Work to Begin This Month to Shore Up Wissahickon Streambanks

Maura McCarthy, Executive Director, Friends of the Wissahickon

Click the map for a larger version.

The long-awaited stabilization of three major streambank collapse sites along Forbidden Drive is set to begin the week of June 17, with construction expected to be completed by the end of September. The locations, which have continued to erode since the collapses, are: 

  1. Approximately 1,000 feet downstream from Valley Green Inn
  2. The Mt. Airy Avenue pedestrian bridge
  3. Immediately downstream from the Kitchen’s Lane Bridge

Project design involves three tiers of integrated components: stabilizing the bank toe, (which is especially susceptible to water erosion because of its location between the regular and low water levels) with large rock; reforming and stabilizing the bank above the toe using vegetated soil lifts (similar to terraces), and reforesting the upper bank slopes adjacent to Forbidden Drive with a combination of native trees, shrubs, and herbaceous seeding. 

To tackle this complex work, FOW hired two ecologically-driven restoration and land-use solutions companies. RiverLogics Solutions, based in Wellsville, is leading the project work to install rock-toe stabilization and is coordinating with Applied Ecological Services from Brodhead, WI for the vegetated soil lifts on the streambanks. This summer, AES will heavily seed the soil lifts and upper banks and will return in November or December to install dormant live stakes within the soil lifts. Dormant live stakes are woody cuttings with the branches removed, and are often used to stabilize streambanks. They will also plant potted trees and shrubs on the upper banks. This multifaceted project will also include removing trees, trenching and installing boulder walls, grading slopes, and rehabilitating the trail. 

Watch Your Step!

Construction mobilization will begin the week of June 10, a week ahead of when the actual work begins. The staging work zone for materials and machines will be set up at the bottom of the Jannette Street access trail in Roxborough, near the intersection of Forbidden Drive. 

Construction will begin at the most northern site, downstream from Valley Green Inn. While work is going on at each site, Forbidden Drive will be narrowed to about 12 feet to allow for temporary fencing of the work zone to contain materials and machines and to maintain adequate passage for emergency vehicles. The fencing will remain in place until the construction at this site is completed. It will be removed and relocated when the crew moves downstream to the next project site. 

Throughout the construction, heavy equipment will periodically move along Forbidden Drive, carrying materials and equipment to the project site. All vehicles will follow the 7 m.p.h. speed limit on Forbidden Drive, will be marked with safety flagging, and will use audible warning signs.  

Stay especially alert if you’re using the park during this time. Don’t assume that equipment operators see you. At all times, give heavy equipment the right of way, slow your pace and keep children, dogs and horses under control and at a safe distance. When approaching work locations, remove earbuds or headphones. Under no circumstances should any park user enter work zones. During the construction period, please stay out of the work zones and heed safety signage at all times — even when crews are not working. 

For more information about Friends of the Wissahickon, visit the website at