Urban flooding disrupts economies, public safety, and more, report says

College Station, Texas — Flooding caused by an increasing number of intense storms is a national challenge and significant source of economic loss, social disruption and housing inequality across the United States, says a new report from Texas A&M University and the University of Maryland (UMD).

The first to assess the national scope and consequences of urban flooding, the report calls on the administration and Congress to bring together representatives from state, municipal and tribal governments, nongovernmental organizations, and the public to define responsibilities and implement a variety of actions at the local level.

The recommendation is one of nine presented in the report to help governments at all levels take control of the growing threat.

Texas A&M University President Michael K. Young said Sam Brody with A&M’s Galveston campus and Gerry Galloway with UMD have put forth real and immediate measures everyone can take to help ensure millions of people are safe from these disastrous floods.

“As we have witnessed for ourselves here in Texas, urban flooding is a serious threat to lives, property, and economic and infrastructure development,” Young said. “This unprecedented study is a wake-up call for the entire nation that urban flooding is a growing and dangerous problem, but likewise enormously powerful and exceptionally useful as it outlines feasible remedial approaches and solutions.”

Texas A&M University System Chancellor John Sharp said these researchers have discovered major threats and troubling trends that need to be addressed.

“Most Americans will be surprised to learn that much of the country’s urban flooding occurs outside traditional 100-year floodplains,” said Sharp, who was chosen to head the Governor’s Commission to Rebuild Texas after Hurricane Harvey. “The work by the Texas A&M System and the University of Maryland is another example of how research universities serve the public good. Only by understanding the problem can we find the solutions.”

Galloway, Glenn L. Martin Institute Professor of Engineering with UMD’s Center for Disaster Resilience, said urban flooding is a more prevalent problem than many people have thought.

Urban flooding has historically been thought of as something that occurs in only a handful of major cities, said Galloway, who is a former Faculty Fellow, Class of 2016-17, with Texas A&M’s Hagler Institute for Advanced Study.

“This report affirms that communities across the country are in fact facing similar — and escalating — challenges and that the principal responsibility for addressing the issue rests with local governments where their unique issues can be addressed,” he said.

Urban flooding occurs when rainfall runoff exceeds what the landscape can absorb or the drainage system can move. As communities convert more land into roads, buildings, and other impervious surfaces, drainage systems — themselves often aging, undersized, and difficult to maintain — reach capacity faster, leaving flood waters to devastate homes and businesses.

“The frequency of these events erodes the economic stability, health, and safety of a community over time. And the impacts can be felt miles from a stream channel or water body,” said Brody, director of the Center for Texas Beaches and Shores on the Galveston Campus.

To characterize the extent and impacts of urban flooding in the United States, the Center for Texas Beaches and Shores at A&M’s Galveston campus and UMD’s Center for Disaster Resilience surveyed storm-water and floodplain management practitioners with knowledge of more than 350 municipalities in 48 states. The survey was also supplemented by multiple discussions with government agency and professional organization focus groups.

The survey revealed that:

• 83 percent of the 388 question respondents indicated they had experienced urban flooding in their community;
• 46 percent of the 325 question respondents indicated that urban flooding has occurred in numerous or most areas;
• 85 percent of the 296 question respondents had experienced urban flooding outside the Special Flood Hazard Area; and
• 51 percent of the 325 communities represented by question respondents had been affected by moderate or larger urban floods.

The research team confirmed the survey responses with a detailed spatial analysis of federal flood-related data and information collected by state and nonprofit groups. While no single agency tracks urban flooding directly, the team found over 3,600 events in the National Oceanic and Atmospheric Administration’s flood loss database from 1993 to 2017 indicating severe rainfall flooding.