ANALISA DEBIT BANJIR AKIBAT PENGARUH PERUBAHAN TATA GUNA LAHAN DAERAH ALIRAN SUNGAI KONTO KABUPATEN MALANG

Abstract

River flow is a crucial component in environmental ecosystems. Flood events occurring in river flow areas can cause damage, particularly to human life necessities. This research aims to analyze flood discharge due to land use changes in the Konto River Watershed, Malang Regency. The research method used is calculation with Nakayasu's Synthetic Unit Hydrograph (SUH) and simulation of the HEC-HMS application using land use, rainfall, and river discharge data. The average runoff coefficient values for the Konto River are as follows: 2013 (0.0722), 2014 (0.0753), 2015 (0.0753), 2016 (0.0749), 2017-2018 (0.0753), 2019 (0.0754), 2020 (0.0807), 2021 (0.0794), 2022 (0.0814), and 2023 (0.0835). Based on the HEC-HMS simulation results, the maximum discharge of the Konto River at various return periods is as follows: 2-year return period (27.10 m3/s), 5-year return period (28.10 m3/s), 10-year return period (28.60 m3/s), 25-year return period (29.40 m3/s), 50-year return period (29.90 m3/s), 100-year return period (30.40 m3/s), 200-year return period (30.90 m3/s), and 1000-year return period (31.90 m3/s). This research concludes that land use changes in the Konto River Watershed, Malang Regency, can affect flood discharge. This is evidenced by the percentage change in runoff coefficient values due to land cover changes (15.65%) and the percentage change in peak discharge values from the HEC-HMS simulation results (17.71%).