Effects of Digital Elevation Model Resolution on Estimates of Flood Damage in Westbrook, Maine

Accurate predictions of flood damage and economic losses are increasingly important as historically low-probability floods have become more common. Digital elevation models (DEMs) are essential to flood modeling as they define stream channel and floodplain morphology, the accuracy of which influence estimates of flood damage. The city of Westbrook, Maine experiences episodic flooding of the Presumpscot River; therefore, flooding in Westbrook was simulated with HAZUS, a model created by the Federal Emergency Management Agency. The model is designed to assess the costs associated with hazard scenarios including riverine flooding. HAZUS was run for a 100-year return period flood with both ⅓ arc-second (10 m) and 1 arc-second (30 m) DEMs. The ⅓ arcsecond DEM represents the highest resolution currently available for the study area. Preliminary results, based on a census-block-level structure inventory provided with the model, suggest that DEM resolution has a significant impact on damage and economic loss estimates that vary by census block and structure type. Further modeling using parcel-level inventory data for Westbrook will refine these results