Department of Earth and Environmental Science

Indian Ocean Tsunamis - Environmental and Socio-Economic Impacts on the Malay-Thai Peninsula.

We used a suite of research methods drawn from both the natural and social sciences to elucidate the immediate pre- and post-tsunami trajectory of events and impacts associated with the 2004 tsunami catastrophe in the Indian Ocean along the west coast of the Malay Thai Peninsula. We selected five study sites with different physiographic conditions which varied in nature and scale of social and physical impacts resulting from the tsunami: (1) Koh Phi Phi, Thailand; (2) Koh Lanta, Thailand; (3) Khoa Lak, Thailand; (4) Langkawi, Malaysia; and (5) Penang, Malaysia. This is a currently funded NSF project, thus we are only able to present a summary of completed research from the latter study site.

We made measurements of land elevation, tsunami flow depth, number and direction of waves, and sediment deposit character and thickness. For example, the scientific survey of the northern and western coasts of Penang revealed that the maximum water depth was 5.9 m above MSL and eye-witness accounts suggest that splash was approximately 12 m above MSL. Detailed litho- and biostratigraphic investigations of the tsunami deposits revealed that the sediment sheets rise in altitude and taper landward with an unconformable base, and showed numerous sedimentary packages and do not show any fining upward/downward sequence. The grain size was dominantly unimodal, well sorted and composed of medium and coarse sands. The sediment contains a mixed assemblage of onshore and offshore microfossils. There is a lower abundance with larger test size in the tsunami deposited sediment compared to the pre-tsunami material. The eye witness accounts of the tsunami indicate unusual events prior to arrival of the first wave, most notably, a major drawdown of the water surface prior to the arrival of the first tsunami wave. The first wave was accompanied by extremely loud sounds and came ashore as a broken wave or a bore. Eye witnesses affirmed that there were three waves in Penang; the second was the largest and produced most of the damage, although some witnesses suggested the third. Both these waves were heavily laden with mud which was deposited well inshore of the coastline. The initial response to the disaster happened in a bottom-up fashion responding to distress calls. The priority was to ensure the lines of communication were kept clear and to ensure the security of vacated properties. The Social Welfare Department was primarily responsible with assistance from NGOs for providing basic needs for evacuees. Fisherfolk, coastal residents and coastal business people were severely affected economically by the tsunami. None of the informants from these groups had any insurance coverage for natural disasters and the amount of compensation was not sufficient to meet the full costs repairs and/or losses. We believe that social capital plays a crucial role in response and recovery activities.