ABSTRACT
On 26 December 2004, following an earthquake of 8.9 Richter scale off Sumatra coast in Indian Ocean, large seismic sea waves had hit Andaman-Nicobar Islands and east coast of southern India (Figure 32.1). These seismic sea waves are popularly known as Tsunami waves. Tsunami waves traveled a distance of 3000 km from Sumatra to east coast of India within few hours at a speed of about 160-250 m/s (600-900 km/h). In deep sea, these tsunami waves were unnoticed because they are only few centimeters to a meter high. But they have long wavelength of hundreds of kilometers and wave periods of 100-1000 s. In shallow sea, tsunami waves travel at a speed of 10 m/s but grow 10 times taller than deep-water waves. Therefore, large wavelength, long wave period and high velocity are accounted for high-destructive nature of the tsunami waves (Ward, 2002). As the result, the shallow water tsunami waves can modify the coastal topography, inundate coastal areas and destroy coastal habitats. But in open coasts such as bay, estuaries, creeks and lagoons, the effect of tsunami wave is marginal as they provided conduit to the tsunami waves runoff. During recent tsunami, several coastal marine habitats have been affected by largescale sedimentation and seawater inundation. Among them, the Andaman and Nicobar Islands, Pichavaram Mangroves and Pulicat Lagoon are the most significant and socio-economically important coastal marine ecosystems. Already these habitats are under severe anthropogenic stress; no doubt, the effects of recent tsunami have long-term impacts to jeopardize livelihood of sizable coastal population living in the coastal areas. Therefore quick review of recent tsunami, its impacts and implication to the coastal community has been carried out in the following sections.
