St. Louis County, Missouri

County collaborates across communities to solve flooding issues

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. 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
998,581
Homes
439,309
Businesses
94,670
Source: US Census Bureau.

Mitigation actions

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, roughly 9,000 acres had been preserved in St. Louis County as state and local parks. 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. The Greenway flooded in an April 2017 flood event when the region received record-breaking rainfall.

In 2007, the town of Valley Park built a $49 million, 3.2-mile 1-percent-annual-chance 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, 2016, and 2017. The levee provided flood hazard reduction to 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 East-West 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.

"If there was no parkland around [the Meramec River], there would have been businesses and residential places that would have been flooded [owing to the April 2017 rains]."
Mary Grace Lewandowski, director of community planning at East-West 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 late 2016 indicates that the Valley Park levee may have been built too high, exacerbating flooding in downstream communities, including Fenton. Similar claims were made in the aftermath of the April 2017 floods around Valley Park.

Flood mitigation resources

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