Watersheds and Subwatersheds

A Watershed Approach To Localized Drainage Problems

A watershed is a definitive boundary from which all water drains, running downhill, to a shared destination — a river, pond, stream, lake, estuary, or in the case of Strawbery Banke Museum, the now-filled Puddle Dock Inlet. Within the watershed, there are smaller sub watersheds which further divide and direct water flow. In the urban setting, curbs, gutters, and roof lines change the dynamic of how the landscape drains.

The diagram to the right illustrates the delineated watershed in which the Strawbery Banke Museum is located and its pervious and impervious surfaces. The diagram below illustrates the direction of surface flow in the subcatchments.

Today, rain that falls within the museum’s watershed is collected and directed to the City storm drain system and eventually enters the Piscataqua River via an outfall structure located within Prescott Park. Each subwatershed within the larger watershed is hydrologically connected by the subsurface drainage network.

Historical maps and photos show that the “Puddle Dock” area of the Strawbery Banke Museum campus was once a tidal inlet. As the low point, it was the primary source of relief to the watershed. Since this inlet was filled at the turn of the 20th century, the primary source of relief shifted to the closed pipe infrastructure located under both Strawbery Banke Museum and Prescott Park.

This presents a risk to Strawbery Banke when the drainage infrastructure is unable to release runoff from the watershed. During high tide, the stormwater pipe outfall located in Prescott Park is submerged and therefore stormwater cannot properly discharge from the system. When a high tide coincides with a significant rainfall, unmanaged stormwater within the Strawbery Banke Museum watershed accumulates on campus with no means of escape.

WATERSHED

WATERSHED BOUNDARY

HISTORIC PUDDLE DOCK

SUBWATERSHED BOUNDARY

MUSEUM EXTENTS

SURFACES

BUILDING ROOFTOPS (CONTRIBUTE TO STORMWATER BURDEN)

ROADWAYS & SIDEWALKS (CONTRIBUTE TO STORMWATER BURDEN)

GARDENS, LAWN, & WOODLANDS (MITIGATE STORMWATER BURDEN)

SURFACE FLOW

MUSEUM EXTENTS

WATERSHED BOUNDARY

SUBWATERSHED BOUNDARY