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Tides to Storms

TIDES TO STORMS: Assessing Risk and Vulnerability to Sea-level rise and Storm Surge: A Vulnerability Assessment of Coastal New Hampshire

Portsmouth, New Castle, Rye, North Hampton, Hampton, Hampton Falls and Seabrook

In September 2015 the Rockingham Planning Commission completed the Tides to Storms project to assess the vulnerability of coastal municipalities and public infrastructure to flooding from expected increases in storm surge and rates of sea-level rise. The project’s purpose was to develop a regional scale understanding of what and where impacts from sea-level rise and storm surge will occur on New Hampshire’s coast. The study did not include an assessment of the specific degree of damage nor estimate monetary losses to specific sites or properties.

In addition to the regional vulnerability assessment, an assessment report and map set were prepared for each of the seven coastal municipalities. Municipalities were provided maps and an assessment of risks to roadways and supporting transportation infrastructure, critical facilities and infrastructure, and natural resources. Each report includes recommended actions that municipalities can take to help adapt and improve resiliency to changing conditions caused by storm surge and sea-level rise. The Rockingham Planning Commission gratefully acknowledges the participation of the coastal New Hampshire municipalities and their officials, staff, boards and commissions in the preparation of this project.

Regional Vulnerability Assessment Report and Map Set

Note: Due to their size the regional map set is contains in a zipped folder containing individual map files (PDFs).

Executive Summary

Regional Vulnerability Assessment Report

Regional Vulnerability Assessment Map Set

Sea-Level Rise MapsSea-Level Rise + Storm Surge Maps
Extent of Projected Sea-Level Rise-NorthExtent of Projected Sea-Level Rise + Storm Surge-North
Extent of Project Sea-Level Rise-SouthExtent of Projected Sea-Level Rise _Storm Surge-South
Infrastructure and Transportation Facilities-NorthInfrastructure and Transportation Facilities-North
Infrastructure and Transportation Facilities-SouthInfrastructure and Transportation Facilities-South
Roads and Transportation Infrastructure-NorthRoads and Transportation Infrastructure-North
Roads and Transportation Infrastructure-SouthRoads and Transportation Infrastructure-South
Regional Evacuation RoutesRegional Evacuation Routes
Existing/Recommended Conservation LandsExisting/Recommended Conservation Lands
Wetlands, Aquifers, Wellhead Protection AreasWetlands, Aquifers, Wellhead Protection Areas
Agricultural Soils of Local/State ImportanceAgricultural Soils of Local/State Importance
Sea-Level Rise and Sea-Level Rise + Storm Surge
Regional Zoning Districts
Regional Land Use
Sea Level Rise MapsSea-Level Rise + Storm Surge (SS) Maps
SLR 1.7' Depth of FloodingSLR 1.7' + SS Depth of Flooding
SLR 4.0' Depth of FloodingSLR 4.0' + SS Depth of Flooding
SLR 6.3' Depth of FloodingSLR 6.3' + SS Depth of Flooding

Municipal Vulnerability Assessment Reports

This project was funded by New Hampshire Homeland Security and Emergency Management (HSEM) through a Pre-Disaster Mitigation Grant from the Federal Emergency Management Agency (FEMA). Additional funding for this project provided by the NH Department of Transportation through Federal Highways Administration.Technical support and data provided by NH GRANIT.

Use and Applicability of the Tides to Storms Reports and Maps:

The purpose of the regional and municipal vulnerability assessment reports is to provide a broad overview of the potential risk and vulnerability of state, municipal and public assets as a result of projected changes in sea-levels and coastal storm surge. This report should be used for preliminary and general planning purposes only, not for parcel level or site specific analyses. The vulnerability assessments performed were limited by several factors including the vertical accuracy of elevation data (derived from LiDAR) and the static analysis applied to map coastal areas subject to future flooding which does not consider wave action and other coastal dynamics. Also, the identification of flood impacts to buildings and infrastructure are based upon the elevations of the land surrounding them, not the elevation of any structure itself. The changes in sea-level used as the basis of the vulnerability assessment are based on a plausible range of sea-level scenarios as depicted in the 2014 National Climate Assessment and New Hampshire Coastal Risks and Hazards Commission Science and Technical Advisory Committee 2014 report, and are not projections or estimates. The assumptions that underlie the sea-level scenarios should be reviewed on a regular basis.


Project Overview

The Tides to Storms 2 – Climate Adaptation Implementation project engaged New Hampshire’s seven Atlantic coastal municipalities in implementing recommendations from the Rockingham Planning Commission’s (RPC) Tides to Storms Vulnerability Assessment (2015). In response to RPC’s solicitation to provide technical assistance, each municipality self-selected their project as follows:

Portsmouth – research strategies to address coastal flooding in zoning and building codes

New Castle – community outreach about the role of coastal buffers in reducing flooding impacts

Rye – prepare a Coastal Risks and Climate Adaptation Chapter for the Master Plan

North Hampton – prepare flood protection provisions for existing buffer standards in the zoning ordinance

Hampton – prepare amendments to the floodplain development standards in the zoning ordinance

Hampton Falls - community outreach about the role of coastal buffers in reducing flooding impacts and assist Master Plan committee in incorporating Tides to Storms information in the master plan

Seabrook - prepare a Coastal Risks and Adaptation Chapter for the Master Plan (adopted in November 2016)

The Tides to Storms 2 - Climate Adaptation Implementation project was funded by a grant from the Northeast Region Ocean Council through a U.S. Fish & Wildlife Funding Grant.