Enhancing Urban Flood Management for Ungauged Watersheds through Adaptive Mesh Refinement and Equation-based Flow Dynamics

Urban flood modelling in ungauged watersheds remains challenging due to rapid runoff dynamics and interactions with complex urban terrain. This study developed a 2D-hydrodynamic model for an ungauged basin using high-resolution DEM and land-cover data forced by 15-minute rainfall inputs. It compares Shallow Water Equations (SWE) and Diffusion Wave Equations (DWE) in simulating peak discharge, lag time, and hydraulic behaviour. SWE generated higher peak flows and longer response times, whereas DWE produced smoother hydrographs with faster wave propagation and improved numerical stability. Adaptive mesh refinement enhanced hydraulic representation and significantly reduced numerical volume errors compared with uniform meshes. The study contributes a hydraulically consistent framework that evaluates governing equation choice and mesh strategy using adaptive refinement and internally derived rating curves for structured comparative analysis in ungauged urban watersheds, offering a practical pathway for flood-risk assessment in rapidly urbanizing, data-scarce regions.