PENDUGAAN EROSI, SEDIMEN, DAN SKENARIO PENGUNAAN LAHAN MENGGUNAKAN ArcSWAT2009 (Studi Kasus : DAS Batang Arau, DAS Batang Kuranji, dan DAS Batang Air Dingin)

Hydrological model that is used in this study is ArcSWAT2009 Model (Arc GIS Soil and Water Assessment Tools 2009) that can predict accurately erosion and sedimentation. This study aims to (i) predict erosion, sedimentation, and land use scenarios, (ii) to test the suitability of the model, (iii) perform the best landuse scenarios in order to reduce the rate of erosion. The research is conducted in the SWP (Regional Unit Management) Arau Watershed consists of three watersheds, namely Batang Arau, Batang Kuranji, and Batang Air Dingin Watershed. Data that is used for analysis is climate, soil characteristics, and daily sediment discharge from year 2002-2011. The results show that the amount of erosion and sedimentation in Batang Arau Watershed is respectively 167,70 tons/ha/year and 36.378 tons/year, the number of erosion and sedimentation in Batang Kuranji Watershed is 173,47 tons/ ha/year and 70.775 ton/year, while the number of erosion and sedimentation in Batang Air Dingin Watershed is 341,68 tons/ha/year and 51.459 tons/year. These results indicate that level of erosion hazard (TBE) in Batang Air Dingin is heavy, while the Batang Arau and Batang Kuranji is medium. Calibration and validation results of the SWP (Regional Unit Management) Arau Watershed shows SWAT Model is very goodin predicting erosion and sedimentation on a monthly basis, while the daily scale is still not accurate. Landuse scenarios performed in order to reduce the rate of land erosion. The scenario method is based on combination of the erosion hazard level (TBE) for the category heavy and very heavy on each HRU (Hydrologic Response Unit) and based on spatial planning contained in the unit area of watershed management Arau. The results of landuse scenarios successfully reduce erosion at Batang Arau Watershed is 18.82%, Batang Kuranji Watershed is 4.67%, and Batang Air Dingin Watershed is 1%