Verification of a Synthetic Rainfall Model Based on the ArRR and Satellite Rainfall

Abstract

Synthetic rainfall is needed as an input in the analysis of design flood. This research intends to conduct the verification of a synthetic rainfall model based on the ArRR and satellite result. The rainfall data is as the main component in obtaining the design, detail design, operation and maintenance of effective water resource infrastructure. Rainfall data is often used for the analysis of flood balance, flood frequency distribution, estimation of river discharge, and design of water structure. However, the main constraint in designing the water resource infrastructure is less available rainfall data temporally and spatially. The limitation of available rainfall station number causes inaccuracy in analyzing the area mean rainfall. Therefore, sometimes the correlation between recorded data from the rainfall station and water estimation station does not show a positive and strong correlation. This is due to less rainfall data that are spatially representative in the watershed upstream. The verification is carried out in the Ciliwung Hulu watershed. The methodology consists of ArRR analysis of the two extreme rainfall events, then the ArRR is analyzed using the synthetic rainfall model equation that is applied for watershed areas < 750 km2; in the end, we spatially compared the satellite and observed rainfall. The analysis of the ArRR value is based on the formulation as follows: ArRR_i=(0,026FB-0,307*Re_i+1,184 Q_(i+lag)/A+0,693)/(C_ArRR.K_ArRR ). The lag time that is used is 3 h based on the analysis of time to peak by using the Nakaysu hydrograph by assuming that the run-off coefficient is 0.35. The spatial comparison between satellite and observed daily rainfall on February 19, 2021, and October 28, 2021, shows that the rainfall distribution pattern is more similar with adding the ArRR synthetic rainfall station than with only using the ARR station.