Analysis of Sedimentation Quantity and Its Handling in the Downstream of Tukad Unda Klungkung using Hec-GeoRAS

Abstract

The river is one part of the water resources infrastructure, in addition to drive the water, river is often transporting sediment. Sediment is the result of erosion and is part of problems in the river. Unda watershed having their regional coverage is quite wide, so that erosion that causes to the passage of it is estimated that sedimentation large enough. This research analyze the total weight of the sediment that is settles on the downstream Tukad Unda and compare the analysis of sedimentation between USLE method and sedimentation method in HEC-RAS by supporting ArcGIS and HEC-GeoRAS so that can describing the shape of look over profile of to scatter the sediment that was formed, as well as the efforts to overcome the problems.  The data used in the form of watershed area, soil type, rain and river flow. Furthermore, the method used is Universal Soil Loss Equation (USLE), the application of HEC-GeoRAS and ArcGIS. The results showed the average erosion that occurred in the last 10 years amounted to 30.57 tons/ha/year, then the results of the HEC-GeoRAS analysis showed that the river bed profile changes experienced a significant silting of 2,365 m3 using the application and 2,654 m3 with USLE method. Countermeasures can be done by normalizing the riverbed with regular dredging at the stationing point UD 64-60 then at the stationing point UD 55-57 and at stationing UD 45-41 in accordance with the analysis results obtained through the HEC-GeoRAS application.