In flood mapping and dam breach analysis, engineers and planners define inundation areas through flow modeling. A crucial input for this analysis is a comprehensive topographic surface of the area of interest and any upstream zones. These areas can span hundreds of kilometers and cover thousands of square kilometers.

Previous studies have indicated that low-resolution topography can results in larger inundation areas, greater flow volumes, and faster flood streams. However, a comparison of flow modeling using two sets of topographic data over the same area (SRTM DEM and a PhotoSat survey from high-resolution satellite imagery) reveals that low-resolution inputs can sometimes lead to an underestimation of flood distance, flood timing and inundation area. This can lead to significant differences in estimating the number of impacted structures and people, which ultimately impacts planning efforts.
This presentation will illustrate how variations in the resolution and accuracy of input topography can significantly impact the outcomes of flood mapping and dam breach analysis.