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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]

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]

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]

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]

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]

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]

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 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]

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]

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]

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 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]

Abstract: Indian River Inlet is located at roughly the mid-point of the Atlantic coast of Delaware and connects the ocean to two Delaware inland bays. Jetties constructed in 1940 have maintained the inlet for navigation purposes but have also acted as a barrier to net northerly alongshore sediment transport causing downdrift erosion. A mobile, land-based bypassing system was initiated in 1990 in an effort to counteract this erosion. Beach profile data from 1985 (pre-bypassing) until 2008 are used to investigate the effect of the sand bypassing system on beaches adjacent to the inlet. The downdrift beach experienced horizontal shoreline erosion between 10 and 60m during the pre-bypassing period but accreted 10–20m during the bypassing period. The mean shoreline location on the updrift beach during bypassing is 10–20m landward (erosion) of its position during the pre-bypassing period. Empirical orthogonal function (EOF) amplitudes from analyses performed on mean-removed elevation surfaces during the periods of highest bypassed volume (average of 83% of design rate) showed that the influence of the bypassing system on the downdrift beach extends to about 1500m of the inlet. An EOF analysis showed that different morphologic responses were evident following the initiation of bypass operations. Temporal variations of shoreline and beach morphology were correlated to the temporal variations in bypassing rates on the downdrift beach only. The downdrift beach response was greatest near the inlet for larger bypassing volumes. Correlation in these instances occurred with a roughly 1-year time lag suggesting that the beach quickly redistributes the bypassed sand. EOF amplitude and shoreline response are weakly correlated to bypassed volumes when the system bypassed smaller volumes (average of 56% of design rate) of sand suggesting that there is a minimum bypassing rate, regardless of yearly variability, below which the effect on the downdrift beach is obscured. [Copyright &y& Elsevier]

Abstract: An approach to deriving the transfer time of sediments within alluvial plains by using the variation of the U-series nuclides in sediments collected along rivers is presented in this article and discussed in the light of new data from samples from different locations within the Ganges watershed and its outlet. These data indicate that the upstream-downstream variation of 238U-234U-230Th disequilibria in the sediments, with different variation trends for suspended and coarse-grained sediments, is probably a general feature of all Himalayan rivers flowing across the Indo-Gangetic plain. The data therefore confirm the occurrence of very different transfer times within the plain, depending on the sediments granulometry, with much shorter transfer time for the fine-grained (a few ky or less) than for the coarse-grained sediments (100 ky or more). A new solving approach, using a parallel stochastic Quantum-behaved Particle Swarm Optimization (p-QPSO), has been developed for identifying the unknown parameters of the model necessary for the determination of the transfer time. The data of sediments collected at the Ganges outlet show significant variations of the 234U/230Th activity ratios for the fine-grained sediment end-member collected in 2004 and 2008. Such variations indicate that the fine-grained sediments transit quickly (a year or less) within the plain. The highly variable activity ratios might be the result of quickly changing weathering intensities. Conversely, the U-Th variations observed for the 2004 and 2008 bedload from the Ganges basin cannot result from a short sedimentary transfer time. They probably result from the dredge sampling procedure, which might be influenced by local placer effects controlling the abundance of U and Th carrying minerals. Dredging may not allow the sampling of a representative bedload, hence it may cause an artificial mineralogical and, therefore, an U-Th variability for bedload sediments collected at different periods. At this stage, the transfer time uncertainty induced by this variability is difficult to assess. [Copyright &y& Elsevier]

Indian Remote Sensing-P4 (IRS P4) Ocean Color Monitor (OCM) data is used to understand seasonal variations in suspended sediment (SS) dispersal pattern in the near-shore waters of the Central West Coast of India. Four distinct patterns of sediment dispersion are observed. (1) During monsoon, plume-like sediment dispersion seaward is observed especially in the mouths of rivers. (2) As the monsoon progresses, there is northerly transport of sediments with anticlockwise pattern within the plumes. (3) During NE monsoon, sediment concentration is less and its transport is southward. (4) During premonsoon, SS concentration is high in the near-shore water and transport is landward. Sequential OCM data analyses indicated the influence of tidal currents, especially during premonsoon in the vicinity of the river mouths on sediments dispersion. During rising tide, sediments move into the estuary, and during falling tide they flow seaward resulting in erosion and formation of shoals. Sediment-dispersal patterns largely follow wind and wave patterns, a characteristic feature of the mesotidal coast. Presence of a number of mudflats within the estuary along with the siltation in the channels suggests that a net landward transport of sediments occur in the region. [ABSTRACT FROM AUTHOR]

Spit growth is observed across many rivers of the central west coast of India. Studies on the seasonal dynamics of the spits of the central west coast of India on the basis of the multidate satellite images LISS III, landsatTM data, panchromatic camera (PAN) data etc. in a geographic information system (GIS) environment using ERDAS imagine 9.0 version followed by field-check and wave data analysis have been discussed in this paper. All types of spits such as paired spits, winglike spits, single spits, etc. are observed along the coast of Karnataka, central west coast of India. Spit growth is responsible not only for shifting of the river mouths, but also for rapid changes in estuarine morphology and in turn on the sedimentation process. It is observed that river mouths with a spit across them have a submerged bar in front of them, whereas rivers devoid of spits are also devoid of submerged bars in front of them. This spatial association of spit and submerged bar is believed to have a genetic relationship. Along the coast many perpendicular faults and uplifts have been observed. Rate of spit growth, along with their direction and inland drainage pattern, suggest a role of sea-level changes and tectonic control in addition to alongshore currents. Rapid spit growth is observed near the inferred tectonic axis. Seasonal dynamics and modification in the spit configuration are related to alongshore drift as well as the wave refraction around the mouth of the rivers. [ABSTRACT FROM AUTHOR]

Abstract: Variations in erosion were quantified across the topographically and morphometrically asymmetrical central Ladakh Range in NW India to elucidate erosion and sediment transfer processes across space and time and to gain insight into how mountains erode and evolve. Morphometric analysis and 10Be cosmogenic nuclide analysis of 14 fluvial sediment samples from active channels in six catchments conducted across the mountain range constrains 100ka timescale erosion rates for catchments on the northern side of the mountain range and are between 56±12 and 74±11m/Ma, while catchments on the southern side of the mountain range to between 20±3 and 39±8m/Ma for the last ~300ka. Maximum elevation from swath analysis across the range shows a strong correlation with the ELAs of 382 contemporary glaciers. The higher erosion rate to the north likely relates to tectonic tilting of the central Ladakh Range and to active rock uplift on the northern side of the range along the Karakoram Fault. Morphometric analysis shows that the maximum and average elevations increase at nearly the same rate on a catchment-scale across the central Ladakh Range, with higher elevation on the northern side. This suggests that greater erosion on the northern side of the range is not keeping pace with rock uplift. Moreover, long-term denudational unloading does not play a significant role in the tectonic tilting of the central Ladakh Range. [Copyright &y& Elsevier]

In order to have an understanding of the coastal processes along the southwest coast of India (8u49 N, 77u 339 E to 8u139 N, 77u149 E), a data set available for the changes in beach width for a period of 5 years (1993-1998) over a length of about 50 km was categorized and analysed in relation to the seasons. Since the study area is densely populated and was also affected partially by the great Indian Ocean tsunami, a freshmeasurement campaign of beach profile changes up to a water depth of 6 m at four different locations along the coast was carried out. These measurements have been adopted to validate a finite difference-based numerical model that employs the empirical formulation of Larson and Kraus (1989) for the prediction of beach profile changes. We simulated the offshore wave climate from National Centre for Environmental Prediction wind data using the Wave AnalysisModel (WAM), whereas the nearshore wave climate was derived by adopting theMIKE21 ParabolicMild Slope module. Results compared well with each other. The prediction from the numerical model revealed that the average onshore-offshore transport varies from about 50 to 200 m3 y21m21 width of the beach. [ABSTRACT FROM AUTHOR]

We discuss geomorphic processes in the vicinity of river mouths of the central west coast of India using the Venkatapur River as a representative. Multidate satellite image analyses, wave-refraction patterns, time-series beach section studies, and sediment characteristics were used to understand the geomorphic processes operating in the region. Multidate image analyses indicated a significant readjustment of mouth configuration as well as shoal features; spit growth northward across the Venkatapur River and other rivers of the region, e.g., the Gangavali, the Sharavati; a shift of the river mouth northward; narrowing of the river mouths; and development of submerged bars across the river mouths, etc. The beaches to the north of the Venkatapur River mouth showed erosion (retreated landward), whereas the beaches on the southern side of the river mouth accreted (grew seaward/alongshore). In general, the beaches showed accretion during postmonsoon and premonsoon intervals, and erosion during monsoon. Sediments on the beach are medium to very fine grained (1.38-3.45 Ø) and moderately to poorly sorted (σ = 0.3-0.81), suggesting low-energy conditions during deposition. During the premonsoon period, resuspension of sediments occurs, and these sediments move landward and into the estuary, especially during high tide. Wave-refraction pattern shows wave divergence in the mouth of the river and wave convergence away from the river on either side during the premonsoon (March to May) period, leading to a wave shadow area in front of the river mouth. These processes lead to sedimentation in the estuary and dynamic changes in the vicinity of the river mouth. [ABSTRACT FROM AUTHOR]

Abstract: The newly constructed port in 2001 at Ennore, on the southeast coast of India near Chennai, with breakwaters on either side (north and south) has been causing large-scale changes in nearshore morphology. Beach profiles and shoreline positions along 25 km coastline of Ennore were measured at regular intervals during 2001–06 to understand the sediment transport patterns in the region. At the same time the results of wave hind-casting and wave transformation modeling were incorporated in LITDRIFT model to compute the sediment transport rates along Ennore coast. The model results are compared with the sediment transport values obtained from beach profile measurements. The performance of the model at different locations within the study area with variable wave conditions has been examined. The annual net sediment loss (−) versus accumulation (+) were estimated for two smaller study areas (cells) containing ten regularly spaced beach profiles numbered from north to south, BP1-5 in cell I and BP6-10 in cell II. For the cell I region, which is protected by the Ennore shoals and where human interference is minimum, the annual net sediment supply is +0.02×106 m3 as obtained from beach profile measurements while the model gave a value of +0.014×106 m3. For the cell II region where there is large human intervention by way of Ennore port development and breakwater construction, the annual net sediment movement as obtained by the beach measurements is −0.14×106 m3 while the model gave a value of −0.154×106 m3. It is found that the performance of the model is satisfactory and the model may be used successfully to study sediment dynamics along any coastline provided one has detailed understanding of the coastline orientation, nearshore topography, cross-shore bathymetry and prevailing annual wave climate. Based on the sediment transport data and beach profile measurements the beach and shoreline changes for transect locations BP-1 to BP-10 are also critically examined in this paper. [Copyright &y& Elsevier]

A detailed study of sediment components and selected metals has been carried out in two mudflat cores collected from the creeks of Kalinadi Estuary, India, in order to assess the variations in distribution of sediment components, metals, and the controlling processes, including early diagenetic movements, if any. Grain size analyses reveal the possibilities of three episodes of deposition in a highly varying depositional environment with overall fining up of the cores. Organic carbon (OC) is comparatively high in muddy Core KM, which was collected from a more sheltered creek with a narrow mouth in the estuarine interior, than sandy Core KH, which was collected from a creek with a wide mouth nearer to the sea. Geochemical data show an upper zone of marked enrichment of all trace metals, including Fe and Mn, in both the cores. The variations in sediment components as well as associated metals between the two cores reveal variations in controlling factors including the morphology setup. The distribution of trace metals in Core KH are controlled by the proportions of finer fraction of sediments, degradation of organic carbon, and redox-sensitive Fe and Mn oxides, while the distribution of trace metals in Core KM are probably controlled by the finer sediments as well as by redox-sensitive Fe and Mn oxides. [ABSTRACT FROM AUTHOR]

In an estuarine channel the tidal asymmetry, sediment transport, and morphology are interconnected. To maintain a stable channel, we need to take tidal asymmetry into account. A relationship connecting tidal asymmetry and sediment transport rate has been used to evaluate the relative merits of channel modification through numerical simulations. Two criteria have been identified for ensuring the channel stability: (a) maintaining ebb dominance and (b) minimizing the spatial gradient in the net sediment transport function (q). Using these criteria for a test case, we have evaluated Hooghly estuary (east coast, India), where heavy sedimentation is experienced and a permanent solution is needed. The approach provides better insight into the sedimentation pattern in a semidiurnal tidal process in a shallow estuary with braided channels. Among the factors affecting tidal asymmetry, the relative phase difference (β) between M2 and M4 current constituents has a major influence and is thus responsible for the sedimentation pattern. Through numerical study it was found that a combination of deepened, uniform channel with enhanced ebb flow led to a favorable β, indicating less deposition. [ABSTRACT FROM AUTHOR]

Abstract: The construction of multiple dams and barrages in many Indian River basins over the last few decades significantly reduced river flow to the sea and affected the sediment regime. More reservoir construction is planned through the proposed National River Linking Project (NRLP), which will transfer massive amounts of water from the North to the South of India. The impacts of these developments on fertile and ecologically sensitive deltaic environments are poorly understood and quantified at present. In this paper an attempt is made to identify, locate and quantify coastal erosion and deposition processes in one of the major river basins in India—the Krishna—using a time series of Landsat images for 1977, 1990 and 2001 with a spatial resolution ranging from 57.0 m to 28.5 m. The dynamics of these processes are analyzed together with the time series of river flow, sediment discharge and sediment storage in the basin. Comparisons are made with similar processes identified and quantified earlier in the delta of a neighboring similarly large river basin—the Godavari. The results suggest that coastal erosion in the Krishna Delta progressed over the last 25 years at the average rate of 77.6 ha yr−1, dominating the entire delta coastline and exceeding the deposition rate threefold. The retreat of the Krishna Delta may be explained primarily by the reduced river inflow to the delta (which is three times less at present than 50 years ago) and the associated reduction of sediment load. Both are invariably related to upstream reservoir storage development. [Copyright &y& Elsevier]

A multilevel breadth-averaged numerical model has been developed and applied it to the Gulf of Khambhat to study the tidal circulation, salinity, and suspended sediment transport. The model is fully nonlinear and uses a semiexplicit finite difference scheme to solve mass, momentum, and advection diffusion equations in a vertical plane. A turbulent kinetic-energy scheme is used to parameterize the vertical transfer of momentum, salinity, and suspended sediments. The model is forced by prescribing the tidal elevations along the open boundary of the analysis region. The tide in the gulf is mainly represented in the model by the semidiurnal M2 constituent. A freshwater discharge from the landward end is also considered for this study. The erosion and deposition are computed by empirically developed source and sink terms in the suspended sediment equation. Numerical experiments were carried out to simulate the tidal circulation, salinity intrusion, and suspended sediment transport in the gulf region. The computed M2 tide and salinity at two different sets of coastal stations were validated with the available observations. [ABSTRACT FROM AUTHOR]

The north Chennai coast, on the east coast of India, experiences severe erosion caused by waves, and an area of the beach about 600 m wide has eroded over the past 120 years. To protect the seafront, natural stones were dumped by government agencies along the coast for a distance of about 6 km, and in the process, a short beach pocket 400 m long was left unprotected for various reasons. Because the property of a chemical factory located in this 400-m stretch of beach pocket suffered damage caused by erosion, and because the need for a wide beachfront was stressed by local fishermen, an alternative method of protecting the beach was suggested. The proposal involved construction of an S-type rubble sea wall about 100 m long on the southern end of the beach pocket. This paper discusses the numerical model studies conducted to determine the configuration of the S-type rubble sea wall and its effectiveness in beach protection. The model studies suggested a length of projection of 14 m with a radius of curvature of 310 m for the S-type sea wall to achieve the desired performance. Field studies conducted on the 40-m-wide and 400-m-long beach pocket with the 100-m-long S-type sea wall indicate that the sea wall is effective in protecting the beach. [ABSTRACT FROM AUTHOR]

Abstract: The Brahmaputra River finds its origin in the Chema Yundung glacier of Tibet and flows through India and Bangladesh. The slope of the river decreases suddenly in front of the Himalayas and results in the deposition of sediment and a braided channel pattern. It flows through Assam, India, along a valley comprising its own Recent alluvium. In Assam the basin receives 300 cm mean annual rainfall, 66–85% of which occurs in the monsoon period from June through September. Mean annual discharge at Pandu for 1955–1990 is 16,682.24 m3 s− 1. Average monthly discharge is highest in July (19%) and lowest in February (2%). Most hydrographs exhibit multiple flood peaks occurring at different times from June to September. The mean annual suspended sediment load is 402 million tons and average monthly sediment discharge is highest in June (19.05%) and lowest in January (1.02%). The bed load at Pandu was found to be 5–15% of the total load of the river. Three kinds of major geomorphic units are found in the basin. The river bed of the Brahmaputra shows four topographic levels, with increasing height and vegetation. The single first order primary channels of this braided river split into two or more smaller second order channels separated by bars and islands. The second order channels are of three kinds. The maximum length and width of the bars in the area under study are 18.43 km and 6.17 km, respectively. The Brahmaputra channel is characterised by mid-channel bars, side bars, tributary mouth bars and unit bars. The geometry of meandering tributary rivers shows that the relationship between meander wavelength and bend radius is most linear. The Brahmaputra had been undergoing overall aggradation by about 16 cm during 1971 to 1979. The channel of the Brahmaputra River has been migrating because of channel widening and avulsion. The meandering tributaries change because of neck cut-off and progressive shifting at the meander bends. The braiding index of the Brahmaputra has been increasing from 6.11 in 1912–1928 to 8.33 in 1996. During the twentieth century, the total amount of bank area lost from erosion was 868 km2. Maximum rate of shift of the north bank to south resulting in erosion was 227.5 m/year and maximum rate of shift of the south bank to north resulting in accretion was 331.56 m/year. Shear failure of upper bank and liquefaction of clayey-silt materials are two main causes of bank erosion. [Copyright &y& Elsevier]

The study region located north of Chennai city on the East coast of India is facing shoreline erosion/accretion related problems after the introduction of Ennore Port during 2001. For the present study 25 km of coastal stretch has been taken up, which comprises Ennore port region. natural sandy beaches of Kattupalli Island, which is a turtle breeding ground and Ennore Creek and Pulicat Lake inlets, with a total coastal settlement population of 25,000 people. After the introduction of breakwaters for the port, beach erosion and accretion are considered as critical problems, resulting in damages to the natural set up of the coastal region in the study area. Analyses of coastal dynamics and vulnerable zones of erosion and accretion along the coast were performed during the present study which are highly useful for the development of strategies for heath erosion/accretion management. Four major categories of shoreline changes were observed in the study region, viz., 1) Beach accretion south of Ennore Port, 2) Beach fill erosion north of north breakwater of Ennore Port, 3) Almost stable coastline at the central part of the study region and 4) Shifting inlet of Pulicat Lake. Quantitative analyses are made from shoreline survey using Real Time Kinematic GPS, beach profile survey in four identified transects, characteristics of environmental parameters such as tides, waves, currents and sediment nature in the near shore region. Long shore sediment transport was computed for four cells using numerical modeling package to quantify the changing littoral drift in study region. Results show reduction in sediment transport from -0.66 X 106 m³/year on the southern side of Ennore port to -0.57 x 106 m³/year on the northern side of Ennore Port. [ABSTRACT FROM AUTHOR]

Although, a variety of methods have been employed to determine sediment transport along Goa coast, the results differ in some sections. Fifteen studies have been reviewed, compared, re-assessed and a corrected shore drift map of the Goa coast is prepared and presented. Advantages and limitations of these methods are discussed. The present review and re-assessment confirms that, though sediment transport is bi-directional, the long-term net shore drift direction along Calangute and Colva beaches is southward. The overall net shore drift direction along Goa coast is also towards south. It is qualitatively determined that except for 3 short drift cells, shore zone has long-term stability. Finally, it is concluded that landform indicator study using remote sensing can be an effective method for determining tong-term net shore drift along the coast. [ABSTRACT FROM AUTHOR]

The beaches of Chavara and Manavalakuruchi of the southwest coast of India have rich heavy mineral concentrations with distinctive spatial and temporal distributions. Both locations exhibit high concentrations of heavy minerals on the northern sides of the headlands, with practically no concentration on the southern sides. Cross-shore, the sediments become less rich in the heavy minerals offshore. During the rough monsoon when the winds are onshore the concentration of heavy minerals along the mid-tide line of the beaches is considerably higher than during the calm non-monsoon when swell prevails. The concentrations of heavy minerals alongshore were highest in zones where the beach with relict sediments of high mineral content is eroding. We find that the patterns observed in the heavy minerals along the Chavara coast can be explained by a single hypothesis dependent on the presence of a source and the winnowing of the more easily entrained low-density fractions. The pattern appears to be slightly different for Manavalakuruchi coast where the zone of hundred percent enrichment is adjacent to the river mouth, indicating an additional source of river input. Analysis of wave and current data showed the dominant role of waves over coastal currents in the transport of these sediments and the wave-induced thresholds for initiation of motion indicated that the heavy component is less easily moved than the white sand (quartz) constituent. We suggest that the patterns can be explained by winnowing of the white sands from the eroded beach sediments during the stormy monsoon leaving higher enrichment at the beach. In the swell period of the post-monsoon, the erosion ceases as the asymmetric swells re-establish the beach, bringing proportionally more of the more-easily entrained white sediment shorewards, thereby explaining the reduced enrichment at this time. The cross-shore reduction in heavy minerals may be simply explained as an inverse relationship to distance from the beach source. The longshore distribution is a response to the presence of the source of black sands on the northern sides of the headlands. The headlands may simply act to isolate the source, thereby explaining the tendency for high concentrations on one side only. [ABSTRACT FROM AUTHOR]

Effective discharge plays a major part in sediment and nutrient transport, landscape modification, and river restoration. However, a complete understanding of effective discharge is still missing because of heterogeneity in various fluvial processes. The present study investigates the role of effective discharge for suspended sediment transport in a regulated macrochannel river system, the Brahmani River, India. The natural flow-sediment regime and channel pattern of the Brahmani River have been altered by the Rengali dam. The effective discharge is estimated with both analytical and deterministic methods using long-term hydrological data. The results show the control of regulated flow and sediment regime in the post-dam period contributes to the reduction in effective discharge (1849 m3/s to 820 m3/s), where frequent moderate floods are able to transport a maximum portion of sediment load. An effective discharge integrated stream power curve is formulated, which accurately predicts the channel transition (from sinuous to weakly braided) in the post-dam period. Finally, the proposed probability of braiding captures the chute formation correctly, which further highlights the hierarchy of energy dissipation and morphological continuum in the Brahmani River. A conceptual plot showing the link between observed geomorphic units, morphological analysis and process-based stream power estimation. [Display omitted] • Effective discharge converges to a moderate flood in the macrochannel Brahmani • Effective discharge integrated stream power curve predicts the channel transition • River goes through transition to accommodate effective discharge in inset channel • Proposed probability of braiding accurately captures the chute formation [ABSTRACT FROM AUTHOR]

Background: Central Himalayan forested catchments provide fresh water supply and innumerable ecosystem services to millions of people. Hence, the understanding of linkages between forests and water is very crucial for availability and quality of water at catchment scale. Therefore, the present study aims to understand the hydrological response of two forested catchments (namely, Arnigad and Bansigad) in the Central Himalayan Region. Methods: Three-years' data (March, 2008 to February, 2011) were collected from meteorological and hydrological stations in Arnigad and Bansigad catchments. The present paper describes the mean hydrological response of these forested catchments investigated through detailed field investigation. Results: The annual hyetograph analysis revealed that the rainfall at both the catchments was highly seasonal, and wet-period (June–September) plays a key role in catchment functioning. Exceedance of rainfall threshold of ~ 200 mm (~ 10% of annual rainfall) significantly increased streamflow generation in both catchments. In Arnigad, the stream was perennial with a mean baseflow of ~ 83 mm per month (~ 6% of annual baseflow) whereas, Bansigad had greater seasonality due to lack of streamflow during the pre-wet-period (March–May). Separation of hydrographs in Arnigad and Bansigad catchments i.e. stormflow (6% and 31%, respectively) and baseflow (50% and 32%, respectively) helped to understand the probability of flooding during wet-period and drought during dry-period. The forest ecosystem in Arnigad displayed healthier hydrological functioning in terms of reduced stormflow (82%), and enhanced baseflow (52%), soil moisture (13%), steady infiltration rate (22%) and lag time (~ 15 min) relative to Bansigad. These enhanced values indicated soil capability to store water in the forested catchment (Arnigad) and helped to understand the volume of water (discharge) that was available during dry-period. The lower denudation rate at Arnigad by 41% resulted in decreased suspended sediment (18%) and bed load (75%) compared to Bansigad. Further, the enhanced dissolved solids in the Arnigad stream resulted from the higher organic matter generated in the forest floor. Conclusion: This study shows that rainfall during the wet-period was the main driver of hydrological functioning, whereas, forests provided substantial services by regulating water balance, soil moisture and sediment budget through different mechanisms of forest components at catchment-scale in the Central Himalayan Region. [ABSTRACT FROM AUTHOR]