Land-Use Change, Runoff Coefficient, and Flood Vulnerability Dynamics in Urban Sub-Watersheds

Abstract

Urban flood vulnerability has increased alongside land-use change, which alters watershed hydrological responses. This study examines the relationship among land-use change, the runoff coefficient (C), and flood vulnerability across 10 urban sub-watersheds in Samarinda City from 2010 to 2021. The methodology integrates multitemporal land-use analysis, hydrological modeling, and Light Detection and Ranging (LiDAR)-based two-dimensional (2D) hydraulic simulation using the Hydrologic Engineering Center’s River Analysis System (HEC-RAS), together with a multidimensional flood vulnerability assessment. The results indicate substantial increases in built-up areas, higher runoff coefficients, and expanded flood inundation. Both the global and parsimonious regression models (Models 1 and 2) were statistically significant based on the overall F-test (p = 0.0003 and  = 0.0012, respectively), while the runoff coefficient showed the most consistent association with flood vulnerability (p = 0.009 in Model 2). Subgroup analyses of underdeveloped and developed sub-watersheds (Models 3 and 4) showed similar positive trends but were not statistically significant overall and were therefore treated as exploratory findings. These findings suggest that the runoff coefficient may serve as an integrative hydrological indicator linking land-use change and flood-vulnerability dynamics. Integrating multi-period Land Use / Land Cover (LULC) analysis, LiDAR-based hydraulic modeling, and vulnerability assessment may support more adaptive flood mitigation strategies in rapidly developing urban watersheds.