Evaluasi Perubahan Penggunaan Lahan dan Limpasan di Sub-DAS Cidangiang DAS Cidanau Provinsi Banten

Abstract

Perubahan penggunaan lahan akibat tekanan pertumbuhan penduduk dan perkembangan kawasan industri berpotensi meningkatkan limpasan permukaan di suatu daerah aliran sungai. Penelitian ini bertujuan mengevaluasi dampak perubahan penggunaan lahan tahun 2021 dan 2025 terhadap volume limpasan permukaan di Sub-DAS Cidangiang, DAS Cidanau menggunakan metode Soil Conservation Service-Curve Number (SCS-CN), dengan analisis spasial berbasis citra Esri Land Cover 10 m, data Kelompok Hidrologi Tanah, dan data curah hujan CHIRPS terkoreksi bias. Hasil menunjukkan perubahan lahan tergolong kecil, dengan lahan terbangun bertambah 70,1 ha (+0,4%), sehingga nilai CN tertimbang tidak berubah, tetap 72,9 pada kedua tahun. Limpasan permukaan hasil simulasi meningkat 270%, dari 121,2 menjadi 448,5 mm/tahun, sejalan dengan kenaikan curah hujan tahunan sebesar 76,6%. Perbandingan rasio limpasan terhadap curah hujan menunjukkan variabilitas curah hujan jauh lebih dominan menjelaskan perubahan limpasan dibandingkan perubahan lahan, sehingga dampak perubahan lahan belum tertangkap secara tegas dalam periode ini.

Land use change driven by population growth and industrial expansion has the potential to increase surface runoff in a watershed. This study aimed to evaluate the impact of land use change in 2021 and 2025 on surface runoff volume in the Cidangiang Sub-Watershed, Cidanau Watershed using the Soil Conservation Service-Curve Number (SCS-CN) method, with spatial analysis based on 10 m Esri Land Cover imagery, Hydrologic Soil Group data, and bias-corrected CHIRPS rainfall data. Results showed land use change was relatively small, with built-up area increasing by 70.1 ha (+0.4%), so the weighted CN value remained unchanged at 72.9 in both years. Simulated surface runoff increased by 270%, from 121.2 to 448.5 mm/year, consistent with a 76.6% rise in annual rainfall. Runoff-to-rainfall ratio comparisons showed rainfall variability was far more dominant in explaining runoff change than land use change, so the impact of land use change was not clearly detected within this period.