Sediment distribution study in the Gulf of Kachchh, India, from 3D hydrodynamic model simulation and satellite data

Abstract

A fully 3D finite difference baroclinic hydrodynamic model 'COSMOS' is applied to the Gulf of Kachchh (GoK) to study tidal variation, ocean currents, residual tidal current, sea surface temperature distribution, etc. The 'COSMOS' is based on the hydrostatic and Boussinesq approximations and uses a vertical double sigma coordinate with a step-like grid. In addition to the momentum and continuity equations, the model solves two-transport equations for salinity and temperature and an equation of state to include baroclinic effects. The other objectives are quantitative assessment of suspended sediments by analyzing SeaWiFS data and understand the relation between residual tidal currents and erosion, movement and deposition of sediments. The model results showed that the dominant current system within GoK is controlled by the simulated tidal and residual tidal currents variation. The residual tidal current velocity reduces from the surface towards the bottom. The residual surface current velocity distribution displays cyclonic eddy continuity regions within the GoK. It is concluded that bottom topography variation plays an important role in determining the distribution of residual current velocity and thereby sediment distribution. The residual current velocity distribution map showed conformity with the gross geomorphic subdivisions and the sediment distribution map of Gulf of Kachchh. The suspended sediment plume pattern followed the current pattern obtained from modeling. The model results of the sea surface temperature of the December month showed good agreement with the temperature structure and the pattern obtained form NOAA/AVHRR data.