Tsunami impacts and mitigation plans for the Khoa Lak (Andaman Sea), coastal areas of Thailand

• Main Author: Wathanaprida, Somsak
• Published: University of East Anglia 2010
• Subjects: 363.349409593
• Online Access: http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.569340

To build a tsunami-resilient coastal community it is fundamental to understand the characteristics of past tsunami patterns and likely impact of possible future events. The MOST model (Method of Splitting Tsunami) and ComMIT (Community Model Interface for Tsunami) were used to model patterns of water levels, wave speed and direction, and inundation distances resulting from the 2004 Indian Ocean tsunami on the Khao Lak coast of Thailand. The model of the 2004 tsunami was calibrated against estimates of water depths made along the coast in early 2005; an M, = 9.3 earthquake in the model was found to best match observations. The model was verified against a variety of other evidence, including digital photographs and video clips taken on the day of the tsunami, mainly from two sites along the Khao Lak coast at Nang Thong and Bang Niang beaches, together with aerial surveys and a tide-gauge record. The timing and extent of water recession prior to the arrival of the first wave, the heights and number of the subsequent waves, and the inundation distances corresponded well providing confidence in the application of the MOST model to this coastal region. Historical evidence suggest that tsunami of the magnitude of 2004 are rare (200-700 y) so for mitigation planning in the Khao Lak area a smaller tsunami genic-earthquake (M; =8.9) was chosen (l00-500 y). Sensitivity to the choice of M, was also considered. The tsunami from such an event is similar in its character to the 2004 event, less extreme but still highly destructive, reaching the Khao Lak coast in ~ 2 h 15 min, and preceded by receding water levels. The first wave (5.0-6.5 m high) arrives 2h 25 min after the earthquake travelling at 6-8 mls at the coastline.