Learn about our historic flood methodology.
The First Street Foundation Flood Model has developed a method in order to recreate historic flooding events. The model has been used to recreate both riverine flooding events as well as the flooding associated with coastal storms like hurricanes, tropical storms, and nor’easters. To create the catalog of events, First Street relied on hydrologic models and public data sources detailing the impacts of flooding. Many of these methods were first tested and validated against remotely sensed satellite imagery of existing water after flooding events in order to validate methods for accuracy.
River flooding events are recreated by analyzing historic USGS stream gauge readings during the time periods associated with identified flood events. The historic simulations are then evaluated for correlation recorded high water marks and insurance claims of flooding made during the event. Major coastal flooding events are recreated through a combination of AD-CIRC+SWAN modeling and geospatial analyses based on specific storm characteristics, such as Hurricane Katrina and then compared to the terrain of the area using a digital elevation model. These recreations are then compared to recorded high water marks and calibrated to align with those observed water depths. In the recreation of both riverine and coastal surge events, comparisons against the First Street adaptation database are performed to see if there are any flood control structures in the extents of the model in order to accurately account for known protections against historic flooding events.