A thesis submitted in partial fulfillment of the requirements for the degree of Master of Engineering, School of Engineering and Technology

Thesis (M.Eng.) - Asian Institute of Technology, 2005

This thesis deals with the study of recent tsunami sediments of the December 26, 2004 tsunami event at an undisturbed 1600m x 630m large coastal plain at Bang Lut Beach in the Pang Nga Province of Thailand. The field work included reconnaissance of more than 30 km of coastline and coastal plains to select this appropriate location, a topographic survey, an assessment of beach erosion and the sedimentological characterization of the in situ deposits in 77 trenches. The laboratory work comprised of sieve analyses and processing of images taken under the microscope. It was found out that the tsunami sand sheets' average thickness is 7.8 cm and the volume is 49.14 m3/m of coastline. The eroded beach sand volume is a fraction of the total deposit volume. The deposit thickness' is influenced by the local topography and the distance from the shoreline. The deposits fine inland and show the general tendency to fine upward in the sediment column. Alternating fine-coarse sand layers at nearshore locations as well as normal grading patterns in the sediments further inland indicate four major hydrodynamic regimes during deposition. The detected bi-modality in grain size distribution suggests a dual-source of the deposits. The results on the aspect ratio analyses of grains indicate that more elongated particles were transported further inland.