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Environ Geol (2009) 58:815832 DOI 10.1007/s00254-008-1558-8
ORIGINAL ARTICLE
Distribution of coastal cliffs in Kerala, India: their mechanisms of failure and related human engineering response
Avinash Kumar P. Seralathan K. S. Jayappa
Received: 5 July 2008 / Accepted: 17 September 2008 / Published online: 3 October 2008 Springer-Verlag 2008
Abstract The 560-km-long Kerala coast is characterised by long barriers with narrow beaches and steep cliffs. Distribution of cliffs from nine sections measuring a cumulative length of 63.5 km is evaluated in ArcGIS Software using topomaps and eld survey data. The cliff sections in the southern coast comprise both permeable and impermeable rocks, whereas those along northern coast are comprised of either Precambrian crystalline and/or Tertiary formations. Notches, caves and even small arches are developed in Cannanore, Dharmadam and Kadalundi cliffs, where only primary laterites are exposed to wave attack. Stacks composed of laterite and Precambrian crystallines found in nearshore of cliffed coast indicate recession of shoreline. Mass wasting, mudslide and mudow type of cliff failures are common in permeable to semi-permeable rocks, whereas rotational sliding, rockfall and toppling failure are found in hard rock cliffs. Retreat of cliff sections are induced by natural or anthropogenic activities or both. Rate of recession vary from a few centimetres to one metre/ year depending upon the nature of lithology, structures and recession agents acting upon the cliffs. Various methods of cliff protection for e.g. hard structuresrevetments, groins, seawalls, breakwater and jettiesand soft measures articial reefs/marsh creation, oating breakwaters, beach
nourishment, beach scraping and vegetation plantingare suggested.
Keywords Coastal cliffs Lithology Proles
Recession Protective measures India
Introduction
Globally, an estimated 80% of the open coast is backed by sea cliffs (Emery and Kuhn 1982; Bird 2000). Wherever the rocky shores containing weakly resistant sedimentary units, soft-rock cliffs are exposed to wave action, have a tendency towards instability and rapid retreat. Coastal cliffs generally form by undercutting due to marine erosion followed by subsequent collapse of large rocky boulders (Woodroffe 2002). Predictions of coastal cliff recession are essential for an appraisal of cliff protection options and for coastal land use planning (Hall et al. 2000a). In recent years the problem of soft coastal cliff recession has been the subject of considerable research attention (Lee 1997; Hutchison et al. 1998; Hall et...