Floodplain Conservation as a Flood Mitigation Strategy: Examining Costs and Benefits

There has been growing interest among local governments in floodplain conservation as a flood damage reduction strategy. We evaluate one such investment—a greenway along the Meramec River in St. Louis County, Missouri. We estimate the opportunity costs of the conservation investment less the avoided flood damages from retaining the land as open space. To estimate avoided flood damages, we undertake a parcel-level analysis using the Hazus flood model, a GIS-based model developed for FEMA that includes a hydrology and hydraulics model coupled with a damage model relating flood depths to property damage. We examine the distribution of damages across parcels, demonstrating that careful spatial targeting can increase the net benefits of conservation. Finally, because creation of the greenway was motivated by the range of benefits it would provide, including aesthetic and recreational benefits, we undertake a hedonic model to estimate the capitalization of proximity to the greenway in property values. We find that the benefits of increased property values are roughly equal to the avoided flood damages, and that taken together, the floodplain conservation has generated net benefits.