Tsunami Effect on a Coastal Lake in India

Abstract

Introduction Kalpakkam (12 34N Lat. and 80 11E Long.), situated on the east coast of India about 80 km south of Chennai (Figure 1), is known for existence of nuclear facilities, such as Madras Atomic Power Station (MAPS) and Prototype Fast Breeder Reactor (PFBR). The entire site covers approximately 1,500 ha. It is bestowed with a number of natural water bodies in the form of backwaters and lakes. One of them is a tiny brackish water lake (Kokilamedu lake) situated on the isolated northeastern side of the campus. It covers an area of 0.75 sq km during monsoon period, and the spread shrinks to 0.5 sq km during summer. The average depth is about 1 m and has a maximum depth of 3 m. The lake provides a conducive environment for the waders as well as for other aquatic and terrestrial fauna that inhabit the rich flora in and around the lake. A 50-m width strip of sand bream, which is covered by Casuarina and Pandanus, forms the barrier between the lake and Bay of Bengal. Occasionally, seawater intrusion into the lake takes place during high tides. Apart from the avian guests who visit during winter, the endemic avian fauna of the lake is comprised of some important bird species like pelicans, painted storks, black headed ibis, etc., along with fishes and amphibians. This lake has attracted the attention of ecologists due to two important events that have taken place during the last decade. During May 1995, a massive fish kill was observed, and this was attributed to natural eutrophication coupled with anoxic condition and high temperature (Venugopalan et al., 1998). The other important event which has affected the lake ecology is the mega December 2004 tsunami, which completely inundated the lake with seawater and brought massive amount of sediment from the sea into the lake (Satpathy et al., 2007, 2008). An increase in seawater influx was noticed after the event of the tsunami, which narrowed the sand barrier and destroyed the vegetation between the lake and the sea. Sketchy data available prior to tsunami revealed that the lake characteristic was close to a freshwater one. In spite of the above two events, no systematic and comprehensive scientific investigation on the lake ecology was available till August 2006. Considering the ecological importance of the lake, a scientific investigation with respect to various ecological parameters has been initiated since September 2006, with the following objectives: