Flood Analysis and Estimating Economic Losses in an Affected Area (Case Study: Cikapundung Watershed)

Abstract

The Cikapundung Watershed is part of the Citarum watershed, which functions as the main drainage of the center of Bandung City. High exploitation of space and water resources can trigger flooding, as is often the case in the Cikapundung watershed. Flooding can be caused by rapid population growth, land degradation, and climate change. In this study, four types of methods were used to analyze rainfall frequency, and the type III Log Pearson distribution method was found to meet the requirements for use. A match test was carried out using the chi-squared method and the Smirnov-Kolmogorov method. Hydraulics analysis was carried out by the HEC-RAS method with different return periods to calculate the depth of flooding. HEC-RAS was used because it is considered highly compatible and relevant to geatographic information systems. The return periods modeled with HEC-RAS were 2, 5, 10, 25, 50, and 100 years. Based on the calculation results, the Cikapundung watershed runoff coefficient in 2020 was .43. The increased return period suggests that the area of flood inundation is becoming wider. The downstream impacts of wider flood inundation include all sectors that are more affected by flooding. This causes losses to increase as the flood payback period increases. The total estimated loss for the 25 return periods of flood events in the Cikapundung watershed is around 1,124 million rupiah, and the affected population is around 700,000 people.