<![CDATA[Flooding on the Tangerang-Merak Toll Road at KM 50+000–51+000, Cikande, in January 2026 disrupted the national logistics corridor. This study evaluates the macro-level causes of inundation through integrated hydrological analysis using a Geographic Information System (GIS) approach with scoring, overlay, and hydrological modeling techniques across 14,516 spatial units in the Cidurian Watershed. The evaluation covers spatial drainage capacity, Digital Elevation Model (DEM), flow accumulation, SWAT+ modeling, and its alignment with the Cikande Industrial Area Detailed Spatial Plan (RDTR). Analysis indicates that 96.2% of the study area has low drainage capacity, an average Curve Number of 94.2, and a surface runoff ratio of 0.83. The flooding mechanism is identified as compound flooding involving three simultaneous processes: local channel tailwater submergence driven by high Cidurian River levels, backwater accumulation in upstream toll road depressions, and overtopping across the road body. DEM analysis confirms Bakung Village as the flow pathway and Songgom Jaya Village as the final accumulation zone. The findings confirm that the flood stems from the interaction of main river overflow, loss of hydraulic gradient, and watershed capacity limits rather than local drainage constraints alone. Three technical mitigation scenarios are recommended: elevating the road, river normalization with embankments, and expanding cross-drain capacity integrated with collector drains and downstream normalization.]]>
