Effects of High-Quality Elevation Data and Explanatory Variables on the Accuracy of Flood Inundation Mapping via Height Above Nearest Drainage

Abstract. Given the availability of high quality and high spatial resolution digital elevation models (DEMs) from the United States Geological Survey’s 3-Dimensional Elevation Program (3DEP) derived from mostly Light Detection and Ranging sensors, we examined the effects of these DEMs at various spatial resolutions on the quality of flood inundation map (FIM) extents derived from a terrain index known as Height Above Nearest Drainage (HAND). We found that using these DEMs improved the quality of resulting FIMs at around 80 % of the catchments analyzed when compared to using DEMs from the National Hydrography Dataset Plus High Resolution program. Additionally, we varied the spatial resolution of the 3DEP DEMs from 3, 5, 10, 15, and 20 meters and the results showed no significant overall effect on FIM extent quality across resolutions. However, our experiments demonstrated a significant burden on the computational time to produce HAND. We fit a multiple linear regression model to help explain catchment scale variation in the four metrics employed and found that the lack of reservoir flooding, or inundation upstream of river retention systems, was a significant factor in our analysis. For validation, we used Interagency Flood Risk Management Base Level Engineering produced FIM extents and streamflows at the 100 and 500 year event magnitudes in a sub-region in Eastern Texas.