Comparing Flood Models from Federal Emergency Management Agency (FEMA) and First Street Foundation’s Flood Factor to Evaluate Flood Risk in the Rouge River (MI) Watershed.

Keywords: Flood management, Flood risk, risk assessment, flood hazard areas, Michigan, Flood Factor, FEMA, GIS, geospatial analysis
Abstract Type: Paper Abstract

Abstract

Pluvial and fluvial flooding are intensifying due to increasing temperatures, precipitation, and rapid urbanization. Such developments place an increasing number of people and capital at risk, which calls for public flood management as well as household level adaptation measures. This study aims to compare existing flood extent from Federal Emergency Management Agency’s (FEMA) National Flood Hazard Layers and First Street Foundation’s Flood Factor to analyze the percentage of properties at risk in the Rouge River Watershed of Southeast Michigan. Properties under FEMA’s special flood hazard zones are compared against those representing a high Flood Factor and delineated to evaluate the flood risk based on their extent and land use. FEMA’s flood zones are mapped based on historical data which may not consider intense rainfall, a growing problem as the atmosphere warms. First Street’s Flood Factor model is created using federal elevation, rainfall data and coastal flooding estimates from hurricanes, thus resulting in updated maps which show a vast increase in risk compared to official estimates. Analyses identified almost a 5% increase in the number of parcels at risk in the 500-year floodplain of the watershed. To further validate these additional at-risk parcels, a flood susceptibility map of the watershed using a Multi-Criteria Decision Analysis (MCDA) model was created. This overall estimation of flood hazard areas in this study is an important approach for an effective flood management measure and will further contribute while making critical decisions regarding flood mitigation procedures and protection of the anthropogenic and natural environment.