Dr. B. Kesava Ramprasad
Principal Civil Hydrographic Officer
National Hydrographic Office,
Email: [email protected]
Hazard is the probability of occurrence of a damaging phenomenon within a specified period of time and within a given area (Varnes, 1984). Natural disasters are of various types like earthquakes (tsunami), floods, landslides, forest fires, thunderstorms and volcanic eruption etc. The recent Tsunami induced earthquake of magnitude 9.0 of focal depth 30km, which was occurred with epicenter (3.298°N, 95.779°E) on 26th December 2004 (00:58:50 UTC), had swept thousands of lives and property in the south-eastern countries viz., Indonesia, Sri Lanka, India, Thailand, Somalia, Myanmar, Maldives, Malaysia, Tanzania, Seychelles, Bangladesh, Kenya and South Africa (source: USGS). The epicenter of the earthquake was identified at off Sumatra Coast of Indonesia in the Indian Ocean. Apart from the tsunami generated casualties it is also likely that direct earthquake induced damages has also affected the Andaman and Nicobar group of islands. The earthquake has taken place in most active seismic region characterized by tectonic features of North South trending Indo-Burma ranges in the north, Andaman-Nicobar islands and the Sumatra fault system in the southeast. According to the available fault plane solutions (USGS) the event took place because of thrust type movement. The tsunami induced waves also causes the land erosion, cutting of unprotected shore edges. On the other hand landslides creating mass destruction in the hilly regions.
In the Himalayan mountain areas Landslides are frequently triggered by rainfall in the region under the influence of a monsoon climate and this is responsible for a variety of human and environmental impacts. Freezing and thawing due to snow and swelling action of rainwater had built up shearing stresses to a level that exceeds the shearing resistance of the slope, forming weathered metaquartzites along with inner bedded sericite quartzite and a thin vencer of regolith along most vulnerable and weakest surface. Massive rock-fall taking place following incessant rains and cloud burst which widened the enlarged joints. Slope failure is also a major cause for these landslide disasters and was reported by many studies related to the Himalayan region. The advances in the field of Geographical Information System (GIS) improved the quality presentation with accuracy of positions in real coordinates. This latest technology has been used effectively for preparation of cadastral maps, town planning, flood assessment, landslide zonation maps, drought assessment, irrigation projects, telecommunications and other administrative purposes. The information generated in all the above could be used for Coastal Zone Management and further Tsunami related disaster management. Disaster Mitigation could be possible only through the proper understanding of the hazard occurrence phenomena, planning and management of natural resources.
