Numerical simulation of erosion and deposition at the Thailand Khao Lak coast during the 2004 Indian Ocean tsunami

A case study was conducted for the Thailand Khao Lak coast using a forward numerical model to understand uncertainties associated with interpreting tsunami deposits and relating them to their tsunami sources. We examined possible effects of the characteristics of tsunami source, multiple waves, sediment supply and local land usages. Numerical results showed that tsunami-deposit extent and thickness could be indicative of the slip value in the source earthquake near the surveyed coastal locations, provided that the sediment supply is unlimited and all the deposits are well preserved. Deposit thickness was found to be largely controlled by the local topography and could be easily modified by backwash flows or subsequent tsunami flows. Between deposit extent and deposit thickness, using deposit extent to interpret the characteristics of a tsunami source is preferable. The changing of land usages between two tsunami events could be another important factor that can significantly alter deposit thickness. There is a need to develop inversion models based on tsunami heights and/or run-up data for studying paleotsunamis.