Environmental assessment of the south coast of Sri Lanka, with special reference to the 2004 tsunami

Following the 2004 tsunami in Sumatra, Sri Lanka experienced >30,000 confirmed deaths and disruption of livelihood. Damage to coastal ecosystems was less than anticipated, especially in comparison with reported impacts from unsustainable development. This research examines tsunami related damage against a background of anthropogenic pressures. Fishery changes were determined through interview of three generations of fishers targeting frigate tuna. Significantly higher values for best day’s catch and largest specimen ever caught were obtained by older fishers than younger ones. Values were also significantly higher during early years, providing clear evidence of resource decline and the ‘shifting baseline syndrome’. Most fishers reported posttsunami decline in frigate tuna, but mainly from a larger new generation of fishers, rather than extra boats provided by aid money or (direct or indirect) biophysical impacts from the tsunami. The number of boats post-tsunami increased significantly in all research areas, which could result in further catch decline. The perceptions of 500 Sri Lankan fishers about the influence of risk factors on tsunami death toll and house damage are quantified). Mangroves, coral reefs and sand dunes afforded protection against tsunami damage (67–94% of fisher responses), as did housing and roads. Fishers believed rivers/estuaries, concave coastlines and hotels exacerbated impacts. For comparison, multi-variable models for death toll, housing damage, inundation area and distance are built, incorporating both natural and developmental risk factors. Bathymetry is the only factor significantly associated with all indicators of impact. Mangroves and marsh were not a significant factor in final multivariable models. However, in terms of inundation, sand dunes were identified as protective, while bodies of water exacerbated damage. The extent of agreement and variance between modelling results and the opinions of fisher questionnaires is critically examined. Research findings highlight the need for better coastal management. While the role mangroves in tsunami protection remains equivocal, their known role in providing many other ecosystem services suggests that mangroves warrant greater conservation attention in Sri Lanka, in the face of coastal development pressures. Coastal policy and conservation priorities should be influenced by scientific research (e.g. the tsunami model in this thesis) as well as traditional ecological knowledge and opinions from indigenous people. Factors shown to provide tsunami protection often cannot be altered by human intervention (e.g. topography and bathymetry). However, sand dunes could potentially be preserved to reduce future impacts. Tsunamis are rare events and further research should be carried out to determine which risk factors are important for more frequent events (e.g. monsoon). The needs of coastal communities should always remain paramount in considerations of future tsunami and environmental policies.

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