The White Clay Creek and its setting
The White Clay Creek watershed is one of only a few relatively intact, unspoiled and ecologically functioning river systems remaining in the highly congested and developed corridor between Philadelphia and Newark, Delaware. White Clay Creek drains more than 69,000 acres in southeastern Pennsylvania and northwestern Delaware (Table 1). A great deal of sediment from the rolling hills of Chester County, Pennsylvania, is eroded by water and other forces and is carried into the White Clay, probably accounting for the creek's name. For most of its course the creek runs through the rolling Piedmont region, dropping over the Fall Line to the Atlantic Coastal Plain near Newark before veering eastward to empty into the Christina River. The Piedmont is physiographically and geologically distinct from the Atlantic Coastal Plain due to the weathered crystalline rocks, metamorphic and igneous, that underlie its surface. Most of the crystalline rocks are Paleozoic in origin. The ancient rocks were first deposited, then uplifted, folded, metamorphosed and over time eroded to their present level. This process produced the characteristic rolling hills, plateaus and stream valleys of today's Piedmont region.
The Atlantic Coastal Plain, a relatively flat area, is punctuated by large tidal wetlands. The coastal plain is underlain by layers of sedimentary deposits formed from marine sediments, glacial outwash and aeolian (wind-produced) materials.
Normal rainfall (averaging 44 inches per year) supplies enough water to support a mature deciduous forest and an extensive freshwater tidal wetlands system downstream. Its underlying stratum of Cockeysville Marble marks the White Clay Creek watershed as an important source of drinking water. The marble layer supports a high-yielding aquifer, which also supplies continuous and relatively high base flows in the stream.
The stream itself features forest-flanked steep banks and cobble-bottomed beds in some places, and dramatic gorges cleaving low-lying floodplain in others. In general, as the stream moves south and eastward from the upland regions in the north to the Christina River, its landscape evolves from successional meadows to agricultural fields and forested ridges, to large blocks of mature forest broken up by stretches of suburban and urban development.
A sweeping range of uses from urban through suburban to rural characterizes the watershed as a whole; patterns include residential, commercial, office, industrial, institutional, agricultural, utilities and others (Table 2). Development in the Pennsylvania portion of the watershed is largely rural with a few small towns and villages and some suburban clusters. In the Delaware portion, the City of Newark and rampant surburbanization characterize much of the watershed, but by contrast, several large tracts of public open space flank the river in this state as well.