(Online Course) Contemporary Issues for IAS Mains 2012: Yojana Magazine - Climate Change and Disaster Management Coastal Areas
Yojana Magazine
Climate Change and Disaster Management Coastal Areas
It has been projected that along the Indian coast sea level would rise by 39 to 57 cmby 2050 and 78 to 114 cmby 2100 due to climate change (Unnikrishnan et al, 2006). The coastal zone in India, particularly the east coast is vulnerable to hydro meteorological hazards such as cyclones, floods and geophysical hazards like tsunami. Meteorological data show that more than 1000 cyclonic disturbances occurred in the Bay of Bengal during the last century.
Q. How Coastal bioshelds can reduce the impact of natural disasters.
For a long time, local communities living around mangroves and other coastal vegetation have been aware of the effectiveness of this vegetation as shields against cyclones, storm surges and tsunami. For example, the people of Tamil Nadu state, have been calling mangrove forest as “aalayaathi kaadu” for thousands of years (“Aalai” means waves and “aathi” means mitigate and “kaadu” means forest). This traditional wisdom is supported by experimental studies in the field and laboratory. Theoretical studies on wave forces and modelling of fluid dynamics suggest that tree vegetation may shield coastlines form tsunami damage by reducing wave amplitude and energy. Analytical models show that 30 trees - either mangrove or non-mangrove - per 100 m2 in a 100 m wide may reduce the tsunami flow pressure by more than 90% (Hiraishi et al, 2003). Effectiveness of a coastal forest in mitigating the impact of natural hazards depends on the width, density and structure of the forest and the tree characteristics (height and diameter at breast height). A study indicates that for a tsunami wave height of 3 m, the effective forest width – mangrove or non-mangrove - is about 20 m and for 6 m high tsunami wave the effective width of forest is about 100 m. It has also been estimated that trees with 10 cm diameter at breast height is effective against 4.6 m tsunami waves and 35 cm diameter for 7m ( FAO, 2006). However, empirical and field based evidences were not available for long time. The super cyclone of Orissa in October 1999 and tsunami in December 2004 provided opportunities to collect field based evidences on the role of coastal vegetation in reducing the impact of such natural disasters.
