Delaware River, PA

The Delaware River is a major river on the Atlantic coast of the United States. The Delaware was explored by Adriaen Block as part of the New Netherlands Colony, and was named the South River to mark the southernmost reach of that colony.

The river meets tide-water at Trenton, New Jersey. Its total length, from the head of the longest branch to Cape May and Cape Henlopen, is 410 miles (660 km), and above the head of the Delaware Bay its length is 360 miles (579 km). The mean freshwater discharge of the Delaware River into the estuary is 11,550 cubic feet (330 m³) per second.

The Delaware River constitutes, in part, the boundary between Pennsylvania and New York, the entire boundary between New Jersey and Pennsylvania, and most of the boundary between Delaware and New Jersey.

The main, west or Mohawk branch rises in Schoharie County, New York, about 1,886 feet (575 m) above the sea, near Mount Jefferson, and flows tortuously through the plateau in a deep trough, impounded at one point to create the Cannonsville Reservoir, and then becoming the state boundary of N.Y and Pennsylvania at the 42nd parallel, until it emerges from the Catskills. Similarly, the East Branch begins from a small pond south of Grand Gorge in the town of Roxbury in Delaware County, flowing southward toward its impoundment by New York City to create the Pepacton Reservoir, the largest reservoir in the New York City water supply system. The confluence is just south of Hancock.

 
Delaware above Walpack Bend, where it leaves the buried valley eroded from Marcellus Shale bedrockFrom Hancock, NY the river flows between the Pocono plateau and the raised shale beds south of the Catskills. The river flows down a broad Appalachian valley, passing Hawk's Nest overlook on the "Upper Delaware Scenic Byway". At Port Jervis it enters the Port Jervis trough. Below Port Jervis, New York, the Walpack Ridge deflects the Delaware into the Minisink Valley, where it follows the southwest strike of the eroded Marcellus Formation beds along the Pennsylvania–New Jersey state line for 25 miles (40 km) to the end of the ridge at Wallpack Bend in the Delaware Water Gap National Recreation Area. The Minisink is a buried valley where the Delaware flows in a bed of glacial till that buried the eroded bedrock during the last glacial period. It then skirts the Kittatinny ridge, which it crosses at the Delaware Water Gap, between nearly vertical walls of sandstone, quartzite, and conglomerate and then passes through a quiet and charming country of farm and forest, diversified with plateaus and escarpments, until it crosses the Appalachian plain and enters the hills again at Easton, Pennsylvania. From this point it is flanked at intervals by fine hills, and in places by cliffs, of which the finest are the Nockamixon Rocks, 3 miles (5 km) long and above 200 feet (61 m) high.

At Trenton there is a fall of 8 feet (2.4 m). Below Trenton the river flows between Philadelphia and New Jersey before becoming a broad, sluggish inlet of the sea, with many marshes along its side, widening steadily into its great estuary, Delaware Bay.