The Merriam Drainage District (MDD) maintains the Turkey Creek channel within the district’s boundaries in Merriam, Kansas. The channel consists of sections of stacked rock wall and triangular channels with riprap protection.
As part of annual inspections, Benesch identified several areas along Turkey Creek where the rock walls are being undermined. If the erosion of material from under the wall was not addressed, the bottom layer of rock would eventually drop causing the wall above it to shift. Based on these issues, the MDD requested Benesch to design grade control structures along the creek to stabilize the creek bed and protect the walls.
In the past, two types of projects had been considered to stabilize the wall – removal and reconstruction of the wall or the placement of a concrete slab underneath the wall to fill the void. While both methods could be effective, they are expensive and are only cost effective when dealing with relatively isolated areas of erosion. The areas identified in the 2018 inspections were too lengthy for those methods to be cost effective.
The creek bottom in this area consists of limestone bedrock on which streambank protection is provided by a limestone rock. The creek is approximately 60 feet wide and maintains a consistent baseflow throughout the year. The Turkey Creek watershed is mainly urban/suburban with a large percentage of impervious surface. The size and nature of the watershed results in increased peak flows and high velocities which cause the identified streambank erosion. To provide a cost-effective solution to the streambank erosion, we have recommended the installation of nine rigid weir grade control structures to stabilize the streambed.
In addition to coordinating with the multiple utility companies that cross the creek, Benesch is coordinating this work with the United States Corps of Engineers (USACE). The USACE is planning to begin the design of a large flood control project along Turkey Creek which will integrate the structures constructed by the MDD.