Adaptation measures and how they are included in flood projections

Learn about our adaptation methodology.

 

Importance of adaptation 

Unmanaged flooding can lead to a natural disaster event resulting in financial, social and structural ruin. By experimenting with flood risk reduction projects, also known as adaptation measures, humanity has gained valuable insight as to how to effectively deal with flood events all over the world. Adaptation to flooding has gained popularity over time, especially as populations have increased near waterways and along coastlines. 

 

Communities thrive near water by learning to live with water. There are many different ways communities have been able to navigate flood events, however there is not one central repository that holds the information on the types of flood adaptation structures, costs, or benefits of these measures. Without this information, flood hazard models cannot fully portray the truth of what happens to water during rain storms, river flooding, and tidal and surge events. In our efforts to create as accurate a flood model as possible, the First Street Foundation’s Data Team decided to create the nation’s first flood adaptation database. 

 

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Rain Flooding 

 

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Riverine Flooding

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Tidal Flooding 

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Surge Flooding

 

Including adaptation in flood models 

Flood hazard models cannot give a complete picture of risk without a complete picture of what structures exist to alleviate flooding. 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 grey 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. 

 

Adaptation types overview

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.

 

Green infrastructure

Green infrastructure projects have the ability to protect places inland from them and provide long term benefits to the communities they serve. Natural systems can protect against storm surge by providing friction to slow wave velocity, such as mangrove forests, and the ability to absorb stormwater, like marshes. For example, wetlands have 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. 

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Rain garden, a type of green infrastructure project, used to alleviate rain related flooding, in Washington DC.

 

Grey infrastructure

Grey infrastructure projects are engineered structures that are built from hard, impervious materials such as concrete. Often, grey 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 grey flood infrastructure, such as seawalls, culverts, and tide gates. If a design standard is known for these structures, such as the return period it was built to withstand, then that number is included in the flood modeling process. If it is not known, then two other methodologies are relied upon to incorporate any known grey flood infrastructure projects into the flood models. 

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Galveston Seawall is 7 miles long and helps protect the city from hurricanes - Galveston, Texas

 

Flood Factor adaptation methodologies 

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. Available for researchers on our API are: name of structure, type of structure, scenario, return period and source. This database of adaptation features, gathered from hundreds of data sources, is available on our API for interested researchers. Our database includes various properties of each feature including the project name, type of structure, flood scenario, return period, and data source. 

 

Finding 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. 

 

For tracking dams, seawalls, shoreline characteristics, and natural areas, researchers relied on resources such as the State-level GIS databases, Coastal Zone Management Authorities, the Georgetown Climate Adaptation Clearinghouse, and groups such as the American Society of Adaptation Professionals (ASAP). The Army Corps of Engineers provides two datasets, one of levees and one of dams. The levee dataset is checked to make sure that the polygons that represent the leveed area are correct, by verifying the vectors are in the correct place and geometries valid. The dam point dataset is used to find major dams to make sure that tidal waters do not flow past them in the models incorrectly. From these multiple reference points, local or state officials are contacted to see if the adaptation structure has been digitized and if not then it is included for digitizing in-house into the final adaptation service area file. 

 

Digitizing adaptation features for Flood Factor 

The Adaptation Team strives to include flood adaptation features that served at least ten properties or were digitized from a bulk dataset and combined served over ten properties in the Flood Model. 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. 

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Map by Sharai Lewis-Gruss
Map data ©2019 Google

Three pump station adaptation feature areas, shown in pink, serving many blocks of Hollywood, Florida. The pump stations become useless here as they are inundated with flood water during this 100 year food scenario. 

 

Adaptation flags

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.

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Stormwater vault that serves 397 properties in South Wilmington, Delaware. 

 

Not all places have flood adaptation measures in place and therefore not all properties will receive an adaptation flag on Flood 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. 

 

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Levee that serves 3,565 properties throughout many towns of Idaho. 

 

Adaptation features with historic flood events 

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. 

 

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!

 

Learn more

Adaptation and flood projections

Understand how flood control projects reduce flood risk

Understand how stormwater management plans reduce rainwater runoff

How can community science and local knowledge improve the Flood Model?

 

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