Traditional engineered bank stabilization techniques such as riprap armoring and gabion baskets are commonly used as stream stabilization solutions in places where spot fixes are preferred over a more comprehensive stream restoration design. This is especially true is areas where existing infrastructure is compromised or failing, where stream banks are encroaching on private property, and near public amenities like parks and trails. Traditional engineered solutions can pose stability and maintenance risks and often look out of place in natural settings. Bioengineering solutions like vegetative walls can be used in place of traditional bank armoring to improve aesthetics and reduce long-term maintenance costs.

 

AECOM designed a vegetated wall to stabilize the eroding stream banks adjacent to an elevated sewer crossing in Blackwater Creek, a fifth order stream located in the City of Lynchburg, Virginia. Woody debris had accumulated behind the pillars of the elevated sewer line, causing lateral erosion of the stream banks which compromised the large sewer interceptor running perpendicular to the stream. AECOM’s design utilized vegetative wall geobags to reconstruct the stream bank and armor the area adjacent to the recently exposed areas of the sewer line. Geobags are filled with a sand and soil blend, anchored with geogrid and duckbills into a compacted backfill, planted with live stakes and then hydroseeded so that the final structure blends in with the natural surroundings.  When properly designed and installed, these vegetated walls  will last longer than other engineered solutions and will require less maintenance over time.

 

This presentation will describe the benefits of bioengineered stream stabilization techniques and design considerations for the use of these materials in infrastructure protection and stabilization projects.  Lessons learned from construction will also be discussed.