Continued Social Distancing Critical for US Regions Where Flooding and COVID-19 Are Set to Collide

April 13, 2020 | 10:57 am
Kristy Dahl
Principal Climate Scientist

New county-level projections for the spread of COVID-19 make clear that reducing direct social contact with one another gives us the best chance of minimizing the chances for cripplingly high coronavirus infection cases in the coming weeks. In regions that could experience significant flooding this spring, strong social distancing measures could reduce the total number of COVID-19 cases by more than two-thirds, from more than 600,000 cases to roughly 170,000.

That means that continuing to reduce social contact with one another will also be the best way to limit the confluence of high COVID-19 infection rates and flood events.

Juan Declet-Barreto and I recently wrote about our analysis identifying parts of the country that were at risk of both flooding and high coronavirus infection rates this spring based on NOAA’s seasonal flood outlook and infections projections by Drs. Jeffery Shaman and Sei Pen of Columbia University.

While the flood outlook has not changed and still applies to the spring season, the COVID-19 landscape is very different than it was two weeks ago, in terms of both the number of cases and the number of states that have issued shelter-in-place orders. Using new infections projections from Shaman and Pei that incorporate data through April 5th, we have updated our analysis of which US counties may need to prepare for a high number of infections that coincide with flooding events.

Where is the risk of flooding high?

Areas at risk of moderate or major flooding this spring, according to NOAA’s seasonal flood outlook.

NOAA’s seasonal flood outlook indicates that areas home to 128 million people and spanning 23 states are at risk of experiencing flooding this spring. One of the primary reasons for that widespread flood risk is that precipitation was above normal last fall and winter, so rivers and streams are running high and, in many places, the ground is saturated.

The past month has brought additional wet weather to much of the central US, with parts of some states up and down the Mississippi River basin experiencing 200% of their normal precipitation. And just this past weekend, severe weather across much of the southeastern US necessitated flood warnings in several states. 

Precipitation has been higher than normal (blues and greens) for much of the central US over the last month, which increases flood risk.

That wetter-than-usual weather over the last few months means that many rivers and streams are already above their flood stage. Parts of Arkansas, Louisiana, and Mississippi that encompass the Lower Mississippi River, for example, are already experiencing minor to moderate flooding. 

As of April 12, 2020, stream gauges throughout the central US were above their flood levels.

Last year’s flooding throughout the Midwest was devastating. With families, farmers, and their communities still struggling to recover, this year’s flooding comes at a time when resources are stretched, nerves are frayed, and the coronavirus pandemic is sweeping through the nation.

Where could the threats of flooding and COVID-19 overlap?

The degree to which a community experiences flooding this spring will depend primarily on the weather. But the latest COVID-19 infections projections indicate that the number of COVID-19 cases in our communities will depend heavily on the degree to which we reduce physical contact with one another.

The maps below show the areas at risk of flooding this spring (as above) with two different scenarios for the number of COVID-19 cases in each county between now and May 16.

In the first scenario, social contact within each county is decreased by an additional 20% each week until the number of cases in that county starts to decrease. That modest reduction in social contact would ultimately result in more than 600,000 cases of COVID-19 in the counties that also carry a risk of moderate or major flooding this spring.

In this 20% weekly reduced contact scenario, some counties that could see both high numbers of COVID-19 cases and either moderate or major flooding contain populous metropolitan areas, including Atlanta, GA; Madison, WI; Mankato, MN; Panama City, FL; Slidell, LA; and Springfield, MO.

Now contrast that with a scenario in which social contact in each county is reduced by 40% per week until the number of cases in that county starts to decrease: 

If social contact is decreased by 40% weekly until infections begin to decline, areas at risk of moderate or major flooding this spring could see roughly 170,000 cases of COVID-19.

This more substantial reduction in social contact would result in roughly 170,000 cases of COVID-19 in areas also at risk of flooding this spring. That’s less than one-third of the 600,000+ cases projected for the 20% reduced contact scenario. While some cities still pop out in this map, the number of infections in those cities is projected to be much lower as a result of the decrease in social contact. For instance, Madison, WI, would see roughly 1,800 cases of COVID-19 as opposed to nearly 43,000 with the higher infection spread scenario, and Slidell, LA, would see roughly 1,100 cases as opposed to more than 17,000 with the higher infection spread scenario.

How we get through this spring season

My colleagues and I have written extensively about how we, as a nation, can better prepare communities for both coastal and inland flooding in the face of a changing climate. With FEMA strapped for staff who can respond to disasters, and with the expectation that climate change will bring increasingly frequent extreme rainfall events, it is critical that we begin to get out ahead of flooding events to reduce the toll they take on people, their families, and their communities. This is especially true for communities of color and those struggling with poverty, who stand to lose the most when disasters strike.

In the short term, federal, state and local authorities must put contingency plans in place to help protect and prepare communities, anticipating that climate and extreme weather-related disasters might strike at the same time as the COVID-19 and associated economic crises are still unfolding. Congress should provide more funding and resources now to help FEMA and other disaster response agencies get ready ahead of time.

What these latest infections projections show, though, is that in this moment we cannot let up on the social distancing practices we have begun in recent weeks.

For the millions of us who have been largely confined to our homes the past few weeks, the early signals we’ve seen this week that suggest that social distancing is slowing the spread of the virus in some places are making our confinement more bearable. But we cannot take them as license to pop in to see a friend, visit a neighbor, or host a play date for our increasingly feral children (no, it’s not just yours).

Staying the course and heeding local guidance on staying indoors could spare hundreds of thousands of people from contracting COVID-19. And for those living in areas at risk of flooding in the coming months, that would translate to a much-reduced risk of experiencing a dangerous, community-level confluence of COVID-19 and flooding at the same time.