Author(s): Tatiene Pereira; Guilherme Reis; Kamila Santos; Klebber Formiga

Linked Author(s): Kamila Almeida dos Santos, Klebber Formiga

Keywords: Copernicus DEM; Digital elevation models; Flood mapping; HEC-RAS; LiDAR; Urban flooding

Abstract: Digital Elevation Models (DEMs) are important for accurate flood simulations, but how different DEM sources affect small-scale urban flood modelling remains poorly understood This study evaluated the influence of three global, open access Digital Elevation Models (Copernicus DEM, NASADEM, and . Topodata), on urban flood modelling to determine their technical viability for extreme event simulations under budget constraints. The methodology integrated bathymetric surveys via Acoustic Doppler Current Profiler (ADCP) and the definition of a 100-year return period design flood. Flood extents were simulated using HECRAS 6.0, with LiDAR-derived data used as the validation benchmark. Results indicated that Copernicus DEM achieved superior performance, yielding the lowest Root Mean Square Error (RMSE) and Percent Bias (PBIAS), alongside the highest Pearson correlation coefficient (R). Although it underestimated the inundated area by 18%, it demonstrated high accuracy in depth representation. Conversely, NASADEM underestimated the flood extent by 30%, while Topodata, despite a numerical proximity in total area (3% overestimation), exhibited poor spatial precision and severely overestimated flood depths. It is concluded that reduced DEM spatial resolution leads to a systematic tendency to underestimate flood extents and overestimate local depths. Consequently, Copernicus DEM emerges as the most robust alternative for urban hydraulic modelling in the absence of high-resolution data.

DOI: https://doi.org/10.64697/iahr.proc.hic2026.45

Year: 2026