Delaware River

New Jersey's Major River

Jesse Fried • Oct 03, 2017

The Delaware River used to be so abundant in aquatic life that NJ's Lenape indians would catch fish by wading into the water and herding them into net enclosures. Today, the shores of its broad bay and estuary are at home to many oil refineries and chemical plants, in an urbanized corridor from Wilmington, DE to Philly to Trenton. Upstream from here though, things become more natural. The Delaware holds the proud distinction of the only undammed major river remaining on the East Coast. Its ecosystem is unusually healthy, and in fact the Upper Delaware and its tributaries are famous for trout fishing.

The headwaters of the Delaware are way up in the middle of nowhere in Upstate NY, northwest of the Catskills, almost in the Mohawk Valley. Because of the peculiarities of Central NY's bedrock geology and glacial history, these streams flow south for a long distance through hilly uplands rather than a short distance north to join the Mohawk river. The Delaware's upper branches and tributaries have formed deep gorges through the mountains and hills of the Western Catskills as they wind their way south. In two locations, the river valleys are impounded for NYC's water supply, creating the Pepacton Reservior on the East Branch and the Cannonsville Reservoir on the West Branch (below these, there are no more dams all they way down to the bay). The gorge of the East Branch is particularly dramatic, maxing out at around 1200 feet deep near the town of East Branch, a few miles upstream of where the branches meet at Hancock.

The united river turns southward and cuts deeply through resistant Devonian sandstone in uplands between the Catskills and the Poconos, until it finally reaches New Jersey! From here to the mouth of Delaware Bay, the Delaware demarcates our state's entire western border. At Port Jervis, the triple-boundary between NY, PA and NJ, it pours into a broader, fertile valley underlain by softer shales and limestones, just west of the Kitatinny Ridge. Here is Minisink Island, a major crossroads on the pre-colonial road network, where political councils were held. The Delaware flows southwest through this valley, paralleling the ridge until the Delaware Water Gap, staying generally straight except for Walpack Bend, where it switches from flowing across a layer of soft Devonian bedrock to soft Silurian bedrock.

The Delaware Water Gap is an amazing spot, with an article of its own. Here the river turns dramatically to the southeast and cuts through the Kitatinny Ridge. It then crosses the Great Valley, surrounded by a very fertile plain, until, joined by the Lehigh River, it passes through a gap in the Highlands below Scott's Mountain at Phillipsburg. The scenery here is pretty too, but not nearly as dramatic as the Kitatinny gap. The river continues to wind through the Highlands, straightening out in a southeastern direction again once it reaches the Piedmont on the other side. The rolling terrain of Hunterdon county along its banks remains a largely agricultural region. Below Phillipsburg, the long defunct Delaware Canal follows its banks.

Things abruptly change at Trenton, located, like many Eastern industrial cities, on the "fall line" between the Piedmont and thecoastal plain. The Delaware makes another sharp turn here, back to the southwest, following the boundary between the coastal plain (on its NJ side) and the Piedmont (on the PA side). The famous "Trenton Makes, the World Takes" bridge spans it. Below Trenton, its waters are navigable and tidal. Passing through towns and suburbs leading up to Philly and Camden, where it receives the Schuylkill, it begins to widen, and slowly turns back to the southeast. In extreme South Jersey, by Cumberland County, the full-fledged Delaware Bay opens up, with swampy shores on both sides. An abandoned bay beach resort is located somewhere down in this largely rural region. Finally, passing Cape May, its waters become indistinguishable from the Atlantic.