Extreme events, intrinsic landforms and humankind: post-tsunami scenario along Nagore-Velankanni coast, Tamil Nadu, India

Extreme oceanographic episodes have regularly afflicted the east coast of India. Storm surges strike annually, devastating for a period of 24-36 h, and inducing a run-up of 9 m and inundations reaching 35 km. Comparatively, the December 2004 tsunami,appeared after 63 years, lasted for I h and caused a run-up of 6.5 m, with flooding up to 0.8 km inland. Whereas storm surges devastate vast areas, the tsunami destroyed areas within 80 m from the dune. Major impacts are: erosion and breaching of dunes, destruction of shore front dwellings, formation of inlets and new water bodies. Extreme events confirmed that sand dunes and dense forests possess an innate capacity of attenuating wave up-rush, evidenced respectively by negligible overwash, and by modest damage only to a narrow frontal casuarina strip of 10 m average width. Recurring storm surges are of greater societal concern than an occasional tsunami.