Kajian Erosi & Sedimentasi Akibat Perubahan Tataguna Lahan Daerah Aliran Sungai (Studi Kasus DAS Betung Sub DAS Pebari-Jelitik Kabupaten Bangka)

Abstract

Tin mining activity by the local community of Bangka Belitung has caused quite a serious damage. The changes in land use, especially of watershed land, have increased the number of degraded lands in Bangka Belitung Island Province. From 2006 to 2011there had been an increase in the run off-CH ration by 2% especially in Ajang Mabat and Mancung Watersheds, Bangka Regency and West Bangka Regency. The same goes for the potential of land erosion due to the forests changing into mining areas, which increased by more than 25% for the same period and fitted into the category of severe erosion (BP.DAS Batusa-Cerucuk,2013). Pebari-Jelitik Watershed, the object of this study, has an area of ± 3762 Ha and is a part of BetungWatershed of Bangka Regency that has an area of 14.282 Ha. The soil types are:Aluvial, Kambisol, and Podsolik; most of the area is catchment area that has 0%-8% slope.The land cover consists ofhousing, moor/field, mining area, and plantation. The magnitude of erosion in Pebari-Jelitik Watershed obtained using USLE equation is 1.016.052,6ton/year, or an average of 270,083 ton/ha/year, which fits into the category of class IV (severe). Based on the analysis using the Mayer-Peter andMuler (MPM) equation, the amount of sediment that goes into Pebari-JeitikRiver caused by land erosion is 38.384,78 ton/year in the upstream, 55.119,78 ton/year in the middle,and 52.753,60 ton/year in the downstream. The cause of erosion in the Pebari Jelitik Subwatershed is caused more by the percentage of C value (coefficient of Run Off) which is more than 60% and highly influenced by land use. The value of P (soil management factor) = 1, shows that in the subwatershed there is no soil conservation effort. The material of soil erosion goes into Pebari-Jelitik River and causes a highly unnatural sedimentation in Pebari-Jelitik River. Erosion and Sedimentationare real evidences that the number of degraded lands in Bangka Belitung will continue to increase due to the changes in land use.