Kansas City sits at the intersection of many rivers — the Missouri River separating downtown from the Northland, the Kansas River in Wyandotte and Johnson counties, and Turkey Creek, the Blue River, Mill Creek and Brush Creek forming a spider web across the bistate area.
And this is no accident, said Heather Schmidt, the stormwater program manager in Johnson County.
“Whenever anybody develops or settles anywhere, they want to be by the stream,” Schmidt said. “It’s their water source, and it’s their source to get things away. And that’s always been problematic, because they also get flooded out.”
Twice a year, during thunderstorm season in the springtime and the autumn, the Kansas City area deals with flooding. And this poses a danger not only because it can cause car accidents and dangerous currents, but also because the stormwater can absorb dangerous chemicals from construction sites, fertilizers and animal waste.
As the climate crisis causes more severe thunderstorms with short bursts of heavy rainfall, here’s how Johnson County works to prevent dangerous flooding and how homeowners can take steps to mitigate flooding with a rain garden, or using rain barrels and native trees.
How water impacts geography
Johnson County has a complex watershed — some water feeds into Mill Creek and eventually the Kansas River, and in the east it feeds into the Blue River or Brush Creek and into Missouri.
Although the state line represents an important governmental boundary in Kansas City, floodwater does not respect state lines. And when flash flooding occurs, it can create a regional crisis that requires collaboration from cities and counties across both Kansas and Missouri.
“We border Lenexa, Overland Park, (Wyandotte County) on the north or the river,” said Tammy Snyder, the stormwater program manager in Shawnee. “Stormwater flows downhill. So every city is going to take the repercussions, you know, the impact of the stormwater runoff.”
If Mill Creek floods, for example, the water runs from Olathe through Lenexa and Shawnee into the Kansas River, which has floodplains in Edwardsville and Kansas City, Kansas.
Prior to the formation of Johnson County’s stormwater management department, the many small municipalities in the county struggled to manage stormwater in their isolated city departments.
One severe example was in 1977, when a flood in the northeast corner of Johnson County and the Country Club Plaza killed 25 people. After 16 inches of rain, the water level of Brush Creek rose to 22 feet, flowing with thousands of times the normal volume of water.
By 1990, the mayors of smaller cities like Fairway, Mission Hills and Westwood started advocating for the Kansas Legislature to create a county-level department with more funding and power.
“Those cities are really small, and they don’t have a lot of staff, and they don’t have a lot of revenue coming in,” Schmidt said. “So to address the big cost of stormwater management, and especially with respect to flooding, they were going to need some help.”
Today, the department has two primary tasks: first, to minimize flooding by strategically managing drainage in flood-prone areas, and second, to set standards that would minimize stormwater pollution. By imposing requirements on construction and managing fertilizers and ice melt, the department ensures that the water itself poses less of a threat to human health when stormwater levels rise.
Much of the stormwater infrastructure is underground, diverting and carrying stormwater to the rivers beneath roadways.
“Unless water comes onto your property, you go to sleep and wake up the next day, and you say, ‘Oh, thank goodness it rained,’” Snyder said. “You don’t notice the billions of dollars of infrastructure underground that we have constructed over the years to help mitigate and contain that stormwater runoff.”
Development can contribute to flooding
As new developments in Johnson County pop up, new parking lots, streets and lawns can cause problems.
These impervious surfaces don’t allow the ground to absorb the stormwater. So instead of the water flowing into the soil to be absorbed by a complex system of native plant roots, it flows down a street, picking up bacteria-covered sediments, ice melt and dog feces.
Eventually, if that stormwater starts to pool, it can block roads, damage houses and erode the natural waterways.
“All new development, they have to capture the runoff from the impervious areas, and they have to detain it on the property and then release it slowly to prevent downstream flooding,” Snyder said. This has been a requirement since the 1990s.
About a decade ago, the Mid-America Regional Council published a guide for best stormwater management practices — the result of a collaboration between counties and cities across the Kansas City area, Schmidt said. Among these practices are some regulations for new developments.
For example, “stream buffers” prohibit developers from constructing too close to streams, and the county requires a special kind of fencing around some construction sites to make sure that construction materials don’t make it into creeks and rivers.
How a Johnson County rain garden can prevent flooding
Traditional grass lawns also contribute to flooding. As plants, their roots and soil absorb some rainwater, but they’re much less effective than native plants.
This is because many developers, particularly in the 1980s and 1990s, intentionally stripped the most absorbent soil from construction sites for a profit.
“The best soils are also very infiltrative, and normally when people develop, they clear up the topsoil and sell that because it’s highly lucrative,” Schmidt said. “And then when they’re establishing lawns back on where they are building, usually there’s not a lot of topsoil brought back in.”
When the lawn is finished, there’s only a few inches of soil on top of nonabsorbent clay. Compared to a native plant ecosystem, where roots extend several feet below the ground, the few inches of roots in a lawn can only absorb a small fraction of the water.
It’s for this reason that Johnson County’s stormwater department, in collaboration with 16 cities within the county, launched its Contain the Rain program, which offers a 50% reimbursement for homeowners installing a rain garden with native trees, flowers and bushes.
A rain garden is a diverse garden with native plants, such as copper iris, blue sage and marsh milkweed, built in a low spot of a yard to collect rainwater instead of letting it run down the street. The soil also filters the water as it flows downward, so that it’s clean when it reaches the creeks and rivers.
The program’s website has guidelines for how to apply for a reimbursement, what plants are best, how to dig the garden and the best kind of mulch to use.
Beyond helping to mitigate flooding and cleaning rainwater in Johnson County, a rain garden with native plants also requires much less maintenance and watering and supports pollinators.
For homeowners who live in neighborhoods with restrictive homeowner associations, other alternatives include rain barrels, which can be placed under a drainage pipe, or native trees.
People who are interested should submit an application before starting on their project to ensure that they get reimbursed. There’s a limited budget for every city, and reimbursements are given on a first-come-first-served basis. The staff can help homeowners design the garden and locate native plants in nearby nurseries.
“It’s all about capturing the water and keeping it on your property, filtering out the pollutants,” Snyder said. “And, it’s a beautiful, natural area that promotes beautiful native plants. So it’s a win-win.”
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