A draft of the upcoming Flooding and Stormwater Management Plan for Ambler Area Watersheds was completed in October of this year. The 4.1 square-mile study area is located at the center of the 64 square-mile Wissahickon Creek Watershed and includes three tributaries – Rose Valley, Honey Run/Stuart Farm, and Tannery Run, and four municipalities – Ambler, Upper Dublin, Whitpain, and Lower Gywnedd.
The Plan documents flooding and water quality problems, and then identifies and prioritizes stormwater management improvements that can reduce these problems. Updated flood plain maps are also included in the Plan. The Stormwater Management Plan was produced by the Temple University Center for Sustainable Communities (Temple CSC), an organization that develops and promotes new approaches to protect and preserve quality of life through sustainable development.
At a November 12th public meeting, Temple CSC summarized the Ambler plan for an audience of about 100 residents from Ambler and surrounding communities. Jeff Featherstone and Rick Fromuth first summarized the underlying data collection and modeling efforts that support the plan’s findings. They then presented the new preliminary flood plain mapping completed by Temple CSC, noting that an overall increase in the footprint of the 100- and 500-year flood plain [compared to existing Federal Emergency Management Administration (FEMA) maps] results in an increase in the number of homes and commercial buildings in the floodplain.
The Temple team then summarized a suite of upstream stormwater management improvement projects that if implemented would soak up and infiltrate runoff, reducing the amount of downstream flooding issues. These projects include stormwater basin retrofits, infiltration trenches, and stream bank restoration. Temple also identified four site-specific areas where stream channelization projects, and culvert, bridge, and dam modifications, would help reduce flooding impacts.
A question and answer period followed the presentation, with the Temple presenters and representatives from FEMA and the U.S. Army Corps of Engineers on hand to provide responses. Primary concerns expressed by area residents included the monetary impact of the revised flood plain mapping (e.g. increases in flood insurance coverage), and sources of funding to implement the proposed stormwater management projects.
The Ambler Plan has five core implementation strategies:
- Adoption and Enforcement of New Flood Insurance Rate Maps
- Implementation of Stormwater Improvement and Flood Control Projects
- Adoption and Enforcement of Municipal Stormwater Ordinances (including soon to be finalized Wissahickon Act 167 Stormwater Management Plan).
- Participation in FEMA’s Community Rating System
- Flood Warning in the Ambler Area Watersheds