USING HAZUS-MH AS A FLOODPLAIN MANAGEMENT TOOL: TWO SOUTHERN ILLINOIS CASE STUDIES

Federal Emergency Management Agency's HAZUS-MH (Hazards U.S. Multi-Hazard) flood model is a GIS-based disaster risk assessment tool, which estimates the potential economic, societal, and infrastructure impacts of flooding. Coupling of HAZUS-MH with state-of-the-art hydraulic modeling tools allows for a quantitative assessment of river engineering and floodplain projects on flood risk. We have used HAZUS-MH as a floodplain management tool (1) to assess the exposure to flooding along the Middle Mississippi River (MMR) floodplain in southern Illinois and (2) have begun testing sensitivity to the resolution of building inventory data.

Assessment of total potential flood losses along the MMR in southern Illinois was completed using the national-level HAZUS-MH data. A polygon shapefile delineating the 100-year floodplain along the MMR was determined using 100-year flood profiles from the U.S. Army Corps of Engineers' Upper Mississippi River Flow Frequency Study. A raster layer was subtracted from a high-resolution DEM for the study area to produce a flood inundation layer. Potential flood losses along this reach would be approximately $4.9 billion, excluding transportation infrastructure. Of the total damages, close to $3.8 billion would be to residential homes, and $849 million would be commercial infrastructure.

In order to assess the limitations of the national-level HAZUS-MH data, models using (1) national-level data (level I analysis) and (2) using detailed building inventory (level II analysis) were run for Jackson County, IL. The detailed building inventory was compiled from county assessor records and included function of the building, assessed value, and number of floors. The HAZUS-MH level I analysis shows at least moderate damage to 91 buildings and two critical facilities, 617 households displaced, and the total economic loss estimate of $75.37 million. The HAZUS-MH level II analysis of the same study area shows moderate damage to at least 250 buildings and 8 critical facilities, 1,376 households displaced, and total economic losses of $82.69 million. The discrepancy between the two HAZUS-MH models needs to be considered for future modeling and if possible, updated data and level II analyses should be used.