Cimahi River Benchmarking Flood Analysis Based on Threshold of Total Rainfall

Abstract

Flood in Cimahi city coming from the overflow of Cimahi river is a disaster that often occur in the middle Cimahi and extends downstream region namely Bandung Regency which is still included in the Cimahi Watershed. Flood in Cimahi can earlier be estimated when the design intensity of rainfall determined and calculate the flow of the river from upstream to downstream.The purpose of this study was to determine total rainfall that caused the peak river discharge of Cimahi river in upper and middle cross section and could easily received. The method used in this study is an early warning flood with benchmarking discharge based on rainfall-runoff models in the Cimahi watershed derived from unit hydrograph synthetic Nakayasu of Cimahi river. The results obtained from this study is the peak discharge of the Cimahi river upstream at Q= 1.41 m3 / s and in the middle of the cross section of Q = 2.12 m3 / s. Based on the measurements obtained bankfull discharge Cimahi river upstream cross section of 191.8 m3 / s and bankfull discharge in the middle cross section is 556.26m3 / s. With the drainage coefficient of Cimahi city based on land use obtained 0,57, then obtained a threshold total rainfall causes of flooding in the upper and middle is respectively as high as 239 mm and 460 mm. Threshold of Rainfall, bankfull discharge and Cimahi river cross section in this research integrated on the map namely Benchmarking Flood Diagram of Cimahi City that can be published to stakeholders and the public.