Oyster River (New Hampshire)

The Oyster River is a 17-mile-long (27 km) river in Strafford County, southeastern New Hampshire, United States. It rises in Barrington, flows southeast to Lee, then east-southeast in a serpentine course past Durham to meet the entrance of Great Bay into Little Bay. The bays are tidal inlets of the Atlantic Ocean, to which they are connected by a tidal estuary, the Piscataqua River. The freshwater portion of the river is 14.1 miles (22.7 km) long, and the tidal river extends 2.9 miles (4.7 km) from Durham to Great Bay.

The Oyster River reaches tidewater at the base of a dam in the center of Durham, just west of the river's crossing by NH Route 108. Due to siltation, the river is only fully accessible to motorized boats west of the Durham Water Plant for approximately 3 hours on either side of high tide. Boaters have noticed the increasing effect of siltation on navigation since 1998.

The Oyster River valley, like the rest of New England, was entirely covered by ice during the last continental glaciation. Remnants from the Ice Age in the watershed include glacial erratics and kettle holes such as Spruce Hole Bog, 0.5 miles (0.8 km) south of the river in Durham.

Ever since European settlers came to the Oyster River they have altered its flow and taken its resources. In the 1600s, before people had a major effect on the river, Great Bay, into which the Oyster River flows, was a port where sturdy oceangoing ships could anchor at a place called Durham Landing. But as time passed, settlers built dams and cleared the forests for farmland. As forests diminished, soil usually held in place by tree roots started to wash into the river, causing its waters to fill with silt. By the 1800s, oceangoing ships were unable to reach Durham Landing except at extremely high tides.

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