MARINE GEOLOGY AND COASTAL EROSION PROCESSES OF PATTAYA BAY, EASTERN THAILAND

Seven aerial images serials, covering 1952, 1967, 1974, 1994, 1996, 2002 and 2011, were used to calculate the coastal erosion areas in Pattaya Bay by GIS interpretations. The results clearly showed a decrease in the beach width from 35 m to 5 m. Also, there has been an apparent average rate of erosion of -0.78 m/y between 1952 and 1974 and of -1.8 m/y between 1994 and 2011. In addition, the use of the MEPBAY program to inspect the coastal stabilization of Pattaya Bay indicated the erosion patterns of Pattaya Bay. To understand the coastal erosion processes, bottom sediment movements within the Southeast and Northeast Monsoon seasons, were inspected and found to correspond with the stronger wind speed and affected wave direction. Also, the changing land use patterns around the beach, pipeline system and coastal structures affected the coastal stabilization of Pattaya Bay.The features of erosion were interpreted from six bathymetry maps of Pattaya Bay covering the years 1975, 1983, 1995, 2000, 2003 and 2011. These indicated that there is accumulated sediments offshore. Marine geology using boring log data revealed Holocene offshore sand bars with mud particles in the same pattern as that at the shore of Pattaya Bay. From this information, it can be concluded that the problem of erosion in Pattaya Bay in recent years has become more significant. With the current rate of coastal erosion, Pattaya beach is forecasted to have disappeared within five years.