Protective function of natural coastal ecosystems against the impact of tsunami: A case study from Medilla to Godawaya in South-eastern Sri Lanka

Abstract

Tsunami-related environmental impact on the coastal ecosystem from Medilla to Godawaya (27 km) in south-eastern of Sri Lanka were documented through a rapid assessment methodology, with the objective of gathering scientific evidence on more interior landscapes. The methodology. Included the study of qualitative ecological parameters and quantitative analysis of structural damage to trees and modification of ground features in sites just behind the narrow strip of land facing the sea. Once the beach front features were correlated with above damage scores, it was observed that mature and intact sand dunes have functioned as an effective barrier against the tsunami wawes, thereby protecting inland ecosystem and human settlements. Intact and broad stands of mangrove and Pandarus vegetation have also served as a frontline defence by absorbing the wave energy of Tsunami. Coastal wetlands, including mangrove swamps, salt marshes. Broad estuaries and lagoons also have diffused the destructive power of sea- water and sediments brought in by the tsunami waves, thereby protecting managed landscapes such as paddy fields and settlements. In additions, it was noted that coral reefs, rocky beaches and sandstone reefs have reduced the energy of incoming waves. Moreover, it was observed that tsunami waves have penetrated inland with a greater force in areas where natural sand dunes have been exploited and /or converted into managed landscape such as Coconut plantations and home gardens. Areas, where nearby coral reefs have mined or destroyed by previous bottom set netting. Were also considerably damaged by tsunami waves. Hence, the presence of healthy natural ecosystem components in coastal belt assist in minimizing tsunami impacts considerably.