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For Immediate Release
March 25, 2020


Nathalie Morison, NHDES Coastal Program
(603) 559-0029

Science and Technical Advisory Panel Releases Part II of New Hampshire Coastal Flood Risk

Summary: Guidance for Using Scientific Projections

Portsmouth, NH – The New Hampshire Department of Environmental Services (NHDES) announces the release of Part II of the 2019-2020 New Hampshire Coastal Flood Risk Summary, Guidance for Using Scientific Projections (Guidance). The importance of preparing for hazardous conditions and events is at the forefront of everyone’s mind as the coronavirus takes a significant toll on our society. The new Guidance highlights the importance of preparing for a different hazard, increased coastal flooding, that New Hampshire is expected to face due to climate change.

Released by the University of New Hampshire (UNH) in March 2020, the Guidance provides science-based and user-informed guiding principles and a seven step approach for incorporating updated coastal flood risk projections into private, local, state, and federal projects, including planning, regulatory, and site-specific decisions-making.

The Guidance presents a framework based on tolerance for flood risk that is intended to help decision makers:

- Select and plan for relative sea-level rise (RSLR) estimates that range from 1.3-2.3 feet by 2050, 2.9-6.2 feet by 2100, and 4.6-11.7 feet by 2150, under the assumption that global greenhouse gas concentrations will stabilize by the end of the Century. Higher RSLR estimates are advised should decision makers prefer to assume that global greenhouse gas concentrations will continue to grow through 2100 and that the rate of ice mass loss from Antarctica will accelerate even more rapidly;

- Adjust current coastal storm surge depths and extents, and augment existing floodplain management and protection standards to account for RSLR;

- Assess risks associated from increasing groundwater levels which are projected to rise as a percentage of RSLR up to 3 miles inland from the coast;

- Account for projected increases in extreme precipitation by multiplying present-day extreme precipitation rainfall estimates by at least 15%; and

- Identify and evaluate adaptation options to minimize coastal flood risks.

It is imperative that decision makers recognize that RSLR, coastal storms, RSLR-induced groundwater rise, extreme precipitation, and freshwater flooding pose an increasing threat to New Hampshire’s public health and safety, public and private structures and facilities, livelihoods and economies, and natural, historic, and cultural resources. Proactive planning for these coastal flood risks is essential to save lives and money, sustain quality of life, mitigate crises and conflict, and avoid the degradation of New Hampshire’s most vulnerable coastal areas. As a result, the Guidance directs decision makers to “create a bold vision, start immediately, and act incrementally and opportunistically” and lays out eight additional guiding principles, including prioritizing equity and justice for socially vulnerable populations, protecting natural, cultural and historic resources and public access, and supporting greenhouse gas reduction policies to help avoid the worst coastal flood risks.


“We have been studying this issue for a long time and it’s very clear we now must start taking definitive actions. The Guidance, solidly grounded, enables New Hampshire to begin incorporating best available

coastal flood risk information in all decisions in order to minimize future damages and protect the natural resources that make this state a great place to live, work, and play. This Guidance is a critical step toward helping coastal New Hampshire prepare for what is coming, and NHDES looks forward to working with its many partners to implement it in order to mitigate future flood risks,” said Thomas O’Donovan, Director, NHDES Water Division.

The Guidance follows Part I: Science, which was released in August 2019 and provides a summary of best available science relevant to coastal flood risks in New Hampshire, including updated projections of relative sea-level rise, coastal storms, groundwater rise, precipitation and freshwater flooding. Together, Part I and Part II of the New Hampshire Coastal Flood Risk Summary meet the requirements of RSA 483-B:22, which directs NHDES to supervise updates to the 2014 Coastal Risk and Hazard Commission Science and Technical Advisory Panel report, Sea-Level Rise, Storm Surges, and Extreme Precipitation in Coastal New Hampshire, Analysis of Past and Projected Trends, at least every five years.


“UNH is incredibly proud to be part of this collaborative effort that translates complex climate science into actionable steps for people to follow. As we have seen in the past few weeks as the current pandemic has unfolded, the steps we take now to prepare for future risks can be critical to our wellbeing,” said Dr. Cameron Wake, lead author of Part I: Science.


To oversee development of the 2019-2020 NH Coastal Flood Risk Summary, NHDES convened a Science and Technical Advisory Panel comprised of representatives from the New Hampshire Department of Transportation, New Hampshire Homeland Security and Emergency Management, New Hampshire Office of Strategic Initiatives, New Hampshire Department of Administrative Services, New Hampshire Fish and Game Department, New Hampshire Department of Natural and Cultural Resources, Rockingham Planning Commission, Strafford Regional Planning Commission, UNH, as well as representatives from coastal municipalities and the New Hampshire Coastal Adaptation Workgroup. Part I: Science was developed by a team of scientific advisors from UNH and was reviewed by STAP members and an external panel of regional climate experts. Part II: Guidance for Using Scientific Projections was prepared in partnership with the STAP, UNH, and NHDES and underwent public review throughout September 2019.

Upcoming opportunities to learn more:

The NHDES Coastal Program, in partnership with UNH Cooperative Extension, NH Sea Grant, and the Piscataqua Region Estuaries Partnership, will hold the first round of online training opportunities focused on the 2019-2020 New Hampshire Coastal Flood Risk Summary on March 30 and 31, 2020.

For the General Public

Monday, March 30, 2020


ONLINE WEBINAR To register, visit:


For Municipal Staff, Boards and Professionals

Tuesday, March 31, 2020


ONLINE WEBINAR To register, visit:


Both webinars will be recorded and posted to the NHDES website at

Additional in-person trainings will be scheduled in the future.

For more information:

2019-2020 New Hampshire Coastal Flood Risk Summary Part I: Science (2019) – Part II: Guidance for Using Scientific Projections (2020) –



Kirsten Howard

Coastal Resilience Coordinator

NHDES Coastal Program

(603) 559-0020


Nathalie Morison

Coastal Resilience Specialist

NHDES Coastal Program

(603) 559-0029