Peran Tutupan Hutan terhadap Pendugaan Debit Banjir Rencana di DAS Cimanceuri sebagai Dasar Pengelolaan Daerah Aliran Sungai

The Role of Forest Cover in Flood Discharge Estimation in the Cimanceuri Watershed

Abstrak

Design flood discharge is crucial for designing hydraulic structures to control flooding in watersheds. The most accurate way to estimate design flood discharges is through frequency analysis or empirical methods based on long-term historical discharge data. However, such long-term data are rarely available in Indonesia. This study aims to analyze the differences in the design flood discharge estimation model using the Rational Method and the SUH-Nakayasu Method, and the role of forest cover in the calculation of design flood discharge in the Cimanceuri Watershed. The results of the study showed that the Rational Method resulted in a higher estimated design flood discharge compared to the Nakayasu Method. Based on CHIRPS with a 2−100 year recurrence period of 61.4 mm/day−118.9 mm/day, the Rational Method produces a design flood discharge of 109.2−212.3 m³/s at land use conditions (C) = 0.20 and 119.1−231.6 m³/sec at C= 0.24, while using the SUH-Nakayasu Method of 45.1-87.5 m³/sec at C = 0.20 and 53.7-104.1 m³/sec at C = 0.24 conditions. The composition of land use that produces a C value has a significant effect on the increase in peak discharge, and the role of forests is very large in the reduction of the C value.