Little Conewago Creek Floodplain Restoration

The Little Conewago Creek Floodplain Restoration is a proposed best management practice to fulfill local and regional water quality obligations while best serving the needs of Dover Township and West Manchester Township residents. This resource is intended to share updates on the ecological restoration project and educate the public on this innovative approach to community planning and resource management.

The restoration effort will address historical impacts and degradation along nearly 8,000 feet of the Little Conewago Creek and its tributaries, while providing over 30 acres of floodplain enhancements through wetland restoration and native riparian vegetation establishment. This project will provide significant ecological and water quality benefits, while providing pedestrian connections between Dover Township’s Mayfield Park and West Manchester’s Little Conewago Creek Conservation Area.

Project partners involved with this project and the development of this resource include:

Dover Township and West Manchester Township are both participants in the  York County Regional Chesapeake Bay Pollutant Reduction Plan (PRP)  developed in conjunction with 43 municipalities and the County of York. The County PRP represents a collaborative regional effort to fulfill state and federally mandated obligations of the Pennsylvania Department of Environmental Protection (PADEP) Municipal Separate Storm Sewer (MS4) permit. These requirements address sediment and nutrient discharges to local surface waters within the Chesapeake Bay watershed such as the Little Conewago Creek (see map below). The current goal of the County PRP is to reduce sediment loading entering the Chesapeake Bay watershed by over 6.4 million pounds per year.

Dover Township completed a similar restoration project nearby, the Fox Run Floodplain Restoration, in late 2020 at Eagle View Park. That effort serves as a successful example of the many benefits possible through ecological restoration in York County.

The project supported the York County Regional CBPRP objectives and fulfills stormwater management requirements associated with the Township’s new Eagle View Park.  

The story of this restoration project was highlighted in a 2021 Bay Journal Article by Ad Crable:  Floodplain restoration earns PA town its dream park .

In addition to providing Dover Township the opportunity to construct active and passive recreation at Eagle View park, the Fox Run Floodplain Restoration helped to:

• Rehabilitate 4,062 linear feet (LF) of tributaries to Fox Run;
• Restore 5 acres of historical floodplain wetlands;
• Establish 10 acres of riparian wildflower meadow;
• Provide flood mitigation, stormwater management, habitat creation, educational and recreational opportunities; and
• Create a new 0.75 mile trail and bridge, connecting Dover Area Middle School to the park and surrounding neighborhood.

In 2023, Dover Township was awarded the  Pennsylvania's Governor Award for Environmental Excellence  for the restoration effort. Visit Eagle View Park and explore the restoration from sunrise to sunset at 2480 West Canal Road, Dover, PA 17315.

The Little Conewago Floodplain Restoration will implement a similar holistic approach on a larger scale, spanning Dover and West Manchester Townships. See  Section 4  to learn more about the benefits of this restoration approach.

The Little Conewago Creek Watershed encompasses 65.4 square miles to its confluence with the Conewago Creek. 30% of the watershed is in Dover Township, and 9% of the watershed is in West Manchester Township. The Little Conewago Creek Watershed is predominantly comprised of agricultural land (45%) and developed space (34%), with the remaining area occupied by forested land (source:  ModelMyWatershed ).

The drainage area to the downstream end of the project site is roughly 24 square miles. Once the floodplain restoration project is completed, the restored floodplain and wetlands will treat over 1/3 of the entire Little Conewago Creek Watershed's runoff, providing substantial water quality improvements for the local community and surrounding region.

The Little Conewago Creek and surrounding drainage area to the project site have incurred human impacts dating back to the earliest record of European settlement. Grist mills existed both upstream and downstream of the project area. These mill dams would have contributed to the extensive legacy sediments observed throughout the project reach.

Legacy sediments are thick layers of fine deposits accumulated in valley bottoms as a result of human activities, which occurred extensively during early colonization and continued into the 20 ^th  century. The accumulation of these sediments was exacerbated by the central role of mill dams in the country’s economic growth. These dams created ponds of slower moving water upstream allowing sediment from muddy flows to settle and fill in the stream bed and ponding area over time. Once the dams were removed, the creek cut through the sediment to create the channel you see today with steep vertical banks that are highly susceptible to wash out during rain events, and contributing to the pollution in the Chesapeake Bay.

Emig's Mill was a grist mill located approximately 5,200 linear feet upstream of the project site, where South Salem Church Road crosses the Little Conewago Creek (source:  The Society for the Preservation of Old Mills - Mid-Atlantic Chapter, 2022 Mid-Atlantic Mill Map ).

Neiman's Mill was located approximately 1,500 linear feet downstream of the project site, where Carlisle Road crosses the Little Conewago Creek. The dam for Neiman's Mill would have been located upstream of the mill house, closer to or even within the restoration project extents at various iterations in its history.

The influence of these historical impacts persists today and, in the case of the Little Conewago Creek, far overshadow the impacts of present-day land uses and water management practices in their effect on water quality and ecological function. The legacy sediment impairment present throughout the restoration reach results in the following negative impacts:

Prior to the centuries of human impacts that have led to the severe degradation present today, floodplains of the Little Conewago Creek watershed and throughout the mid-Atlantic region were characterized by multi-channel systems connecting wetland complexes, which contained diverse herbaceous vegetation with intermittent trees and shrubs resistant to high flows.

"Before European settlement, the streams were small anabranching channels within extensive vegetated wetlands that accumulated little sediment but stored substantial organic carbon...The characteristics of the pre-settlement sediments and organic material suggest that valley bottoms were broad...wetlands with small, shallow anabranching and chain-of-pool streams that experienced frequent overbank flow, which is consistent with accounts by early explorers of ubiquitous swampy meadows and marshes fed by springs at the base of valley side-slopes.”

The proposed restoration design will attempt to re-establish those evidenced historical conditions within the context of modern-day land uses and constraints. The result will be a stable, yet dynamic stream system within an expansive floodplain-wetland system. Floodplain vegetation will be dominated by diverse native grasses, sedges, rushes and herbaceous forbs, and include wet-tolerant tree and shrub species. The proposed vegetation community will support ecological diversity, native habitat, system stability and aesthetic appeal.

By removing the legacy sediment over-burden and restoring the defining characteristics of the evidenced natural condition, the project will:

While most of the work will take place on public land, the success of the Little Conewago Creek Floodplain restoration project hinges on the effective collaboration and support from neighboring landowners, allowing temporary access for the restoration activity and willingness to uphold the restored condition long-term. Dover Township and West Manchester Township are grateful to the project's neighboring landowners for their participation and support which serves the local community and greater region.

Construction is anticipated to begin in December 2025 or early 2026. The following activities can be expected during construction:

Native vegetation is slow to establish and may take multiple growing seasons to reach full maturity. Please be patient and understand that natural ecosystems take time to develop. During the first several years after construction, regular management will occur to prevent undesirable invasive species from overtaking the slower-growing native plantings, and to ensure that instabilities don’t develop until dense, mature vegetation can provide adequate protection. During these first few years, annual reports will be submitted to the PA Department of Environmental Protection and United States Army Corps of Engineers to ensure that the restoration is functioning as intended.

Traditional infrastructure has a designed useful life and requires more intensive and costly maintenance, and ultimately replacement. However, once fully established, the restored system is naturally self-maintaining, functioning as nature intended. This means that the benefits will persist long into the future, while the input costs diminish.