Piscataqua River Watershed
Sagamore Brook originates in a boggy area, west of a farm on Peverly Hill Road. The brook passes under the road, near several commercial buildings, and then flows into a salt marsh, which sits on both sides of Lafayette Road. Several large businesses border the salt marsh where the brook crosses Lafayette Road. A majority of the land surrounding this marsh is within the New Hampshire Division of Forests and Lands’ Urban Forestry Center. This area is largely undeveloped, in contrast to the rest of Sagamore Brook’s shoreline. The brook flows east from the marsh, and passes through a residential along Route 1A. It flows past numerous homes, businesses, and docks, until it joins the Piscataqua River.
South Mill Pond sits in the heart of downtown Portsmouth. Its entire shoreline is surrounded by development, including several athletic fields and parking lots. Water flowing out of the pond passes under Marcy Street, and then joins the Piscataqua River.
Harvey Brook flows out of a small marsh area, along the New Hampshire Turnpike. It flows north through a narrow strip of landscaped area along the highway and then passes under the Route 4 on ramp. The brook then joins Hodgson Brook in the area between the Spaulding Turnpike and the New Hampshire Turnpike.
Hodgson Brook flows out of the developed area around the former Pease Air Force Base. The brook passes under Corporate Drive, and then turns south along the Spaulding Turnpike. It then flows into the area where several highways converge, passing through culverts under the Spaulding Turnpike, Ashland Avenue, the New Hampshire Turnpike, and Route 1. The brook passes under several smaller roads on the outskirts of downtown Portsmouth, where its shoreline is bordered by numerous businesses and parking lots. Hodgson Brook flows into North Mill Pond which sits along the Boston and Maine Railroad tracks. The eastern shore of this pond is mostly industrial, dominated by railroad facilities, while the western shore is mostly residential, with many homes and a park. The pond water flows out of the pond, under a bridge on Route 1, and joins the Piscataqua River.
The Piscataqua River forms Portsmouth’s eastern border with Maine. Its shoreline is completely developed, beginning with the Pease International Trade Port terminals, and changing to apartment buildings and marinas as it passes downtown Portsmouth. The river flows around several developed islands as it passes downtown and flows under the bridge on New Castle Avenue. Marshes and mud flats form along the shoreline as the river approaches its mouth. The Piscataqua River passes into New Castle on its way to the Gulf of Maine.