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Seacoast Transportation Corridor Vulnerability Assessment & Plan

Issue

Coastal storms and flooding already threaten state and local transportation infrastructure in New Hampshire’s seacoast. These risks are expected to increase with sea-level rise, causing potential daily inundation of some transportation assets within the next 80 years. Sea-level rise and other climate change impacts will need to be considered as municipalities and NHDOT maintain or replace aging existing transportation assets and design and construct new systems. Effective adaptation to increasing coastal flood risks will depend upon coordination among transportation decision-makers, municipalities, regulators, and other authorities to share information and develop consistent (or complimentary), transparent methods to ensure a safe and functioning NH Seacoast Transportation Corridor (STC).

Area of Interest & Risk Summary

Route 1A, Route 1, and I-95—the primary roadways running from North/South—and Route 101 and Route 286—the

primary evacuation routes running East/West along NH’s coast—are all vulnerable to sea-level rise and sea-level rise induced groundwater rise in certain areas. Route 1A—a road that runs immediately adjacent to the Atlantic Coast and connects NH’s most popular beaches, tourist amenities, and working waterfronts—sustained significant damage in the March 2018 Nor’easters, resulting in a Presidential Disaster Declaration and FEMA Public Assistance. According to the Tides to Storms analysis conducted by the Rockingham Planning Commission in 2015, 43% of the 18 miles that make up Route 1A will be inundated twice daily by 2100 under a high sea-level rise scenario of 6.6 feet. This flooding will significantly impact transportation networks and their derived services, including the 18,000 drivers that use the road every day in peak summer season. Route 1 and I-95 are situated further inland and are fortunately less vulnerable to flooding; however, they are vulnerable to sea-level rise along specific road segments, see higher traffic volumes than Route 1A, and are expected to absorb additional traffic burden in the event parts of Route 1A are closed.

Goal

Enhance regional coordination in New Hampshire for transportation networks vulnerable to sea-level rise and other coastal hazards in order to maximize information sharing, identify opportunities to fill data gaps, and develop shared understanding of options for future transportation planning.

Timeframe

October 2019 to March 2021

Corridor Advisory Committee

Coming Soon!

Vulnerability Assessment Documents and Reports

Coming Soon!

Tentative Work Plan

  • CAC established and convened for kick-off meeting - March 2020
  • Transportation, climate, and existing vulnerability information compiled - March 2020
  • Travel demand model analysis and vulnerability assessment completed - May 2020
  • Adaptation options identified and prioritized - September 2020
  • Recommendations and resilience criteria for project prioritization developed - October 2020
  • Plan developed for monitoring and reevaluation - October 2020
  • STC Vulnerability Assessment Report and Plan finalized and published - January 2021
  • Two outreach events completed - March 2021

Partners

  • NHDES Coastal Program | Kirsten Howard, Nathalie Morison, Kevin Lucey
  • Rockingham Planning Commission | Tim Roache, Dave Walker, Julie LaBranche, Christian Matthews
  • NHDOT | Ann Scholz, Roger Appleton, William Rose
  • UNH | Jennifer Jacobs, Jo Daniel
  • Seacoast municipalities | Newington, Portsmouth, New Castle, Rye, North Hampton, Hampton Falls, Hampton, Seabrook, Exeter, Stratham (representatives to be designated by municipalities)

This project was funded,in part, by NOAA’s Office for Coastal Management under the Coastal Zone Management Act in conjunction with the New Hampshire Department of Environmental Services Coastal Program.