Darby Creek (Pennsylvania)

Darby Creek
Darby Creek in Darby, Pennsylvania
Other name(s)	Church Creek, Derby River
Basin features
Main source	small valley in Treddyffrin Township, Chester County, Pennsylvania between 420 and 440 feet (130 and 130 m) 40°02′23″N 75°27′39″W / 40.0398°N 75.4607°W / 40.0398; -75.4607
River mouth	Delaware River in Delaware County, Pennsylvania 0 ft (0 m) 39°51′40″N 75°18′50″W / 39.8610°N 75.3138°W / 39.8610; -75.3138Coordinates: 39°51′40″N 75°18′50″W / 39.8610°N 75.3138°W / 39.8610; -75.3138
Progression	Delaware River → Delaware Bay
Basin size	77.2 sq mi (200 km2)
Tributaries	Left: Little Darby Creek, Miles Run, Ithan Creek, Longford Run, Colleen Brook, Cobbs Creek Right: Thomas Run, Camp Run, Lewis Run, Hermesprota Creek, Muckinipattis Creek, Stony Creek
Physical characteristics
Length	26 mi (42 km)
Discharge	Average rate: 10 to 17 cubic feet per second (0.28 to 0.48 m3/s) (two measurements) (at Foxcroft)

Darby Creek (historically known as Church Creek or the Derby River) is a tributary of the Delaware River in Chester County, Delaware County, and Philadelphia County, in Pennsylvania, in the United States. It is approximately 26 miles (42 km) long. The watershed of the creek has an area of 77.2 square miles (200 km²). It has twelve named direct tributaries, including Cobbs Creek, Little Darby Creek, Ithan Creek, and Muckinipattis Creek. The creek has a low level of water quality for most of its length. A reach of it is considered to be impaired by habitat modification, siltation, and flow variability stemming from urban runoff and storm sewers. The creek is slightly alkaline.

Darby Creek flows through a narrow valley in its upper reaches and a tidal flat in its lower reaches. The creek is in the Piedmont Uplands and Atlantic Coastal Plain physiographic provinces. Major rock formations in the watershed include the Wissahickon Formation. Three small dams historically existed on the creek, but were removed in 2012. The watershed of the creek is largely developed, with roughly half a million people inhabiting it. Most of the watershed is in Delaware County, but some parts are in Chester County, Philadelphia County, and Montgomery County. The watershed is part of the Lower Delaware drainage basin.

Historically, the Lenni Lenape people inhabited the area in the vicinity of Darby Creek. By the 17th century, the Dutch and Swedish had arrived in the area, followed some years later by the English. Numerous mills of various types were eventually build along the creek and several railroads traversed the watershed. In modern times, grants by various organizations have been awarded to improve the creek and its watershed. The Darby Creek Valley Association operates within the watershed. Part of the creek's length is designated as a Coldwater Fishery and a Migratory Fishery, part is a Trout Stocked Fishery and a Migratory Fishery. Various species of fish, including redbreast sunfish, eels, and trout, inhabit it. Several areas in the vicinity of the creek are listed on the Delaware County Natural Areas Inventory. These include the Darby Creek Mouth Mudflat, the John Heinz National Wildlife Refuge, and the Ithan-Darby Creek Wetlands. A reach of the creek is navigable by canoe.