Thousand Acre Marsh

Site Description

  • State: Delaware
  • County: New Castle
  • Ownership: Private


  • Thousand Acre Marsh: 1193 acres

Ecology and Management

Thousand Acre Marsh is an impoundment located along the Chesapeake & Delaware Canal in northern Delaware. As the name implies, the impounded area covers approximately 1,000 acres. The impoundment provides important habitat including for numerous herons from the nearby heron rookery at Pea Patch Island, the largest in the Mid-Atlantic region (Parsons 2002). According to eBird, the impoundment hosts over 200 bird species. The impoundment is considered a focal site in the International Shorebird Survey, a monitoring program for migratory shorebirds (Chan and Schulte 2003).

The ownership of Thousand Acre Marsh is complex. The water control structure is integrated in DE Rt. 9 and is owned by the Delaware Department of Transportation. The impoundment itself is owned by several landowners and DNREC. Due to this mix of ownership there is not a strategic management plan, but the impoundment is generally managed for waterfowl with high water levels in winter and an annual draw down in summer.


Thousand Acre Marsh has experienced some storm damage including occasional damage to the water control structures. However the impoundment is bordered to the east by DE Rt. 9 and to the north by the C&D Canal, limiting the risk of severe damage and breaching from coastal storms.

Human Value

The site is a popular birding destination in Delaware. During hunting season Thousand Acre Marsh is a destination for both waterfowl and deer hunters.

Literature Resources

Below is a list of articles describing research occurring at or near the impoundments:
  • Catts, W. P., and T. Mancl. “To keep the banks, dams and sluices in repair”: an historical context for Delaware River dikes, New Castle County, Delaware. Dover, Delaware: Delaware Department of Natural Resources and Environmental Control; 2013.
  • Chan, S., and S. Shulte. A Plan for Monitoring Shorebirds During the Non-breeding Season in Bird Monitoring Region Delaware – BCR 30. Manomet, Massachusetts: Manomet Center for Conservation Sciences; 2003.
  • Parsons, K. C. 2002. Integrated management of waterbird habitats at impounded wetlands in Delaware Bay, USA. Waterbirds 25:25-41.