Overtopping Case Study

The Missouri River had two major flooding events during the Spring of 2019. During the first flood in early spring, stretches of Interstates I-29 and I-680 were closed after being overtaken by the swelling Missouri River. After the river receded, sections of the slope adjacent to the roadway had eroded.

After the flood damage, Iowa Department of Transportation worked to add resiliency to the roadway slope. Iowa DOT engineers selected the Grid Tied Concrete Block Mat (GTCBM), Flexamat, to provide the needed armor. Flexamat® gave the Iowa DOT a permanent solution.

Grid Tied Concrete Block Mats, also known by it's acronym GTCBM, are erosion control mats consisting of concrete blocks embedded into a high strength geogrid. Grid Tied Concrete Block Mats are packaged in rolls. The roll design allows for efficient transportation of the GTCBMs, as well as efficient installation.

Installation speediness was an important factor in choosing Flexamat. These were emergency repairs to reopen the highway and future flooding was imminent. The Iowa DOT needed a solution that could be installed before future flooding and offer immediate protection.

Another advantage was that Flexamat® had a low-profile height that is safe for vehicular traffic. Adding a guardrail was not required when the Grid Tied Concrete Block Mats are utilized for roadside protection

As the installation was nearing completion, the Missouri River crested over the highway for the second time of Spring 2019. This stretch of highway was closed for over two weeks due to flooding. The GTCBM Flexamat® protected the roadway slope from erosion. After flood waters receded, the highway was reopened immediately.

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