Flood disasters in Indonesia have shown an increase, both in magnitude and frequency. In fact, the area, depth, and duration of inundation tend to increase. Current flood control focuses on increasing river capacity: widening and/or deepening the cross-section of the river and controlling surface runoff by building storage upstream of the watershed. The storage requirement depends on the surface runoff rate in the upstream watershed. This study aimed to find the formulation of the most optimal watershed storage volume requirement through the correlation of flood discharge and surface runoff in the upstream watershed area. The results of the study found the optimum watershed storage volume capacity and produced 2 (two) representative equations to calculate the upstream watershed storage volume (WSVO) based on 2 (two) river slopes (slope 0.1, slope 0.01). WSVO is intended to facilitate the determination of the storage volume capacity in the upstream area if complete data, both primary and secondary data are not available.

No abstract