New UCS Analysis: Coronavirus and Flooding Set to Collide in US

Note: An updated analysis can be found in this newer blog post.

Juan Declet-Barreto codeveloped this analysis.

Last week, when the National Oceanic and Atmospheric Administration (NOAA) released its seasonal forecast for the spring flooding season, I was jolted into a reality that some people in the US are already experiencing: extreme weather stops for no virus.  Just days after NOAA’s forecast came out, the flooding arrived:  floodwaters  from heavy rains in central and southern Ohio required the evacuation of dozens of people, leading one local sheriff to state “God knows how we will figure it out with COVID-19.”

For communities already strained and tense, waiting and hoping, grieving and fearful, NOAA’s flooding forecast paints a grave picture in which they must—somehow, some way—meet the intertwined challenges that severe flooding and a pandemic present them.

Using data from epidemiological researchers at Columbia University and NOAA’s seasonal flood outlook, we analyzed where the dual challenges of flooding and coronavirus infections are poised to hit the United States hardest between now and the end of May.

No forecast is ever perfect, but with climate-related threats on the horizon and the coronavirus potentially hindering our ability to safely cope with those threats (and vice versa), these forecasts provide the best available insights at this time into the questions of where our limited resources and most careful strategic planning may need to be deployed.

Areas at risk of flooding this spring

Record-breaking flooding across the Midwest and Northern Great Plains last year caused an estimated $10.8 billion in damage to homes, businesses, crops, and infrastructure. This year’s forecast indicates that 23 of our 50 states could experience flooding. It warns: “This spring season, 128 million people face an elevated flooding risk in their communities, with 28 million at risk for moderate or greater flooding, and 1.2 million at risk for major flooding.”

Overall flooding is not expected to be as severe as last year’s, but there is a great deal of overlap between the areas that experienced flooding last year—and may still be recovering—and those that could be hit again this year. The flooding of 2019 was deadly and costly and many communities are still struggling to recover, all without the added burden of a deadly disease outbreak.

NOAA classifies flooding into three categories of increasing severity: minor, moderate, and major. The NOAA spring outlook includes “river and overland flood threat on the scale of weeks or months” but it does not include flash flooding that can only be predicted days in advance.  As a nation we can plan for this seasonal flood risk, but must also expect to deploy additional resources for flash flood risks with little advanced warning.

Minor flooding typically does not pose a threat to life or property on its own but can be hugely disruptive—both physically and economically—as roads, bridges, and critical infrastructure like hospitals can become inaccessible. But moderate and, especially, major flooding present significant threats to life and property and can necessitate evacuation. The disruption from this flooding can impede the movement of healthcare workers and other essential personnel, as well as vital goods and supplies, like food and medical equipment. So it’s those last two categories—shown in yellow and red, respectively, in the map above–that we chose to focus on.

At a time when we must keep distance between each other and isolate ourselves in our homes, flooding and evacuation this spring are particularly worrisome. This will be significantly more worrisome for communities where the number or percent of people infected is particularly high.

Areas projected to see the most coronavirus infections

Over the last two months, the number of confirmed US cases of COVID-19, the illness caused by the novel coronavirus, has grown to roughly 55,000 at the time of this writing, though the actual number of people infected is likely to be much higher. The spread of infections in the coming months will depend in part on how effectively measures designed to reduce the transmission of the virus—such as social distancing and shelter-in-place directives—reduce contact between people.

To assess where flood and coronavirus risks intersect most acutely, we relied on data graciously provided by Drs. Sen Pei and Jeffrey Shaman, researchers at Columbia University. Pei and Shaman modeled the potential spread of the virus on a county-by-county basis over the next six months under four different scenarios by running 100 simulations of their transmission model for each scenario. The projections are based on observed cases through mid-March and do not incorporate specific measures implemented by states and localities over the last few weeks.

You can see Pei and Shaman’s excellent work on this topic in the New York Times. And you can download their data and read more about their methodology on the software development platform, github.

For the purposes of our analysis, we looked at the total number of COVID-19 infections per county between Feb 21 and May 31, 2020, based on a scenario in which transmissibility of the virus is reduced by 25 percent as a result of measures designed to reduce contact between people.

Areas at highest risk for both threats

We looked at both the estimated absolute number of COVID-19 cases by county as well as the percent of residents that would likely be infected in that county this spring. When we overlay these two statistics on top of NOAA’s flood outlook, distinct stories emerge and states and counties where the threats converge come into focus.

Looking at how the percent of infected residents intersects with spring flood risk gives us a sense of a county’s capacity to mount an effective emergency response to flooding. For instance, in counties where a large percent of the population is infected, a higher proportion of people evacuating during a flood could increase the spread of the virus or require isolation, a condition that could be difficult given the typical nature of emergency shelters.

Our analysis shows that the areas facing both the highest infection rates and flooding risks tend to be rural areas where access to health care facilities may be more limited. These include some of the same areas hit hard by flooding last year, such as eastern South Dakota and eastern Iowa. Both regions are at risk of experiencing major flooding in the months ahead, and both include a number of counties that are presently projected to have 25 percent or more of the population infected by the coronavirus in the same timeframe. Meanwhile, portions of Louisiana, Mississippi, and Georgia would face similar rates of infection and a risk of moderate flooding.

To put those infection rates into context, Louisiana has among the nation’s fastest-growing rate of infection as of today and, with far less than 1 percent of its population currently infected, fire department crews in places like New Orleans are dangerously understaffed as their members fall sick with COVID-19. In Illinois, where infection rates have soared in recent days, the shortfall in the number of hospital beds could reach upwards of 38,000 in the coming weeks.

The percent of the population infected points to challenges ahead for rural counties facing flooding, but it’s the absolute number of infections in a given county that provides a better indicator of the magnitude of the challenge of ensuring the public health and safety of communities as they cope with and recover from flooding.

The areas where major or moderate flood risk intersect with high numbers of infected residents include several towns in the South—Atlanta, Baton Rouge, and Little Rock—as well as several in the Midwest that experienced flooding last year, such as Sioux Falls, Cedar Rapids, and Kansas City. In these places, the sheer number of infected people who may need to evacuate their homes could severely burden health care and emergency evacuation facilities.

Preparing more fully than we have in the past

In the weeks and months ahead, our resources and capacity for coping with disasters will undoubtedly be stretched very thin. We are already experiencing a shortage of coronavirus tests and essential medical supplies that is putting healthcare workers and their families in danger, for example, and many health care facilities are expected to be overrun as they have been in places like Italy. And with only 35 percent of Federal Emergency Management Agency (FEMA) employees available to be deployed (as of March 23) and these intertwined crises brewing, we may face a shortage simply of boots on the ground.

Yet the forecasts for flooding and infection spread give us a glimpse at what lies ahead–both in the immediate future and the future of our strained and interconnected world. And with that glimpse comes the opportunity to start preparing now.

Here are some ways those preparations could take shape.

Focusing on the immediate: At the national level, we must understand the nature of these two problems and their potential intersection so that available resources can be deployed swiftly to where they are most needed. The science we have will certainly evolve over time, but we can already be using the best available data to begin mobilizing resources.

Federal bodies such as the US Army Corps of Engineers (USACE), the National Guard, and FEMA have a critical coordinating role to play in efforts to address shortfalls in hospital beds and assist in funding emergency shelters, for example. And organizations like the Red Cross, which operates shelters in times of emergencies, are setting new guidelines to ensure that evacuation centers don’t become epicenters of infection.

At the state and local level, states can be thinking about where the combined risks of infection and natural disasters are highest when identifying facilities that could be temporarily converted to shelters or medical facilities. Resources can then be allocated in proportion to the identified risks.

Mayors up and down the Mississippi River, much of which flooded last year and could again this year, are already thinking about the compound risks of flooding and coronavirus, and will need to continue monitoring the situation locally in cooperation and with support from federal and state agencies.

Finally, at the individual level, we must all act responsibly in this dire moment by heeding or exceeding local guidelines for sheltering in place at home and maintaining a safe social distance from others when we are outside our homes. And we must begin gathering official guidance and formulating safe, sensible plans for our families in the event of disruptive local flooding.

The month of March has turned much of the world on its head this year and we know, in the US, the worst of the pandemic is yet to come. It’s deeply challenging, from the relatively-privileged but monotonous task of sheltering in place, to worry over paying the bills and the strain on the economy, to fear for the health and very lives of our loved ones, to the courage it takes to show up to high-risk jobs, to surviving the illness itself. It’s a lot. But it’s not all. The natural world moves on and the rains come, then the fires, hurricanes, and heat will follow. These are historic times and together we must mount an historic response.

Many of my colleagues contributed words and thoughts to this post, including Rachel Cleetus, Brenda Ekwurzel, Carly Phillips, Erika Spanger-Siegfried, and Shana Udvardy. This data is available upon request. The specific trajectory of the coronavirus in the US will undoubtedly differ from the predictions shown here. We will provide updates as possible given the rapidly evolving and fluid nature of the pandemic.