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What DC’s July 2019 Flash Flood Can
Teach the Nation About Flood Preparation

Due to the torrential rainfall that hit DC in July 2019, the local river levels rose 4 feet in less than 30 mins, wreaking havoc with local homeowners. This heavy rainfall, about as much as the area typically sees in an entire month, sparked widespread flash flooding, illustrating how floods can happen at a moment’s notice almost anywhere in the country.

Photographs from that time show rising rivers, flooded subway stations, and underwater city streets – scenes that were utterly unfamiliar to residents of the nation’s capital.

Americans in all parts of the country face a growing need for flood insurance, but many aren’t prepared. There are a lot of misconceptions out there about who’s at risk and how often flooding happens. Here’s how agents can use DC’s 2019 flash flooding as a way to educate customers about risk.

Background: Flash Floods 101

According to the National Severe Storm Laboratory, flash floods “occur when heavy rainfall exceeds the ability of the ground to absorb it.” They can occur anywhere in the country where rain falls, and they are often dangerous because waters can rise rapidly within minutes or hours of the heavy rainfall.

In DC’s case, the storm lasted about five hours and overwhelmed the region’s stormwater systems, prompting the National Weather Service to issue its first-ever flash-flood emergency declaration for the area. Water levels at Cameron Run in Alexandria, Virginia, rose more than seven feet in half an hour.

Many homeowners may think flash flooding is something that only happens around rivers, but that’s not the case. Many places are prone to flash flooding, including densely populated areas and those near dams, mountains, steep hills, canyons, and wildfire burn.

Our flood risk video series provides a strong foundation of knowledge for understanding how and why floods happen.

Extreme Rainfall Is on the Rise

The type of rain and subsequent flooding that hit DC in 2019 is often described as “historic flooding” from a “100-year storm.” In the past, these designations have been used to characterize exceptionally intense storms that have a one-percent statistical chance of happening in any given year. 

However, with heavy rainfall becoming more frequent as global temperatures increase, the likelihood of so-called 100-year, 500-year, and 1,000-year storms increases as well. According to research published by DC’s Department of Energy and Environment, the 100-year precipitation storms of today will actually be 25-year storms by the 2050s. In other words, they will be four times more likely by mid-century.

To brush up on the latest data surrounding increased flood risk, watch “Is Flood Risk on the Rise?” in our online video library.

Communicating Flood Risk to Homeowners

Because weather patterns and flood risk are in flux, terms like “100-year flooding” can be misleading to homeowners. Agents are in a prime position to educate homeowners about lifetime risk in their area and clear up any confusion. Here’s some talking points.

1. Explain what terms like “100-year flood” actually mean.

Plain and simple, a “100-year flood” does not mean one flood every 100 years. Take Ellicott City, Maryland, for example. About an hour’s drive outside of DC, this town suffered a “1,000-year” flood in July 2016 and then another in May 2018, just two years later. Or Houston, Texas, which saw its third “500-year” flood event in as many years when Hurricane Harvey hit in 2017.

These terms make it seem like the flooding should only happen once every 1,000 years or perhaps that an area hasn’t flooded that badly in 500 years. Unfortunately, this is not the case – and it wouldn’t be the case even if flood events weren’t in flux.

The 100-year terminology was originally used to simplify the idea that a certain place had a one-percent chance (or one out of 100 chance) of happening each year. 

2. Explain what “one percent chance” means over the course of homeownership.

When homeowners hear they may live in a place that only has a one-percent chance of major flooding each year, that may sound great. But it’s important to note that a 100-year flood event in one year does not reduce the probability that another one could happen the next year, or the next.

It’s similar to flipping a coin. Getting heads the first time does not make it less likely that you’ll get heads again. There’s still a 50 percent chance.

That’s why experts are starting to recommend communicating flood risk in a different way: by putting it into the context of the length of homeownership.

For example, if a homeowner lives on a 100-year floodplain – what FEMA calls the Special Flood Hazard Area (SFHA) their house has a one-percent chance of flooding in any given year. That means that, over the life of a 30-year mortgage, the home has a 26 percent chance of flooding. The longer a person lives in that home, the more likely they are to experience a major flood event.

Research indicates that 41 million people live on a floodplain with a one-percent yearly risk of flooding – and many are unaware of it.

3. Refresh your talking points with our video library.

To paraphrase FEMA, anywhere that receives rainfall can flood, and flash flooding can happen in a matter of minutes. For more information on floods and communicating risk to customers, stop by our extensive video library and keep yourself apprised of the changing world of flood.

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