Flood analysis of Buntung River and the structural measures in Sidoarjo Regency

Abstract

Sidoarjo Regency as one of the downstream areas of the Brantas River Basin is prone to flooding. This study aims to simulate the flood discharge and inundation in Buntung River, a river passes through Sidoarjo City area with several time return periods and to discuss its physical flood mitigation. Data needed in this study are Rainfall Data for 3 Rain Stations, topography map, cross section of river stream, and land use map. Based on these data, a flood flow analysis plan is then performed using the Nakayasu synthetic hydrographs method. The inundation is simulated using HEC-RAS with 10, 25, and 50 years return periods. Based on the calculation, Buntung River flood discharge with return period of 10, 25, and 50 years return periods is 151,342, 196,923, and 233,981 m3/s respectively. The inundation extend of 25 years return period is reaching 0,53 m height above the bank along Sta. P0 to P1. The study reveals that the existing cross section cannot accommodate the design flood for at least 25 years return period. Therefore, normalization is essential for river improvement. The channel is design with river cross-sectional shape of double trapezoidal. The size of the earth dike is 0.60 m above the flood water level with 3.0 m width and 1:2 channel slope. The designed river channel improvement increase the channel depth from -3,56 m to -4,07 m in Sta. P1. The normalized channel could accommodate the design flood and would be beneficial for increasing the urban area safety from flood disaster.