OPTIMIZATION OF LAND USE TO REDUCE SURFACE RUNOFF AND EROSION IN KURANJI WATERSHED

Abstract

Changes in land cover in the Kuranji watershed (22,460 hectares) increased very rapidly along with the increase in the number of people using land due to the impact of the September 2009 earthquake. Therefore, an appropriate land use model is needed so that surface runoff and erosion can be reduced. This study aims to determine the value of surface runoff using rational methods and soil erosion using a modified universal soil loss equation model based on land units with a total of 22 samples and to determine land cover optimization using the Spatial Multi Criteria analysis (SMCA) technique. Scenario determination is also based on maps of conservation, protected areas, and cultivation as well as the spatial plan of Padang City. The results showed that erosion that exceeded the tolerance limit was found in 5 samples. A site with mixed gardens and a very steep slope had an erosion rate of 16.60 tonne/hectares/year, and an erosion rate at settlements area with a slightly steep slope of is12.53 tonne/hectares/year, mixed gardens with a steep slope of 8.57 tonne/hectares/year. The settlements with a flat slope of 19.43 tonne/hectares/year, and 17.85 tonne/hectares/year. The optimal way to reduce erosion is to convert 0.83% of shrubs and 4.51% of mixed gardens located on steep/very steep slopes into conservation areas and protected forests; thus, erosion can be reduced by up to 70-80%; while the built-up area (settlement area, industrial area, etc.) is developed on a flat slope.