Clear Creek project adding curves, increasing long-term ecological benefit of waterway

Clear Creek is getting back into shape.

The small body of water that runs east from near the small town of Conroy in Iowa County and into the Iowa River is returning to its more natural, flowing shape as part of a multi-million dollar, collaborative project between the city of Coralville and the U.S. Army Corps of Engineers.

The areas of the creek being restored lie entirely within Coralville, with two portions of the project flowing near Interstate 380 and a third rolling through near the quarry.

The project is estimated to cost roughly $4.1 million and will be funded through the retroactive sale of credits earned by the city.

Project restoring natural flow, enhancing wetland qualities

The Clear Creek project will reestablish the water's "sinuosity" — its natural curves — in an effort to slow the flow of water. That will help manage erosion in the area, among other benefits.

In the last 100 years, the creek has gone from a curvier configuration to a considerably more straight-line flow along much of its route through Johnson County, Coralville Parks and Recreation Director Sherri Proud said.

A comprehensive study of the creek showed that in 1930, the creek had a sinuosity value of 1.81. Before this project, that had fallen to just 1.1. This project as proposed added stream length and gained some of that bending and curving nature back, bringing the value up to 1.38.

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The project is also establishing a gradual, sloped bank that will better ease into the water. Proud said in its prior configuration, the banks of the river practically dropped straight down.

The future configuration allows people to walk right up to and even into the creek and better appreciate and enjoy the nature in and around the water, Proud said. It also opens up much of the space previously obstructed by trees.

"The stream was right beside the bike path, but you really couldn't see much of it," Proud said. "And now you canride your bike and know you're going right by it."

Construction work is expected to be completed by August. Most of the work at two of the "reaches," the areas being restored as part of this project, will be completed by July.

Many trees surrounding the creek, especially along the banks, were taken down as part of the project as erosion posed a significant threat. This is because they sat too close to the creek, which allowed water to seep around the roots of the tree and "erode all around" the soil in that area, Proud said.

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The project also is inserting boulders underneath the surface of the water, another thing that "aerates" the water, slowing the flow and thus, the likelihood of erosion.

At "Reach One," the portion of the project near the Coralville quarry, crews will plant a variety of wetland plant species and a number of trees. Proud said that soil-filled "burritos," wrapped in biodegradable fiber and strewn across the banks of the creek, help keep the established shape of the stream bank in place.

"Years from now, there'll be a lot of foliage and it will be very beautiful," Proud said. "It'll just take a little time to watch how those trees and everything grows."

Mitigation bank refers to city's role, not the creek itself

This project is all part of a collaborative Stream Mitigation Bank project approved by the Coralville City Council in collaboration with the U.S. Army Corps of Engineers, Proud said.

In this case, the "bank" does not refer to the additional slope being added to the river but instead the process in which the city collects credits, like a bank collects currency, to sell back to area businesses during specific projects.

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This Clear Creek project will generate over 75,200 of those stream mitigation credits and the sale of credits is expected to help offset the project's total cost of $4.1 million, Proud said.

"Then, we turn around and are able to sell those credits to people who are impacting streams and waterways," she said.

Developers are essentially buying "investments" in the city's bank now, Proud said, which provides them with a certificate they can point to down the line that says they are offsetting the environmental cost of their actions by making a financial investment in the bank, Proud said. In return, the city receives some money from developers to further offset any environmental impacts elsewhere.

The bank has already sold some of its credits in the first of multiple rounds spanning the next few years. This includes a range of projects involving both the city and private developers in the area.

Ryan Hansen covers local government and crime for the Press-Citizen. He can be reached at [email protected] or on X, formerly known as Twitter, @ryanhansen01.

This article originally appeared on Iowa City Press-Citizen: The ecological, financial impact of Coralville's Clear Creek project