NATIONAL
ESTUARY
PROGRAM
VULNERABILITIES TO CLIMATE CHANGE
The Piscataqua Region Estuaries Partnership (PREP) is a collaborative watershed program that works in New Hampshire and southernmost Maine to protect
and restore the Great Bay Estuary and Hampton-Seabrook Estuary. In 2008, PREP was awarded a $50,000 grant from the U.S. Environmental Protection
Agency's "Climate Ready Estuaries" initiative to conduct a detailed vulnerability assessment of how climate change is likely to impact existing road and
stream networks within the Oyster River watershed, which is an important coastal river that empties into the Great Bay Estuary in New Hampshire.
Due to climate change, the frequency of extreme rainfall events is increasing in New England. At the same time, watersheds are being altered by impervious surfaces associated
with development, such as roads, roofs, and parking lots. Both of these factors contribute to greater quantities of water running off the land and increase the potential for damag-
ing floods. Many of the culverts currently found under New England's roads were not designed to safely pass the amount of water that can be anticipated due to these changes.
This means that during future flood events road/stream crossings are likely to fail, which could result in damage to infrastructure and property, loss of life, and degradation of
aquatic ecosystems.
THE NATIONAL ESTUARY PROGRAM IN ACTION Piscataqua Region Estuaries Partnership
To address these challenges,
PREP convened a technical team
to conduct a climate adaptation
pilot project in the Oyster River
watershed in southeastern New
Hampshire. The immediate ob-
jective of the project is to identify
specific road/stream crossing
culverts that are threatened with
failure as a result of impacts from
increasingly extreme storm
events due to climate change, as
well as from future hydrologic
modifications due to watershed
development. The intent of the
project is to develop a practical
adaptation strategy to proactively
reduce negative climate change
impacts on stream habitat and
road infrastructure.
The study approach utilizes
geographic information system
(GIS) watershed modeling tech-
niques to examine the hydrologic
impact of several climate change
and land use scenarios on
existing culvert infrastructure.
Through the field efforts of staff
from PREP, the Town of Durham,
the NH Fish and Game Depart-
ment, and the Strafford Regional
Planning Commission, all the
major culverts in the watershed
(110 culverts) were assessed
and mapped with a standardized
protocol.
Data on culvert capacity, vegeta-
tion cover, slope, soils, permea-
bility, roads, and land use have
been compiled into a GIS model
that calculates runoff volumes
for current and projected future
precipitation patterns. For the
model of future conditions, two
build-out analyses were devel-
oped for the study watershed
EFFECTIVE
EFFICIENT
ADAPTIVE
COLLABORATIVE
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based on current zoning ordi-
nance regulations: one that as-
sumes full build-out based on
existing patterns of develop-
ment, and one that incorporates
available Low Impact Develop-
ment (LID) techniques. Global
climate model output is being
used as the basis to estimate
mid-21 st century storm event
magnitudes and return intervals
for various global greenhouse
gas emission scenarios devel-
oped by the Intergovernmental
Panel on Climate Change.
Utilizing the model results, the
project team is developing rec-
ommendations for culvert im-
provements based on risk, cost,
and infrastructure lifespan con-
siderations. Project results pro-
vide a specific climate adapta-
tion plan strategy to local
communities, evaluate the con-
tribution of LID techniques in
mitigating development impacts
at the watershed scale, and pro-
vide a repeatable methodology
for application to other National
Estuary Programs and other
coastal watersheds. "We want-
ed a project that could demon-
strate tangible environmental,
economic, and social impacts
associated with climate change,"
says Derek Sowers, PREP Proj-
ect Manager. Sowers hopes this
project will act as a catalyst for
inspiring local communities to
take other proactive measures
to adapt to changing conditions.
Sowers notes, "Citizens and
community leaders need to un-
derstand that climate change
impacts are happening and will
only get more severe over the
next 50 years - we can plan for
and adapt to those impacts now
or respond to them in crisis
mode as they play out in our
communities and incur much
greater environmental and eco-
nomic costs."
Visit www.prep.unh.edu to
learn more about this and other
PREP efforts.
EPA's National Estuary Program
(NEP) is a unique and successful
coastal watershed-based program
established in 1987 under the
Clean Water Act Amendments.
The NEP involves the public and
collaborates with partners to pro-
tect, restore, and maintain the wa-
ter quality and ecological integrity
of 28 estuaries of national signifi-
cance located in 18 coastal states
and Puerto Rico.
For more information about the
NEP go to www.epa.gov/owow/
estuaries.
The NEP: Implementing the Clean Water Act in ways that are Effective, Efficient, Adaptive, and Collaborative.
EPA-842F09001
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