First Street Foundation's National Flood Adaptation Database

In order to create a national model with complete coverage of the contiguous United States, the First Street Foundation Flood Model relies on nationally available data that consistently represents the hydrologic conditions of the United States. However, most of this data represents the natural environment better than the modifications made by human activity that impact hydrology and therefore flooding. To make this model as accurate a representation of actual flood risk as possible, First Street has spent considerable time and effort to build a database of “grey” and “green” infrastructure and adaptation projects that affect the flow of water and therefore flooding.

Grey Flood control projects include a variety of traditional infrastructure solutions like levees, pump stations, and flood control channels. Many green infrastructure projects also contribute to flood reduction, such as wetland restoration, floodable open space, retention basins, and creek rehabilitation projects. The First Street Foundation Flood Model also records and accounts for climate adaptation projects such as beach renourishment projects that are designed to counteract the effects of rising seas.

This data is collected from state, county, and city agencies across the United States. It is digitized by drawing the area for which a structure is providing flood protection and assigned a level of protection provided. These service areas can range in size from a few residential blocks to a small city. Each feature is associated with one or more sources of flooding for which it provides protection. Estimates of the level of protection are based on the return period to which it will continue to function.

This data is accounted for in the hydraulic and hydrologic model in several different ways. In most places, water is blocked within the model from entering a service area. This is similar to how a levee operates in real life, blocking water from entering a given location and pushing it somewhere else. Importantly, water is not removed from the model. In other cases like various runoff reduction green infrastructure projects, the service area of the project represents a change in the underlying soil classification within the hydrologic model. This replicates the way green infrastructure projects reduce runoff from their service area. In still other projects such as pump stations, the service area represents an adjustment to the flow of water in an area. Just as a pump station has a certain flowrate at which it will continue to be effective, even in an event beyond its design standard, this is represented in the model by removing an amount of flooding from an area equivalent to the modeled flow in the project’s service area at the design standard. So a pump station designed for a 5 year event would always remove the equivalent of the 5 year event, even in a 100 year event.

You can download a sample of the database through Zenodo. If you wish to acquire the adaptation database, you can do so by reaching out to First Street Foundation here.