Peak discharge estimation to evaluate and monitor the Gumbasa Watershed performance, Central Sulawesi, Indonesia

Abstract

One of the appropriate strategies to evaluate watershed health is by determining peak discharge. This is associated with the influence of frequent floods and landslides on the changes in the carrying capacity of Gumbasa watershed. It was also attached to the accelerated forest and land degradation due to encroachment, especially in the upstream. This study aims to determine the estimated peak discharge of three sub-watersheds, including Lindu, Palolo, and Gumbasa to monitor and evaluate the performance of the main watershed. This was conducted using a rational method with a combined and average flow coefficient approach, while the rainfall intensity was calculated based on the longest concentration time. The results showed the flow coefficient in the Palolo and Gumbasa downstream areas were 0.45 and 0.57, respectively and these were closer to 1 more than the 0.12 recorded for Lindu. This means some of the rainwater is flowing on the land surface, thereby causing high peak discharge, especially in the downstream. Therefore, it is necessary to conserve and restore land through reforestation and rehabilitation to minimize the flow coefficient and peak discharge.