St. Louis County, Missouri

County collaborates across communities to solve flooding issues

Two different approaches to flood mitigation planning in St. Louis County, Missouri demonstrate the value of collaboration between communities to support long-term mitigation efforts that benefit everyone, while also illustrating the negative impact of loose regulations that allow new developments in the floodplain.

Photo by Louis Sohn - FEMA

Community facts

Population
1,003,362
Businesses
94,670
Homes
438,425
Source: US Census Bureau.

Mitigation actions

The Meramec River is one of the longest free-flowing waterways in Missouri. There is a constant risk of flooding, which has caused millions of dollars in damage to many small towns. Communities along the river have taken various approaches to mitigating these risks, with very different results.

The two projects outlined below demonstrate that when communities work together to craft long-term flood mitigation solutions, it can benefit a much larger population, but when they work in isolation, what helps one city may hurt another. Community leaders throughout St. Louis County have been working together for three decades to create the Meramec River Greenway, a program to acquire land along 108 miles of the river and conserve it as parks and wetlands.

As of 2013, the organization had preserved roughly 9,000 acres of floodplain. FEMA estimates that the buyouts and conservation of land prevent an average of $7.7 million in flood damage annually, while the project also provides parks and recreational areas that benefit residents throughout the county.

In 2007, the town of Valley Park built a $49 million, 3.2-mile 100-year levee to help reduce the flood risk to its 7,000 residents from floods. The project, which was paid for jointly by the US Army Corps of Engineers and the community, significantly reduced the cost of flood insurance within the leveed area in Valley Park, improved home values, and prevented flooding during events in 2008 and 2016. The levee protected Valley Park's residents, but some argued that it worsened flooding issues in communities downstream.

Benefits of mitigation

Economic benefits
$7.7 million
Total monetized benefits
Return on investment
78.1%
Estimated return on investment
Other benefits
$22.9 million
Estimated recreational and aesthetic value is more than 3 times the avoided flood losses
Source: Kousky, Carolyn and Walls, Margaret, “Floodplain Conservation as a Flood Mitigation Strategy: Examining Costs and Benefits,” Resources for the Future.

Project challenges

Lack of developmental regulation in the floodplain has had significant consequences for one community

One issue is unregulated development in the floodplain, says David Wilson, senior manager of environment and community planning at EastWest Gateway Council of Governments, the metropolitan planning organization for the St. Louis region. He notes that in 2010, two buildings were constructed at a narrow point in the river, creating a dam that pushed water back into the town of Fenton. According to Wilson, there were no regulatory barriers to construction of the buildings in that location, despite the risks.

“We have had terrific successes in acquiring land and easements, but all it takes is one private owner or city leader willing to give permits for construction in the floodplain to do significant damage to the overall effort”
David Wilson, senior manager of environment and community planning at EastWest Gateway Council of Governments

Future considerations

High floodwaters cause a busy intersection to close.
Photo by Steve Zumwalt - FEMA
“The lesson," says David Wilson, "is that when city leaders collaborate to create long-term flood mitigation programs that meet the needs of the broader community, the financial, social and economic benefits can be substantial”

The lessons in St. Louis County are twofold: communities should cooperate in order to develop successful long-term flood mitigation actions; and regulations should restrict building in the floodplain. While local communities have benefited from substantial flood mitigation efforts, there are concerns that the lack of cooperation has led to mixed results in some areas. For example, a report released in September 2016 indicates that the Valley Park levee may have been built too high, exacerbating flooding in downstream communities, including Fenton.

Flood mitigation resources

Below is a non-exhaustive list of other flood mitigation information resources.