Flood models can’t accurately forecast risk without considering flood mitigation structures. First Street created the nation's first flood adaptation database, ensuring Flood Factor considers protected areas.
Unmanaged flooding can lead to a natural disaster event resulting in financial, social and structural ruin. There are many different ways communities have adapted to flooding, however there is not one central repository that holds the information on the types of adaptation structures, their costs, or benefits. In our efforts to create as accurate a flood model as possible we decided to create the nation’s first flood adaptation database. Use Risk Factor to find the only property-specific flood risk assessments that consider flood mitigation structures.
How do adaptation structures improve the accuracy of the Flood Model?
In an effort to create as accurate a flood model as possible, the First Street Foundation’s data team created the nation’s first flood adaptation database. The purpose of adding flood adaptation structures to the modeling process is to increase the accuracy of the flood inundation layers. By researching and locating green and gray infrastructure, scientists are able to mark an area as either protected or semi-protected from flooding. Close attention is paid to whether a structure is designed to protect against pluvial, fluvial, tidal flooding or some combination of the three. Additionally in the case of seawalls, the elevation above nearby ground surface is collected in order to model overtopping scenarios.
Identifying and researching adaptation projects
Insights on local histories of flooding and the construction of flood-protection infrastructure can be found in a variety of ways including news reports, public meeting minutes, and foundation funded studies. It is possible to find all kinds of information in these reports such as information on when projects were built, how much they cost, who paid for them, the community or area they serve, and what type of scenario they were created for. A great deal is learned about what types of flooding is most intrusive to a place within this research stream in addition to what has been done to address it. Adaptation data is sourced from State-level GIS databases, Coastal Zone Management Authorities, the Georgetown Climate Adaptation Clearinghouse, Army Corps of Engineers and groups such as the American Society of Adaptation Professionals (ASAP).
Adaptation types included in the Flood Model
Adaptation data collection and “ground truthing” takes place across both coastal and inland areas. This data includes thousands of adaptation features like dunes, wetlands, and levees. It also includes “green” and “gray” space hybrid measures along with other geo-engineered efforts like seawalls and pumps.
Mangrove forests can protect against storm surge by providing friction to slow wave velocity. Marshes can absorb stormwater. Wetlands have the capacity to store large volumes of water depending on the dominant species of flora. These areas not only protect communities from flooding, but they also provide valuable outdoor spaces for recreation. Natural flood mitigation measures included in the First Street Foundation Flood Model includes:
- Oyster reefs
- Living shoreline
- Coral reefs
- Living breakwaters
- Sediment accretion
Dunes prevent beach erosion and prevent water from reaching critical infrastructure along the coast.
Built green infrastructure
Green infrastructure is a cost-effective solution to prevent flood damage that uses vegetation, soils, and natural processes to manage water and create a healthier environment. Green infrastructure included in the First Street Foundation Flood Model includes:
- Marsh/Wetland creation
- Marsh/Wetland enhancement
- Marsh/Wetland restoration
- Rain Garden
- Retention pond
- Beach nourishment
- Earthen berm
- Open space preserve
- Floodplain restoration
Rain garden, a type of green infrastructure project, used to alleviate rain related flooding, in London, Ontario.
Gray infrastructure projects are engineered structures that are built from hard, impervious materials such as concrete. Often, gray structural types are used in conjunction with one another and/or in tandem with green infrastructure projects to reduce flood risk. There are multiple kinds of gray flood infrastructure, such as seawalls, culverts, and tide gates. Gray infrastructure included in the First Street Foundation Flood Model:
- Pump deployable
- Pump station
- Stormwater vaults
- Tide gate
- Pervious pavement
- Detention basin
- Infiltration basin
Galveston Seawall is 7 miles long and helps protect the city from hurricanes - Galveston, Texas
Adaptation features on Risk Factor
Once as much data as possible is gathered on adaptation structures and the areas they protect from flooding events, these data are digitized into polygon service areas. Some adaptation infrastructure completely protects an area, such as levees, while other methods reduce flood depths, like pumps. Areas that get completely removed from the flood layers are mostly leveed areas or those behind hurricane protection systems. Attention is paid to what scenario the systems were built to withstand. For example, if a barrier is built to withstand flooding up to the 100 year fluvial event, then flooding will be removed for 100 year and below fluvial events. The structure of the adaptation service area files includes the name of the structure, type of structure, flood scenario the structure protects the area for, return period, source of the data, year built, and any additional notes on information relevant to the structure.
Digitizing adaptation features
The Adaptation Team strives to include adaptation features in the Flood Model that have served at least ten properties or were digitized from a bulk dataset and combined served over ten properties. All adaptation features are drawn as polygons in order to interact with our flood model either by removing or reducing flood waters based on the methodologies applied for the specific feature type.
Three pump station adaptation feature areas, shown in pink, serving many blocks of Hollywood, Florida. In a 100 year flood scenario, the pump stations, inundated with water, become ineffective, Map by Sharai Lewis-Gruss, Map data ©2019 Google
Once adaptation features are digitized, they overlap with all of our parcel data. These areas are considered service areas to any property that they overlap. For example, a stormwater vault in South Wilmington, Delaware is specifically built to serve a set number of blocks. These blocks will be drawn around and included in the service area of this adaptation feature. Once that polygon is drawn, our statistics are derived from these boundaries by comparing the location of a parcel to those adaptation areas. If a parcel falls within the zone boundaries, the property will receive a flag stating that the property is being served by this adaptation measure.
Not all places have flood adaptation measures in place and therefore not all properties will receive an adaptation flag on Risk Factor. In some cases your neighbor could receive an adaptation flag and your property will not. In the case of a levee many properties will fall just outside of the protection zone of that levee. If your property is within the zone it will receive a flag that it is being served by the levee. If your property is not within the zone it will not receive the flag. The Flood Model is detailed enough to spot the difference from neighbor to neighbor.
Levee that serves 3,565 properties throughout many towns of Idaho.
Historic flooding mitigated by adaptation features
Some adaptation features have a known year built date. In the case of those features, they are able to be applied to historic storm simulations. When adaptation features exist in areas during the time of the historical flood event, the design standard for each individual adaptation feature was compared against the return period of the event. This gives the historical flood simulation even greater accuracy because any known adaptation feature in the given area is able to be applied to the hazard model.
Want access to the nation’s first adaptation database?
For commercial use or non-profits, academics, or public sector professionals needing data at a property-level, First Street Foundation provides access to property-level flood risk statistics for purchase. Bulk data is available for easy integration for flood risk statistics. Property-level statistics include information from the national adaptation database for the geographic area selected for purchase.
If you are interested you can get pricing for property data here and fill out the following form to complete a request. For multiple states, nation-wide data or partnership requests, you can fill out the form here. We will get back to you with pricing or access information based on your request
Continuing adaptation research
This is the first time a national database of this kind at this scale has been created. The Adaptation Team continues to collect information on the flood infrastructure that exists across the country to make sure the Flood Model includes as many adaptation projects as possible. If you know of any projects that are not shown today, please help the team by providing any level of detail you can. The adaptation database contains 23,000 features today. We know there are more projects to include and value your input!