Historic Properties Climate Change Vulnerability

Photo of Gates Street Historic Houses
Gate Street, Portsmouth, NH

Supported by funding from the National Park Service (NPS) under the Hurricane Sandy Pre-Disaster Mitigation grant program the State of New Hampshire Division of Historic Resources, the City of Portsmouth has recently embarked on a Historic Resources Climate Change Vulnerability Assessment and Adaptation Plan. On the heels of a Coastal Resilience Initiative in which the City mapped areas most vulnerable to sea level rise and severe coastal storms, this study is incorporating results of the newly adopted 2016 Downtown Historic Register District with the City’s a 3-D Massing Model and the City’s property valuation database to develop an economic and cultural valuation of its historic properties. The valuation methodology uses economic, historic, cultural and flood water vulnerability measurements to characterize, risk-assess and prioritize key historic assets in the City. The project integrates the quantitative data (e.g., flood elevation, topography, structure-type, and economic value) with the qualitative data (e.g., historic survey forms, National Park Service designations) to develop a Historic Resource Valuation and Risk Assessment Map.

The project also focuses on four target areas to evaluate the economic impact of flooding and sea-level rise in a variety of land uses and settings. Strawbery Banke, a national historic monument representing early colonial settlement in northern New England, is being carefully evaluated for both sea-level change and rising groundwater or seepage impacts to the historic structures. An older section of the South End neighborhood is also being assessed and includes private, historically significant homes; a first-period cemetery; and the culturally significant Prescott Park. In the downtown, the study is evaluating impacts of sea-level rise for the working waterfront, where both commercial and industrial uses continue to operate and depend on land-side, support services. An area of historically significant homes and cemeteries along the North Mill Pond is additionally being studied with the notion that adaption strategies will have broad applicability to the larger Mill Pond areas in downtown Portsmouth.

The study includes a multidisciplinary team of local and regional practitioners who are integrating a wide variety of economic, environmental, cultural, historic (including archeological) and engineering factors. Using innovative visualization, valuation, and modeling tools the team has developed a method with broad-based applicability to other coastal communities to promote resiliency.

Property Owner Survey

During the summer of 2018, the Planning Department will be surveying the most at-risk historic structures in the City for storm surge and coastal flooding events. This survey will allow our department to get a better understanding of the vulnerabilities affecting the Portsmouth Historic District and ways we can adapt our historic structures for future severe weather events and coastal flooding. The results of this survey will be compiled into a database and used for the creation of a property map detailing structures at risk for groundwater flooding and will support future planning efforts.  Please follow this link to fill out the online survey.