DERIVATION OF THE CRITICAL RAINFALL LEVEL NEEDED FOR AN EARLY FLOOD WARNING IN THE UPPER CITARUM RIVER BASIN INDONESIA

Abstract

Rainfall is one of the common triggering factors of the flood. Bandung City is located in
the Upper Citarum river basin. Parts of the city, such as Bojong Sari, Bojong Soang, Cieunteung and
Andir Sub district, are in natural floodplains. During the wet season, these areas are frequently flooded.
This study analyzed the critical rainfall level that potentially caused flooding. The Hydrologic

Engineering Centres Hydrologic Modelling System (HEC-HMS) rainfall-runoff model and the 1D HEC-

RAS model were applied. A six storm pattern was simulated to determine the critical rainfall that
generated the water depth that was equal to or greater than the critical water surface depth at specific
points in the river. Hypothetical rainfall events are used to investigate the response of the river basin at
critical cross-sections. It can be considered by different temporal distributions. The amount of rainfall is
assumed to be distributed uniformly. The conclusion of this research is that the storm pattern (rainfall
depth and rainfall duration) plays a crucial role in determining the critical rainfall at the flood location.
The critical rainfall in a specific location is affected by the position at the river cross-section (in the
upstream or the downstream area) and the bank full capacity of the river cross-sections.