Prairie landscapes are known to provide valuable ecosystem services, including floodwater retention, which have been widely studied for the Prairie Pothole Region and the Great Plains in the Midwestern United States. However, research specific to surface water ecosystem services provided by coastal prairies remains sparse. In particular, few hydrologic and hydraulic (H&H) modeling studies exist that explore the ability of coastal prairie to contribute to storm water mitigation in the flood-prone Gulf Coast region. This study employed H&H modeling to understand the impact of changes to overland characteristics of a remnant coastal prairie in Houston, Texas (the Katy Prairie) on its storm water detention and flood mitigation potential. Results from the fully distributed hydrologic modeling in this study have allowed quantification of the overland detention storage provided by native prairie vegetation, estimating an excess of 0.6 acre-ft/acre greater than current developmental standards for Harris County, Texas. This is one of the first quantitative studies proving that if coastal prairie is developed according to Harris County jurisdiction, rainfall-runoff would be exacerbated in the watershed. In addition, the unique, multi-faceted modeling regime has provided insight on the overland flow behaviors of prairie potholes, an inherent depression feature of prairie terrain, by demonstrating depression storage capacity for rainfall-runoff. Overall, this study has suggested rehabilitation of coastal prairie landscapes would provide substantial hydrologic benefits and may be a key aspect of a coastal resiliency plan in the face of climate change.