When it rains, it pours – and then it floods. It’s an all too familiar pattern of more frequent, significant rain events, like this summer’s Hurricane Isaias, brought on by climate change. A well-functioning watershed captures, stores, and slowly releases rainfall (and snowmelt too) into a body of water, such as a creek, stream, or river. Continuous development within the 64-square-mile area of the Wissahickon Watershed in Montgomery and Philadelphia counties exponentially increases surface runoff and overland flow. This increased flow we see during and after storm events erodes the streambanks throughout the watershed, adding sediment and pollution to, and, ultimately, degrading the habitat and water quality of the Wissahickon Creek and its tributaries. Conserving the land in this vital watershed protects not only this source of drinking water for a third of Philadelphians, but also the infrastructure and habitat for local wildlife surrounding and within the Creek.
To address the impact of this growing challenge, Friends of the Wissahickon (FOW) and Wissahickon Trails (formerly the Wissahickon Valley Watershed Association) continue to work with our regional partners and invest millions of dollars in capital improvements throughout the Wissahickon watershed like the ones below.
FOW’s much-awaited Forbidden Drive Streambank Stabilization Project, completed last fall, stabilized the major streambank collapse sites along the Philadelphia section of the Wissahickon Creek near Valley Green Inn, the Mt. Airy Avenue pedestrian bridge, and the Kitchen’s Lane Bridge. Conservation-driven construction practices used soil lifts (similar to terraced “steps”) that crews populated with native seeds and plants. Over time, the mature plantings will naturalize and become established growth that will support the multifaceted engineering work, while integrating into the landscape and reducing the force of water coming off the stream and hillside. The future Lavender Trail (Gully North) Project is another large-scale example for FOW’s commitment to protect the Creek’s quality. It will target one of two major erosion sites on this trail, around the Chestnut Hill Avenue/Crefield Street interchange, which is one of the largest sources of sediment discharge into the Creek. We hope that design and permitting for this stabilization and planting project will be completed later this year.
After more than five years of planning, Wissahickon Trails is spearheading the Wissahickon Headwaters Stream and Riparian Restoration Project which will restore and stabilize the stream channel and reconnecting it with its floodplain along 1,775 linear feet of a the Wissahickon Creek in the PECO Right-of-Way power line corridor. Working with PECO on the project, as well as partners Upper Gwynedd Township and Merck, Wissahickon Trails will be able to turn this property along a highly eroded stretch of the Creek into an actual floodplain, which will slow down the force of the water and allow it to percolate into the ground, catching it where it hits, instead of flowing downstream. Construction, which was supposed to have begun in March, has been delayed by the coronavirus pandemic, but crews are currently working to stabilize the area and avoid further damage from flood waters and hope to complete the work in the fall. Flood tolerant plantings will be installed, which, over time, will look and work as a functioning ecosystem.
As flood watches continue to make headlines in our region, FOW and Wissahickon Trails continue to work with watershed groups and municipalities, such as the 12-member Wissahickon Clean Water Partnership, on planning, research, and advocacy efforts that will advance the future resiliency of the vital watershed that plays such a critical conservation role.