Coastal, Harbour and Ocean Engineering

Vegetation along a coastline could significantly protect the foreshore area from natural disasters such as storm surge and tsunami. In these circumstances, the flexibility of the vegetation stems in the green field belt is understood to play a predominant role in the dissipation of momentum of the approaching waves. Complication in modelling the rigidity of the plantations, both experimentally and numerically, is the leading cause of insufficient knowledge on vegetation modelling. Group of cylinders in vertical direction is expected to reiterate the typical characteristics of emergent vegetation. In the present study, characteristics of wave transmission with respect to relative water depth, wave run-up on slope, surf similarity parameter, and vegetal resistance under the action of regular waves were studied.

A breakwater structure is designed to absorb the energy of the waves. Design of flexible rubble mound structures is complex as it involves various aspects such as complex wave-structure interaction, interlocking characteristics of armour, friction between armour and secondary layer. Several empirical formulae such as Hudson formula and Van der Meer formula are available for preliminary or conceptual design of unit weight of armour. It is a universal practice to finalize the section of breakwater based on hydraulic model tests in wave flumes/wave basins to confirm the conceptual design evolved using empirical methods. The hydraulic model tests are essential to simulate the complex wave-structure interaction as well as correct prototype site conditions of seabed slope, water level, etc., can be simulated in the wave flume or wave basin. This paper outlines the approach to these studies and discusses the relative merits of the concepts considered for repairing or restoration of the damaged structures. In 1973, the Maharashtra Maritime Board (MMB) had constructed breakwater of 457 m length for development of Bhagwati Bunder Port, Ratnagiri and since then it has been serving the port by providing the tranquil conditions in the harbour area. However, due to action of hostile forces of waves over the years and being the flexible rubble mound structure, the breakwater has suffered considerable damage. In this context, the MMB has proposed to restore the existing breakwater and also extension of 200 m for prevailing wave tranquillity inside the harbour basin, approached Central Water and Power Research Station (CWPRS), Pune to conduct wave flume studies for design of restoration works. The conceptual design of breakwater was worked out using empirical methods. The wave flume was carried out for its hydraulic stability of restoration of existing breakwater and also for proposed extension of 200 m breakwater at various bed levels. The cross-section consists of 12 t tetrapod units in the armour layer from the root to (−) 9 m bed level for trunk portion. The section consists of 15 t tetrapods in the armour for roundhead portion of breakwater at (−) 9 m bed level have been suggested. The sections were found stable up to a significant wave height (Hs) of (+) 5.0 m and design maximum breaking wave height of (+) 6.35 m (H1/10). The details of studies for the restoration of damaged breakwater at Bhagwati Bunder Port have been discussed in this paper.

In the field of ocean engineering, rogue waves have been a critical phenomenon demanding attention over the past few decades, with their visible occurrence and their influence on the marine structure being repeated. The random isolated extreme events have posed a challenge in our ability to develop a well-defined description of such waves. There have been several studies in the past on the simulation of these events in 2D using experimental facilities and numerical tools with different theoretical approaches. However, completeness in the description of the extreme events is questionable owing to the non-consideration of their directionality. The three-dimensional studies are predominantly numerical in the literature, and 3D laboratory studies are scanty due to the challenges involved and thus, leading to an incomplete description of the rogue waves and their characteristics. A comprehensive theory should represent a physical representation of the scenario and simulate these events in numerical or experimental work. Based on this background, one could provide a wave field statistical distribution. However, we are yet to reach and gain an insight into the phenomenon. Nevertheless, it is imperative to understand where we are and the central questions to achieve the target. This paper is intended to give a comprehensive review of literature narrowing down to simulation challenges and the generation of these three-dimensional waves in laboratories. Furthermore, a simplified method used to generate the focused directional wave in deep water is briefly discussed. Also, the paper reports the preliminary results of the 3D directional focusing waves with different breaking scenarios for deep water conditions in the wave basin facility at the Department of Ocean Engineering, IIT Madras.

As the frequency of occurrence of the coastal hazards increasing along with sea level rise the number of hard structures installed to mitigate the beach erosion, flooding needs to be increased or upgraded. Attention on strategically utilizing the ecosystem service provided by vegetation to tackle such hazard is increasing in the coastal engineering field as the negative impact on the environmental and ecological system is less in this approach compared to conventional approach. The resistance offered by the vegetation meadow on wave energy depends on the submergence ratio, density of the plant per area, the rigidity of vegetation, and also on hydrodynamic characteristics. Prediction of behavior and effect on the wave propagation is necessary to determine the degree of effectiveness of the vegetation field in coastal defense. The physical model study which involves laboratory testing of small-scale models is one of the tools to examine and verify the effectiveness of structure under the action of the wave. The present paper focuses on the review of physical model study, their key findings and highlighting the criteria based on which material is selected to model the various real plants.

Before finalizing the layout of breakwaters for a harbour, it is necessary to obtain an acceptable level of wave disturbance within the harbour basin. This is required to facilitate safe berthing of desired variety of ships in the harbour. Also, to address the problem of scarcity of land in highly populated coastal zones of India, it has been very important to mitigate the erosion at the shoreline. In view of this, it becomes necessary to predict the effect of coastal structures on shoreline and save usable land. In the present study, an attempt is made to check the effect of a proposed fishing harbour on the wave tranquillity inside the harbour and the probable effect on the shoreline due to littoral drift thereof. For this purpose, the site of Murdeshwar coast located by the side of a 500 m × 370 m normal headland at the central west coast of India is selected. The proposed fishing harbour consists of only one breakwater of length 820 m and width 120 m at the south side with an opening from westerly direction. Numerical modelling is done to arrive at erosion-accretion pattern on both sides of the proposed harbour over a period of 10 years. The wave tranquillity studies are conducted for assessment of wave tranquillity in the proposed harbour using MIKE 21 software. Littoral drift model used for the analysis of the shoreline changes determining the coastline position. According to the studies, the yearly net sediment transport is about 0.064 Mm3 from south to north direction and the gross transport is about of 0.178 Mm3. Numerical modelling revealed that the headland existing at the north of the harbour plays major role in tranquillity in the harbour basin as well as in establishing the shorelines at the site.

Design of fishing harbour is always site specific with required consideration of prevailing waves, tide and current conditions. In most of the cases when development is exposed to sea, the wave is the single parameter which affects the design considerations. Generally, the action of the waves is the principal cause of wave disturbance and movement of the sediment inside the harbour. The fishing harbour layout should be optimized enough to get the desired wave tranquillity inside the harbour with minimum siltation criteria. In the present paper, the case study of a already existing fishing harbour Marvanthe has been discussed which at present is facing high impact of waves and siltation inside the harbour basin and the studies undertaken may helped to over-come this problem. The location at Marvanthe is fully exposed to the incident waves from the Arabian sea with maximum significant waves of upto 4.0 m height. Numerical Model MIKE 21-SW, BW and LITPACK were used to evolve the optimum layout for the fishing harbour. Two alternative layouts; one having entrance in north direction and other layout having mouth opening in south direction, were assessed through numerical modelling. It is found that both layouts are providing enough tranquillity inside the harbour. However, the littoral drift studies shows that the net littoral drift is towards south so the mouth opening towards north may require periodically dredging at entrance. Hence, the layout having south side opening was recommended for the proposed Marvanthe fishing harbour. The details of the studies have been described in this paper.

Essar Bulk Terminals Limited (EBTL) operates a Port Terminal at Hazira, Gujarat on the west coast. EBTL has carried out reclamation of 350 Ha area for the proposed future development of the port. Reclamation was carried out by utilizing dredged material from deepening of the navigational channel and turning circle. However, in every monsoon, there is depletion in the area of the reclamation. The reclamation adjacent to the channel is eroded, and a hump is formed in the approach channel. Hump recurred even after dredging that area to the original depth and this hump causes difficulty in the navigation of the vessels along the approach channel. It is observed that there is considerable erosion on the corner of reclamation and the eroded sediments get deposited in the approach channel resulting in the formation of hump. The wave impact on the reclamation is the main reason which results in the erosion of reclaimed area. Three-phase wave modelling is used for modelling the wave conditions in the area of vicinity to understand and determine a method to arrest the formation of the hump. A regional model is developed with wind time series as the input. From the results, time series of wave parameters was obtained near the entrance of gulf of Khambhat. The output wave parameters were used for the local mathematical model encompassing the reclamation, and the wave climate at the reclamation is simulated. To reduce the wave impact on the reclamation corner, submerged breakwater consisting of length 300 m, 3.5 m height above the chart datum, located at 150 m to the west of the channel and 100 m away from the shoreline is considered. The results indicated that the proposed solution of submerged breakwater is effective in reducing the wave impact and thus erosion; which will prevent the formation of the hump and the results are discussed in the paper.

The estimation of future sea level rise (SLR) under the changing climate at India’s major ports is necessary considering India’s large port infrastructure, spread across its ~7000 km of coastline. In this study, the future SLR for next 30 years is predicted using a combination of general circulation models (GCMs) and artificial neural networks (ANNs) to take advantage of both physics-based as well as data-driven approaches. For every port, monthly means of six climatic causal variables, namely sea surface temperature, precipitation, sea level pressure, surface salinity, wind speed, and surface height above geoid were used as input to the ANN to obtain the output of monthly mean sea levels. In the training, past sea levels recorded by tide gauges were used as output. The climatic input variables pertained to eleven different CMIP6 GCMs with SSP2-4.5 as the future climate scenario. Using the trained network and for every GCM, monthly sea levels were predicted for next 30 years, where the input was the future causal parameters. The rate of SLR was determined by fitting regression to the variation of the sea levels against time. This process was repeated for all GCMs. The median of all such GCM-yielded SLR, derived for each port, was compared with the same based on a software protocol called: SimCLIM which is based on the use of GCMs alone. It was found that such ANN-based SLR rate at major Indian ports was lower than the SimCLIM-based one, and it varied from 1.94 mm/year (Chennai) to 4.11 mm/year (Mumbai). The proposed approach is site-specific and hence more appropriate to use than the spatially averaged projections from SimCLIM or satellite data.

Tapi estuary near Surat city in Gujarat has vital importance due to its conducive hydrodynamic aspects. This led to development of large number of coastal infrastructures. The river bifurcates into two branches, viz. main Tapi river channel and Dumas creek. Several companies like Essar, L&T, RIL, NTPC, KRIBHCO, ONGC, MAGDALA AND GUJARAT AMBUJA CEMENT LTD have come up along the banks of Tapi channel. All ports have developed their captive jetties and successfully harnessed the power of ports to propel their economic growth. Port development in Tapi estuary requires intermittent dredging in channels and the estuary consists of many channels. Developing a deep channel would involve considerable capital dredging and necessitate maintenance dredging in future. Essar Bulk Terminals Limited (EBTL) has developed all weather Deep-Draft Terminal which is advantageously located on the western shore of Tapi Estuary that has come up with a very ambitious proposal of developing a common navigational channel for all ports by deepening the Tapi channel and Dumas creek. The proposal includes widening and deepening of the channel to 12 m depth, and the dredged material is intended to reclaim area between both the channel which comprises Kadia bet and Mora bet with the intention to develop a port city. To check the impact of proposed reclamation from wave perspective wave transformation, wave tranquility and changes in shoreline studies carried out and described in this paper. MIKE21-SW and BW models are used for wave studies and LITDRIFT and LITLINE modules of LITPACK that are used for shoreline evolution studies. The model studies indicated that the proposal is feasible from the wave tranquility and littoral drift aspects.

Coastal flooding caused by riverine flow or storm surges, or the combined river flow and storm surges induced by tropical cyclones produce significant causalities and huge loss of properties in low-lying areas. The successive or co-occurrence of riverine flow and storm surges exacerbates the flood risk more than due to individual occurrences. The efforts to reduce the aftereffect of coastal flooding motivated many studies to simulate compound floods using the combinations of hydrodynamic and hydraulic models. These models are combined in loosely coupled or tightly coupled ways. Due to its faster computations, the existing studies often employed the loosely coupled model developed using the 2D storm surge model and 2D flood models or simple 1D–2D research codes. So far, the suitability of the loosely coupled approach to analyse the compound flood effects from river flow and storm surge has not been dealt with in detail. Further, the models developed based on the tightly coupled approach are very few, and their application has proven that these models suffer from model instability and computational burden. Therefore, an unstructured grid-based river-bay model is developed in this study for the stable and efficient simulation of coastal floods.

Fisheries sector is a powerful sector for employment generation as it stimulates growth for a number of subsidiary industries, most importantly it is the source of livelihood for a large population in India. A fishing harbour, intended to provide better landing and berthing facilities to fishing craft requires feasibility studies that consist of Hydrodynamics, sediment transport, Shore line changes and Wave tranquility studies. Wave propagation studies play a very important role in deciding the orientation and length of the breakwater in fishing harbour layout. The Mathematical model study is one of the tools to help in finalizing the most suitable harbour layout for inventive and cost-effective solution. The present paper describes a case study for the proposed development of a fishing harbour at Thrikkunnapuzha, Alappuzha district in Kerala state for finalization of layout from wave tranquility considerations using mathematical model techniques. Two-dimensional mathematical model MIKE-21 SW has been used for the wave climate transformation from offshore region to near-shore region. The model provides the Incident wave conditions in the near-shore region, which are likely to affect the harbour basin area. MIKE-21 BW model has been used for wave propagation in the near shore region and inside the fishing harbour basin. Based on the findings of MIKE-21 BW model simulations which are carried out for four different fishing harbour layouts for the incident wave direction from SSE, South, SSW, SW, WSW, West and WNW, the predicted safe berthing operation in terms of number of days in a year are found out. It is observed that there are appreciable differences in the layouts with concern of hydraulic aspects such as permissible wave height in the harbour basin. Based on the minimum non-operational days, easy manoeuvring of boats and other coastal phenomena like tidal hydrodynamics and littoral drift, etc., suitable layout is suggested. Thus it can be stated that for assessing the wave tranquility, mathematical model is the reliable technique for determining the fishing harbour layout.

West coast of India has got a flatter continental slope as compared to East Coast, resulting into the long navigational channel on the West Coast Ports, such as New Mangalore Port and Cochin Port. Wave refraction takes place in the long navigational channel, as they travel, resulting in very good wave attenuation at the entrance to the Port. An attempt has been made to study this phenomenon. Wave propagation from deep water to the shallow coastal regions has different processes as compared to wave propagation from shallow region to inside the port or coastal area. In order to accommodate these processes two mathematical model MIKE 21 SW and MIKE 21 BW have been used. Wave transformation from deep water to mouth of navigational channel has been done using MIKE 21 SW model. Results of same indicate that WNW, West, 259°N (along the navigational channel), and WSW wave directions are predominant at the entrance to the channel. All these wave conditions are used for wave propagation along the navigational channel. Analysis of these data has indicated that wave propagation along the channel has maximum attenuation as compared to wave with some angle with channel alignment. It is also seen due to refraction of wave energy from the side slope of navigational channel, wave energy concentration is seen on side slopes. It can be concluded that long navigational channel is good from the wave tranquillity aspects.

The Gulf of Khambhat (GoK), formerly known as the Gulf of Cambay situated between Saurashtra peninsula and main land of Gujarat. The peculiarity of GoK is due to its funnel shape geometry which has width of 80 km at the mouth and funnel down to 25 km over a longitudinal reach of 140 km. This inherent important geometric characteristic of GoK results to form the quarter wavelength resonance of the tides. Tides which are semi-diurnal type with a large diurnal inequality, get amplified significantly from South to North due to its geometrical shape and varying bottom friction coefficients (Nayak and Shetye (May 2003) Tides in the Gulf of Khambhat, west coast of India estuarine. Coast Shelf Sci 57(1–2):249–254 [2]). In the North Arabian Sea, the maximum tidal range is found in GoK with an average tidal range of 10 m near to Bhavnagar which is situated at West coast of GoK and around 25 km away from Dahej, which is situated at East Coast of GoK. However, during the data collection at Dahej, the minimum tidal range observed was 3.8 m on 25th February 2018 at 11:45 h., while maximum tidal range was 9.77 m on 4th March 2018 at 12:45 h. Large tidal range is responsible for maximum tidal currents and morphological changes in the GoK. The coastal parameters, viz., tide, tidal currents, suspended concentration, type, and particle size of the bed material are essential and required to be collected for specific site to provide as input parameter to mathematical model studies. This paper describes about coastal data collection at Dahej, in GoK. Highly sophisticated self-recording type Acoustic Doppler Current Profiler (ADCP) were used for current measurement and self-recording type M/s. Vale-port make Wave cum tide gauge was used for water level measurement. To analyse suspended sediment concentration, water samples were collected at different locations at different stages of tide during spring and neap tidal condition. Bed samples were also collected at different locations to analyse the type of bed material. The field data collected would be used for calibration and validation of the model to address the siltation problems near the berthing area in the port of Dahej.

Mandwa port is situated on the West coast of India which connects Mumbai to Alibag by establishing inland water transport to reduce travel time and traffic on the road. The port comprises a breakwater of length 360 m and a navigational channel of length 1.8 km, 150 m wide dredged initially to (−) 4.0 m below Chart Datum (CD). The clear depths in the channel are required be maintained at about 2.5–3.0 m below chart datum throughout the year. At present, the port is facing severe problem of sedimentation in the navigational channel. The sedimentation in the approach channel and in the harbour areas occurs mainly due to the deposit of the sea-borne suspended sediments in the dredged areas. There is no significant contribution in the overall sedimentation due to the littoral or river discharges. The annual sedimentation in the approach channel is about 2.0 m, and this would not facilitate availability of clear depth of more than 2.5 m throughout the year in the channel and in harbour area. In order to mitigate this problem of sedimentation two proposed scenarios were studied, namely, proposed condition-I with additional dredging in the channel and harbour areas and other proposed condition-II with modification in the channel alignment (orientation) to align it along the currents to reduce sedimentation in the channel. The MIKE-HD/MT model was utilised for the studies which was calibrated with the collected field data. In second proposal, length of channel slightly reduces by about 100 m. In first proposal, both initial cost and maintenance cost would increase marginally, while in second proposal, initial cost of dredging will be very high as new approach channel needs to be dredged but its maintenance cost will be much less. The detailed findings of this study would be discussed in the paper.

The beach profile changes form the primary aspect of the field study in understanding coastal processes as they vary concerning different coasts, site conditions, and wave characteristics. In this study, beach profile changes on an open coast and near an estuary are quantified through field investigations conducted over a couple of years. The changes in the beach profiles are compared temporally and spatially. The data was collected on the first spring of every month using Real-Time Kinematic Global Positioning System (RTK-GPS) from May 2017 to April 2019. The accuracy of data collected using RTK-GPS is 8–15 mm. The study areas are considered an open coast in Devaneri, Tamil Nadu, and near an estuary with its mouth being trained by a pair of training walls in Karaikal, Puducherry, India. Both the sites are located along the Southeast coast of India and are 300 km apart. The open coast has remained constant with minor changes in the profiles, and the one near an estuary coast undergoes significant changes seasonally and spatially. It is observed that the presence of coastal structures dictates the terms in the erosion/ accretion process on the coast.

One of the critical segments of the Indian coastline currently being studied for its intricate hydro and sediment dynamics is the Konkan coast, which makes up the bulk of the Western Ghats. The study region focuses on the numerical modelling of the Goa, South Maharashtra, and Karwar coastal stretches. This work includes calculating sediment transport rates in the north Konkan coast's nearshore sections and the 2D coupled numerical modelling of hydrodynamics and sediment transport. Waves, tides, currents, and winds were taken into consideration. One month of post-monsoon simulations from mid-December 2018 to mid-January 2019 was performed using the model. It was discovered that the model findings were in excellent agreement with the data. Sediment circulation was found to be mainly in a north and cross-shore direction. The sediment transfer was evaluated between several depth contours, including 0–2, 0–5, 0–10, 0–20, and 0–30 m of water. Over 386 kms, the average sediment transport rate for the area between 0 and 2 metrres of water was roughly 4.75 Mm3/year. According to the model's findings, there is significant sediment movement between 10 and 20 m of water (133 Mm3/year). During the simulated period of post-monsoon 2018, it was discovered that the total sediment transfer throughout the coastline length between 0 and 30 m of water was about 144.5 Mm3/year.

Field observed data on coastal processes is one of the essential requirements for evolving long-term plans and coastal protection measures. In view of this, for collection of such data, a scheme of Coastal Management Information System (CMIS) is being implemented by the Government of India under the on-going Scheme ‘Development of Water Resource Information System (DWRIS)’ of Ministry of Jal Shakti, Department of Water Resources, River Development & Ganga Rejuvenation (MoWR, RD & GR). CWPRS is the implementing agency for coastal data collection at North Maharashtra and South Gujarat. Two sites were identified for CMIS, viz. Satpati in North Maharashtra, Nani Danti-Moti Danti in South Gujarat by CWPRS with the help of respective state governments. These sites were identified considering the vulnerability of coastal erosion and severity of its impact on local population and need for coastal data collection for providing a comprehensive coastal protection plan for these areas. The total duration of the project is about three years wherein various coastal data such as coastal bathymetry, wave, tide, tidal currents, shoreline changes and cross-shore profile, suspended and bed sediments, river /creek discharges, winds, rainfall, temperature, humidity, etc., is being collected during different period of all the seasons and processed so as to be used at front-end and linked to Centralised Data Centre (CDC). The data collection program comprises of procurement of standard equipments following the government procedure, its installation at sites, and collecting data in standard format. The present paper discusses about the practical problems, while implementing this program at sites, challenges faced during the pandemic and its impact on CMIS program, and strategies adopted to overcome these challenges. General data trends observed at these sites will also be presented.

Over the past few years, India has faced different super cyclonic storm (SuCS) rises from the Bay of Bengal (BOB) source. “AMPHAN” is another powerful reported tropical cyclone (TC) after the Odisha SuCS of 1999. It made landfall with incredible atrocity along the coast of Odisha and West Bengal (WB) states of India and the Hatiya islands of Bangladesh (BD) on the same day. It caused massive devastation and damage along the coastal regions, specifically Sundarbans. It causes inevitable disturbance to the people dependent on the fragile landscape for life and biodiversity, which entailed a careful study to evaluate the resilience of structure and emergency maintenance response. The current paper analyzes the effect of wind on the structure after tracking down the cyclone path based on India Meteorological Department (IMD) records. Further, the study of the impact on structure and bridge during the post-AMPHAN period compared to the pre-AMPHAN situation. This paper also presents a comprehensive disaster mitigation report illustrating the damages with photographs, which helps to understand the catastrophic intensity caused by the cyclone.

A very severe Cyclone Yaas hit the Digha Coast and adjoining coastal areas in West Bengal on 26.5.2021. Process of landfall commenced from 8.30 A.M and it continued for about four hours to complete the whole process. Maximum Storm Surge Level recorded at Digha was about 7.20 m. Maximum wind velocity observed at Digha was about 150 km/h with direction s-s-e. Many places in Howrah, North 24 Parganas, South 24 Parganas and East Midnapore districts got marooned on 26.5.2021 after sea water and river water gushed into villages following damage to river embankments due to high storm surge soon after Cyclone Yaas made a landfall near Dharma Port in Odisha on 26.5.2021. About 156 km of river embankments in these districts were either damaged or breached. Embankments along rivers Hooghly, Rupnarayan and Haldi were damaged at several places causing the disaster. A number of villages and settlements in the riverine areas of these districts were inundated. Affected areas include Digha, Tajpur, Mandermoni, Haldia of East Midnapore district. Breaches in river embankments left thousands of villages and settlements inundated in areas like Kakdip, Sagar, Ghoramara island, Patharpratima, Bakkhali, Sandeshkhali, Mousuni island, Fraserganj and Hingalganj in South 24 Parganas. In East Midnapore, nearly 12 blocks were marooned due to surge in sea water and river water levels. Water overtops Guard Wall at Digha and New Digha on 26.5.2021 morning with embankment breach and destruction of Guard Wall at several places. Entire Sea Embankment from Sankarpur to Tajpur was badly affected due to cyclone. In Mandermoni, several hotels and shops were destroyed. This paper reports damage caused due to Cyclone Yaas in West Bengal. Preventive measures to be taken in case of future storms to minimize damage and loss of life have been discussed.also.

Due to human intervention and nature’s fury, coastal morphology is continuously changing. Some time, longshore transport equilibrium is disturbed due to manmade coastal structure or due to natural wave attack. In such conditions, heavy erosion or accretion takes place at the coastal site. Coastal erosion is loss of land area due to action of waves, currents, winds and gradual increase in the sea level due to global warming. Coastal erosion is a severe problem needing immediate attention to this in an effective manner with a scientific base for evolving suitable design of coastal protective structure. In present paper, some coastal protection measures were evolved for the vulnerable site Sasihithlu, Dakshina Kannada District Karnataka along the west coast of India. Some shops and other buildings have been totally demolished by the severe shore erosion at the present site. Near the site, there is a combined river mouth for two rivers named as Sambhavi river and Nandani river. The mouth is located in the open coast and subjected to high waves of up to 4 m associated with the significant littoral drift. As a result, the severe erosion has been taking place at the south of the river mouth near Sasihithlu. In order to stabilize the shoreline near Sasihithlu, suitable coastal protection measures were suggested by using numerical model LITPACK. For shore protection at Sasihithlu, the performance of two types of protective measures, i.e. groyne field and offshore breakwaters, was assessed through model studies. From model studies, it was found that with six groyne in series, maximum 10 m of accretion would take place between the groyne fields after 10 years. While with offshore breakwaters, maximum 4 m of accretion would occur between the shore and offshore breakwaters in 10 years. The suggested coastal protection works are expected to stabilize the eroding coast line at Sasihithlu.

Extremely severe cyclonic storm Tauktae traversed along the west coast of India during 14–19 May 2021 and reached its peak on 17 May 2021. The cyclone passed along the Goa coast on 16 May 2021, wherein the eye of the cyclone was about 100 km from the coastline. The effect of this cyclone was felt severely along the coastal stretches due to increased wave and wind effects over the beaches. The influence of the Tauktae cyclone on beach morphology has been studied in this paper. A total coastal stretch of about 27 km long in South Goa and 7 km in North Goa is considered. Beach profiles at 9 locations were measured before and after the cyclone, and volumes on the foreshore were compared. The cyclone waves and wind impact on the beaches resulted in erosion at most locations. The retreat of the berm was between 5 and 16 m, while the foreshore erosion volumes ranged between 25.82 and 132.5 m3/m. Profiles measured between 8 and 27 June, i.e. within one month of the cyclone passage, showed varying rates of accretion/erosion. Further measurements of monthly profiles are carried out. The cyclone impact on the beach profiles in terms of changes in morphology features and beach volumes is presented in this paper.

Coastal structures are built to provide permanent solutions to safeguard the harbouring operations. The structures such as breakwaters and seawalls are important infrastructures that are commonly built near coasts and have strong influences in bringing changes to the shorelines. The combined effect of these structures was studied in the present paper with two typical sites located in different bays situated in Andaman and Nicobar Islands and west coast of the country. Both the sites were studied for the shoreline dynamics by imposing seawalls and breakwaters as hard structures. MUS harbour was located within a crenulated shape of the bay in Nicobar Islands and was provided with permanent harbour facilities. The shoreline and part of the breakwater have been damaged under tsunami waves of 2004. A seawall was proposed inside the bay to protect the shore. The impact of the seawall in the neighbouring locations was studied to arrive at the optimal length of seawall in the presence of the shore parallel breakwater. The other harbour is located at Navabag, west coast of India that is situated between the two headlands with a small inlet at the north headland where tidal flow with sediment causes hindrance to the navigational boats. In this case study, the impact of the shore perpendicular breakwater for channelising the flow in the presence of the seawall was studied. A 1-D model in flexible mesh was set up for both the sites for the known site conditions. Based on the simulations of shorelines for different periods, the optimum length of seawalls of 450 m at MUS harbour and 500 m length of breakwater at Vengurla site were arrived. The effect of breakwater of length 500 m at Vengurla site is 1 m and 2.5 m of deposition of sediment in a span of 10 and 30 years, respectively.

The growth in international trade has made the developing countries to concentrate more on the development of their infrastructure, like roads, airports, seaports, which play an important role within the development of the economy. The government is committed to the sustainable development of Indian shipping industry, and the increase within the maritime economic happenings has encouraged a rapid development within the port sector. Hazira is a suburb and a transshipment port within the Surat City within the Gujarat state of India. It is located at the west most end of Surat. Hazira is one amongst most significant the ports of India and therefore the most important element of Surat Metropolitan Region. The town is the industrial hub of India and is found on the bank of the Tapti River, eight kilometres away from the Arabian sea. Deendayal Port Trust, Gujarat features a proposal to determine ROPAX Jetty in Hazira, Gujarat as a part of the ambitious project from PMO India. A two-dimensional mathematical model MIKE21 HD was used to study the hydrodynamics within the vicinity of the proposed ROPAX jetty area. The impact on the hydrodynamics within the vicinity of the proposed ROPAX jetty was studied with the assistance of mathematical model. The current measured at two locations varied from 0.3 m/s to 1.1 m/s in existing condition and reduces marginally in the order of 0.1 m/s at C1 location and 0.05 m/s at C2 location after proposed ROPAX jetty. The results from the hydrodynamics studies suggest that there aren't any significant changes within the flow pattern and no cross flow observed during the simulation. It absolutely was suggested that the project is executed and further maintained with maintenance dredging within the channel for smooth functioning of the project. This project will help immensely for saving time travelled by road and also reduce the gap between Hazira, Gujarat to Gogha, Gujarat from around 384 km to merely meagre 80 km.

The coastlines of islands are always under threat by various environmental agencies. Coastal changes do happen by a wide range of oceanic processes. Comprehensive understanding of the coastal processes regulated by coastal hydrodynamics and the consequent movement of sediments is vital to the formulation of coastal zones management strategies. It is imperative to protect the dynamic environment against those processes cost effectively with minimal or no impact on neighbouring coasts. Some of the bay environments are protective from the seas naturally. However, coastal structures like breakwaters that were built for creating tranquil conditions provide hindrance to the movement of sediment passing alongshore. This study pertains to the study of estimation of this sedimentation by different methods for a harbour located in Car Nicobar Islands, viz. (1) Empirical methods, (2) Numerical modelling in 1D, and (3) Numerical modelling in 2D. The harbour is subjected to the seasonal variation in sedimentation, and in SW monsoon, the estimation with 2D model studies is 2200 m3/m with little or no sedimentation in the harbour in other seasons and annual net variable littoral drift towards north direction varies inside the crenulated shape of the bay from 2300 m3/m to 4600 m3/m with a cumulative annual net drift of 0.26 to 0.32 Mm3as simulated through 1D model. The longshore sediment drift as estimated by empirical methods varies from 0.28 to 0.31 Mm3 for a typical slope of sea bed and breaking wave height. The estimated littoral drifts with 1D model are in agreement with the sand transport 2D simulations and empirical estimations.

Coastal areas play a vital role in the socio-economic development of a country because seaborne trade remains the cheapest method for importing and exporting large quantities of merchandise all around the world. Kasargod Fishing Harbour (12° 28′ 32.71” N and 74° 59′ 36.14” E) in Kerala state is situated at the confluence of the Northern creek and the downstream of the river Chandragiri. With the help of mathematical model studies from the considerations of wave tranquillity and littoral drift, a 700-m long curved breakwater as extension of northern breakwater was evolved to provide protection and tranquil conditions at the inlet, which would help in manoeuvring of the trawlers/boats of the fisherman through the entrance of inlet channel. A depth-averaged numerical model using MIKE 21 FM software has been developed to study tidal circulation in the creek inlet and nearshore region and to assess the changes likely to occur in hydrodynamics and siltation pattern in navigational channel and harbour region due to the proposed expansion. The model studies indicated that the maximum current magnitude of the order of 0.5 m/s and 0.75 m/s occurred in the inlet channel during non-monsoon and monsoon season, respectively. During high flow in the monsoon season, only ebb currents would persist in the inlet channel and during ebbs, irrespective of seasons a circulation always persists on the south side of the southern breakwater. Also, it is indicated that as compared to other nearby regions, sediment deposition in the inlet channel is quite less. However, a maintenance dredging of in the inlet channel would be required periodically for smooth functioning of the channel and manoeuvring of fishery boats.

The benefits of mangroves to the environment, people, and ecosystems are enormous. Mangroves play an essential role in processing, absorbing, and treating Carbon Dioxide, some greenhouse gases, and act as a giant reservoir to store these. Vietnam, with a 3260 km long coastline, has four major regions, i.e., the North-west coast, the Northern Delta, Central coast, and the coast of Southern Vietnam. The coastal Mangroves in Vietnam play the role of barrier to protect it from saline intrusion, coastal erosion, and destructive climate change. However, there are many challenges to their sustainability. Recently, the Vietnam mangrove has changed in quantity and quality. The mangrove area in 1943 was over 400 000 ha which has reduced to 164 701 ha in 2017 (a decrease of 60%). There are many reasons for such declines, such as war, sea-level rise, anthropogenic activities, climate change. Human activities such as traditional logging, non-timber, traditional fishing and aquaculture, exploitation of mangrove produce, and interaction between agriculture with mangrove have affected its sustainability. Economic and tourism dynamics have caused pressure on the mangrove ecosystem. This study highlights the issues and challenges of mangrove development, management, and rehabilitation in Vietnam based on the theory of sustainability with the Driver-Pressure-State-Impact-Response (DPSIR) model. This model is reviewed from the socio-ecological point of view—a tool for assessing the interaction among the environment, ecology, and society. The study provides a comprehensive overview of the risks and hazards from the environment and human activities’ point of view. Further, the study focuses on socio-ecological pressure, challenges of mangrove conservation and response of mangroves in Vietnam.

Nearshore wave climate is an important factor for development of any port or harbour. Wave propagation inside the harbour should always be within the allowable safe limit for berthing of ships/boats. The wave propagation inside the harbour is minimised by providing proper sheltering through breakwater. The projection of breakwater should ensure minimum silt entry in the harbour, thereby reducing the dredging inside the harbour. Numerical modelling for present study is conducted for development of fishing harbour at Shiroor, Karnataka, on the west coast of India. Modelling is carried to derive the nearshore wave climate using Numerical spectral wave model (MIKE-21 SW). Wave propagation inside the fishing harbour was analysed using Numerical Boussinesq wave model (MIKE-21 BW) and the shoreline prediction by using LITPACK model. Near the point of interest at −7.5 m depth, the wave transformation studies indicated that predominant wave directions were from 225° N to 290° N directions, i.e. the site is exposed to predominant waves from SouthWest (SW) to WestSouthWest (WSW) directions and waves of significant height of about 3.0 m waves reach the proposed site. Wave climate inside the fishing harbour was assessed for the layout proposed by the project authority consisting of Northern breakwater of length of 205 m and Southern breakwater of length 315 m with 80 m wide opening from the westerly direction. The tip of the breakwater is proposed at (−) 3.3 m. The Numerical model studies carried out by using MIKE-21 BW model for this proposed layout indicated that the significant wave heights in the harbour basin would be are generally in the range of 0.25 m–0.10 m and the layout was adequate to provide desired tranquillity less than 0.3 m in the harbour basin for all the directions. Numerical model studies for shore line have shown that the net drift is towards the North direction and accretion would take place on the Southern side of South breakwater and erosion on the Northern side of North breakwater. Thus, the mathematical modelling studies to evolve fishing harbour layout satisfy tranquillity criteria and also ensure minimum siltation in the harbour basin. With the construction of proposed breakwater, there will not be significant changes in the existing shorelines on the North and South of breakwater.

Breakwaters are sound massive structures devised for providing tranquil conditions to facilitate loading and unloading operations at the berths, wharfs and jetties in harbour areas. The cost of breakwater construction governs about 70–80% of total capital cost of the coastal engineering project. Considerable economics can be achieved by using small-scale physical models which help in avoiding disastrous mistakes in prototype design. The present study emphasizes on the role of physical wave models for establishing wave tranquility conditions for the development of a jetty and passenger cruise terminal at Bhagwati Bunder in Ratnagiri district, Maharashtra, India. The part construction of west or commercial breakwater up to a length of 457 m was over in 1973. Maharashtra Maritime Board has proposed development of cruise terminal and jetty to cater to passenger ships with length of 245 m and draught of 7.9 m. The permissible wave limit for berthing operations at passenger jetty has been considered as 0.50 m. The physical wave model studies at geometric similar scale of 1/120 were conducted at CWPRS which consists of a three-dimensional model tray shallow wave basin equipped with the Random Sea Wave Generation facilities with SCADA control. The physical wave model studies were conducted for 100 m as well as 200 m extension of the existing breakwater for the three predominant wave directions, viz. WSW (Hs = 4.0 m, Tp = 12 s), West (Hs = 4.0 m, Tp = 12 s) and North West (Hs = 1.8 m, Tp = 6 s). The studies indicated that about 70–80 days will be lost for operation at the passenger berth during the monsoon season under existing condition. With 100 m extension of existing breakwater, the downtime will be about 10 days at the passenger berth during the monsoon season. The 200 m extension will provide just adequate wave tranquility throughout the year at the passenger berth for ship size of 245 m length with wave permissible limit as 0.50 m. The physical model studies were very useful in visualizing the complex interaction of wave patterns inside the harbour which helped in evolving the wave tranquility conditions at different berths, jetties, wharfs, etc.

The increase in population and coastal infrastructure demands a rigorous assessment of coastal vulnerability for extreme events. The predictions by Intergovernmental Panel for Climate Change (IPCC) indicate that climate change will severely impact coastal regions, river systems, urban infrastructures and increase the frequency of inundation along coastal areas. This study emphasizes the need to use extreme events and socioeconomic data to evaluate the vulnerability of a given coast. This paper presents the vulnerability assessment of the Chennai coastal region using eight variables: coastal elevation, coastal slope, rate of shoreline change, tidal range, sea level rise, storm surge, Adyar flood and land use and land cover. A Coastal Vulnerability Index (CVI) is calculated by integrating the physical and social–economic variables. The Coastal Vulnerability Index for shoreline erosion ranges from 15 to 21 with a mean value of 18 and a standard deviation of 1.6, while the Coastal Vulnerability Index for inundation ranges from 4.1 to 12.7 with a mean value of 7.3 and a standard deviation of 1.4. The vulnerability maps show the exposed regions around river Adyar that are highly vulnerable to coastal erosion and floods, especially due to extreme events. The assessment indicated the variation in the vulnerability of inundation around the Chennai Port regions and the low vulnerability of the shoreline erosion in this region. The vulnerability assessment suggests that planning and adaptation of the coastal ecology for the future needs are to be performed with extreme caution.

The coasts are exposed to hazards that are natural (global warming-induced sea-level-rise, river mouth closure by siltation, changing climate with the increased frequency of cyclonic storm surge, coastal flooding, tsunami, etc.) and due to anthropogenic activities (shoreline erosion, sewage treatment plants, desalination plants, etc.). There are several coastal protections that are in vogue for a specific (single) hazard around the world and different advanced techniques available to protect and preserve the coasts from such hazards. Apart from combating the hazards, there is rapid progress in coastal development. All of these might have provoked the thought of the necessity of the coastal management information to the scientific and engineering coastal working community. The Coastal Management Information System (CMIS) mainly focuses on the in situ data collection of environmental data for the planning, design of structures and schemes for sustainable coastal conservation and development. The monitoring parameters are wave, current, wind, tide, bathymetry, beach profile, shoreline, sediment characteristics in near-shore as well as offshore in case estuarine coasts the riverine data such as river current, discharge, conductivity, temperature along with the depth in a different location from sea to 2 km were measured. Although three coastal sites with different coastal features, Devaneri in Tamil Nadu, Ponnani in Kerala and Karaikal in Puducherry, were selected for this purpose, salient details only for the site along Karaikal are reported herein.

Management of solid waste is one of the most pressing challenges faced by municipalities across the world. Increased consumption and improper disposal have led to the accumulation of solid waste in many urban areas, resulting in detrimental impacts on the atmosphere, hydrosphere and biosphere. In particular, coastal areas that accommodate over 60% of the global population face severe deficits in solid waste management, resulting in far-reaching impacts on water quality and the fragile marine ecosystem. The commonly adopted practices of uncontrolled burning, open dumping and unscientific landfilling contribute to significant emissions of greenhouse gases, leading to global warming and climate change. This article discusses the development and performance evaluation of a decentralized technology for management and resource recovery from solid waste generated in coastal areas, with increased resilience to climate change, by mitigating the greenhouse gas emission arising from the scenario of open dumping. The coastal village of Vichoor (Tamil Nadu, India) was selected as the study area, and the quantity and composition of waste generation were assessed. Baseline studies revealed an absence of systematic solid waste management in the study area. Organic fraction contributed to over 55% of the generated waste. An integrated municipal solid waste management scheme was devised, involving primary source segregation, collection, secondary segregation and resource recovery. Infrastructural provision for composting organic waste in a composting yard was adopted, which also doubled as a secondary segregation unit. Methane emission was assessed for scenarios involving open dumping of waste and windrow composting of the organic fraction. A reduction of 316.29 kg CO2 eq/T of waste was observed by adopting the proposed practices over open dumping, thus proving to be a potential solution to combat climate change due to greenhouse gas emission from solid waste management. Long-term sustainability of the system was ensured by active community level participation and revenue generated from the sale of recyclable inorganic fraction and the generated compost.

Presently, there are limited techniques to identify submarine groundwater discharge (SGD) zones in the coastal regions due to the dynamic and invisible nature of the phenomenon driven by natural and anthropogenic factors. The driving factors for SGD include but are not limited to groundwater potential (hydraulic head), groundwater occurrence (type of aquifer: confined/unconfined), aquifer characteristics (hydraulic conductivity /transmissivity), aquifer thickness, the topography of the area, land use–land cover area, recharge–discharge pattern, sea level rise, dynamics of tides tidally driven oscillations, density-driven convection, and thermal convection. Considering some of the crucial factors, we have tried to develop an index that can help in indicating potential locations for SGD along the coastal regions based on easily accessible data. The most important factors which indicate the potential of SGD are groundwater level with respect to mean sea level (or hydraulic gradient (S)), groundwater occurrence (G), degree of pollution due to seawater intrusion in a coastal aquifer (D), transmissivity (T) or permeability of aquifer (K), and aquifer thickness (A). Based on this understanding of governing factors, the present work proposes SGDTA (highlighted acronym) index model to identify potential locations for SGD. The data required for this model are readily available with various agencies without any detailed investigation, so this index model is advantageous to delineate the potential location prior to a thorough investigation of SGD. Finally, we successfully demonstrate this model's first-hand application by identifying the SGD zones along the Bhavnagar district coast.

Submarine Groundwater Discharge (SGD) is the continuous flow of groundwater under favourable hydrogeological and hydrological settings, which carries nutrients, traces metals and other contaminants to the sea coast and influences the coastal ecosystem. Therefore, integrated site-specific field investigations are necessary for identifying the SGD zones and its magnitude assessment for sustainable development of the coastal ecosystem. An attempt has been made to identify the potential SGD zones along the 485 km long coastline of Odisha using the groundwater level data and physico-chemical analysis of groundwater, pore water and sea water samples. The areas having an occurrence of groundwater level above mean sea level (more than tidal amplitude) together with the absence of any significant seasonal/diurnal variation in groundwater levels were identified as probable SGD zones. In situ measurement of basic water quality parameters (temperature, pH, salinity, EC, DO, etc.) was carried out at every 3–5 km intervals along the coastline for sea water (44), pore water (43) and groundwater (36) samples using portable multiparameter water quality kit during the field investigation. The pore water samples, indicating low salinity (<25 ppt) and low EC values (<35 mS/cm), were considered to be suspected SGD. A total number of seven such suspected zones were identified along the coastal tract of Odisha. The pore water salinity in these seven locations is found to be 14.6 ppm (Chaumukh–Balasore), 3.05 ppt (Chandipur–Balasore), 3.71 ppt (Madanpur–Balasore), 19.79 ppt (Pentha–Kendrapara), 18.9 ppt (Beleshwar–Puri), 12.59 ppt (Golden Beach, Puri) and 0.46 ppt (Nolia Nuagaon, Ganjam) in the proximity of sea coast between low tide and high tide. The nutrients (Nitrate, Phosphate and Silica) analysed in the pore water samples also have shown elevated signatures for the identified zones, thus support possible SGD and need further conformation using stable isotopes, sea surface temperature and radon measurements.