Hydrologic analysis in regions with complex terrain is essential for understanding and mitigating the risks associated with extreme events, such as floods and landslides. This study evaluates the accuracy of hydrologic analyses using freely available Global Digital Elevation Models (GDEMs) in comparison to a nationally verified, high-resolution Digital Elevation Model (DEM). The study area, encompassing both an urban coastal plain and a mountainous region, presents unique challenges for hydrologic modeling due to its diverse topography. Results revealed significant discrepancies between free GDEMs and the high-resolution DEM in the urban coastal plain, where GDEMs showed notable deviations from ground-truth data. However, the mountainous region exhibited fewer differences, suggesting that topographic complexity influences DEM accuracy more significantly in flatter, urbanized areas. While free GDEMs are valuable for general mapping applications, they may lack the precision required for accurate hydrologic analysis in vulnerable regions. This research underscores the critical importance of high-resolution DEMs in enhancing flood risk assessments and supporting effective hazard mitigation strategies in complex terrains such as Jeddah's urban coastal plain and mountainous areas.