City of Leavenworth, Kansas
Water Resources Solutions (WRS) was part of a design team tasked with restoring approximately 300 linear feet of degraded stream bank along Three Mile Creek in Leavenworth, Kansas. Due to the degradation of the existing stream bank, the parking lot at the top of bank was being threatened. In addition, bank erosion and gullying had caused fencing along the top of bank to fall into the channel. The erosion also began to endanger the integrity of abutment of the pedestrian/roadway bridge at the downstream end of the project reach.
WRS was responsible for the hydraulic and hydrologic modeling and the channel design, including slope stability analysis. The project reach is located along Three Mile Creek, approximately 500 feet upstream from the confluence with the Missouri River, extending downstream from S. 2nd Street to a pedestrian bridge. The toe of the left descending bank had continued to erode away, causing the upper bank to slump down, threatening the recently constructed parking lot at the top of bank. Design challenges included contaminated soils at the project site and also providing a design which provided optimal space at the top of bank.
To meet the design challenges, the design included reestablishing the pre-eroded toe of slope alignment and protecting it with longitudinal peaked stone toe protection. Above the stone toe protection, a vegetated geogrid-reinforced slope was designed to provide a stable slope while providing optimal green space at the top of slope. The vegetated geogrid-reinforced slope consisted of fill material wrapped in erosion control fabric placed in 1-foot lifts with layers of geogrid evening spaced up the slope. The vegetation included restoring the stream bank with native vegetation. Two riprap grade controls were designed to grade stabilize the channel.
WRS performed the hydraulic modeling of the existing condition and proposed channel improvements using U.S. Army Corps of Engineers Hydrologic Engineering Center River Analysis System (HEC-RAS) modeling program. WRS completed the slope stability design of the vegetated geogrid-reinforced slope was performed using GeoStudio Slope/W design software. Final plans and specifications for the channel improvements were completed, and the FEMA No-rise Certification submittal was prepared by WRS. The project was completed in Spring of 2018.