is now displaying two different indicators for flooding risk for all properties.

Last week began displaying flood hazard information for each of the 110 million homes currently listed on its site. It is the only major on-line real estate listing company taking this step so far. is including two indicators for flood risk for each property: (1) FEMA’s flood plain map data showing special flood hazard areas, and (2) First Street Foundation’s Flood Factor, which provides a flood risk rating for the specific property.

First Street Foundation is a non-profit “research and technology group defining America’s Flood Risk.” The organization first published Flood Factor, an on-line searchable tool of nation-wide flood hazard information, earlier this summer.

Part of the intent of Flood Factor is to provide more property specific information than FEMA’s flood plain maps. The model calculates the probability of tidal, riverine, rain and storm surge flooding and incorporates elevation data, local flood mitigation structures, and historic flood records. The resulting scale (right) is intended to be, and in fact is, clear and understandable. leadership spoke to this in a recent story on NPR: “’It’s really important for consumers to know this,’ says Leslie Jordan, senior vice president of product at People who are hoping to buy a house need to know the true cost of purchasing and maintaining the building, including the cost of insurance and repairing damage. If flooding is a potential problem, Jordan says they should know about it before they make an offer.”

For example, here’s the probability of flooding over five year increments for a particular real property in Anne Arundel County, Maryland — a 99% chance of flooding within 30 years.

In checking random listings in the Chesapeake Bay watershed, the flood risk information does not always seem to immediately appear for each property. However, it is there for many, and sometimes pops up when a listing screen is refreshed. Perhaps, a slight kink in a new system.

The cost of dealing with natural disasters is enormous. First Street Foundation details the overall cost nationwide.

All of this occurs in an environment of increasing frequency and magnitude of flooding and other disaster events, driven by climate change. Last week, the New York Times described the federal government’s shift to “unavoidable relocation of entire neighborhoods” and substantial grant program funding to support it. A prior story in March described pressure for cities and counties to even use eminent domain to do so.

(Photo: UMCES)

While many cities and towns in the watershed struggle with increasing flooding — Norfolk, Annapolis, Alexandria and more — relatively few whole communities face the issue more profoundly than Dorchester County, Maryland, on
the Eastern Shore.

An August Baltimore Sun story on Dorchester illustrates the depth of feelings and conflicts that arise. To go or to stay. To mitigate or to retreat. To leave historic structures in place or to move them. To support buyouts of property owners or not. (Photo: UMCES)

“‘Dorchester County is a good example of our canary in a coal mine,’ said Michael Scott, dean of the Henson School of Science and Technology at Salisbury University, who has spent years mapping land losses in the county. ‘These same issues are coming to a county near you. It’s just a matter of when or where.'”

Roughly 5.5 million existing homes were sold in the US each year from 2015 through 2019. As flood risk is increasingly factored into buyers’ decisions through data like is now providing, and some whole communities may be on the move, the dynamics of the past will change. How will the impacts play out on the broader landscape?

“When you’re watching your backyard wash into the Chesapeake Bay, we’re not talking about the philosophies of climate change anymore. We’re
talking about public safety now,”


Jim Bass, Coastal Resiliency Program Manager at Eastern Shore Land Conservancy, in the Sun story.


Jonathan L. Doherty



Lightning Update is a regular communication of the Chesapeake Conservation Partnership. Any opinions expressed are those of the authors and do not necessarily reflect positions of the Partnership or member organizations.
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