Many Pennsylvania townships and other Municipal Separate Storm Sewer System (MS4) permit holders are required to reduce sediment and nutrient loadings to streams flowing through their jurisdictions. Aquatic Ecosystem Restoration Research performed at the Big Springs Run flood plain restoration project documents the reductions in sediment and nutrient loadings that can be achieved by removing legacy sediments and restoring the original footprint of valley bottom streams and wetland complexes.
The Big Springs Run restoration project was initiated in 2011; monitoring data collected from 2004 to the present documents project impacts. Visit http://www.bsr-project.org/ to view a rich depository of publications, journal articles, reports, fact sheets, and graphics presented by Franklin and Marshal College and their partners. Background information is provided on the original research concept:
- That legacy sediments deposited during the earlier colonial agricultural period on the Piedmont Plateau filled the valley floors, particularly behind the many mill pond dams constructed during that era.
- As these dams are removed and/or degrade and as stormwater run off volumes increase due to more recent urbanization, excessive stream bank erosion occurs as the often many feet of legacy sediments and associated nutrients are washed back into waterways.
The Big Springs Run research suggests a way forward for reducing sediment and nutrient loading, and reaping additional ecological and economic benefits:
- The legacy sediments themselves have an economic value as high-quality, nutrient-rich topsoil. Ongoing research at Franklin and Marshall, in partnership with Lancaster Farmland Trust, is determining the market value of these excavated sediments, which could be used to offset costs of future legacy sediment removal projects. As an example, the approximately 20,000 tons of legacy soil removed from Big Spring Run was sold for a brownfield renovation in the City of Lancaster.
- Removing legacy sediment reduces rates of stream bank erosion; the Big Spring Run data shows the project is now capturing about 12 percent of total sediment coming into the system from upstream sources.
- Nitrogen and phosphorous loadings associated with legacy sediments are reduced. Further reductions in reactive nitrogen (that can cause eutrophication) are gained through the interactions of plants and microbes in the restored landscape.
- Restore the stream channel and associated wetlands to their original elevations, regaining flood storage capacity that can help reduce flooding issues.
- The potential to uncover viable native plant seed banks that along with new restoration plantings can better compete with invasive species. Several species of wetland plants have emerged at Big Spring Run that were not planted during the restoration process; the viability of buried seeds is one of several possible explanations.
- Restore fish and wildlife habitat in the restored stream bed, wetland, and riparian areas.
The Big Spring Run project demonstrates that while the land we view today may be profoundly altered from pre-European settlement conditions, thoughtful restoration techniques may uncover multiple benefits for our own communities and our downstream neighbors and natural resources. We recommend you spend some time on the http://www.bsr-project.org/ site to learn more about this project.