EXTREME RAINFALL EVENTS ARE ON THE RISE

On the evening of July 8, between two and five inches of rain fell in west-central Chicago in just one to two hours, which caused flash flooding. The heaviest rainfall was 5.12 inches in 90 minutes, recorded at a rain gauge west of the United Center.

This was an extreme event by Chicago norms.

Six days later, another major city, New York City, experienced flash flooding triggered by heavy rainfall. More than two inches of rain fell in Central Park during a one-hour period. According to New York City Emergency Management officials, this was the second-highest one-hour total ever recorded there.

Later in July, both cities faced more extreme rainfall and more flash flooding.

Extreme rainfall events are becoming more frequent in the United States. Climate Central researchers analyzed hourly rainfall data from 1970 to 2024 across 144 U.S. cities and found that 88% show greater intensity, regardless of the local climate. Hourly rainfall rates are now, on average, 15% higher than in 1970, with the largest increases in the Upper Midwest, Northern Rockies and Plains, and Ohio Valley.

More intense rainfall compounds flash flood risks, increasing their likelihood and severity. The most serious flood impacts are loss of life and injuries. Floods can also damage property, such as homes and their contents, motor vehicles, commercial and government buildings and their contents, crops, livestock, property stored outdoors (e.g., construction materials), roads, and public transportation systems (e.g., parts of the New York City subway system), among other items.

Flooding can cause natural gas leaks, explosions, and fires, which damage property and possibly claim lives. Flash flooding may also cause disruptions to services, including power, water, sewer, and trash collection. Loss of property or its use, or essential services might reduce income, increase expenses, or both. Oftentimes, significant losses caused by flash flooding are not insured.

Among the many consequences of flash flooding, the loss of one’s home can be especially challenging for households, often exceeded only by serious injury or death. Home provides shelter and protection, serves as a refuge, shapes our identities, and largely determines our health.

The sudden loss of one’s residence can be emotionally traumatic and financially devastating. Recovery can take years, especially for low-income households.

Yet most residential flood losses remain uninsured across the United States, including in metropolitan areas. In almost seven in 10 of the 380 Metropolitan Statistical Areas (MSAs) in the U.S., 90% or more of expected flood losses are uninsured, according to research sponsored by the Society of Actuaries. 

In short, underinsurance of the flood risk is a widespread problem in the U.S. Not having flood insurance makes it much harder to recover from flood damage. Unless addressed, this challenge will worsen as rainfall and flash flooding increase.

Actions to help your clients

What actions can help change the impacts of flash flooding? Help your clients understand their flood exposures. Free resources like from FEMA’s National Flood Insurance Program Floodsmart, the NOAA’s National Weather Service Interactive Flood Information Map, and First Street’s Flood Factor® Flood Risk Model Methodology can help clients learn about their flood exposures.

Remember, awareness is the first step in deliberately managing any risk. Clients who are unaware of risks cannot manage them.

Discuss with homeowners the steps they can take to mitigate the risk of flash flooding. Examples of helpful free information sources include FEMA’s Protect Your Home from Flooding Low-cost Projects You Can Do Yourself and the Center for Neighborhood Technology’s Homeowner Guidance Urban Flooding Baseline. These tools help homeowners understand the steps they can take over time to reduce their flood exposure.

Explain to your clients that flood risk is widespread and not limited to coastal areas. Standard policies typically exclude flood coverage; however, flood insurance is available through the National Flood Insurance Program (up to $250,000) and private insurers. Offer a flood quote to avoid an errors and omissions claim.

If NFIP limits are inadequate, also offer the client an excess flood insurance quote. Adequate coverage will not prevent extreme rainfall, but it will support financial recovery.

Actions to help your community

In addition to helping your clients manage their flood risks, you can take action as a public citizen to help reduce flash flooding in your community. Help members of your community learn about these risks and how they can manage them. Consider volunteering to speak on this topic at local clubs, professional organizations, schools, colleges, and universities. You can also offer to be interviewed by local radio, TV, and newspapers to help educate the public about flood exposures and insurance.

Enhancing your knowledge about the factors that affect the likelihood and severity of flash flooding, as well as ways to mitigate or modify them, can help you advocate with community (and regional, state-wide, and national) leaders for community-based flood mitigation efforts. 

The built environment, topography, soil composition, watershed health, and the adequacy of early warning systems all impact the likelihood and severity of flash flooding. Each of these can be influenced to some degree over time.

• Built environment. The built environment comprises bridges, buildings, parks, roads, streets, and essential systems, including water, power, and transportation networks. Most structures and surfaces are impermeable (e.g., concrete roads), preventing water from passing through and causing water to collect, especially in low areas.
  
  

Replacing concrete and asphalt with permeable pavement reduces the risk of flash flooding by allowing water to filter through. Promoting flood-resistant building materials restricts unwanted water entry into buildings.

• Topography influences the likelihood and severity of flash flooding in several ways. Water runs off more quickly from steeply sloped locations than from flat lands, with water pooling more likely in narrow valleys. Water moves toward the lowest point, making accumulation more likely at low elevations.
  
  

Multiple waterways, including lakes, rivers, streams, and creeks, all provide points for water to accumulate, making flooding more likely and more widespread, as evidenced by recent flooding in Milwaukee. 

Changing elevations of homes, ensuring adequate stormwater drainage, installing levees and, for coastal areas, restoring dunes can all help address topography issues.

• Soil composition. Soil composition directly influences flood risks. For example, sand readily absorbs water, but hard clay does not. Heavily compacted soils, common in arid areas, increase flood risks. The soil composition can be modified to enhance water absorption.
  
  

Adding organic matter, such as compost or manure, or planting cover crops, can increase floodwater uptake.

• Watershed management. A watershed consists of a land area that channels rainfall and snowmelt to creeks, streams, and rivers, and eventually to outflow points such as reservoirs, bays, and the ocean. The natural environment, including topography, soil composition, vegetation, and wetlands, has a profound influence on the health of watersheds.
  Topography and soil composition were mentioned above. Therefore, the focus below is on vegetation and wetlands.
  
  

Trees and other vegetation absorb rainfall and help slow the speed at which rainfall hits the ground. Native trees and plants suited to local climates are particularly well-suited for water absorption. Plants and trees also help stabilize soil through their root systems, making flooding less likely. 

By making tree and shrub plantings affordable, accessible, and widespread, communities can help reduce the effects of heavy rainfall.

Preserving or restoring wetlands also helps manage flood risks. Wetlands encompass a variety of habitats, including bogs, marshes, and swamps. Wetland plants have a unique ability to absorb water, supporting the role of wetlands in storing water. 
Wetlands act as transition zones between land and water. They limit the intrusion of flood waters into unwanted places on land. Advocating for wetland restoration can help ensure that it happens.

• Early warning systems. Flash flood warning systems do not prevent floods, but they do save lives. The National Weather Service issues flash flood warnings and flash flood emergency alerts, the latter indicating that a flash flood is imminent. Supporting local efforts to disseminate these alerts and helping those affected effectively understand their next steps can make a significant difference.

Summary

Scientific data show that extreme rainfall events have become increasingly common and severe over the last several decades. This is true throughout the country, including in cities, where 83% of the U.S. population is concentrated.

The rainfall events themselves may last only an hour, but recovery from them can take years. While some debate the causes of such events, the consequences are clear: deaths, disruptions of lives and income, and catastrophic property damage.

Helping clients learn more about flood risks and their management, including the value of flood insurance to help them recover financially from a flood loss, helps make their future more secure.

Your efforts do not have to stop there. Getting involved in advocacy for community management of flood risks can lead to more informed community decisions about built environments, topography management, soil and watershed management, and early warning systems. 

All of these factors can change, shaping flood risks for the better.

The author

Dr. Lisa Gardner is the associate director, Content and Research, at the Risk & Insurance Education Alliance. Her experience includes more than three decades as a professor in higher education where she taught courses about risk management and insurance, statistics, and finance, and provided programmatic leadership.