What is urban flooding? - Visit First Street to check your risk

Have more questions? Submit a request

Urban flooding occurs when city landscapes cannot absorb excess water after prolonged periods of intense rainfall, river overtopping, or storm surge.

Changes in the environment have already increased flooding across the United States, particularly in coastal and low-lying areas. As these trends continue into the future, 1.7 million more American properties will be at risk, and the damage and cost of flooding will continue to add up.

Urban flooding impact?
Check your risk level by entering your address.

Urban flooding on First Street

The First Street Flood Model considers the risk of flooding from rain, river, and storm surge. Urban flooding is incorporated into the model with special consideration given to the infrastructure, development, and water management systems that exist in urban areas. Use First Street to learn if your home is threatened by urban flooding so you can prepare for and mitigate risks before they become a reality. 

Development patterns 

Non-environmental factors like development patterns and structural failures of dams and levees are also exacerbating flood risks. Expanded development in coastal areas and floodplains simultaneously puts more people and community assets at risk, increases the amount of impervious (non-absorbent) surfaces like concrete, and destroys natural flood protections like wetlands. Flood control measures like levees, seawalls, gates, and pumps also pose a serious threat if not regularly maintained and upgraded.

Sea levels are rising

Most of America’s coast is experiencing rising seas caused by global ice melt, thermal expansion, changes in ocean circulation, and local land sinkage. Sea level rise makes high tides higher, which puts more pressure on coastal drainage systems. Higher seas also lead to higher storm surges from hurricanes and other storms, resulting in deeper floods that travel farther and last longer.

Screen_Shot_2022-05-13_at_7.52.34_AM.png

An overflowing levee near Lake Providence, Louisiana May 18, 2011. (Reuters / Eric Thayer - stock.adobe.com)

Extreme rain events are increasing

As the atmosphere warms, there is more evaporation and more water available for rain, which contributes to changing weather patterns and flood risks. Extreme rain events are increasing in duration, intensity, and frequency, which causes more urban and flash floods, and more flooding from overflowing rivers and streams.

The impact of extreme rain

Within a 22-month period between 2016 and 2018, Ellicott City Maryland saw two extreme rainfall events that caused flash floods, as the grounds were unable to absorb the sudden, high volume of rain that fell within hours. Each event had a 0.1-0.2% chance of occurring in a given year.

Screen_Shot_2022-05-13_at_7.52.49_AM.png

Ellicott City, MD 2018 after flash floods turned its main street into a raging river. (Libby Solomon/The Baltimore Sun via AP)

Learn more

 

Articles in this section

Was this article helpful?
12 out of 17 found this helpful
Share