Environmental Impacts of Tsunami and it’s Rehabilitation

Prof. D.M.S.H.K. Ranasinghe
Department of Forestry & Environmental Science, University of Sri JayewardenepuraTsunami, the Killer Wave swept nearly two thirds of the coast of Sri Lanka on 26th of December, 2004. The coastline especially the Eastern and the South Western suffered a major blow, rendering more than 40,000 dead, about 900,000 displaced. Most of the physical infrastructure including houses, hotels, and common facilities like railway, roads, buses, bridges, power and telecommunications were damaged. Many people living on the shoreline and adjacent areas lost their livelihoods.

A rapid assessment of the damage of the coastline starting from Dehiwala in the South Western Coast all the way to Jaffna Peninsula showed that the almost all the aspects of environment, including economic, socio-cultural and ecological suffered a great blow from the Tsunami waves. The economic loss was assessed in the range of more than 1.5 billion US $ while the socio-cultural damage could not be quantified. With regard to ecological environment, many items which contributed to the ecological stability of the coastal ecosystem were damaged. This includes mangroves, sea grass beds, coral reefs, estuaries and bays along with their fauna and flora, vegetation on the beach and also those in home gardens. Well over 500 million kg of rubble were created by the Tsunami and posed an enormous challenge to the solid waste management system. Debris and sea sand, whether deposited by the Tsunami or by clean up operations has blocked drainage channels in many areas. More than 15,000 wells have become unusable due to salinisation. The excessive pumping of fresh water from inland areas has resulted in salt intrusion to ground water supplies. Several coastal water bodies have been contaminated with salt water, floating material, faecal matter and black sediments and need restoration. The original ecosystem in these areas have been destroyed, natural purification has ceased resulting in highly toxic water bodies.Among the coastal and marine ecosystems, shallow fringing coral reefs suffered more damage compared to the deep ones. Intact coral reefs acted as buffers to minimize the Tsunami damage. Estuaries often acted as channels of entry for the tsunami facilitating damage and salt water intrusion to inland areas. Frontline mangroves were badly damaged while deeper ones were left intact and dense mangroves converted the wave into a flood. Lagoons absorbed tsunami energy, but in doing so lost seasonal sand barriers, their banks scoured. Large vegetated sand dunes stopped tsunami intrusion. Beaches were eroded and scoured losing width and height, mainly from tsunami backwash. There was much debris on most beaches.There was severe damage in near shore areas, including seashore Pandanus and creeper vegetation and inland Palmyrah trees with near shore coconuts less affected, as were inland economic trees. Casuarina plantations proved vulnerable to tsunami damage and by themselves had little protective value, though in place they helped stabilize sand dunes which themselves moderated the Tsunami. Alien invasive species have been spread by the Tsunami to new areas. The paper also lists recommendations for minimizing the environmental damage in the tsunami rehabilitation programme.
Theme talk made at the Tenth Annual Forestry and Environment Symposium held at Kabool Lanka International Training Center, Thulhiriya on 2nd and 3rd 2005 organized by Department of Forestry and Environmental Science, University of Sri Jayewardenepura, Sri Lanka