How flood control structures change flood risk and how this is represented on Flood Factor

Learn about adaptation and flood risk reduction measures.


About adaptation

Communities have been adapting their environment to protect themselves from flood risk for centuries. Development around bodies of water is beneficial for trade and agriculture, and communities have long taken steps to protect those interests from flooding. Accounting for these alterations to the natural hydrology of an area is one of the biggest challenges to building a predictive flood model, especially at a national scale. First Street has spent considerable energy in identifying these structures throughout the country and representing them within the flood model.


Most flood control projects are represented in the flood model in one of two ways - either they reduce the amount of flow and therefore the depth of flooding in an area, or they block floodwaters from entering an area. Levees are the most common flood control structure in the model, and they fall into this latter category. A levee provides protection up to a certain level, based on the elevation of the levee. Once the water reaches higher, it will overtop the levee and enter the protected area. This levee protects a large portion of Cincinnati by providing a barrier against the Ohio River. 



It is still possible for stormwater to get in behind a levee, and if proper designs are not in place, flooding will build up behind it. Many levee areas are also quite large and have stormwater management systems built within them. These systems could experience their own flooding problems in extreme events so flooding does appear in the Flood Model within leveed areas.


The other group of adaptation projects reduce the amount of flooding in an area. Pump stations are one good example of this. A pump station will have a set capacity of water it can remove from an area, typically quantified as a flow rate (gallons per minute). Similar to a levee, this will provide protection up to a certain point. However, a pump station can continue to operate and reduce flooding you may experience. This example of a pump station in Norfolk, VA shows that there is still flooding within the pump station service area, though it is less than in neighboring areas due to the influence of the pump station.



Adaptation failure

Any infrastructure project relies on proper operation and maintenance to continue to be effective and provide protection to its community. The Flood Model does not account for this sort of failure. The model shows what inundation looks like while structures are working as designed. However, by including this adaptation information, Flood Factor aims to communicate that protection by adaptation does not mean that there is no risk. Levees breach and pump stations fail. Some of the largest floods in the country’s history were worsened by a failure of operations and infrastructure. This is why Flood Factor communicates whether a property benefits from protection by a flood control structure. In order for that protection to remain in place, communities must invest in their infrastructure and engage in proper operations and maintenance.


Flood risk reduction projects

Information on Flood Factor comes from the First Street Foundation Flood Model. This model considers 40 different adaptation types when calculating and validating flood projections. 


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 submitting this flood protection project user input form. The adaptation database contains 23,000 features today. We know there are more projects to include and value your input!


Learn more

Protect low-lying areas with open spaces preservation

Preserve natural drainage systems

Learn how green infrastructure reduces flooding and improves water quality

Use infiltration basins to store stormwater runoff

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


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