<![CDATA[Land use land cover (LULC) change driven by urbanization in the Cakung Watershed, Jakarta, has significantly increased peak flood discharge. This study employed a quantitative approach using secondary data. LULC classification used the Random Forest algorithm in ArcGIS, applied to Landsat 5 and Landsat 8 Level 2 imagery, and the hydrological model was calibrated and validated using observed streamflow data. The watershed was divided into four sub-watersheds: Cakung Hulu–BKT, Buaran–BKT, Jatikramat–BKT, and Cakung Hilir. The study aimed to calibrate and validate the HEC-HMS model and to determine the effect of LULC change on flood discharge in the Cakung Watershed. The HEC-HMS simulation performed excellently during calibration (7 January 2024) and the first validation (11 April 2024), yielding NSE of 0.842–0.892, RSR of 0.30–0.40, and PBIAS of −1.06% to −0.78%. The second validation (4 August 2024) declined to a satisfactory level (NSE = 0.595, RSR = 0.60, PBIAS = −10.75%), yet the parameters remained reliable. LULC changes during 2000–2024 increased CN by 1%–4% and impervious area by 18%–182%, indicating reduced infiltration and expanded built-up areas, which raised design flood discharge across all sub-watersheds. Cakung Hilir produced the highest peak discharge (120.30 m³/s), while Cakung Hulu–BKT showed the largest increase (12.89%). The results showed that higher CN and impervious area values corresponded to greater flood discharge. Therefore, LULC change is a contributing factor to increased flood discharge in the Cakung Watershed.]]>
