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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]

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]

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]

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: Suspended particulate matter (SPM) collected at regular stations from the Mandovi and Zuari estuaries indicates that the peaks of high SPM coincide with peaks of high rainfall and low salinity and also with peaks of moderate/low rainfall coupled with high salinity during the monsoon. The estuarine turbidity maximum (ETM) is a characteristic feature, it occurs in the channel accompanying spring tide during the monsoon and pre-monsoon, and shifts to the bay on neap tide during post-monsoon. ETM remains at the same position in the Mandovi River, both during the monsoon and pre-monsoon, whereas in Zuari it stretched upstream during monsoon and migrates seaward of the channel during pre-monsoon. The ETM coincides with the freshwater–seawater interface during the monsoon and is formed by the interaction between tidal currents and river flows. The ETM during pre-monsoon is associated with high salinities and is generated by tidal and wind-induced currents. The turbidity maximum on neap tide during post-monsoon may be due to the erosion and resuspension of sediments from the emergent tidal flats and transport of these turbid waters into the bay. Funneling effect of the narrowing bay in the Zuari estuary and associated physical processes effectively enhance the magnitude of the currents and transports sediments to the channel. SPM retention percentage indicates that the estuarine channel is prone to siltation. [ABSTRACT FROM AUTHOR]

Abstract: The concentration of dissolved and particulate Re have been measured in the Narmada, Tapi and the Mandovi estuaries in the Arabian Sea and the Hooghly estuary in the Bay of Bengal. Re concentration in water and particulate matter of these estuaries is highly variable. Re in river waters analysed varies from 1 to 41pmol/kg, the lowest in the Mandovi and the highest in the Mahi river. Re concentrations in the rivers analysed except in the Mandovi river are higher than the average global riverine Re concentration of 2.1pmol/kg. Based on this study and the available data, the contemporary global annual flux of dissolved riverine Re is estimated to be ~350×103 mol with an average concentration of ~9.2pmol/kg, much higher than the earlier estimates. Residence time of Re in the oceans based on this estimate is 175,000years, ~4 times lower compared to earlier estimates. Re behaves conservatively in all the estuaries studied. Re concentrations of seawater in the Bay of Bengal and in the Arabian Sea, estimated from the data of the Hooghly and the Mandovi estuaries respectively are ~40pmol/kg, similar to the open ocean Re values of the Arabian Sea measured in this study and the values reported for in other oceanic regions. However, the dissolved Re in the Gulf of Cambay is 2 to 5 times higher, consistent with the high Re measured in the Mahi estuary and in the coastal waters of the Gulf of Cambay. The source of high Re in the Gulf of Cambay seems to be anthropogenic, measurements of Re in rivers and industrial waste waters draining into the Gulf supply amount to ~2300mol of Re annually. This anthropogenic supply coupled with high residence time of water in the Gulf contribute to its high Re. Re concentration in suspended sediments of the Narmada estuary varies from 1 to 2pmol/g, and does not show any discernible trend with salinity. The contemporary global riverine Re supply to the oceans estimated in this study is ~2–4 times higher compared to its removal in the reducing (anoxic/suboxic) sediments, indicating non-steady state of Re in the ocean. High dissolved riverine Re flux coupled with high Re content in the Gulf of Cambay highlights the need of a detailed study of Re in the various global rivers and in oceans including coastal regions and semi enclosed basins of the world to understand its behaviour in various reservoirs and to constrain the residence time of Re in the ocean. [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]