Sayedur Rahman Chowdhury and Nitin Kumar Tripathi

pp. 739 - 748

Abstract

Coastal erosion and accretion in Pak Phanang of southern Thailand between 1973 and 2003 was measured using multitemporal topographic maps and Landsat satellite imageries. Within a GIS environment landward and seaward movements
of shoreline was estimated by a transect-based analysis, and amounts of land accretion and erosion were estimated by a
parcel-based geoprocessing. The whole longitudinal extent of the 58 kilometer coast was classified into six kinds based on
historical trends of erosion and accretion using agglomerative hierarchical clustering approach. Erosion and accretion were
found variable over time and space ranging from 18.4 mm.yr^-1 to 33.65 mm.yr^-1, and periodic reversal of status was also
noticed in many places. Land loss due to erosion as high as about 3 ha.km-1 of shoreline, and land gain as high as about 1.8
ha.km^-1 of shoreline was estimated in different tambons. As high as 1% of total land of a tambon (Nah Saton) was lost due to
erosion, whereas the largest gain was estimated to be slightly over half-percent of the total area in another tambon (Laerm
Talumphuk). In general, southern tambons were more affected by erosion. Estimates of erosion were evaluated against fieldsurvey based data, and found reasonably accurate where the rates were relatively great. Smoothing of shoreline datasets was
found desirable as its impacts on the estimates remained within tolerable limits.