2D Flow Model of Kendal River Sedimentation Effect as Identification of Bandengan Village Flood Management

Abstract

Flooding is one of the hydrometeorological disasters that often occurs on the north coast of Central Java, such as in Bandengan Village. Kendal River sedimentation occurs, which causes flooding. A two-dimensional (2D) flow model is needed due to the influence of sedimentation in the Kendal River channel, especially around the Bandengan Village area. This modelling aims to prove that sedimentation of the Kendal River is one of the causes of flooding. Secondary data on land use and rainfall are used to calculate the design of flood discharge. Primary data collection in the form of sediment samples and river contours as the basis for making Digital Elevation Model (DEM) maps for hydraulics modelling using the HEC-RAS 2D application. The Universal Soil Loss Equation (USLE) Method was analyzed to determine how much erosion potential was formed in the Kendal Watershed. The calculation of the design flood discharge is Q2 of 45.1 m3 /s, Q5 of 62.8 m3 /s, Q10 of 74.7 m3 /s, and Q10 of 91.3 m3 /s. Hydraulics analysis with three situations resulted in existing conditions occurring flooding, conditions without sediment also flooding, and finally, river widening conditions showed no flooding. Erosion analysis shows that the erosion hazard class in the Kendal watershed is low, so there are two indications, namely the transportation of sediment from irrigation canals in the upper reaches of the Kendal watershed and sedimentation accumulated over the years due to the absence of sediment control in the Kendal River. This modelling concludes that sedimentation, small river cross-sections, and the erosion of the Kendal coastal area are the causes of flooding in the area. Handling the issue by widening the river and building sediment barriers in the upstream area can reduce sedimentation and flooding of the Kendal River around Bandengan Village.