Hold Tough

April 10, 2014
Embankment protection in Wisconsin floodplain management project

The city of Appleton, Wis.’s Relocation and Floodplain Management Project included embankment protection at the culvert outflows. The GeoRunner flow protection mat system, developed by Wisconsin company Presto Geosystems, was employed as additional embankment stability on the channel alignment project.

The Apple Creek Relocation and Floodplain Management Project realigned approximately 5,000 ft of channel, created wetland depressional areas and a floodplain storage area, and placed three waterway crossing structures and one bridge. The disturbed lands were planned to be revegetated, and the new channel embankments protected with a turf reinforcement mat (TRM) and GeoRunner mat system at high-impact locations and planted with native vegetation.

AECOM Technical Services Inc. designed the realigned channel to create a meandering, naturalized water feature. The modifications included an 8‑ft bottom flow line width for low flows along the new alignment. The low-flow channel includes riffle-pool complexes installed at appropriate locations for a more naturalized channel. The upper portion of the corridor was excavated to create floodplain storage at the bank-full elevation.

The integrated GeoRunner mat system is designed to protect soils from scour in erosive environments by providing resistance to shear stresses at these high impact areas. The fully connected and anchored system protects embankments from erosion and vegetation loss in areas with intermittent or concentrated flows. The mats are typically placed over a TRM and anchored with an anchor system designed to resist pullout caused by high-flow lifting forces, even in saturated soils.

Because the mats are flexible, they can be anchored to make a tight connection with the landscape grade, reducing potential for undermining of the mats. The open-mesh design allows vegetation growth to be consistent and dense, contributing to the stabilization of the protection system. The system can be driven on by mowing or other lawn equipment for vegetation maintenance.

The channel has sustained several rain events since installation and the embankment protection system is performing to expectations.

Hydraulic performance testing of the GeoRunner system was conducted at Colorado State University Hydraulics Laboratory in accordance with ASTM D6460-7 procedures. The testing determined that shear stress performance increased by a factor of 6.1 with the addition of the GeoRunner and TRM system. Similarly, flow velocity performance increased by a factor of 2.6.