Introduction

Background

The mission of Strawbery Banke Museum is to promote understanding of the lives of individuals and the value of community through encounters with the history and ongoing preservation of a New England waterfront neighborhood.

Water began to infringe on the museum’s ability to serve this mission when both localized and large-scale flooding began to damage both landscape and built features throughout the site. In fact, management of water has been an issue for the campus since the Puddle Dock inlet was filled in over one hundred years ago. As the low point of the neighborhood, the campus has long had an issue with stormwater runoff. In recent years, stormwater has flooded the central lawn, preventing its use as an event space, creating safety hazards when paths are blocked, or maintenance headaches when paths are washed away. Even more concerning, both stormwater and rising groundwater have begun to have a negative effect on the primary asset of the museum: its historic buildings.

In 2021, Strawbery Banke Museum curated an exhibit “Water Has a Memory: Preserving Strawbery Banke & Portsmouth from Sea Level Rise” and staff members have spoken at numerous conferences in recent years to communicate the ways in which a changing climate is endangering the coastal historic resources. Three interconnected issues: management of stormwater, sea level rise, and the resultant groundwater rise have been identified as threats to the buildings and landscape.

Recognizing these ongoing challenges, Strawbery Banke Museum has collaborated with Placework and the Horsley Witten Group to create this campus-wide Stormwater Management Plan (the Plan). To address this issue, the Plan takes a watershed approach to identify the problems and provide recommendations to improve localized stormwater management within the surrounding neighborhoods and the Strawbery Banke Museum campus. Thinking long-term, the Plan aims to alleviate stormwater impacts while maintaining alignment with the museum’s mission to preserve historic buildings and cultural landscapes for today’s visitors and for future generations.

Approach

The Plan began with an analysis of the existing conditions within the campus, and developed site-specific interventions. The opportunities identified recognize and have incorporated the following ideas into their approach:

• The site is part of a larger neighborhood watershed, and therefore most mitigation opportunities involve coordination with the City of Portsmouth and/or neighboring sites.

• Strategies in this report take advantage of the existing stormwater management infrastructure, and seek to retrofit systems already in place.

• The opportunities maximize the use of existing open space to retain and store excess stormwater.

• At least three of the current buildings have elevations that put them at immediate risk of flooding, and approximately half of the Strawbery Banke Museum campus lies within the current and/or future 500-year flood plain.

It is important to note that this Plan focuses on addressing the localized stormwater flooding issues within the Campus and does not include a long term resiliency strategy related to climate change and sea level rise. It is outside of the scope of this report to provide guidance on adaptations to any existing buildings, but it should be noted that many buildings will require future adaptations to incorporate either wet- or dry-flood proofing techniques.

The Plan summarizes the existing conditions and provides preliminary planning and guidance for both maintenance and improvements throughout the Strawbery Banke Museum campus.

Several strategies have been identified and a flexible Action Plan presented. The Plan allows for different strategies to be implemented over time, as specific needs and funding opportunities allow. Ongoing change will necessitate ongoing decision making to best support the needs of the museum.