Coastal Geomorphology of Kerala

Abstract

Coastal geomorphological map of Kerala was prepared on a scale of 1 : 500,000 using LANDSAT imagery. Aerial photographs were used wherever necessary, followed by field checking. The coastal features identified include beaches, beach cliffs. stacks. islands, shore platforms, spits, bars, beach ridges, estuaries, lagoons, mudflats, tidal flats and deltaic plains.

Of the various lineaments identified over the Kerala region. the fault lineaments parallel to the coast as well as those at right angles to it are found to be neotectonically active and control the configuaration of the shoreline primarily.

Of the 560 km shoreline of Kerala, a cumulative 360 km length of shoreline is vulnerable and shows wide fluctuations in its stability. Based on their vulnerability and dynamism, the shoreline is divided into (1) permeable, gently sloping, sandy shoreline (2) semi-permeable, cliffed, sedimentary shoreline and (3) impermeable, crystalline shoreline, arranged in order of intensity of erosion. Apart from the known factors of slope morphometry, lithology and storm-wave generation, the non-parametric factors responsible for coastal erosion include presence or absence of mud banks near-shore and instability of off-shore regions.

The Kerala coast is described as a submergent coast, falling under the 'Terrigenous coast of primary morphologic disequilibrium '. Accordingly, the long-term tendency of coastal evolution is to increase the linear extent of erosional coastal segments at the expense of intervening depositional areas and, when the process goes to completion, a coast of equilibrium results.