Piedmont Basin

The entire Piedmont Basin, 80% of which lies in Pennsylvania, empties into the Delaware River.

Quick Facts

  • Size: 605.3 square miles
  • Size (DE only): 181.9 square miles
  • 2019 U.S. Census Bureau Population: 752,928
  • 2019 U.S. Census Bureau Population (DE only): 422,749
  • States: DE, PA and MD
  • Counties: DE: New Castle | PA: Chester, Delaware, Lancaster | MD: Cecil

Land Cover: The pie charts below show the percent land cover for the entire Piedmont Basin and the Delaware portion of the basin respectively.

Calculations derived from the NOAA Coastal Services Center (CSC), Coastal Change Analysis Program (C-CAP) Land Cover data based on analysis of 2016 Landsat 30m resolution imagery

Learn more about the Piedmont Basin and its watersheds in the interactive mapping application above. Look up an address, filter by basin and watershed, and turn on a variety of different feature layers including schools, land use, and hydrology. You can print a map or the area and features you are interested in or  download a PDF of the Piedmont Basin .


Water Quality

More than 90% of Delaware's Waterways are considered impaired. "Impaired waters" are severely polluted waters that do not meet water quality standards. The state's list of impaired waters, filed with the Environmental Protection Agency, includes bodies of water that suffer from 11 different impairments, the most common of which are pathogens (disease-causing bacteria and viruses) and nutrients.

Pollutants in Delaware waters are often chemicals, such as nitrogen and phosphorus from fertilizer runoff. They can come from specific "point" sources, such as sewage treatment plants, or from "nonpoint" sources, like runoff from lawns, farms, parking lots, and golf courses. Most impairments come from nonpoint sources of pollution, which are difficult to control because you can't see exactly where they originate.

The nutrients entering the Piedmont Basin come from agricultural runoff, urban runoff, and municipal and industrial point source discharges. Septic systems also contribute high amounts of nutrients to the Piedmont Basin's waterways. Raw or inadequately treated sewage is a severe contributor to the declining health of the waters of the Piedmont Basin. This sewage contains pathogens, which are disease-causing bacteria and viruses. The potential daily pathogen output from one person's untreated sewage can equal that of treated sewage from hundreds to even thousands of people, depending on the level of treatment.

Learn more about water quality and impairments by exploring the Delaware water quality mapping application above. Assessment data in this tool is accessed through EPA map services an shows the most recently approved Integrated Report: 305(b) Report and 303(d) List. To learn more about this report, visit the DNREC Division of Watershed Stewardship  report archive .


Wildlife

Delaware's Department of Natural Resources and Environmental Control (DNREC), Division of Fish and Wildlife conducts on-going inventories of natural communities as well as rare and declining species, (e.g., state and globally-rare plants, birds, insects, mussels, reptiles, and amphibians). It maintains a database, both electronic and manual, of its findings throughout the state. To find out more information on the wildlife and plant communities in the Piedmont Basin, visit the DNREC's  Conservation Programs page .

Green Heron at Winterthur by Jim Barnes

The tidal waters of the Christina River support a striped bass fishery and spawning grounds, while the nontidal waters of the Brandywine Creek provide exceptional smallmouth bass fishing habitat. Sampling conducted by DNREC show that there are abundant anadromous fish species present and spawning in the White Clay Creek, including American shad, Hickory shad, White perch, Striped bass, Alewives, and Blueback herring. Efforts to remove the barriers for fish to migrate further up the Brandywine and White Clay Creeks are underway.


Plants

Rue Anemone at Judge Morris Estate by Ariane Mueller

Delaware has more than 1,600 species of native plants. More than a quarter of them are rare and can be found in more than 100 different terrestrial and wetland habitat types.

The Division of Fish and Wildlife, working with the University of Delaware's Institute for Public Administration - Water Resources Center, maintains online databases about plants and plant communities in Delaware. To find out more, visit DNREC's Conservation Programs  Plants and Plant Communities page .

The Piedmont Basin supports a great variety of flora, including many species that are rare or nonexistent in other areas. The Piedmont Basin supports the highest acreage of mature, deciduous woodlands in the state. Forests are composed of a mixture of hardwoods, dominated by oaks, beech, tulip poplar, hickories, and sweet birch on the steep slopes and dry ridge tops, and by box elder, sycamore, sweet gum, slippery elm, red maple, tulip poplar, and sometimes river birch and black willow along narrow stream-side forests.


Recreation

Sunset Lake by Buddy Hellein

Parks, recreational facilities, and open space are an important part of the social, cultural, and physical fabric of the community and are abundant in the Piedmont Basin. The Brandywine Creek hosts many canoe and kayak enthusiasts at public boat landings and commercial liveries. The White Clay Creek State Park, Brandywine Creek State Park, and numerous municipal and state parks provide hiking and biking trails for the community. Freshwater trout fishing is popular in the Piedmont Basin. While public access for boaters is limited, recreational opportunities for non-motorized boats, canoes, and kayaks is quite popular.


Resources

Wilmington by Robert Tuttle

Documentation

Partners


Green Heron at Winterthur by Jim Barnes

Rue Anemone at Judge Morris Estate by Ariane Mueller

Sunset Lake by Buddy Hellein

Wilmington by Robert Tuttle