Analisis Spasial Ukuran Butiran Sedimen di Pesisir Selatan Kabupaten Pacitan, Provinsi Jawa Timur

The southern coast of Pacitan District is one of the areas directly adjacent to Indian Ocean and has a Pacitan Bay. The process of erosion and sedimentation should be known to see the physical condition of the beach. Sediment grain size is part of the sedimentary properties that can provide information about the sediment transport process. Sediment distribution provides description the origin of sediment, transportation history, and deposition conditions. The purpose of this research is to analyze the sedimentation environment by knowing the grain size distribution of sediment. The research benefits are to know the distribution of sediments and to predict coastal conditions in terms of the physical character of the sediments. Method of sampling stratified random areas on each segment along 150x150 meters. Grouping of sediment from sieving result which done in laboratory of P2O LIPI based on Wentworth scale and granulometry test. The result showed that sediment with the type of sand dominates on every beach. The mean value on the oceanic beachfront ranges from 1.36 - 0.20 mm, sorting is very well sorted till moderately sorted, skewness is very fine skewed, and kurtosis is extremely leptokurtic. Beach facing the bay, the mean value 0.19 mm on the west side then becomes 0.36 - 0.43 mm on the east side near mouth of the river, sorting is very well sorted and well sorted, skewness is strongly fine skewed, and kurtosis is extremely leptokurtic.