Coastal processes along the Indian coast - case studies based on synergistic use of IRS-P4 OCM and IRS-1C/1D data

Abstract

The sequential Suspended Sediment Concentration (SSC) maps were generated using IRS-P4 OCM (Ocean Color Monitor) data for selected tide dominated, wave dominated and deltaic coasts around the Indian subcontinent. Patterns of SSC were studied to understand the sediment dynamics, circulation patterns, fronts and consequent impact on coastal processes. Hitherto, unknown sediment plumes extending for large distance into deep offshore areas could be identified from the major deltaic regions. The high temporal capability of OCM data was extremely useful to understand sediment dynamics in tide-dominated regions of the Gulf of Khambhat, the Gulf of Kachchh and the Hoogli estuary. SSC maps in conjunction with corresponding tide and bathymetry data could be sequenced as per flooding and ebb cycles. Development, formation, shifting nature of shoals and sediment curls during a tide cycle could be studied. It is observed that during the North-East (NE) monsoon suspended sediment influx of the Ganga-Brahmaputra system influences the coastal processes along the continental margins of the Orissa and the Northern Andhra Pradesh along east coast of India. The occurrence of cyclone aids in entrapment of fluvial discharge into the coastal waters, leading to a reduced offshore influx into deeper regions of the Bay of Bengal and high sedimentation near to the coast. Seasonal changes along wave-dominated west coast showed net sediment transport from north to south in the pre-monsoon season and south to north in post-monsoon season. Significant onshore- offshore transport along west coast was also observed. The impact of the regional sediment dynamics on the site-specific local coastal environment was studied by integrating observations derived from OCM and IRS-1C/1D data. The paper concludes the utility of Ocean Color Monitor and IRS-1C/1D data in studying various coastal processes and regional sediment dynamics.