Estimation of Extreme Rainfall Changes in the Serayu Watershed Using a Scenario-Neutral Approach

Abstract

Flood disasters are the most frequent and damaging occurrences in Indonesia. They result in destruction, disrupting both economic and community activities. Extreme rainfall serves as one of the triggers for these floods. To mitigate the impact of impending losses, detecting flood disasters is necessary. This research aims to assess the effects of rainfall changes on increased flood risks in the Serayu Watershed using a Scenario-Neutral approach. The data utilised in this study comprise daily rainfall data from 1980-2018, obtained from GPCC, with the research conducted within the Serayu Watershed. The manipulated characteristics of rainfall encompass cumulative annual and monthly rainfall (Jan-Dec), with the upper and lower limits of rainfall changes determined through Mann-Kendall analysis. Daily rainfall data for the 1980-2018 period were generated while preserving the annual and monthly characteristics using an inverse approach, followed by calculating extreme rainfall for various return periods. Based on 132 simulations, the results indicate that excessive rainfall for shorter return periods is more sensitive than more extended return periods. This holds implications for designing flood control structures at both micro and macro scales, necessitating considering climate changes.