies associated with dam break case in Gujarat.

Kokrajhar town is the headquarter of the Kokrajhar district as well as the headquarter of Bodoland Territorial Region (BTR) of Assam. BTR situated in the foothills of Bhutan and the northern part of the region faces common problems like flash floods, erosion, and crisis of drinking water. Many areas in Kokrajhar town submerge during the month of July–August every year. Prevention of urban flooding in Kokrajhar areas has become an important issue due to the hydrological impact on urban development. In this study, the author tried to investigate the causes behind the flood in the Kokrajhar town every year. Also, sustainable measures for flood mitigation in these areas have been chalked up. By physical survey, it is found that the existing drainage system of the Kokrajhar town is under construction and poorly maintained which led to the accumulation of stormwater or waterlogging. At present, the outfall points of the existing drains are on the Gourang River and the Tarang River through a major canal. Various hydrological factors are analyzed by ArcGIS. The stormwater drainage design works are proposed to be implemented in phases from the intermediate to future design period. A proposal for a drainage network has been made where there is no land available for constructing surface drainage. By monitoring the hydrological impact, the flow capacity of the existing drainage system is analyzed and compared with the proposed design drainage system.

The change in land use is going in a faster way in order to accommodate the changes in lifestyle and other socio-economic and infrastructural developments. Rural areas are getting converted to urban areas. The agricultural, barren and other non-productive lands are now used for residential purposes. The basic morphology of land use of an area is under a rapid change. The basic conversion output is a land which was earlier a permeable/semi-permeable area now converted to impermeable or negligibly permeable. Also there is a drastic change in rainfall pattern. The occurrence of short duration and peaky rainfalls is more. These intense rainfalls are the root cause of urban flooding as very less scope of permeability in land is there in urban areas. Few years ago, cities were there with ample scope of drainage of rainwater. But the behavior of same city is different at present era with lot of water logging on the residential and industrial areas. The swamps in the older cities were the places to accommodate the surplus rainwater of the city. These are natural depressions, obviously these also behave naturally. But due to large developments, we are filling these lands in order to be utilized for residential purposes. With the present developments and higher runoff coefficients, the runoff generation is more in an urban area. In order to avoid a probable water logging scenario and to develop a sustainable preventative solution, detention tanks are to be placed for efficient drainage management as well as ground water recharging. The study relates to temporal changes in land use of Bhubaneswar city in connection to the rainfall and corresponding water logging problem in conformity to the temporal variation in temporal land use and land cover.

Urban flooding is becoming a global problem due to changes in rainfall distribution patterns and inadequate infrastructure planning. We see many cities are getting flooded every year worldwide, including Pune, Chennai, Mumbai and Kolhapur in India. We carried out a review of research by different researchers with respect to land use–land cover change detection, the impact of urban sprawl in intensifying the flood hazard of the city, rainfall-runoff modeling using different software, effective storm water drainage management and urban planning legislation to control urban floods. We found that significantly less research is carried out to explore how urban planning is linked to urban flooding. Many times, urban flooding is considered as a result of excess rainfall only and effects of urban developments in the watershed are not considered. The traditional flood control measures will include regular corrective actions of local characters based on analysis done after each flooding. New urbanized areas will generate more runoff, and huge funds will be required to improve the working of structures and proper drainage. Still, it will not stop floods completely worldwide. There is a need for metropolitan region development authority at the early stage of city growth to coordinate effectively between different departments and urban local bodies. Hydrological studies of basins need to be carried out while planning for cities through development plan preparation and expansion of city limits considering growth pattern, increase in paved surface area and ultimately its relationship with runoff. Accordingly, stream sizes and networks can be planned for new urbanized scenarios and hydrological conditions. Different reservations should be proposed for urban facilities considering elevations, contours and flood modeling studies. We conclude that improved urban planning practices and newly updated legislations for urban development can control the endemic flooding problem in many cities in future.

Urbanization has expanded the use of impermeable surfaces, posing issues in dealing with the consequences of climatic changes, such as heavy amounts of precipitation and severity, making cities more vulnerable to urban floods. The study investigates the adequacy of the prevailing storm water drainage network of west zone of Surat city, Gujarat, India. The present study aims to the development of the intensity–duration–frequency curve, rainfall-runoff model, and 1D hydrodynamic model in MIKE+ using the existing topographic and storm water network data of west zone of Surat city. The developed model was used to simulate 2-year and 5-year return period rainfall event in order to determine the maximum discharge at the outlets using the time-area approach. The findings of the study revealed that the current storm water network in west zone of Surat city is insufficient to seamlessly divert the discharge produced by a 5-year return period, 2-h duration rainfall event, necessitating the augmentation of the current network of the west zone, Surat city in the future.

The flood disasters are responsible for causing huge losses across the globe whether tangible or intangible. The land use land cover (LULC) is one of the most important factors which influences the hydrological processes; thus, it is very much important to evaluate the effects of LULC on the urban floods. The Vadodara City in India is prone to very frequent urban floods and the most disastrous floods happened in 1994, 1996, 2005, 2014 and 2019 in the recent years. The goal of this study is to find out how LULC changes affect the flood of the Vadodara City. In the present study, image classification using ArcGIS has been carried out for accounting for the LULC changes. The LULC image shows the continuous increase in the urban sprawl throughout the Vadodara City. Rainfall-runoff model has been developed using HEC-HMS. For the evaluation of flood-influencing aspects, the current study analyses hydrological parameters using the LULC and curve number.

Urban flooding is a serious problem in many regions of the world, and it is a natural calamity that occurs every year. In India, urban flooding is increasing in many cities such as Mumbai, Bengaluru, Delhi, Hyderabad and Patna. Patna city is the congested urban society in Bihar, India. Frequent flooding has been observed in some areas of Patna city due to shrinking of open space, illegal construction, old and chocked drainage system, and lack of waste disposal facilities. Land use affects the urban flooding, and thus, the study of impact of land use on urban flooding is utmost important. In this study, impact of land use changes on urban flooding of Patna city has been studied using Erdas Imagine, ArcGIS, and SCS-CN method during the year 2005–2019. Rainfall data was used to compute antecedent moisture condition, and soil map was used to prepare HSG map. The runoff was computed using the SCS-CN method. The result shows that the change in land use with time affects the curve number and surface runoff. It was found that the built-up area was increased by 22.82% and agriculture land was decreased by 15.48% between 2005 and 2019. During the year 2010–2015, there was a significant change in land use and runoff was increased from 16.8 to 23.72%. This study identified the significant impact of the land use on runoff and consequently on flooding.

Flooding is a widespread, recurring, and devastating natural hazard that occurs all over the world. Estimating stream flow has a significant financial impact because it can aid in water resource management and provide protection from water scarcity and potential flood damage. The objective of the study is to carry out a flood frequency analysis of the lower Tapi River Basin, Surat, and to assess which method is more suitable for finding the return period of particular peak discharge. The lower Tapi River Basin is subjected to severe floods during monsoon times. Gumbel's distribution method, Log Pearson Type III (LP3), and Generalized Extreme value probability distribution methods were employed for simulating the future flood discharge scenarios using annual peak flow data (1980–2020), i.e., 41 years from one gauging station (Nehru Bridge) of the lower Tapi River Basin. As a result, a frequency analysis was carried out to correlate the magnitude of occurrences with their frequency of occurrence using a probability distribution. The estimated design floods for different return periods (Tr), such as 2, 10, 25, 50, 100, 150, and 200, were obtained and compared. At a 5% significance level, three goodness of fit tests were used to the fitted distributions: Chi-squared, Kolmogorov–Smirnov, and Anderson–Darling. Based on the above study, it is concluded that Gumbel’s Distribution method is more reliable for the lower Tapi Basin compared to the other two methods. Hydrologists, water resources engineers, and floodplain managers will all may benefit from the study's conclusions.

Different statistical criteria used for selecting the best fit for distributions are usually “biased” against the tail (large extreme events) as they give more weightage to the central tendency of the distribution. The extreme events are generally designated as the improbable events or outliers having less frequency of occurrence, resulting in the erroneous estimation of their magnitude and frequency. The present study evaluates the usefulness of the decision support system (DSS) to find a suitable class of probability distribution functions depending upon the tail heaviness. DSS analyzes the tail behavior of the sample data based on various graphical methods, viz., mean excess function plot, hill plot, log–log plot, max-sum ratio plot, and concentration profile. Once the distribution class is identified, the best fit distribution from various distributions in the class can be explored. The utility of the DSS is demonstrated through an application to the extreme precipitation data over the Mahanadi River basin. We have considered the gridded precipitation data obtained from the Indian Meteorological Department (IMD)-Pune having a resolution of 0.25°. Results show that almost all the graphical techniques combined to form a decision support system allow us to discriminate the exponential tail with a heavy tail, and one should rely on more than one graphical method for rational conclusions.

An efficient modification of the Muskingum method of flood routing has been verified, which yields the coefficients of Muskingum flood routing equation directly without the use of the graphical procedure. A simple conceptual model of lateral inflow has also been incorporated to account for any lateral inflow or outflow that occurs in the given reach. The incorporation of lateral inflow has been considered through a lateral inflow parameter along with the standard storage and weighing parameters, K and x. It also presents a much effective and direct approach for estimating the routing coefficients for the Muskingum model. Application of this extended Muskingum method has been verified on Karun river of Iran and the respective 6-h hydrograph has been plotted. It showed that the usual curb on the routing coefficients to sum to unity is not applicable in case of lateral inflow. The estimated outputs showed close correlation with the observed outflow.

Flood forecasting plays a key role in the reduction of economic as well as life losses and is considered a challenging task in hydrology. Controlling the occurrence of extreme flood events is not in our hands, but deteriorating the losses is still conceivable. In India, the flood forecasting for most of the basins is based on the deterministic approach which needs to be strengthened for the early warnings and relief measure strategies. Over the world, the focus of the hydrologists and researchers is shifting in the direction of the implementation of ensembles of numerical weather predictions (NWP) for operational flood forecasting. India has made great achievements in building an ensemble prediction system for weather forecasting. Precipitation forecast is available at several spatial and temporal resolutions, but still, it needs improvement in the case of urban and smaller catchments. The paper discusses the need for the development of an integrated approach to hydrologic ensemble prediction system using meteorological forecasts, hydrological and hydraulic modeling, and post-processing for reliable early flood warning systems in India.

Flood is the most common and widespread natural severe weather event. A flood occurs when water levels rise over the top of river banks. In recent times, several Indian coastal cities such as Surat, Mumbai and Chennai have witnessed unprecedented flooding due to various causes such as heavy downpour, releases from the upstream dams, poor urban planning. In the urban flood-prone areas, it is essential to estimate the peak flood, time of peak, flood response of contributing catchments for planning, riverfront development (RFD) works, etc. The extreme rainfall depth and the catchment physiographic characteristics are required for the estimation of peak flood. Surat is one of the cities of Gujarat, situated in Lower Tapi Basin (LTB). The LTB is a flood-prone area and also witnessed at least ten major floods in the past century out of which the worst one was 2006. In view of the above, Surat Municipal Corporation (SMC) has a proposal of RFD for Tapi with in Surat City to minimize the devastation due to flooding as well as improve the aesthetic view. On request of SMC, CWPRS carried out flood estimation study for RFD works of Tapi. The present paper is a case study related to flood estimation at location of interests on Tapi, i.e. Kathore Bridge, Singanpur Weir and ONGC Bridge. For this study, delineation of LTB sub-catchments (i.e. downstream of Ukai Dam) and extraction of the physiographic parameters and also extreme value analysis IMD rainfall data were carried out. Estimation peak flood of contributing catchments of LTB for 25-yr, 50-yr and 100-yr return periods were carried out by adopting the CWC flood report (sub-zone-3B). Further, the peak flood of LTB catchments and Ukai Dam discharges were considered for the estimation of peak flood at location of interests.

The present study examines the purpose of interlinking of rivers, which benefits mankind. It primarily focuses on interlinking the rivers by creating a system of manually developed canals where the river water is not attainable. The proposal is based on diverting the surplus water from the rivers receiving the high floods to the deficit rivers by connecting the manually developed canals. So, it will assist in diverting surplus water to the deficit rivers in case of necessity. The idea is to design canals that connect the rivers Godavari, Krishna, Pennar, and Cauvery to control floods and use surplus water for irrigation and other purposes. Manning’s method is used for the design of canals. Flood frequency analysis has been shown for these four rivers. This analysis played a major role in executing the plan. According to the flood data, the rivers Pennar and Cauvery have had very low floods over the years, whereas the rivers Godavari and Krishna experience the high number of floods. So, the flood water is set to be diverted to the rivers Pennar and Cauvery. These auspicious results have enlarged the potential of success in planning. The main objectives are to draw water from the Godavari River to the Krishna River (Detailed notes on “Krishna River” by Wikipedia), from the Krishna River to the Pennar River, and from Pennar River to the Cauvery River. This can be ended by linking the reservoirs situated across these rivers by the link canals.

Optimization in the design of spillway and energy dissipator is one of the crucial parts of the safety of the dams. Most of the hydropower projects are planned/under construction/commissioned in the north and north-east region due to high hydropower potential. Due to the steep slopes and fragile geology, the soil erosion rate is high during snowmelt and monsoon causing severe sedimentation problems. Considering topography, geology, and other site constraints, the design of a spillway is a challenging task for the design engineers. The design of the spillway for each project is unique and site specific. Physical model studies are an indispensable tool for analyzing the flow and optimizing the design of various components of spillway before execution at the site. The present paper emphasizes the role of the physical model to optimize the design of spillway and its appurtenant structures for the Arun 3 dam spillway, Nepal, which is under construction at the site. The sluice spillway is designed for passing the flood and flushing of sediments from the reservoir. Considering the dual purpose of the spillway, extensive studies were carried out for various ranges of discharges up to design discharge of 15,710 m3/s for gated and ungated operation of spillway at CWPRS, Pune. Parametric studies were carried out especially for optimizing the design of ski-jump bucket considering the various upstream reservoir water levels and downstream tail water levels to achieve the satisfactory performance of energy dissipation. The findings obtained from the studies for the said project are discussed in detail in the paper. The physical model studies became useful to design the structure economically and hydraulically efficient.

Auxiliary spillways are generally provided to supplement the main or service spillways for augmenting the discharging capacity and will be operated when floods in excess of the capacity of the service spillway are to be encountered. Though they serve as secondary spillways, the functions of auxiliary spillways extend to flushing of floating debris, floating ice formations from the reservoir, especially in Himalayan regions where ice formation is expected due to climatic conditions. The energy dissipators for these spillways are different from that of the main spillways and are governed by site specific conditions. Overtopping has been the most common cause of failure of embankment dams due to inadequate spillway capacity in most of the cases. Failure of dams thus becomes a major concern in providing safety assurance and rehabilitation. It is of utmost important to estimate the design outflow flood/PMF accurately with the latest available methods/techniques to design the spillways for flood management. Providing additional spillway/auxiliary spillway with proper design along with the service spillway at the conceptual stage of the project itself perhaps will avoid the problem of reassessing the spillway capacity of existing dams and providing alternative solutions to manage the exceptional flood events as is being done in recent times for existing projects. Provision of additional spillway/auxiliary spillway needs hydraulic model testing for adopting the most efficient and techno-economically feasible design. This paper describes the hydraulic model studies conducted at CWPRS, Pune, for few hydro power projects wherein various hydraulic aspects considered for evolving safe and efficient design of auxiliary/additional spillways that forms part of the main spillways and efficacy of the energy dissipators of these spillways for managing the flood.

The ski jump spillways with ski jump buckets are used commonly to deflect the jet far away in downstream spillways when it is not possible to provide a hydraulic jump type dissipator. The bucket deflects the high velocity jet into the air and discharges into a plunge pool at a considerable distance away from the toe of the dam. To safeguard the dam structure, it is very important to predict the pressure on the plunge pool bed. The characteristics of a jet influences the energy dissipation and pressure on the bed of the plunge pool. In the present study, parameters related to the characteristics of a jet were measured, and pressures on the bed of the plunge pool were estimated with different empirical formulae or plots given by various researchers obtained through experiments or scale models.

The approach channel is meant for diversion of flood towards the spillway. Proper alignment of approach channel minimizes oblique flows in the approach channel and in front of spillway and also improves the discharging capacity of spillway because of favourable approach flow conditions and also, avoid endanger of spillway abutments. An upstream guide bund contributes to this by smoothly guiding the flow towards spillway thereby improving the flow conditions infront of spillway. CWPRS, Pune carried out hydraulic model studies on a geometrically similar 1:140 scale Froudian model of spillway of Polavaram dam to optimize the layout of approach channel and guide bund. Various alternatives of approach channel and guide bund have been incorporated and model studied on the model of spillway to assess the flow pattern in approach channel and performance of upstream guide bund for different flood conditions. The layout comprising of about 2000 m long approach channel with width varied from 1000 m to 450 wide (at narrow section) with 500 m long straight guide bund was recommended. The model studies showed that, with this layout, there was reduction in the velocities near left abutment of spillway when compared with other layouts. Frequent and periodic formation of swirling flows in front of spillway; vortexes shedding along the guide bund, sharp rise of water surface on the outer boundary of vortices were eliminated. Water surface profiles were contained in front of spillway piers and overtopping was eliminated. On the upstream of spillway, maximum velocities of the order of 1.6–7.7 m/s were observed along Ch. 100 m. The layout has been adopted by the project authorities and construction of project is in progress. In this paper, the authors explained the results of hydraulic model studies conducted on various layouts approach channel and guide bund of Polavaram irrigation project, Andhra Pradesh.

Gate lip angle is defined as the angle which is given by the ratio of vertical distance as measured between the skin plate bottom edge and the bottom edge of gate, to thickness of gate as measured from the upstream face of gate bottom edge to the upstream edge of skin plate bottom edge. Gate lip angle has a profound influence on gate vibrations, cavitations and down pull of the gate. Hence lip angle of the gate plays an important role in the design of gate structure. It is unfortunate that in spite of many hydraulic model studies over the years by eminent researchers on a variety of practical and impractical gate bottom lips, no guidance is available to the practical gate designer to determine gate lip geometry. So the model study on gate lip has its own importance so far the gate design is concerned. This paper provides case studies guidelines to know the performance of lip angles from the model study. The results of model studies on geometry of lip angle are presented in this paper. The information from the model studies might be useful to the designers and could be taken as reference for similar type of geometry of lip angle study in future.

The Himalayan region is blessed with perennial rivers and heads required for hydropower generation. This blessing comes with challenges like flash floods, cloudbursts, high sediment load, etc. Low-level spillways, in the form of orifice spillways, are an oblivious choice in this region considering their capacity to flush the sediments during floods. Special considerations for the design of energy dissipators are required for orifice spillways. As an energy dissipator, ski-jump buckets are used in most spillways where tailwater depths are shallow for hydraulic jumps to form downstream of spillways. Most commonly, scour holes occur downstream from the point of impingement of the ski-jump jet. These retrograding scour holes may become a threat to the spillway structure itself and hence need to be assessed carefully. To prevent an uncontrolled erosion of riverbanks and the river bed, a preformed plunge pool is provided. Taking into consideration the geological features at the site and the water jet impact location, the size, location, bed level and the slopes on both flanks of the plunge pool are decided. The physical model studies have traditionally been used to predict equilibrium scour depth and its location and extent. Despite the qualitative nature of these studies, past experiences suggest that the ultimate scour is realized in the prototype after a long period of operation when the rock fragments and behaves as non-cohesive material. Dimensions of the plunge pool including location, width, length, depth and upstream and downstream slopes can be worked out using the model observations. Two such case studies are discussed in this paper where the effect of hydraulically optimized plunge pool in substantial dissipation of kinetic energy of incoming flow jet and reduction in water level fluctuations in the powerhouse tail pool located just downstream of the spillway was observed.

A labyrinth weir allows more flow for a given head and channel width relative to other linear weirs due to the additional crest length. Earlier research explored the correlation between discharge magnification ratio to head to weir height ratio for a different configuration. Discharge coefficient depends on head to weir height ratio, crest shape, crest thickness, apex configuration, and sidewall angle. Continued efforts have been made to develop an equation for discharge coefficient in terms of these parameters. Several equations relating discharge coefficient with head to weir height ratio using polynomial fit up to sixth order for each side wall angle are available in literature. Some investigators related the coefficients of polynomial with side wall angle resulting in a complex form of equation for the discharge coefficient. An attempt has been made to develop a relatively simple discharge coefficient equation involving lesser number of coefficients in terms of head to weir height ratio and sidewall angle. Some of the salient features of the study are described in the present paper.

Government of Gujarat has major proposal of development a multipurpose project, Kalpasar in the Gulf of Khambat. This project consists of constructing a 30 km long dam and concrete spillway of about 2.3 km length with 105 numbers of gates. After completion of this project, it is estimated that about 10,000 mm3 of fresh water could be made available to the Saurashtra Peninsula; along with this other benefits were perceived related to use of the dam to support a transportation link between Surat and Bhavnagar districts, to fisheries development etc. Since year 1995 various feasibility and other studies had been carried out for the project by various research and academic institutes. Various studies are also under progress at CWPRS for the development of Kalpasar project; one of them is hydraulic physical model study to finalize the design of spillway by simulating discharge over spillway along with the effects of sea waves on the downstream of the dam. This dam spillway cum wave basin is a captive model housed in hanger of size 60 m × 40 m and developed to the scale of 1:55 G.S. (geometrically similar). In this model at one end spillway with about 90numbers of gates and on downstream of spillway at a distance of 31.79 m (about 1750 m in prototype), a unidirectional random sea wave generator having wave flap of length 33 m controlled by SCADA is proposed. On this model, it is proposed to test discharging capacity of spillway with full and partial operation of gates along with performance of energy dissipater for various tidal levels with superimposition of waves, water surface profiles for entire range of discharges, pressures over spillway surface under the influence of waves and tides for entire range of discharges. This paper presents the glimpses of the hydraulic design of dam spillway cum downstream wave basin physical model for Kalpasar.

The hydraulic design of the pipeline is generally evaluated for its hydraulic functioning, which involves the assessment of passing the design discharge through it. It depends upon the adequacy of gross head and pipe diameter; precautions need to be taken to avoid water hammer in the pipeline, avoidance of negative pressure, avoidance of air-entrainment. The application of the energy equation shows that parameters such as discharge, pipe diameter, head loss, gross driving head, surface roughness of pipe are interdependent. Design period of the project and aging of the pipeline affect surface roughness and friction losses in the pipeline. The verification of the adequacy of diameter (for pipe with given flow rates, length of pipeline and available gross driving head) involves determination of friction factor with necessary allowance for ageing and calculation of head loss due to friction and form losses. Friction loss refers to fraction of pressure lost by flowing fluids through a pipeline. Form loss is due to the obstructions present in the line of flow, it may be due to change in alignment, may be due to a bend or a control valve or anything which changes the course of motion of the flowing fluid. Desk studies were conducted in CWPRS, Pune to assess hydraulic suitability of MS Pipeline of right bank main canal (Telangana canal), which is intended to divert 6.527 m3/s irrigation water to Telangana. From desk studies, it was found that, considering the roughness coefficient of epoxy enameled steel pipe line as 0.89 mm, the proposed diameter of pipe of 2 m and parallel pipes of 1.6 m each were found to be adequate to carry the design discharge with the available gross head of 16.25 m and the Project is under construction.

Stilling basin with a low Froude number in the range of 2.5–4.5 is associated with appurtenances like chute block, end sill, etc. These auxiliary devices are provided as additional measures for improving the efficiency of the hydraulic jump in the basin. Experiments were conducted on the 2D sectional model of the Polavaram Irrigation Project at CWPRS, Pune, for testing the performance of spillway and energy dissipator. The effect of adding a chute block was compared with the performance of spillways without chute blocks. The objective of the study was to compare energy dissipation in the stilling basin of Polavaram Irrigation project, AP, for spillways provided with chute blocks and spillways without chute blocks.

India being a developing nation, the requirements increase day by day which leads to the crisis of resources. Energy sources are mostly affected because of increase in the mechanisation and different development schemes. Specially if we talk about the energy sector, the increase in the demand is just an effect of urbanisation. As someone said very right, “Everything comes with a price”, so the question is what price you willing to pay? Ample amount of production and distribution of energy becomes a major task today. The environmental aspect and continuous depletion of fossil fuels concern its availability in future and force it to look forward to alternative sources. Sources of energy which are considered to be renewable like hydro, wind and solar can become a boon for the future generation. Currently, in India, the energy contribution by hydropower by utilising water potential is around 12.4% (including small hydropower) of total energy generation, whereas renewable sources share up to 18%. So, there is a need for proper functioning and sustainable methods where the renewable sector can be uplifted. In India, hydroelectric energy capacity is roughly calculated as 148,700 MW having load factor of 60%. In India, the overall hydroelectric power for FY 2019–20 was 156 TWh (excluding SHP) having average CF as 38.71%. This paper reviews major literature on the generation capacity of hydropower. A review on different alternatives available to fulfil the energy demand and to investigate the different types of correlations developed by previous investigators. The study also focuses on small hydropower development its benefits and cause. In India, small hydropower plants contribute around 4671 MW of electricity, and around 526 MW is under construction. Using small hydropower can make a sustainable growth in the energy sector. Furthermore, the study also put forward the suggestions for development in the energy scenario along with policies offered by the government.

A seismic network of microearthquake recorders around a proposed dam site is required to establish to assess the seismicity of the project area. Microearthquake studies are useful in delineating active seismic zones and to assess the seismic potential of the faults in the area which is utilized for selecting suitable location of the project. This paper is based on the study conducted for Sawalkote Hydroelectric Project, Jammu & Kashmir. Seismological network of six observatories at and around the dam axis within the radius of 50 km has been established by installing broadband seismographs for microearthquake measurement in the project area. The seismic activity has been recorded for a period of six months. A total of 387 earthquakes have been recorded within the radius of 200 km with varying magnitude from ML 1 to ML 4.9 from the project site. The ‘a’ and ‘b’ value obtained are 3.323 and 0.516, respectively.

The state of Uttarakhand is situated in the upper reaches of the Indian sub-continent. It is also locally termed as—Dev Bhoomi as it houses many of the famous temples attracting millions of tourists and pilgrims from within and outside the country. This state is also blessed with rivers fed by natural glaciers as well as rains contributing to a huge hydro-power potential. (UJVNL) The main source of income for the state is through hydro-power development and tourism. The state having a hilly terrain does not support the establishment of large industries, and hence, migration is increasing year by year. Thus, promoting hydro-power production and promotion of tourism are some of the feasible options for economic development. If hydro-power development is scuttled, it will be difficult to arrest mass migrations from these states. Uttarakhand has a hydro-power potential of the order of 20,000 MW against which only about 3164 MW (16% approx.) has been harnessed so far (Agarwal and Kansal in Water Energy Int 59, 2017). The state is gifted by nature with rivers like Ganga, Yamuna, Kosi providing an ideal location for hydro-power development. Unfortunately, most of hydro-power projects under development were stayed by The Supreme Court of India (2013) after Kedarnath flood disasters that occurred in Uttarakhand in June-2013. Situation has worsened further after the current Chamoli flood in Feb-2021. In the present paper, authors have discussed about the above flood disasters and their impact on hydro-power development in the state.

Effective and efficient practices towards structural management are necessary in order to get appropriate solution to problems pertaining to the maintenance, rehabilitation and safety of hydraulic structures. Majority of the present hydraulic structures in India are withering due to age and hence pose structural deterioration and distress. Suitable planning, assessment and diagnosis are necessary in order to decipher the cause, so as to implement suitable remedial measures to repair and ensure their safety. Distresses in the body of the dam and canals, viz. fissures, volume expansion, deformation, etc., may lead to structural failure, which can be catastrophic both in terms of property and life. The risk of structural failures can be reduced by regular inspections and monitoring, identifying the deficiencies or flaws and accordingly implementation of a comprehensive rehabilitation measure. In the recent past, the awareness towards dam safety has encouraged the development of numerous techniques, which are capable of identifying the location of seepage through body or foundation of hydraulic structures, hence preventing them from disaster. Here the authors have highlighted the effectiveness of an integrated approach towards deciphering of seepage, through well logging and tracer study in hydraulic structures; and the remedial measures with relevant case studies. Borehole logging and tracer study forms an integral part of non-destructive technique (NDT); hence, they can be extended for delineating the path of seepage through any hydraulic structure(s).

Hydropower, an important and widely used renewable source of energy, has the ability to generate electricity without emitting greenhouse gases thereby providing pollution-free electricity to the human being. As a majority of hydroelectric projects are constructed on dams, it is often necessary to assess the health of the structure and take steps towards attaining its safety. Although a large number of causes may lead to failures of dams and hydroelectric plants, weather events like storms and hurricanes that result in natural flooding and landslides are a major concern. In addition to widespread loss of life and property, the consequences of these natural events often result in seepage problems, either during the pre or post construction stages. Hence, locating the source and path of seepage and incorporating suitable remedial measures plays a significant role in assessing the risk and uncertainty in hydropower development and management. During the construction of Ghatghar Hydroelectric Project, Maharashtra, heavy monsoon caused a natural landslide ensuing heavy seepage at many locations in the approach tunnel of the powerhouse. As this could affect in loss of electricity generation, it was important to establish the source of leakage and delineate the path. Accordingly, tracer studies were undertaken to for identifying sources of seepage by establishing interconnection, if any, between the seepage points in the approach tunnel and the intake of reservoir. This paper signifies the utility of “Tracer Techniques” as a diagnostic tool for seepage mapping and suggesting suitable remedial measures to mitigate it.

Seepage and its control measures are important aspects during the design and construction stages of earthen dams. Despite the fact that all dams are designed to lose some water through seepage, it is always a matter of concern when water finds its way out through a weak area in the dam or works its way through the foundation or abutment, as it can pose a threat to dam safety. This seepage problem will lead to instability of embankments causing sloughing of slopes due to the rising pore water pressure and internal erosion which may further cause piping of embankments. Generally, the seepage analysis is carried out in earthen dams to analyse the phreatic line, the pore pressure within the dam or its foundation, the exit gradient at the downstream face of the dam and the amount of seepage flow that may pass through the dam’s cross sections. Excessive seepage in earthen dams could ultimately lead to its failure. Dam seepage detection often requires integrated use of different techniques. Among these, dye tracer techniques are often always necessary as they are an economic and proven tool providing a detailed perspective into dam seepage investigations. These non-destructive tracer tests facilitate in identifying seepage zone and probable path both qualitatively and quantitatively. The main objective of this paper is to highlight the significance of dye tracer techniques for identifying the seepage in earthen dams along with some important case studies carried out by CWPRS in Kota Barrage, Rajasthan; Rockfill Dam at Sardar Sarovar project, Gujarat; and Salaulim Dam, Goa. The application of these tracer techniques was useful in pinpointing the seepage prone zones, and suitable cost-effective remedial measures were recommended to mitigate the seepage.

A weir is an overflow structure that is constructed across or parallel a river or open channel flow to measure or control the discharge. Weirs may be classified based upon their shape, nature of discharge, width of crest, and nature of crest. The crest length of an arched labyrinth weir is extended by the arch and the provision of notches. In this work, gene expression programming (GEP), a substitute for the traditional regression technique, is persented to estimate the coefficient of discharge (Cd). The experimental data collected from literature has been used for training and validation of the GEP model. Utilising a set of statistical metrics, the proposed GEP models outputs for both the training and validation stages are assessed. Performance of the GEP model is compared with traditional equations-based regression model.

A rectangular basket assembled from a hexagonal mesh of heavily galvanised steel wire, filled with rock stacked atop one another to form a weir structure, is known as a Gabion weir. They are porous structures that can sometimes be vegetated and are considered an aesthetic structural solution with minimal habitat. Recently, the stepped gabion weirs have become a popular structure replacing stepped spillways that can check floods. The performance of an artificial neural network, one of the robust machine learning techniques, is investigated in predicting the inverse relative energy dissipation of the stepped gabion weir. The proposed ANN model in the present study is then compared with different machine learning techniques available in the literature. Based on performance parameters, it is observed that the proposed ANN model has the highest accuracy compared to the GMDH and GEP models in predicting the relative energy dissipation of the stepped gabion weir.

Morning glory spillway is one of the water conveyance structures from the reservoir to downstream and is named due to its horny shape. In this type of spillway, water passes through a vertical shaft, horizontal or nearly horizontal tunnel, and joins the downstream river channel. They are used advantageously at dam sites in narrow canyons with steep abutments. The cost of construction of the morning glory spillway is low due to the use of a diversion tunnel constructed at the time of dam construction as a horizontal tunnel. This paper gives an overview of the morning glory spillway in respect of its hydraulic design considerations and different hydraulic aspects that need to be studied in evolving the efficient design of the spillway. The paper presents the desk study of the tunnel spillway of Lakya Tailing Dam, Kudremukh, Karnataka, studied at CWPRS, Pune, along with the discussion of the behavior of the spillway at the project site. This dam plays a vital role in running the Kudremukh Iron Ore Plant. At the project site, vibrations were experienced while passing the discharge over the morning glory spillway inlet. CWPRS carried out the detailed desk studies considering theoretical design considerations and recommended to provide aeration pipe on the spillway crest and suggested strengthening of morning glory inlet shaft. The study is discussed in detail in the present paper.

Non-destructive testing (NDT) method plays a significant role in the qualitative assessment of civil engineering structures. NDT is defined as the method of inspecting, monitoring and evaluating the strength properties of various types of civil engineering structures without damaging the structure. It is a very safe, fast, cost-effective, and efficient method for assessment of properties of a material. NDT methods are based on the assumption that certain physical and chemical properties of a material can be linked to structural strength and durability. There is a phenomenal rise in construction activities in the field of civil engineering in the recent few years. Testing and quality control are essential at various points throughout the life of construction to ensure its safety. Most significant structures, such as buildings, bridges, and dams, are subjected to extreme stress conditions all the time, and their performance is likely to alter over time. As a result, NDT methods must be used to examine the structural safety of these structures. In the present paper, the most commonly used NDT methods such as rebound hammer, ultrasonic pulse transmission, impact echo, and resonance frequency test methods used for assessment of quality of various types of civil structures have been discussed and illustrated. The fundamental principles of these methods are also explored in regard to their potential.

Hydraulic structures such as dam, powerhouse, aqueduct, and barrages or any other structures are designed to withstand certain level of vibration. These structures produce particular signature of vibrations. A change in the signature of vibrations in these structures or its parts indicates the presence of abnormality. Powerhouse operation is one of the main reasons of vibrations in the dam structure and powerhouse civil structure; thus, periodical vibration monitoring due to operation of generation unit will enhance the performance of the generation unit by minimizing the chances of sudden failure. The effects of vibration sometimes can be very severe. Excess level of vibration can cause reduction in efficiency of generator machinery and may damage the unit. Vibrating machinery can create noise, cause safety problems, and lead to degradation in plant working conditions. Hence, monitoring of vibration gives important information about the structural safety of these structures which helps to take remedial measures for reducing vibrations. The present paper is based on the details of the vibration measurement studies carried out for safety of dam and powerhouse structure during the operation of Unit No. 3 of Kadana Hydroelectric Project, Gujarat, in generation as well as in pump mode condition. Vibrations measured at preselected locations, viz. dam top, near penstock gate, inspection gallery, penstock gallery, generator floor, turbine floor, and turbine pit and at draft tube gate during the operation of Unit No. 3 both in generation mode as well as in pump mode under different operating conditions. Various available international standards have been reviewed to recommend the safe vibration level for the safety of dam, powerhouse structure, and the generation unit. Based on analysis of the vibration results, it has been found that the observed vibration levels are well below the adopted safe vibration levels of the respective structures.

In India most of the dams have become aged. Due to ageing, various distresses have been observed in these dams which has raised apprehensions about structural safety of these dams. For assessing structural safety of the dam’s in-situ material properties are required as input parameters. This paper is based on such a study to determine in-situ strength parameters of stone masonry of Massanjore Dam, Jharkhand. Field studies by flat jack tests were carried out by CWPRS, Pune to compute in-situ stresses, static modulus of deformation and Poisson’s ratio. Evaluated compressive strength of masonry for applied pressure was compared with design strength. The evaluated modulus of deformation, Poisson’s ratio and compressive strength are used for carrying out stability analysis of dam. Six flat jack tests (5-horizontal and 1-vertical) each were conducted on downstream (D/S) face as well as on upstream face (U/S) in random rubble stone masonry. Average Em values by flat jack test for random rubble stone masonry was 12.95 and 15.90 GPa for downstream and upstream faces, respectively. Average Poisson’s ratio values by flat jack test for random rubble masonry was 0.215. The range of evaluated compressive strength of masonry for applied pressure was ranging from 50.09 to 92.28 kg/cm2.

Dams are an integral part of a nation’s assets that provide various benefits in the form of irrigation sources, drinking water supply, flood moderation, power generation, recreation, maintaining flow in the river, industrial use, etc. In addition, there are instances that the dam tops also serve as roads for public transportation thereby causing additional vibration load on the dam body, which is random, periodic or dynamic in nature. Though these forces are minute in nature, yet capable of causing distress in the dam body over the service period of the dam. Anticipated damages on account of failure of dams can be in terms of loss of life, loss of property, natural environment, etc. apart from hampering economic development. Ageing dams need extra care due to distress and long-term stability issues. This paper highlights the potential of vibration engineering technique to monitor the operational safety of the structure over periodic intervals and nondestructive assessment of the quality of concrete. One such hydraulic structure that serves as road for public transportation is the Umiam Dam, forming a part of National Highway-40, linking states in the north-eastern region. Owing to transportation use of the dam top since decades, vibration measurements and in-situ quality assessment has been conducted, to verify the operational safety of the structure. With ever-increasing traffic, owing to economic developments, it is anticipated that distress in the structure may increase abnormally that warrants for prior remedial measure such as diversion of bulk carrier through an alternate by-pass road to safeguard the dam.

Dams are important water resource projects because they provide water for irrigation, hydroelectric power, domestic and industrial needs, fisheries, navigation and recreation activities. Dams are generally constructed in hilly terrains. These dams are susceptible to be affected with earthquake forces, and hence, the safety of dams against earthquake loads is an important aspect during assessment of stability. Failing to consider the earthquake loads at design stage may result in under-safe dam construction which may cause damages in the dams during seismic activities. Dam failure may lead to loss of lives and properties resulting huge economical loss. The safety of dams is required to be ensured by applying the site-specific seismic design parameters during design of the dam. In this paper, the site-specific seismic design parameters obtained by deterministic and probabilistic seismic hazard assessments for Bhatsa dam, Maharashtra, lying in seismic Zone-III, are presented.

The current research focuses on the dynamic study of the 260.5 m high Tehri dam, which spans the Bhagirathi River in India’s Garhwal Himalayas. Since it was constructed in seismic zone-IV, there is a significant risk of an earthquake with a magnitude of 7–8.5 or more on the Richter scale in the area. Earthquakes with hypo-central distances of 50.6 km and 89.7 km from Tehri region occurred in the years 1991 (Uttarkashi earthquake) and 1999 (Chamoli earthquake), respectively, according to the data stored in Strong-Motion Virtual Data center (VDC). Hence, the repetition of such seismic activities in the Tehri region is highly probable. In this paper, numerical modeling is carried out using finite element analysis-based ABAQUS software to simulate a magnitude 7.8 earthquake in Nepal and calculated spectral accelerations. Response spectrum graphs are prepared using SEISMOMATCH, which are validated with IS: 1893:2016 (PART-1), and the spectral accelerations are scaled to 7.8 magnitude Nepal Earthquake in the Himalayan belt, with the help of which maximum acceleration is calculated. Finite element method and approximate methods are compared to obtain the crest acceleration in dam and give satisfactory results.