Manatawny Creek Case Study

MANATAWNY CREEK

Project Name: Manatawny Creek

Client/Project Owner: City of Pottstown Parks and Recreation Department

Project Designer: This project was coordinated by the Delaware Riverkeeper Network and was implemented by the U.S. Fish and Wildlife Service. This project was funded through the Environmental Protection Agency’s 319 program, which is managed by the Pennsylvania Department of Environmental Protection.

Technique(s) Demonstrated: Vanes, Vanes with J-Hooks, Vegetation Alone

Geographical Location: Pottstown, PA

Geomorphic Setting: Manatawny Creek, located in southeastern Pennsylvania, has a drainage area of 238.3 km² (91.6 mi²), a tributary to the Schuylkill River and Delaware Bay. Pottstown, with an estimated population of 21,614 is the major urban center in the watershed. The major uses of land are forest and open space, agriculture, and urban development. The project site was located adjacent to a park that included a trail connection to an urban area of Pottstown over a pedestrian bridge upstream. The project was needed to correct erosion and potential safety problems.

The problem was created by two sets of gabion baskets and the pedestrian bridge that constricted the stream channel. This constriction forced additional stress just downstream thus eroding the streambank near the three willow trees and creating a dangerous situation for park visitors and increased sediment load. This project was part of a larger restoration of the area as follow-up to dam removal.

Performance Period: The project was completed in November of 2002 and has been closely monitored since completion.

Project Description: Two J-hooks were designed to restore the section of Manatawny Creek that had experienced severe erosion. Prior to installation, the banks were regraded and shaped in preparation for vegetation establishment and structure installation. The structures were carefully constructed in the live stream. The J-Hooks were installed in succession on the right bank of the stream to direct flow away from the newly graded bank and into the center of the channel. The rocks used were 0.6 to 1 m (2 to 3.3 ft) angular rocks that were placed carefully and then backfilled at the key. Coir matting was installed upstream of the first structure to provide additional support to the bank. All disturbed areas were then seeded and mulched with straw. The J-hooks were installed over the course of two weeks in November 2002 and have successfully stabilized this section of Manatawny Creek. The project has sustained two winters, included snowfall and freezing conditions.

Photo Documentation:

Right bank of Manatawny Creek prior to construction. Notice active scour and erosion of the bank, which is characteristic of the entire reach prior to installation.	Bank grading and shaping on Manatawny Creek prior to installation.
View upstream of the J-hook installation on Manatawny Creek.	Coir matting installed on the bank upstream from the J-Hook structures in Manatawny Creek.
View upstream immediately following project installation on Manatawny Creek. Note the flow pattern of the stream as it approaches and is directed to the center of the channel by the structure.	View downstream of the finished project on Manatawny Creek. The two J-hooks were installed and the bank was also stabilized with geotextile blankets and straw. Seed was also applied.

All photos and Case Study information courtesy of Delaware Riverkeeper Network.