Remote assessment of net shore drift along the west coast of India
Abstract
Space borne images were analyzed to examine direction, amount and behavior of long-shore drift and its contribution towards deciding areas vulnerable to coastal erosion and accretion along the West Coast of India. Long-term net shore drift direction is determined firstly by studying various coastal landform indicators and secondly by examining offshore turbidity distribution pattern. Landform indicators study suggest that during southwest monsoon period, strong southerly currents are eroding protruded sectors and depositing eroded material, though partially, along varying sectors to the south. Whereas, during the rest of year, under the influence of northerly current, accretion is taking place along retreating sectors which has reflected in development of beach ridges. Turbidity pattern distribution exhibited by satellite temporal images suggests bi-directional shore drift depending upon period of the season. The results of the two studies were found to be comparable. Although sediment-transport is bi-directional, net major sediment transport is southward. The geomorphic study identified possible sediment sources and sinks. Contributions of sources and losses due to sinks are assessed. The sediment balance is positive overall, and is reflected in large spits in the southern part of the study area. Finally, it is concluded that long term shore drift direction, which can be determined comfortably by remote sensing, is season dependent and plays significant role in deciding areas of coastal erosion and accretion and subsequently helps in coastal zone management.
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