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The present paper aimed to assess the sediment distribution pattern, mode of transport, and its interaction with hydrodynamic and topographic conditions at different depths and regions along the east coast of India. About 900 surficial sediment samples were collected and analysed on a monthly basis for the Chennai coastal region at 32 stations from 2013 to 2015. The study region is classified into four types, such as beach, inlet, 5 m, and 10 m depth. Sediment textural and grain size trend analyses were conducted to achieve the objectives. Sediment characteristics for the region were recorded as sandy, equally dominated by unimodal and bimodal at the beach, while unimodal at shallow depths (5 and 15 m). The sediments were medium sand to coarse sand at the beach, mostly fine followed by medium at 5 and 15 m depths. The sediment sorting is dominated by moderately well-sorted sediments; the skewness of beach sediments was negative, while nearshore sediments were found positive; average kurtosis values of sediments were noticed to be mesokurtic. The CM plot depicts that the sediments were mostly derived by tractive current, and the modes of transport are "bottom suspension and rolling" and "graded suspension no rolling" at beach locations and shallow water depths, respectively. The GSTA analysis reveals the annual average sediment transport pattern is northerly. The numerical hydrodynamic study confirms the GSTA and CM plot analysis. The study reveals a stable sedimentary environment south of the Chennai port and instability in the northern part. The study includes large spatiotemporal nearshore sediment data with hydrodynamic conditions, immensely helpful to coastal stakeholders and researchers. [ABSTRACT FROM AUTHOR]

Guru Prasath, J.; Sannasiraj, S.A., and Chandramohan, P., 2024. Nearshore morphological changes due to severe cyclonic storm activity along the east coast of India. Journal of Coastal Research, 40(4), 696–713. Charlotte (North Carolina), ISSN 0749-0208. Nearshore waves, wind, and tidal current mobilize seabed sediments; sort, transport, and redistribute the sediments; and modify the nearshore seabed morphology. Waves play a dominant role in morphological changes among winds, waves, and tidal currents. The nearshore wave breaking induces the initiation of sediment movement, and the associated alongshore current transports a large volume of sediments that tend to either accrete toward or erode from the beach face and seabed. Sediment transport rate in the nearshore waters during cyclones is higher than that under normal conditions. The measured changes due to Cyclone Nivar in November 2020 in the nearshore morphology along the Mahabalipuram coast are examined to understand the response of nearshore morphology to cyclonic wave-induced forcing. The beach-profile measurements across 10 transects at 100 m spacing covering about 1000 m along the coast were measured before and after the passage of Cyclone Nivar as a part of the present field study. The evolving beach profiles during Cyclone Nivar were simulated using the storm-induced beach change (SBEACH) model, which is a cross-shore profile evolution model. The changes due to berm erosion and deposition of nearshore sand bars have been compared from field measurements data and model prediction. The calibrated model was then used to simulate the beach profile response at two other locations along the cyclone-affected coastline to examine the shoreline impact. The calibrated model can be used along the coast to understand the poststorm profiles of the beach with reasonable accuracy. [ABSTRACT FROM AUTHOR]

The study investigates textural characteristics of foreshore sediment along the central Kerala coast. The selected beaches extend from Ponnani in the north to Alleppey in the south along the west coast of India. Samples were collected from foreshore zone at 22 selected locations to assess sediment grain size distribution and its seasonality. Statistical parameters such as mean (M), standard deviation (SD), skewness (Sk), and kurtosis (K) were used to evaluate the textural characteristics. The purpose of the present study was to examine the textural behaviour of coastal sediments in different seasons from November 2014 to October 2015. Textural characteristics show that the sediment samples are unimodal and bimodal with medium and fine grain sand. The standard deviation (sorting) reveals the sediment samples are very well sorted to moderately sorted with a range of 0.24 phi to 1.03 phi, while the skewness values of the sediment samples range from −0.55 phi to 0.32 phi. The CM plot depicts that the foreshore sediments are transported by tractive currents and transporting the sediments by rolling, bottom suspension with rolling. The analysis of Linear Discriminant Function (LDF) illustrates that the sediment samples are accumulated by aeolian or coastal and shallow turbulent environments. [ABSTRACT FROM AUTHOR]

The ravine is often regarded as the worst instance of how water erosion is causing land deterioration. The farmers' livelihoods are often threatened by the ravine's expansion into the surrounding 50 m buffer zone, leaving them with no choice except to work as landless workers. Due to the high expense of ravine restoration, it is not economically possible to begin the process of reclamation in all of the ravine lands at once. As a result, it is necessary to recognize the prospective regions to bring in reclamation activities. In this work, the ravine vulnerability index for the Mahi ravine in Western India was developed using a cutting‐edge hybrid methodology. For the development of the ravine vulnerability index, it was determined that the sand, silt, clay, organic carbon, soil erodibility factor, slope, stream power index, topographic wetness index, sediment transport index, and cover factor were crucial components. Weights were applied to various parameters based on the perceived significance of each parameter in relation to another in the decision matrix of the analytical hierarchical process. The number of iterations made to reach a consistency ratio of under 10% to determine the final priority weights for each parameter. The sediment transport index had the lowest priority weight (1.4), whereas the sand had the highest priority weight (28.5). For reclamation purposes, the prospective active zones inside the designated ravine's 50‐m buffer zone, which covered an area of 63,031 acres, were determined. According to the ground truth‐validated ravine vulnerability index, possible reclamation zones were found in the 16,703 ha (26.50%) region of Mahi ravine, which was given extremely high priority. As per the Mahi ravine's land capacity classification, 20,275 ha (32.16%) of it is arable land, and 18,687 ha (29.65%) of it is non‐arable land that is ideal for soil and water conservation treatments. [ABSTRACT FROM AUTHOR]

Reservoirs and barrages , built across alluvial rivers throughout the world, are losing their storage capacity at an estimated rate of about 1% annually. The pond area of Durgapur Barrage on River Damodar, India, controlled by barrage-gates is no exception. In spite of its service for more than 60 years through judicious gate-operation schedule, it is found that 52% of initial storage capacity Pond has been lost since its inception in 1956. A morphodynamic study of the alluvial Damodar River, extending from Maithon and Panchet dams at upstream to Durgapur Barrage in the downstream, has been done using a numerical model of MIKE-11. Hydrometeorological data of Damodar-Barakar River basin were used to simulate hydrodynamic and sediment transport models for ascertaining annual rate of erosion and deposition during the period 1956–2016. Study shows that about 6 million M3 sediment were transported from catchment through Dam-discharge, a part of which got deposited in the river bed while the remaining 4.9 million M3 washed away downstream through Barrage gates. Although the rate of deposition in the pond area was initially higher during the period 1956–1985, which has subsequently reduced. However, daily deposition increased more or less linearly with the increase in discharge of the river. [ABSTRACT FROM AUTHOR]

The formation of shoals, leading to a reduction in the required depth for navigation, is a perennial problem in approach channels of harbours and estuaries. Likewise, this is a major obstacle to the navigation of larger vessels to the study area reported in this paper. A field study on Kandla creek estuary was conducted to assess the flow and sediment dynamics inside the creek where one of the major ports of India, Deendayal Port, is located. In-situ water and sediment sampling and discharge measurements were carried out for the pre-monsoon, end of the monsoon and post-monsoon seasons in 2019–2020. Further, the grain size analysis and total suspended sediment analysis were done from the collected samples. The results highlight the domination of strong ebb currents in pre-monsoon and flood currents at the end of the monsoon and post-monsoon in the creek, which influences the sediment transport proportionately. The present paper reports the sediment characteristics and the estimated net sediment transport through measurements along with flow characteristics in Kandla creek. The field data presented here will support the researchers in the numerical modeling and validation of hydrodynamics and morphodynamics in the estuaries. [ABSTRACT FROM AUTHOR]

A barred tidal flat has grown in the north of Subarnarekha river estuarine system along the western coast of Bay of Bengal, Talsari, Odisha, over the last twenty years, from 2002 to 2022. The channels form an integral part of the tidal flat and act as conduits for supplying and draining sediments with flood and ebb flows. Multiple drainage basins with quantifiably different channel patterns are identified within the Talsari tidal flat. Two major types of tidal channels, namely through-flowing and dead-end channels, are recognized in the Talsari Tidal flat. Channel morphometric analysis reveals that the sand:mud ratio in the tidal flat sediments, along with slope, tidal range, current strength, vegetation cover and climate, strongly controls the channel pattern evolution in drainage basins within the tidal flat. Channel migration and filling patterns develop distinctly different sedimentary bodies with respect to laterally adjacent flat areas. High-energy climatic storms played an important role in transporting silty-muddy sediments to the tidal flat and also brought changes in channel morphometry along with the development of regionally developed scours. [ABSTRACT FROM AUTHOR]

The ship-generated waves in restricted waterways can influence the behavior of sediment resuspension and bank erosion. This paper explores the case study considering the effect of ship-generated waves in restricted channels. A fully nonlinear Boussinesq model (FUNWAVE-TVD) is used to simulate the ship-generated waves. The sediment transport model adopted in FUNWAVE has been changed to incorporate the modified diffusion coefficients, deposition flux, and an explicit equation for settling velocity and critical shield parameter. The sediment transport model was validated against the experimental results of solitary waves in a wave tank, and model performance in shoreline geometry was reported. The implementation of the moving vessel in the numerical model and its impact on suspended sediment concentration were evaluated against the field measurements in the Falta stretch of the Hooghly river in Indian National Waterway 1. The error value in predicting the depth-averaged suspended sediment concentration by the FUNWAVE module was 97.6%, which has been significantly reduced to 16.3% based on the present modification. The parametric study of the ship waves in a typical restricted waterway of India revealed that the concentration of the sediments gradually decreases from the navigation channel to the river banks due to dissipation in the ship waves. The change in wave height and depth-averaged sediment concentration increases with the increasing depth Froude number. Finally, the impact on sediment transport due to different scenarios, such as the movement of two vessels in close proximity, the passage of vehicles coming from the opposite direction on the navigation channel, the influence of small draft vessels, and the bed morphology changes due to the multiple vessel movements are analyzed and reported. [ABSTRACT FROM AUTHOR]

During their flow through an area, the streams are used to erode, transport and re-deposit sediments in the number of cycles following the climatic variation in an area. This cycle in turn affect the chemistry of these sediments and hence the geochemical study of these sediments helps to understand the palaeo-climate, source-area weathering and provenance of the study area. In order to understand the geochemical classification of sediments, palaeo-climate, source-area weathering and provenance for stream sediments of the Eastern Ghats Mobile Belt (EGMB), 364 stream sediment samples were collected from the area around Daringbadi, Kandhamal district, Odisha, India and analyzed for major oxides, trace elements and rare earth elements. These sediments are geochemically classified as shaly and wacke type, moderately mature and derived through the high intensity of weathering of source rock under warm and humid climatic condition. The positive correlation between Al2O3 and Fe2O3, MnO, and MgO, indicates multiple sources for sediment and these oxides are associated with clay minerals. The discrimination function diagram suggests a felsic igneous as well as quartzo-sedimentary provenance for these sediments whereas the ratio of Al2O3/TiO2 and concentration of V-Ni-Th suggest a felsic igneous source rock. The high concentration of LREE, slight enrichment of HREE and negative Eu anomaly indicate terrestrial or continental crust source rock. Hence the source rock for these sediments are granite gneiss, charnokite and khondalite present in and around Daringbadi area. [ABSTRACT FROM AUTHOR]

The study proposes an efficient method to evaluate the suspended sediment concentration (SSC) relative to the traditional sediment rating curves (SRC) for gauged stations and subsequently to predict the SSC in ungauged stations of a major river basin. Multiple environmental control parameters were collected from 16 stations along the Mahanadi River basin (MRB) during the monsoon season. The hysteresis behaviour of SSC is assessed and therefore considered for modelling SSC using linear mixed-effects modelling (LMM). A basin-scale rating model is proposed using principal component analysis and stepwise multiple linear regression for estimating the unmeasured SSC. The findings show that the MRB acts differently in terms of hysteresis, with distinct dilution and flushing regimes in SRC. LMM outscored SRC by nearly doubling the mean covariance and notably reducing the percent bias between observed and predicted data across stations. However, unlike LMM, SRC could not correctly estimate low and high SSCs of ≤ 0.05 g/l and ≥ 1.5 g/l, respectively. The error metrics of the proposed rating model are within acceptable limits for all ungauged stations. Nevertheless, its efficiency varies due to smaller catchment areas, non-linearity in sediment transport with respect to catchment area, and other sampling issues. As a result, compared to other known models applied on the MRB, this model has the lowest error and seems to be the best in predicting monthly SSC. [ABSTRACT FROM AUTHOR]

The change in the shoreline greatly influences the coastal developments such as maritime trade, fishing activities, coastal transport, and tourism. Due to the requirements of vast developments along the coast near major habitat zones, such as the Karaikal coast along the east coast of India, it is essential to understand the longshore sediment transport (LST) movement to plan for any coastal systems to protrude. A detailed LST estimate has been made with the predicted wave climate using the wind-wave model, WAM. The wave characteristics are compared with the field measurements off the coast considered herein. The LST rates computed using five different sediment transport formulae and the method of integrating the distribution of sediment transport rates within the surf zone have been computed to understand the variations of the estimate in each method. Although the predominant direction of sediment movement is towards the north, there is a seasonal variability of LST based on the prevailing monsoon wind direction. Monitoring and analysis of the LST are important as it is required in designing coastal structures. [ABSTRACT FROM AUTHOR]

Episodic extreme waves caused by cyclones can have catastrophic consequences for coastal zones, including drastic beach morphology changes. The present study analyzed the beach morphological changes from Kakinada to Konapapapeta on the southeast coast of India before, during, and after the tropical cyclone Phethai using field survey and numerical modeling. Beach profiles were collected using Trimble RTK GPS and shoreline tracking was performed with handheld GPS. Numerical modeling was carried out using MIKE software to estimate the sediment transport rate before, during, and after the cyclone. Although the intensity of the cyclone reduced to a deep depression before landfall, several morphological changes were observed. Erosion was higher in the northern sector, where the beach width was less, and prominent scarps were seen throughout this region after the cyclone. The inundation varied from 40 to 120 m during the cyclone due to a storm surge of 0.5 to 1 m. During the cyclone, significant wave heights reached up to 4 m. The gross sediment transport rate is 3 to 13 times greater during the cyclone period than during the non-cyclone period. The maximum gross sediment transport rate during the Phethai cyclone was 1040 m3/day. Sediment transport was estimated for the same site for the non-cyclone year 2019, and the gross transport rate was 26,174 m3. As it is projected that extreme events are likely to increase due to climate change, output from this type of study is vital to environmental managers to assess erosion and develop long-term mitigation plans. [ABSTRACT FROM AUTHOR]

Forecasting of sediment load (SL) is essential for reservoir operations, design of water resource structures, risk management, water resource planning and for preventing natural disasters in the river basin systems. Direct measurement of SL is difficult, labour intensive, and expensive. The development of an accurate and reliable model for forecasting the SL is required. Sediment transport is highly non-linear and is influenced by a variety of factors. Forecasting of the SL using various conventional methods is not highly accurate because of the association of various complex phenomena. In this study, major key factors such as rock type (RT), relief (R), rainfall (RF), water discharge (WD), temperature (T), catchment area (CA), and SL are recognized in developing the one-step-ahead SL forecasting model in the Mahanadi River (MR), which is among India's largest rivers. Artificial neural networks (ANN) in conjunction with multi-objective genetic algorithm (ANN-MOGA)-based forecasting models were developed for forecasting the SL in the MR. The ANN-MOGA model was employed to optimize the two competing objective functions (bias and error variance) with simultaneous optimization of all associated ANN parameters. The performances of the proposed novel model were finally compared to other existing methods to verify the forecasting capability of the model. The ANN-MOGA model improved the performance by 12.81% and 10.19% compared to traditional AR and MAR regression models, respectively. The results suggested that hybrid ANN-MOGA models outperform traditional autoregressive and multivariate autoregressive forecasting models. Overall, hybrid ANN-MOGA intelligent techniques are recommended for the forecasting of SL in rivers because of their relatively better performance as compared to other existing models and simplicity of application. [ABSTRACT FROM AUTHOR]

Flash floods are considered one of the most devastating natural hazards due to a short time scale. Ensemble-based approaches have recently become popular in flash flood susceptibility modeling due to their strength and flexibility with data. This study aimed to incorporate new ensemble approaches to bivariate statistical model, such as the quantitative approach of weight of evidence (WOE) with multivariate statistical models, such as artificial neural networks (ANN), support vector machine (SVM), and the K nearest neighbor (KNN) model. The Uttarakhand state of India was selected as a study area. A flash flood and geospatial database were developed in this regard. In the historical database, a total of 122 flash flood points were identified. A geospatial dataset was created with aspect, plan curvature, elevation, normalized difference vegetation index (NDVI), slope, stream power index (SPI), topographic wetness index (TWI), annual rainfall, distance from river, distance from road, land use/cover (LULC), and sediment transport index (STI) in GIS. Weights were assigned to each influencing factor based on correlation using WOE in R open-source software, then ensembled with ANN, SVM, and KNN. Finally, all models were validated with different statistical indices, and subsequently, their performances were compared. All of the built models performed well, according to the results. However, WOE-ANN outperformed all machine learning models. The results of the study can help local governments and researchers with flash flood management. [ABSTRACT FROM AUTHOR]

The morphometric analysis was carried out on the Halayapura microwatershed in Karnataka, India. Using ArcGIS 10.2.2 and applying the DEM model, the micro-watershed was subjected to quantitative investigation to determine the channel network involved and understand geo-hydrological behavior. In addition, remote sensing and geospatial techniques were used to study the micro-watershed drainage analysis and its associated parameters, such as stream order, stream length, stream frequency, drainage density, texture ratio, form factor, circulatory ratio, elongation ratio, bifurcation ratio, and compactness coefficient for the micro watershed, were evaluated. According to the findings, the stream order ranges from I to IV, with 97 streams in the micro-watershed. Streams of 72, 19, 5, and 1 are found in the I, II III, and IV order, respectively. The bifurcation values range from 3.78 to 5.00, with the average weight around 3.14. The elongation ratio and farm factor are 0.77 and 0.46, respectively. The drainage density of the micro watershed is 5.20 km/km². The form factor, circularity, and elongation ratio contribute to a basin with an elongated shape through decreased flood proneness, erosion, and sediment transport capacity. The results of the microwatershed morphometric assessment are critical for evaluating and managing water resources and selecting a recharge structure for future water management in the study region. [ABSTRACT FROM AUTHOR]

Soil erosion is a severe environmental problem worldwide, especially in tropical regions. The Revised Universal Soil Loss Equation (RUSLE), one of the universally accepted empirical soil erosion models, is quite commonly used in tropical climatic conditions to estimate the magnitude and severity of soil erosion. This study, apart from identifying the role of individual parameters in influencing the results of the RUSLE, also aims at refining the RUSLE results by incorporating the state-of-the-art technique Persistent Scatterer Interferometric Synthetic Aperture Radar (PSInSAR) in a GIS environment by utilizing its ability to measure minute surface changes in millimetre levels. Apart from this novel approach of prioritising soil erosion classes using PSInSAR, the eroding surface conditions were also studied using low coherence value (<0.75 in this study). The spatially and temporally averaged annual soil loss and net soil erosion (2015-2019), derived through RUSLE and transport limited sediment delivery (TLSD) approach, respectively, was improved by spatially integrating the PSInSAR velocity map. The integrated methodological framework is demonstrated for a tropical river basin in South India (Muvattupuzha River Basin [MRB]), which shows a mean rate of net soil loss of 6.8 ton/ha/yr, and nearly 8% of the area experiences deposition. Our approach to improve the accuracy of RUSLE-based soil erosion classes using PSInSAR techniques clearly demarcated the areas that call for utmost priority in implementing management practices. The corollary results show that the very severe soil erosion class is characterized by PSI velocity with higher negative values, followed by the successively lower classes. Results strongly suggest that RUSLE output can be improved as well as validated using a velocity map derived from radar data. [ABSTRACT FROM AUTHOR]

The present geomorphic study analyzes the morphometric anomalies of the lateritic badlands (West Bengal, India) to understand the erosion intensity, triggering factors and landscape evolution using the ALOS AW3D30 DEM and quantitative techniques of various hydro-geomorphic processes (viz., basin morphometry, rainfall-runoff simulation, geomorphic threshold, erosion indices, sediment yield, SPI, and STI etc.). The GIS-based analysis reflects that there is the requitement of minimum drainage area (i.e. 55.71-349.01 m²) to maintain one metre of gully channel in the basins which have the network density of 2.86-13.76 km km-2. The critical slope (i.e. geomorphic threshold) of badland terrain varies from 0.0222 to 0.0407 metre metre-1, having dominance of overland flow erosion to initiate gully heads. The basin-wise SCS-CN and USLE coupling estimates that within the daily rainfall range of 11.41-66.41 mm day-1, the potential sediment yield of gully basins varies from 2.15 to 9.10 t ha-1. The SL index (i.e. 0.81-47.32 m) diagram reflects the beats of gully energy profile due to stream erosion enhancement, slope steepness, resistance of underlying lithologies and active tectonics. Hypsometric integral values of the gully basins, ranging from 0.4 to 0.6, emphasize a low entropy-based fluvial system and development of mature-youthful landform stage. The evolutionary stages of badlands are explained here by the connectivity model and hillslope -- gully -- river coupling system, showing a quasi-equilibrium to complex stage of landscape development at present. [ABSTRACT FROM AUTHOR]

Identifying coastal stretches that are likely to erode under high wave conditions is essential to the coastal management community in addressing beach erosion-related issues. The manuscript presents a case study to predict erosion of a selected beach located on the eastern Indian coast during the 2018 southwest (SW) monsoon season. The pre-monsoon beach topography surveyed using DGPS is used as the initial topographic condition in the morphological model. The model simulates subsequent beach erosion during the SW monsoon season, which is forced by forecast waves. Beach erosion advisories that classify the beach as eroding, accreting and no change are disseminated with a lead period of 10 days. During the SW monsoon period, we have monitored the beach using the dumpy level, and the beach topography during the post-monsoon is generated using DGPS surveyed profiles and are used for model validation. The beach area under erosion observed from the model result is homologous with the in-situ observations. The model shows cross-shore sediment transport to dominate during the SW monsoon, particularly in the central and northern sectors of RK beach. The model estimated shoreline position agrees with the DGPS observations, where the central sector has undergone maximum erosion. The comparison shows the model's ability to simulate beach morphodynamics like landward shifting of the berm crest under a high wave setup and oscillating water levels due to tides. The study highlights the importance of numerical modelling systems that decipher the beach response to the high monsoon waves. Research highlights: Beach erosion forecast system for RK Beach, India. Forecast system is developed using a combination of WAVEWATCHIII and Xbeach. Beach erosion advisories during monsoon period. [ABSTRACT FROM AUTHOR]

The Brahmaputra River in Assam exhibits a typical braided pattern and is characterized by a sediment load comprising of sand and mud. The river contains channel-bars of varied types and dimensions and embraces the world's largest river island — Majuli, which at present is under the effect of severe bank-erosion along its southern margin. The objective of this study is to examine the characteristics of fluvial sedimentation prevailing along the southern margin of the Majuli landmass. Both channel as well as bank sediments were analyzed to understand the mechanism of transportation, depositional process and hydrodynamic behavior. Both channel and bank sediments consist of very fine to medium sand with subordinate amount of silt and mud. Majority of the sediments exhibit well to very well sorting and positive skewness. The Probability curves of grain size distribution indicate transportation of sediments dominantly by saltation mode with minor amount by suspension and surface-creep mode. CM plot suggest transportation by graded suspension (saltation) with subordinate rolling and uniform suspension process by means of tractive current. The internal stratifications are dominated by planar cross stratifications followed by horizontal stratifications, trough cross stratifications, ripple laminated layers and massive sand. The bank sediments in few locations exhibit a general fining upward sequence which ends up with the deposition of a mud layer. The lithofacies sequences of the study area show prevalence of both lower as well as upper flow regime energy conditions indicating fluctuations of energy conditions during their respective sedimentation. [ABSTRACT FROM AUTHOR]

To investigate the evolution of sediment provenances and transport processes in the central Bay of Bengal (BoB) since the Last Glacial Maximum, we present a comprehensive study on the grain size, clay minerals, rare earth elements, and accelerator mass spectrometry (AMS)14C analyses of the core BoB-24 sediments. Six AMS14C dates were obtained from planktonic foraminiferal Neogloboquedrina dutertrei (N. dutertrei) extracted from the core to reconstruct a reliable age model. The assemblage of clay minerals and the (La/Yb) UCC –δEu relationship indicated that the core contained a mixture of sediments from the Himalayas and Indian Peninsula. These results showed that the Himalayas were the main source of erosional materials during 25–6.5 ka BP, whereas those from the Indian Peninsula increased since the mid-Holocene. Between 25 ka BP and 12 ka BP, the sea level was relatively low, and a large amount of terrigenous detrital material were directly transported from the Himalayas and the Tibet Plateau to the study area by submarine canyons, forming a deposition center on the Bengal Fan. Between 12 ka BP and 6.5 ka BP, the sea level gradually rose and the Indian summer monsoon gradually strengthened, whereas the sedimentation rate and the amount of material transported from the Ganges–Brahmaputra River decreased greatly; the deposition center transferred from the Bengal Fan to the shelf of the BoB. Since 6.5 ka BP, the sea level has risen, reaching its present position. A high sea level and a strengthened East Indian Coastal Current resulted in an increase of material contribution from India, while the deposition center was on the shelf of the BoB. Overall, this study confirmed that both sea level fluctuations and variations of the Indian summer monsoon controlled the evolution of sediment provenances in the central BoB and transfer of the deposition center from the Bengal Fan to the continental shelf. This typical sedimentary pattern observed in the northeastern Indian Ocean improves our general understanding of past land–sea interactions. [Display omitted] [ABSTRACT FROM AUTHOR]

One of the natural disasters caused by river meandering is riverbank erosion, which creates social, economic, and environmental problems in the riparian zone and serves as a source of increasing sedimentation levels in the river. Riverbank erosion and bank failure create a complex cyclical process, such as riverbank retreat, which cannot be easily measured and predicted by any model. The meandering flow along the Bhagirathi-Hooghly river has created riverbank erosion and riverbank retreat conditions in several areas, through which measuring bank stability and erosion is quite complex. As a result, the BSTEM model, integrating with HEC-RAS, has been used in this article to measure riverbank erosion and retreat accurately. Riverbank erosion and retreat data for 2019–2020 have been simulated based on data observed from 2016 to 2018 for accurate measurement. In addition, the total sediment yielded from the river bank has been calibrated and simulated with the help of sediment transport formulation in HEC-RAS, which indicates a gradual increase in river erosion at present (2019–2020). This model is expected to help formulate government policy on protecting riverbank erosion and river restoration in the future. [ABSTRACT FROM AUTHOR]

Sandy beaches generally are influenced by various coastal dynamic processes and undergo constant changes. The present study is an attempt to understand the hydromorphodynamic characteristics of a sandy pocket beach situated along the central west coast of India through field observation and numerical modeling. Multiple oceanographic instruments are deployed to capture the actual nearshore hydrodynamics, and sediment transport is measured using the streamer trap method suggested earlier during the premonsoon season. The observed vertical distribution of sediment fluxes showed a typical upward decrease from the seabed to the water surface. It is also noted that nearly 75% of the trap measurements showed that near-bed transport is higher than the depth-integrated values, confirming that the maximum sand remobilization is in the vicinity of the seabed rather than in suspension. The beach profiles of selected transects were measured during the pre- and postmonsoon seasons to understand the bed evolution. A one-dimensional numerical model, developed using XBeach and validated with field-observed values, demonstratively captured the effect of monsoon hydrodynamics on the beach profiles with fair accuracy. The various significant numerical parameters that govern the morphodynamics in the sandy beach are evaluated through a comprehensive analysis. In the end, the simulated beach profile that captures the effect of monsoon and storm are in good agreement with that obtained from field observations, with Brier Skill Scores (BSSs) of 0.69, 0.76, and 0.74 for Profiles 1, 2, and 3, respectively. [ABSTRACT FROM AUTHOR]

Black, K.P.; Baba, M.; Mathew, J.; Kurian, N.P., and Ilic, A., 2021. Guidelines to prepare India's coast for climate change. Journal of Coastal Research, 37(6), 1117–1129. Coconut Creek (Florida), ISSN 0749-0208. India's first coastal protection guidelines for climate-change adaptation are described. The guidelines are holistic, recognizing the links between engineering, economic, physical, legal, social, environmental, and governmental intricacies. Robust protection solutions under climate change for millions of coastal residents may occur only when all these facets are improved within the complex regulatory, budgetary, and practical circumstances in India. Fifty-seven specific guidelines are presented in nine categories ranging from administrative to best-practice coastal protection. An "environmental softness ladder" that ranks coastal protection methods was developed as a scientific tool to guide policy development and project implementation. "Minimum floor level" for safe building was defined for each Indian coastal state using climate-change data produced for the study by Indian and international institutes. Beaches are more stable when the net sediment transport fluxes are close to neutral. "Grand schemes," which make large-scale changes to the coast rather than continuing with piecemeal localised works, are recommended. With diverse dynamics over a long coastline in India, the 4-year study engaged an exceptionally large number of experts, agencies, government bodies, development partners, and other stakeholders. [ABSTRACT FROM AUTHOR]

Black, K.P.; Kulkarni, K.B.; Naik, G.B.; Naik, M., and Mathew, J., 2021. Improving training wall orientation at river and estuary entrances. Journal of Coastal Research, 37(3), 484–493. Coconut Creek (Florida), ISSN 0749-0208. Natural river and estuary entrances adjust in response to the prevailing sedimentary and hydrodynamic environment. In India, during the monsoon rains, the ebb jet can be very large, firing water and sediments along a variable orientation to create the associated ebb deltas. However, once the entrance is trained onto a fixed alignment, this powerful jet "pump" can have adverse impacts. Due to downdrift erosion caused by the entrance training walls at the Old Mangalore Port (Karnataka, west coast of India), the breakwater was modified to reorient the ebb jet in the direction of the longshore drift. The goal was to beneficially use the natural pumping action to drive sand across the entrance without mechanical assistance. Three years of monitoring revealed improvements in downdrift beaches and navigational safety, while maintenance dredging has ceased. The entrance region has deepened by 854,166 m3 after reorienting the ebb jet over the period from October 2017 to February 2020. In contrast, the entrance shoaled by 160,305 m3 over the period from September 2008 to October 2017. The results are relevant to river and estuary entrances with moderate to strong river flows and/or tidal prism. [ABSTRACT FROM AUTHOR]

Coastal currents consist of wind-driven, tidal, surface wave and geostrophic flows. These currents have a major role for nearshore sediment transport, but the measured data availability on coastal currents for the Indian coast is relatively less. This study analyze the variability of coastal currents along with the tides at nearshore and offshore waters during two different seasons (fag end of summer monsoon and initial stage of pre-monsoon) at Vengurla, west coast of India. Results of this study exhibited that the tides at Vengurla are mixed semi-diurnal dominated by solar constituent during summer monsoon (September to October); whereas the lunar constituents dominates during pre-monsoon (February to March). The nearshore current was dominated by the westward flow (sluggish current) during monsoon and south eastward flow during pre-monsoon, whereas the offshore flow (strong current) showed seasonality. At offshore, southerly current dominated during summer monsoon, whereas the northerly current played a major role during pre-monsoon. The current profile analysis at offshore revealed that the gradation of strong current at the surface to the sluggish nature of currents at the bottom and were comparatively higher during summer monsoon than pre-monsoon periods. This study revealed a complex pattern among winds, tides and currents at offshore. [ABSTRACT FROM AUTHOR]

Suspended sediment load is a substantial portion of the total sediment load in rivers and plays a vital role in determination of the service life of the downstream dam. To this end, estimation models are needed to compute suspended sediment load in rivers. The application of artificial intelligence (AI) techniques has become popular in water resources engineering for solving complex problems such as sediment transport modeling. In this study, novel integrative intelligence models coupled with iterative classifier optimizer (ICO) are proposed to compute suspended sediment load in Simga station in Seonath river basin, Chhattisgarh State, India. The proposed models are hybridization of the random forest (RF) and pace regression (PR) models with the iterative classifier optimizer (ICO) algorithm to develop ICO-RF and ICO-PR hybrid models. The recommended models are established using the discharge and sediment daily data spanning a 35-year period (1980–2015). The accuracy of the developed models is examined in terms of error; by root mean square error (RMSE) and mean absolute error (MAE); and based on a correlation index of determination coefficient (R2). The proposed novel hybrid models of ICO-RF and ICO-PR have been found to be more precise than their stand-alone counterparts of RF and PR. Overall, ICO-RF models delivered better accuracy than their alternatives. The results of this analysis tend to claim the appropriateness of the implemented methodology for precise modeling of the suspended sediment load in rivers. [ABSTRACT FROM AUTHOR]

Impact of climate change on glaciers brings the favorable conditions of lakes formation within glacier moraines. These lakes may produce outburst floods and transport the huge amount of debris (debris flow) in downstream settlements. The present study addresses the current knowledge on mass movement activity occurred in the Gangotri glacier area, Garhwal Himalaya Uttarakhand. Temporal response (terminus retreat and frontal area loss) of Meru glacier during 1976–2019 using the images of Landsat (MSS, 1976; TM, 1990, 2011; ETM+, 2001; OLI, 2019) and event of intense mass movement occurred along Meru glacier during 2017 is assessed. Our estimations clearly reveals that the Meru glacier is retreating continuously since 1976 with inconsistent rate. Considering the time span 1976–1990, 1990–2001, 2001–2011, 2011–2019 the terminus receded with 12.42 m y−1, 7.72 m y−1, 6.00 m y−1, 11.50 m y−1 and vacated the frontal area at the rate of 2330.70 m2 y-1, 2185.88 m2 y-1, 1425.18 m2 y-1, 1452.66 m2 y-1 respectively. Field observations and high resolution imagery of LISS IV suggest that the lower area of Meru glacier experienced the event of intense mass movement in July, 2017. This event breached the continuity of left morainic wall of Bhagirathi valley. This mass movement event influenced the initial course of Bhagirathi River (~1559 m length) and also modified the morphology of the Gaumukh region. The precipitation data from Indian Meteorological Department (IMD) and satellite images of different years suggest that the multiple factors such as intense precipitation, large amount of sediment transport from the upper reaches to lower area, slope failure, collapse of frontal part of Meru glacier were the main causative factors for this event. [ABSTRACT FROM AUTHOR]

Understanding the extent to which local factors, including bedrock and structure, govern catchment denudation in mountainous environments as opposed to broader climate or tectonic patterns provides insight into how landscapes evolve as sediment is generated and transported through them, and whether they have approached steady‐state equilibrium. We measured beryllium‐10 (10Be) concentrations in 21 sediment samples from glaciated footwall and hanging wall catchments, including a set of nested catchments, and 12 bedrock samples in the Puga and Tso Morari half‐grabens located in the high‐elevation, arid Zanskar region of northern India. In the Puga half‐graben where catchments are underlain by quartzo‐feldspathic gneissic bedrock, bedrock along catchment divides is eroding very slowly, about 5 m/Ma, due to extreme aridity and 10Be concentrations in catchment sediments are the highest (~60–90 × 105 atoms/g SiO2) as colluvium accumulates on hillslopes, decoupled from their ephemeral streams. At Puga, 10Be concentrations and the average erosion rates of a set of six nested catchments demonstrate that catchment denudation is transport‐limited as sediment stagnates on lower slopes before reaching the catchment outlet. In the Tso Morari half‐graben, gneissic bedrock is also eroding very slowly but 10Be concentrations in sediments in catchments underlain by low grade meta‐sedimentary rocks, are significantly lower (~10–35 × 105 atoms/g SiO2). In these arid, high‐elevation environments, 10Be concentrations in catchment sediments have more to do with bedrock weathering and transport times than steady‐state denudation rates. © 2020 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Two major facies associations are identified in the Upper Kaimur Group of the Son Valley, namely, tidally influenced fluvial channel facies association and tidal sand flat association. Lithofacies supports the Dhandraul Sandstone as the product of a tidally‐influenced fluvial channel and the underlying Scarp Sandstone as a tidal sand flat, which endorse a tide‐dominated estuarine setting. Grain size analysis shows that most of the sandstone samples are medium‐ to coarse‐grained and only small fractions are of fine‐ and very fine‐grained categories. In general, sediments are moderately well sorted, near‐symmetrical to fine‐skewed and leptokurtic to mesokurtic in nature, suggesting deposition under fluctuating energy conditions in different geomorphic domains from a tidally‐influenced fluvial channel to beach settings. Bivariant plots combining the textural parameters imply that marine processes dominate over fluvial processes in the Upper Kaimur Group sediments. Cumulative curves and C–M plot suggest sediment transport mainly by saltation and bottom suspension processes under varying energy conditions. [ABSTRACT FROM AUTHOR]

Sediment transport is one of the major challenging fields in hydrology. The tropical atmosphere, complex topography and occasional extreme precipitation are the fundamental explanations behind this challenge. Thus, the rivers in this situation contain a huge quantity of sediment, which may affect the river hydraulics. Hence, it is required to collect various parameters such as discharge, velocity, rainfall and sediment concentration to analyze the impact of sediment for river engineering practices and management. Therefore, the dataset which is collected from the river may contain outliers and noises. For improving the prediction accuracy of sediment load, we present robust regularized extreme learning machine frameworks to reduce the effect of noise by using the asymmetric Huber loss function named as AHELM and ε - insensitive Huber loss function named as ε - AHELM. Further, the problems are rewritten in the form of strongly convex minimization problems whose solutions are acquired by simple function iterative schemes. To ensure the effectiveness of the proposed approach, we have considered the real-world datasets with two types of noises. Furthermore, the proposed schemes are applied on real sediment load datasets (SLDs) which are collected from the Tawang Chu river of Arunachal Pradesh, India. The results reveal that proposed AHELM and ε - AHELM with multiquadric activation function are performed better for real-world datasets, whereas AHELM and ε - AHELM with sigmoid activation function perform efficiently and effectively for the sediment load prediction. In overall, the experimental results clearly exhibit the applicability as well as the usability of the proposed extreme learning machine with asymmetric Huber loss functions. [ABSTRACT FROM AUTHOR]

Black, K.P.; Reddy, K.S.K.; Kulkarni, K.B.; Naik, G.B.; Shreekantha, P., and Mathew, J., 2020. Salient evolution and coastal protection effectiveness of two large artificial reefs. Journal of Coastal Research, 36(4), 709–719. Coconut Creek (Florida), ISSN 0749-0208. Two offshore reefs constructed at Ullal, Karnataka, on India's west coast, are exhibiting coastal protection benefits. The reefs are large (275 m and 325 m long) and uniquely placed well offshore (600 m and 760 m) in intermediate depths (6 and 7 m below chart datum). Their crests are between low-tide and midtide level. Bathymetric and beach surveys show that sand has accumulated to form two evolving shoreline salients, which are currently 2–3 times the length of the reefs. The salients have grown underwater on the inner shelf to create a large sand-retention zone up to 1 m thick and stretching from the beach to the distant lee of the reefs. The reefs are the first protection structures that have restored the beaches and enhanced sand storage over this broad, severely eroded region, both inshore and on the inner shelf. Prior rubble-mound rock revetments (seawalls) and 50–70-m-long groynes failed to restore the beach in stormy monsoon conditions, while the inner shelf continued to erode. The reefs were designed using a combination of computer simulations, measurements of natural salients in India, and empirical relationships. The methodology that led to the reef shapes/sizes and their position offshore is discussed, along with monitoring results. [ABSTRACT FROM AUTHOR]

Dam‐related downstream adjustments of riverbeds are normally investigated by analysing the trend in sediment supply and high flow events during the pre‐ and post‐dam periods. The required data for existing predictive models is not measured at river gauges, which limits the application of these tools. We derived the frequency of sediment‐transporting streamflow events (T*) and upstream sediment supply (S*) in the pre‐ and post‐dam periods with widely available gauged records and predicted changes in the downstream riverbed by adapting an existing model. Ten gauging stations in the Godavari River Basin, India, located downstream of dams, were chosen as study sites. Annually surveyed cross‐sections at each site validated the accuracy of the predicted dam‐related downstream changes. Then, a regression equation (R2 = 0.75) was established between T*/S* (independent variable) and changes in the downstream bed elevation (dependent variable) for the Godavari Basin. We recommended that similar local empirical equations be formulated for larger river basins. Models of large‐scale rainfall‐runoff and sediment transport processes that can account for the influence of dams, such as the Soil & Water Assessment Tool, can be paired with the proposed regression equation to estimate dam‐related downstream erosion and deposition with globally available data. [ABSTRACT FROM AUTHOR]

Paleobeach ridges in and around the Digha coast, West Bengal, India give significant information about the sea regression in eastern Indian coast during Holocene. Beach ridges paralleling the Bay of Bengal coast in West Bengal and a few remnants beach ridges further landward in Kanthi (West Bengal) and Jaleswarpur (Odisha), give a tentative boundary of the north eastern most palaeo-shoreline. From optically stimulated luminescence (OSL) dates of the Paleobeach ridges, it is suggested that around 500 YBP, the sea was near Kanthi and around 378 YBP the sea was near Jaleswarpur (35 km inland). After that, the sea sequentially regressed in phases towards south and attained the present position at Digha. The Photogeology & Remote Sensing (PGRS) Study of different satellite imageries (2006 onwards) along with the Survey of India Toposheets (1930, 1972) of Digha area indicates that the coast line to be steadily regressed in the east of Digha, whereas, it shows fluctuation in the west of it. This fluctuation of strand line position may be due to the differential sediment influx through the Subarnarekha river mouth with time. Regional neotectonic activities also play a role in shaping the coast. The concave orientation of the beach ridge plains to the present shoreline reflects the supply of sediments in the direction of palaeolongshore currents. The shape of the inner beaches shows that the deposition prograded north-west wards. Major type of cross-beddings present in the Paleobeach ridges represented by low angle laminated sand, indicates the wide seaward dipping part of longshore bars. The grain size analysis of the sediment samples of the beach ridges indicate positively skewed and mesokurtic. The mean size of resultant sediments is finer, indicating that the energy level or turbulence of the eroding processes was incapable of transporting sediments coarser than the mean size of the source sediments. [ABSTRACT FROM AUTHOR]

Thomas, J.; Velamala, S.N., and Prasad, K.V.S.R., 2019. Numerical simulation of tidal constituents in Thane Creek and the Ulhas estuary, west coast of India. Journal of Coastal Research, 35(2), 376–388. Coconut Creek (Florida), ISSN 0749-0208. Complex tidal progression in creeks and estuaries attract a large number of researchers around the globe. The main motive of the present work is to study the complex tidal variation of Thane Creek and the Ulhas estuary on the west coast of India. A Delft3D model was applied to simulate its depth-averaged hydrodynamics and tidal propagation along the system, and the calibration and validation of this model revealed its accuracy. The system was classified as hyposynchronous; a gradual decrease in the amplitude was noticed from mouth to upstream in all seasons. The interpretation of the major tidal constituents amplitude and phase, shallow water constituents, form number, and tidal asymmetry showed the dynamic nature of the system. The form number results revealed that the tide in Thane Creek and the Ulhas estuary is mixed semidiurnal. The tidal asymmetry parameter indicated a seasonal variation of ebb and flood current in Thane Creek and the Ulhas estuary, which favors sedimentation processes in the system with consequent erosion and deposition. For the future, these results will help in understanding sediment transport and the corresponding shoreline changes and the biogeochemical processes of this dynamic system and help to establish its sustainability. [ABSTRACT FROM AUTHOR]

Chilika lagoon, one of the largest brackish water lagoons in Asia located along the east coast of India. The rivers draining into the lagoon carry about 13 million tonnes of sediments annually. Because of the cohesiveness properties of the fine sediments, nutrients, heavy metals and other polluted substances tend to bind to the sediment's surface. Consequently, pollutants can be concentrated in the inlets/estuaries, thus being of great environmental interest. In addition, the mudflats occurring are important biotopes for a large number of micro- and macro-faunal species and act as feeding places for a number of birds. To understand the cohesive sediment dynamics, a numerical model, MIKE 21 Mud Transport (MT) coupled with hydrodynamic (HD) was used. The model simulated the relative bed level height and suspended sediment concentrations. The sediment interchange and accumulation between each sectors and Bay of Bengal were evaluated. The suspended sediment concentration is high in the north-east portion of the lagoon while medium and low suspended loads are observed in the eastern and western portion of the lagoon. Bed thickness is very high in the north-western corner of the lagoon covered with Phragmites Karka which facilitate sediment trap. Total bed thickness change is very much pronounced in the northern sector which receives most of the sediments from the Mahanadi river systems as well along the periphery of the lagoon due to drainage. The eastern lagoon shows a net deposition accumulated fraction (5–15 kg/m2) and hence gives enough indication of the sedimentation processes in the lagoon. Further, the results also warrant immediate attention to check and monitor suspended sediment concentration to find out the net deposition trend in the lagoon environment in order to take decisions in minimizing the sediment load. [ABSTRACT FROM AUTHOR]

The complex and unique riverbank erosion characteristics of the Brahmaputra River in India, the fourth largest river in the world in terms of average discharge at the mouth and second only to the Yellow River in China in the amount of sediment transported per unit drainage area, is highlighted with illustrations of the severity of erosion caused at various bank locations. First, the source and the entire course of the river are described. Riverbank erosion mechanisms and existing erosion control measures and their effectiveness in the Assam reach of the Brahmaputra River are described. As part of a joint effort for the first time between U.S. and Indian (local) investigators to understand and find solutions to this mega unique problem of the Brahmaputra River, a set of recommendations, including a phase-wise multiple solutions to the acute and potential riverbank erosion sites along this large river, is forwarded for discussion and getting feed back from international experts. [ABSTRACT FROM AUTHOR]

The present study documents the wood-boring trace fossil Asthenopodichnium from the Palaeocene sediments of the Barmer Hill Formation (BHF) in the Barmer Basin, Western Rajasthan, India. The Asthenopodichnium trace fossils are loosely to tightly packed, pouch-like burrows or almond-shaped structures identified as Asthenopodichnium lignorum, whereas lozenge and J-shaped structures are designated as Asthenopodichnium lithuanicum. The A. lignorum trace markers are considered to be the feeding and dwelling burrows produced by wood-rotting fungi, whereas A. lithuanicum are interpreted as feeding and dwelling burrows produced by Mayfly nymphs and larvae. The sedimentological and palaeontological studies of trace fossil-bearing horizons of BHF suggest freshwater fluvial sedimentary environment with humid to sub-humid climate. [ABSTRACT FROM AUTHOR]

Estimation of Longshore Sediment Transport Rate (LSTR) in the littoral zone is essential for managing and developing any coastal zone. Numerical models are powerful tool to understand and investigate various processes responsible for LSTR in a systematic manner since direct measurement of LSTR is a difficult task. A one dimensional LITDRIFT model was implemented along the Vengurla coast for estimation of LSTR and to analyze the sensitivity of each input parameters towards the computation of LSTR. Major input parameters required for the estimation of LSTR are nearshore wave climate, bathymetry, and sediment characteristics. The nearshore wave data at a depth of 15 m were collected using wave rider buoy in 2015 is used in the present study. Field observations were carried out to survey the regional bathymetry and sediment characteristics. Annual net LSTR along Vengurala coast is relatively less and varies from −7778 to −9015 m3 with an average of −8511 m3. The net direction of LSTR is towards south and gross LSTR is 1.18 × 105 m3/year. The LSTR reveals more sensitivity to coastline orientation and wave direction. A 1° changes in coastline angle and wave direction causes approximately 3000 m3/month difference in LSTR. Moreover, wave height, wave period, and bed roughness has an important role for controlling LSTR. The model results help to identify the role of each parameter contributing towards LSTR estimation and a similar model approach can be applied to other coasts for estimating LSTR in an accurate way. [ABSTRACT FROM AUTHOR]

Sediment transport from mountainous to lowland areas is considered one of the most important geomorphological processes. In the present study, variations in transported sediment loads and dissolved loads have been studied over 3 years (2008–2011) for two forested catchments located in the Lesser Himalayan region of India. Seasonal and annual suspended sediment flux was strongly influenced by amounts of rainfall and streamflow. On average, 93% of annual load was produced during the monsoon, of which 62–78% occurred in only five peak events. Sediment production by the degraded forest catchment (Bansigad) was 1.9-fold (suspended sediment load) to 5.9-fold (bedload) higher than the densely forested catchment (Arnigad). The dissolved organic matter potentially influences total dissolved solids in the stream. Heavy rainfall triggers both stream discharge and landslides, which lead to higher bedload transport. Total denudation rates for Arnigad and Bansigad were estimated at 0.68 and 1.02 mm year−1, respectively. [ABSTRACT FROM PUBLISHER]

Variability in the characteristics of depth-induced wave breakers along a non-uniform coastal topography and its impact on the morpho-sedimentary processes is examined at the island sheltered wave-dominated micro-tidal coast, Karwar, west coast of India. Waves are simulated using the coupled wind wave model, SWAN nested in WAVEWATCH III, forced by the reanalysis winds from different sources (NCEP/NCAR, ECMWF, and NCEP/CFSR). Impact of the wave breakers is evaluated through mean longshore current and sediment transport for various wave energy conditions across different coastal morphology. Study revealed that the NCEP/CFSR wind is comparatively reasonable in simulation of nearshore waves using the SWAN model nested by 2D wave spectra generated from WAVEWATCH III. The Galvin formula for estimating mean longshore current using the crest wave period and the Kamphuis approximation for longshore sediment transport is observed realistically at the sheltered coastal environment while the coast interacts with spilling and plunging breakers. [ABSTRACT FROM AUTHOR]

This study presents a Coupled Coastal Monitoring Framework (CCMF) that integrates remote sensing (CoastSat), video beach monitoring system (VBMS), and numerical modelling to analyse the morphology and hydrodynamics of a structure-influenced beach. A 10.2 km stretch of straight beach with an artificial breakwater along the Kozhikode coast of Kerala, India, is selected for the study. The shoreline change analysis revealed that 38% of the total coast is under erosion, with the northern sector of the breakwater being highly erosive and the southern sector being stable. Continuous monitoring from the VBMS confirmed the stability of the southern sector with varying erosion accretion trends during 2018–21. Coastal morphological features such as double bars, cusps, and rip-like formations were identified through the VBMS, validated and analysed in detail with distinct wave-current interactions and sediment transport through numerical modelling. The study concludes that the breakwater is effectively protecting the beach adjacent to the south but has disturbed longshore transport, potentially leading to increased erosion to the north. The proposed CCMF provides real-time and post-performance monitoring of structure-influenced beaches, enabling timely decision-making at critical locations and appropriate remedial measures for efficient coastal management. • Coupling of satellite remote sensing, coastal video monitoring and numerical model. • Hydrodynamics of breakwater influenced medium energy coast. • Analysis of coastal erosion trends and identification of erosion hotspots. • Extraction of morphological features viz. double bar, cusp and rip channels. • Identification of two less intensity rip hotspots at Kozhikode beach, India. [ABSTRACT FROM AUTHOR]

Chilika, a lagoon along the east coast of India, is undergoing transformation due to frequent shoreline change near inlet(s). Shoreline change near inlet includes change in position and shape of inlet, inlet channel length, and spit growth/erosion. These variable features of lagoon inlet(s) critically depend on alongshore sediment transport (LST) and discharge (water and sediment) from the lagoon to the sea. The LST and the processes responsible for sand spit growth/erosion, considered as important attributes of inlet stability, are the subject matter of the present investigation and hence the study assumes importance. The study includes integration of observational and modeling framework. Observations include nearshore wave, bathymetry, beach profile, shoreline and sediment grain size of spits while numerical modeling includes simulation of the wave using MIKE 21 Spectral Wave model and LST simulation using LITtoral DRIFT. The results indicate that the predominant wave directions as S and SSE, which induces round the year south to north alongshore transport with significant seasonal variation in magnitude. The estimated LST closely matches with previous studies near Chilika inlet and for other locations along the Odisha coast. Besides temporal variability, the study reveals spatial variability in alongshore transport near Chilika inlet and considers it as one of the important attributes along with northward spit growth for inlet migration/closure/opening. [ABSTRACT FROM AUTHOR]

The Chavara coast of southwest India is well known for its rich beach placer deposits which are being commercially exploited by the industries. Replenishment of these resources, which consist of heavy minerals of varying densities, by the hydrodynamic processes is essential for maintaining the stability of the coast as well as sustenance of mining. Rich concentrations of heavy minerals were reported consistently in the beach sediments of this coast in the past, but a systematic reduction in the concentration of the heavies has been reported during the past one-and-a-half decades. This paper, the first in a series of three, emanates from a programme of study launched to understand the mechanisms that manifest the reported changes in the morphology and mineralogy along this coast. In this study the longshore and cross-shore sediment transport rates along this coast have been estimated adopting numerical model studies. The validated LITDRIFT and LITPROF modules of the LITPACK modelling system have been used for computing the longshore and cross-shore sediment fluxes in the surf zone and innershelf region. The net annual longshore sediment transport is northerly in the surf zone where as it is southerly in the innershelf. Detailed analysis of the computed results shows domination of onshore transport over offshore transport. The beach volume change estimated from the measured beach profile on the other hand shows a reduction in the annual replenishment. The domination of the onshore flux as seen in the computations is actually not reflected in the field observations, and this can be attributed to the influence of excessive sand mining by the industries. [ABSTRACT FROM AUTHOR]

This study describes the assessment of reservoir sedimentation of the Patratu Reservoir using Satellite Remote Sensing (SRS). The sedimentation assessment was carried out using satellite data and reservoir water level data from 2006 to 2012. Water spread area was analysed from satellite data. The Normalized Difference Water Index (NDWI) has been used to delineate open water features and to enhance the presence of water surface in satellite imagery of the Patratu Reservoir. Water spread area of the reservoir at a particular elevation on the date of the passing of the satellite was used to develop an elevation-area curve. For the present case, fluctuation of water level was found to vary from 387.096 to 406.152 m. The linear interpolation/extrapolation technique has been employed to assess the water spread area of Patratu Reservoir at different elevations. Further, these areas were used to compute the live storage capacity of the reservoir between two elevations by the Prismoidal formula. From the study, it was found that due to sedimentation, the live storage capacity of Patratu Reservoir has reduced from 101.95 to 89.96 hm3, thus showing capacity loss of 11.76% in a span of 44 years. To increase the live storage capacity of the reservoir it is proposed to adopt manual and mechanical digging combined with flushing for desilting of the deposited sediment.EDITOR D. Koutsoyiannis ASSOCIATE EDITOR S. Kanae [ABSTRACT FROM PUBLISHER]

Accurate estimation of longshore sediment transport (LST) along the entire coastal stretch of Kerala is challenging as the sediment transport pattern varies both spatially and temporally depending on the nearshore wave climate, nearshore bedslope, shoreline orientation, coastal morphology, presence of hard structures etc. While majority of the locations show a net northerly drift, there are certain stretches of the coast which are dominated by southerly transport. For the estimation of longshore sediment transport the three commonly used formulae viz. CERC (SPM (1984)), Van Rijn (1991) and Kamphuis (2002) were considered. After detailed analysis of the computed LST results for different sectors of the coast using these formulae, the formula of Kamphuis (2002) which considers all the important parameters like the nearshore bed slope, sediment grain size and peak wave period in addition to the usual input parameters like the wave breaker height and wave breaker angle was selected as the most appropriate one. To understand the spatial and temporal variation in the LST pattern along the Kerala coast, the LST rates for eight important locations - viz. Trivandrum, Quilon, Aleppey, Andhakaranazhi, Nattika, Calicut, Kannur and Kasargod spread along the Kerala coast were computed adopting the Kamphuis (2002) formula. For computation of the LST rates for the eight locations, the one year site specific nearshore wave data derived from numerical model studies was used. For validation, the results were compared with that of the earlier estimations available in literature. It was observed that even though the net magnitude was of the same range, there were deviations in the direction. However, when the results were compared with field observations (where morphological indicators were used) a reasonable agreement could also be established for the directions. The net annual longshore sediment transport was found to vary between 0.32 x 10 5 m 3 and 2.3 x 10 5 m 3 along the Kerala coast and the net transport direction was pre-dominantly northerly for almost all the locations selected for the study. The maximum gross sediment transport of 12.85 x 10 5 m 3 was obtained for Trivandrum but the net transport for this station was much less, and therefore comparable with other locations. [ABSTRACT FROM AUTHOR]

Chilika Lake, Asia's largest brackish water lagoon, is located in the state of Odisha on the east coast of India. It was designated as a Ramsar site in 1981, being the first Indian wetland of international importance under the Ramsar convention. Siltation of the lake is become a major concern, because it is leading to various geomorphic changes that are affecting the shape and size of the lagoon, which receives a major silt load through the Daya and Bhargovi rivers (both being branches of the Mahanadi river) via the Kathajodi and Kuakhai rivers. The Naraj barrage was constructed at the mouth of the Kathajodi river to regulate its inflow, and also its silt load, into the lagoon. Two observatories are established in the Daya and Bhargovi rivers to determine the quantity of silt entering Chilika Lake through the rivers, with the bed load and suspended (total solids) being measured. Various effects of siltation in the lagoon because of the barrage are analysed in this study, to include the pre- and postconstruction situation. By considering different flood situations in the Mahanadi river, various alternate strategies for operation of the Naraj barrage were studied, with the goal of minimizing the siltation in Chilika Lake. These alternate operation strategies, and their potential effects on the inflow into the lagoon, are analysed and discussed in this report. [ABSTRACT FROM AUTHOR]

Watershed models supported by a geographic information system (GIS) and remote sensing data have proven to be vital research tools for the planning and management of land and water resources at watershed or river basin scales. The present study was undertaken with the objective of evaluating a watershed model for the simulation of streamflow and sediment yield in the Baitarani watershed of Eastern India. The watershed model was calibrated and validated using daily rainfall and streamflow data from 1998 to 2005 and sediment yield data from 2002 to 2005. Other input parameters of the watershed model such as digital elevation model, soil map, and land use/land cover map were generated using GIS. The performance of the model was evaluated using salient statistical and graphical indicators. The model calibration and validation results revealed that the watershed model simulated streamflow in the study watershed with a higher level of accuracy at daily [Nash-Sutcliffe efficiency (NSE) = 0.86 and 0.84] and monthly (NSE = 0.95 and 0.93) time steps during both calibration and validation periods. However, the model simulated sediment yields more accurately at the monthly time step (NSE = 0.91 and 0.90) than the daily time step (NSE = 0.62 and 0.59). During the entire period of sediment simulation (2002-2005), the total model-simulated sediment yield was 1,771 x 10³ tons against the observed sediment yield of 1,799 x 10³ tons with a deviation of approximately 1.6%. It is concluded that the watershed model is suitable for the simulation of streamflow and sediment transport in the study area, and it also has potential for adoption in other watersheds of the Baitarani River Basin as well as in other watersheds of India. [ABSTRACT FROM AUTHOR]

Saravanan, S. and Chandrasekar, N., 2015. Wave refraction pattern and littoral sediment transport along the SE Tamilnadu coast, India. The objective of the paper is to understand the wave refraction pattern and littoral sediment transport along the SE coast of India. There are areas of erosion and accretion observed along the coastal stretch that depend primarily the direction of wave approach, the wave period, and the wave refraction pattern. In the nearshore zone of the study area, the movement of sand alongshore is due to the action of waves and currents. Wave refraction is an important process responsible for effecting changes in coastal configuration. Based on this study, the wave convergent and divergent zones are identified with reference to wave refraction. Longshore sediment transport is higher in the northerly direction than in the southerly direction. The present study of littoral sediment transport implies that the beaches of Kanyakumari, Navaladi, and Ovari have greater transport rates. [ABSTRACT FROM AUTHOR]

The aim of the present research was to investigate the seasonal impact on nearshore beach dynamics and the status of heavy mineral distribution along central Tamil Nadu coast, India. Beach profile measurements were made in 10 profiling sites between Thirukadaiyur and Velankanni on monthly and seasonal basis from January 2011 to July 2012. Using beach profile data, variation in beach width, slope and volumetric changes have been calculated. Beach slope and nearshore wave parameters were used to quantify the longshore sediment transport rate. Beaches between Thirukadaiyur and Karaikkal attained predominant transport rate in northern direction whereas, the rest of the beaches are in southern direction. The seasonal action of wind and wave currents create nearshore bar during northeast (NE) monsoon and frequent berms at tidal zone during southwest (SW) monsoon. Surface sediment samples were collected in each location for quantifying the heavy mineral weight percentage during the period of pre- and post-Thane cyclone. Sediments were also studied by X-ray diffraction (XRD) to evaluate the changes and occurrence of heavy minerals in beach sands. The XRD results show that sediments in the study area have enriched heavy mineral distribution even after strong cyclonic event. It confirms the redistribution of heavy mineral deposits present in the coast. The results suggested that monsoonal action has influenced the seasonal changes in beach morphology and it does not affect the heavy mineral distribution. [ABSTRACT FROM AUTHOR]

The littoral drift regime along the northeastern coast of India was investigated by analyzing coastal drift indicators and shoreline changes based on multitemporal satellite images. The study of offshore turbidity patterns and quantitative estimation of suspended sediments was undertaken to understand the magnitude and direction of movement of sediment fluxes. The study revealed that: (1) the character of coastal landforms and sedimentation processes indicate that the sediment transport is bidirectional and monsoon dependent; (2) multidate, multitemporal analysis of satellite images helps to show the nature of sediment transport along the coast. The dominant net sediment transport is in a NE direction along the eastern coast of India. Finally, this assessment demonstrates the potential of remote sensing technology in understanding the coastal morphometric changes, long-term sediment transport, shoreline changes, and offshore turbidity distribution pattern and the implications for the transport of sediment-associated pollutants. [ABSTRACT FROM AUTHOR]