Disaster management

On December 26, 2004 the gigantic tsunami waves generated due to a great undersea earthquake off the coast of Banda Aceh, northern Sumatra. This earthquake occurred along a thrust fault in the subduction zone where the Indian tectonic plate was going below the overriding Burmese plate. As a result, the ocean floor broke and there was a vertical displacement of about 15 to 20 meters along the fault causing large scale displacement of water and thus, generating tsunami waves.

• Typically, for an average ocean depth of 4 km, like in the Indian Ocean/Bay of Bengal region, the speed of the tsunami waves can go up to 720 km/h or about the speed of a jet airliner. As the tsunami waves approach the shore, the water depth becomes shallower, waves slow down, wavelength becomes shorter and the waves gain larger amplitude or heights and become destructive.

Effect on life and economy

• Tsunami waves destroy boats, buildings, bridges, cars, trees, telephone lines, power lines - and just about anything else in their way. Once the tsunami waves have knocked down infrastructure on the shore they may continue to travel for several miles inland, sweeping away more trees, buildings, cars and other man made equipment. Small islands hit by a tsunami are left unrecognizable.
• After a tsunami strikes, landscapes that previously constituted picturesque beaches or seaside towns become a wasteland. In addition to the destruction of human construction, tsunamis destroy vegetation such as trees, resulting in landslides and coastlines that slip into the sea as deep root systems that previously held land in place are ripped out.

Preparedness in light of NDMA Gudelines

• The 2004 tsunami prompted NDMA to formulate Tsunami Risk Management Guidelines to outline inter-agency roles and responsibilities, tsunami risk preparedness, mitigation and response. 
• In order to reduce risk of tsunami it is pertinent to explore options for effective dissemination of tsunami alert and warning messages generated by INCOIS to the concerned agencies and coastal vulnerable communities exposed to tsunamis in a coordinated manner.
• Structural Mitigation measures, as envisaged in the Guidelines, gives a brief guidance on design and construction of new structures as well as strategies for protecting lifeline and priority structures from tsunamis along the seafront.
• A robust techno-legal regime through efficient land use practices, bioshields, shelter belt plantation and mangrove regeneration with community involvement will also help towards the cause.