Suspended sediment dynamics in Cochin estuary, West Coast, India
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An observational study was conducted in Cochin estuary to examine the relative impacts of tidal and river runoff forcing upon suspended sediment dynamics at different time scales. Time series measurements of salinity and suspended sediment concentration (SSC) were conducted at spring and neap periods of wet and dry seasons. These data were complemented by measurements of tides, currents, vertical profiling of hydrography and turbidity at the main inlet of the estuary. The results showed that SSC was maximum at the main inlet and decreased towards upstream for both seasons. The intra-tidal variations of water column stability suggested that prominent stratification occurred at the main inlet as a result of torrential rain during spring tides of wet season. During neap tides of wet season, the runoff was relatively lower and intense turbulent mixing occurred during the ebb. During dry season, well-mixed (spring) and partially stratified (neap) conditions were noticed. Suspended sediment fluxes were also analyzed using the decomposition method to identify mechanisms of turbidity maintenance at the inlet. The fluxes were dominated by an advective component during both tidal phases of wet season and dry-neap period. In contrast, the tidal pumping was the main contributing process for residual fluxes during the dry-spring period. The residual sediment transport at the inlet was directed outward irrespective of tidal ranges and seasons due to the strong ebb currents with longer duration. These findings are significant for the development and protection of harbors situated close to the inlet in estuaries and for the efficient implementation of an integrated coastal management system.
KeywordsEbb currents Stratification Velocity Temporal variations Tides Sediment fluxes
Authors are thankful to the Director, CSIR-NIO and Scientist In-Charge, Regional Centre, Kochi for their keen encouragement and support. The study forms a part of the project “Ecosystem modeling of Cochin backwaters” funded by Integrated Coastal and Marine Area Management (ICMAM-PD), Ministry of Earth Sciences, Chennai. We extend our thanks to the staff and research students of NIO for their valuable assistance during field collections. This paper work is a part of the doctoral research of the first author, Vinita J. who acknowledges the Council of Scientific and Industrial Research, New Delhi, for the financial support in the form of senior research fellowship. This is NIO Contribution.
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Conflict of interest
The authors declare that they have no conflict of interest.
Human and animal rights and informed consent
This article does not contain any studies with human participants or animals performed by any of the authors.
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