Download Atlantic Climate Adaptation Solutions

Atlantic Climate Adaptation Solutions Association
Solutions d'adaptation aux changements climatiques pour l'Atlantique
Yarmouth: A Case Study in Climate Change Adaptation
Part 2 – Section 1
Future Sea Level Rise and Extreme Water Level Scenarios for
Yarmouth, Nova Scotia
Jonathan Critchley, Justin Muise, Eric Rapaport & Patricia Manuel
School of Planning, Dalhousie University
Halifax, Nova Scotia
May 2012
Report: This report was commissioned by the Atlantic Climate Adaptation Solutions Association
(ACASA), a non-profit organization formed to coordinate project management and planning for
climate change adaptation initiatives in Nova Scotia, New Brunswick, Prince Edward Island and
Newfoundland and Labrador and supported through the Regional Adaptation Collaborative, a
joint undertaking between the Atlantic provinces, Natural Resources Canada and regional
municipalities and other partners.
Project management: Climate Change Directorate, Nova Scotia Department of Environment,
5151 Terminal Road, PO Box 442, Halifax, Nova Scotia, B3J 2P8
Disclaimer: This publication is not to be used without permission, and any unauthorized use is
strictly prohibited. ACASA, the authors, the provinces of Nova Scotia, New Brunswick, Prince
Edward Island, Newfoundland and Labrador, and the Regional Adaptation Collaborative are not
responsible for any unauthorized use that may be made of the information contained therein.
The opinions expressed in this publication do not necessarily reflect those of ACASA, its
associated provinces, or other partners of the Regional Adaptation Collaborative.
The School of Planning, Dalhousie University makes no representations, express or implied, as
to the accuracy, completeness and timeliness of the information, maps, and data contained
herein. The data are for informational purposes only and should not be used for legal,
engineering, or surveying purposes. Decisions made from such information are the responsibility
of the user. The School of Planning, Dalhousie University assumes no responsibility for its use.
The user may not re-sell, sub-license, or otherwise reproduce, publish or disseminate for
commercial purposes data available through this report.
The Town of Yarmouth and the Municipality of the District of Yarmouth advise that all data
provided for use in this report and are generally believed to be accurate and the best information
available. They may, however, occasionally prove to be incorrect, incomplete or out-of-date; thus
data accuracy is not guaranteed.
The utility pole and line data obtained from Nova Scotia Power Inc. provide reference to
equipment for the purpose of performing services. At any given time the configuration of the
actual power system may vary from this representation. The utility pole and line data should not
be relied upon for personal safety.
Acknowledgements: Dalhousie University, School of Planning ACAS project team thanks the
Nova Scotia Department of Environment for the opportunity to contribute to the ACAS program
and to assist in building municipal capacity to address climate change impacts. In particular, we
thank Mr. Will Green, Dr. Dan Walmsley and Ms. Kyla Milne for their guidance and support
throughout the course of these projects.
The research assistants to the projects were honours undergraduate and graduate students in
the professional planning programs of the School of Planning. The skill development and
training afforded to them through participation in ACAS is exemplary of partnerships in educating
young professionals in adaptation planning. The School of Planning, Dalhousie University
thanks NS Department of Environment for this outstanding opportunity.
The project team thanks Mr. Arthur MacDonald, Town of Yarmouth and Mr. Brad Fulton,
Municipality of the District of Yarmouth, and the staff of both municipalities, for welcoming us to
their communities, providing us with local support, and facilitating our work whenever assistance
was needed. Like NS Department of Environment, they too have been instrumental in furthering
the education of our student research assistants.
Thank you to municipal councilors Heather MacDonald, District of Yarmouth and Esther Dares,
Town of Yarmouth, for promoting our projects in the community and to their council colleagues.
i
Thank you to Mr. John Sollows and TREPA (Tusket River Environmental Protection Association)
for their enthusiastic support of our work, for offering guidance on connecting with local
residents, and for helping us to appreciate the beautiful Yarmouth environment.
And, thank you to the many residents of Yarmouth Town and District who showed interest in our
work, who participated in the project, and who gave their time, knowledge and insights to
identifying the risks, challenges and opportunities of climate change impacts.
Cover page photo credit: Zoë Wollenberg
This report is available for download from the ACASA website at: atlanticadaptation.ca
ii
Executive Summary
This study generates nine predictions of sea level rise and extreme water levels for Yarmouth,
Nova Scotia: three predictions for the year 2025 and six predictions for the year 2100. The
predictions are derived from data available in peer reviewed reports and scientific publications.
Year 2025 scenarios use climate change data developed for select municipalities in Prince
Edward Island and Nova Scotia1. Year 2100 scenarios use the regional and local data as well as
global predictions for sea level rise2. These projections also serve as background information for
other studies within the Yarmouth ACAS projects.
Some of the scenarios represent permanent inundation of coastal land due to relative sea level
rise (combining global sea level rise and local land subsidence). Each inundation scenario
includes extreme tides. Other scenarios combine sea level rise inundation with storm surge
generated by large storms such as hurricanes. These predictions draw from records of past
events and are known as extreme water levels. One scenario for extreme water levels combines
predicted sea level rise, Higher High Water at Large Tide (HHWLT) and the 100-year return
storm surge water level. The worst case scenario combines predicted sea level rise with Higher
High Water at Large Tide (HHWLT) and the storm surge elevation generated in 1976 by the
benchmark Ground Hog Day Storm. These extreme storm surge flood scenarios represent
temporary flooding events.
For the year 2025 in Yarmouth, Nova Scotia, relative sea level rise (combining global sea level
rise and local subsidence) is expected to be 0.17 m (higher than observed sea level for the
period 1980 to 1999). The worst case scenario prediction (combining relative sea level rise with
HHWLT and the bench mark storm surge) is 4.41 m. By the year 2100, and using different global
sea level rise predictions, relative sea level rise could range between 1.40 and 1.79 m, while the
worst case flooding scenarios are between 5.64 and 6.03 m.
Predicted sea level rise and extreme flooding were mapped using a digital elevation model
derived from LiDAR data. LiDAR is suitable for mapping elevation to two decimal places.
Example maps included in this report show the extent of potential sea level rise inundation and
storm surge flooding scenarios. Digital data resulting from this study were given to the Town of
Yarmouth and the Municipality of the District of Yarmouth for use in planning and policy
development.
The study shows that there is a range of sea level rise predictions that could be used for
adaptation planning or policy making, depending on planning horizons and decision needs. The
information in this study can help provincial and municipal government planners and decision
makers consider which factors to include in developing or selecting scenarios for climate change
adaptation planning.
Future work should investigate how other jurisdictions select scenarios for use in climate change
policy and planning.
1
2
Daigle, 2011.
Grinsted, et al. 2009; Rahmstorf, 2007; Rahmstorf and Vermeer, 2009.
iii
Glossary and Acronyms
AR4 - Fourth Assessment Report
AR5 - Fifth Assessment Report
CGVD28 - Canadian Geodetic Vertical Datum
IPCC - Intergovernmental Pannel on Climate Change
HHWLT - Higher High Water at Large Tide
GSLR - Globa lSea Level Rise
UNEP - United Nations Environment Programme
WMO - World Meteorological Organization
Vertical Datum - The reference surface for a height system, more specifically the zero elevation
(Natural Resources Canada, 2008).
Canadian Geodetic Vertical Datum (CGVD28) - Mean sea level measured in 1928 at two tide
gauges on the Pacific coast and three on the Atlantic coast, one of which was in Halifax Harbour
and another in Yarmouth Harbour (Forbes et al. 2009).
Higher High Water at Large Tide (HHWLT) - HHWLT is the average of the highest high water
levels recorded in an area. It is calculated using the highest water level recorded yearly, over 19
years of measurement (Fisheries and Oceans Canada, 2003).
Storm Surge Return Period - Return periods represent the average time between occurrences
of an event exceeding a giving level (Environment Canada, 2010). A return period does not
mean that events will happen regularly, however. For example, in any given 100-year period, a
100-year storm surge event may occur once, twice, more than twice, or not at all.
iv
Table of Contents
EXECUTIVE SUMMARY ............................................................................................................ III
GLOSSARY AND ACRONYMS ................................................................................................ IV
INTRODUCTION ......................................................................................................................... 1
IPCC EMISSION SCENARIOS: ........................................................................................................ 2
RATIONALE AND OBJECTIVES ............................................................................................... 3
METHODOLOGY AND APPROACH .......................................................................................... 3
RESULTS AND FINDINGS ......................................................................................................... 5
25-YEAR SEA LEVEL RISE AND EXTREME HIGH WATER LEVEL SCENARIOS AND MAPPING ............... 5
SCENARIO Y1-A25, Y1-B25, & Y1-C25 ......................................................................................... 6
100-YEAR SEA LEVEL RISE AND EXTREME HIGH WATER LEVEL SCENARIOS AND MAPPING .............. 6
SCENARIOS Y1-A, Y1-B, & Y1-C ................................................................................................... 6
SCENARIOS Y2-A, Y2-B, & Y2-C ................................................................................................... 7
CONCLUSION AND RECOMMENDATIONS .............................................................................. 7
REFERENCES ............................................................................................................................ 9
TABLES, FIGURES, AND MAPS ............................................................................................. 11
APPENDIX A –SEA LEVEL RISE AND EXTREME WATER LEVEL SCENARIOS FOR 2025, 2055, 2085
AND 2100. .................................................................................................................................. 17
APPENDIX B – REALISTIC SCENARIOS AND PROBABILITY .............................................................. 18
v
Introduction
This section presents 25 and 100 year sea level rise and extreme water level scenarios for the
coastal areas of the Town of Yarmouth and the Municipality of the District of Yarmouth that have
been mapped for the purposes of the Atlantic Climate Adaptation Solutions (ACAS) project. The
sea level rise scenarios are based on the latest scientific studies that include not only sea
volume expansion, but also contributions from melting glaciers and ice sheets3. The reported
predicted sea level rise ranges from an increase of 0.17 m by the year 2025 to an increase of
1.4 m to 1.79 m by the year 2100. Storm surge factors, including 100 Year Return Period Storm
Surge and benchmark storm event water levels are added to the sea level rise scenario.
Included in all the scenarios is an estimate of isostatic rebound of the Earth’s crust following
deglaciation.
Scenarios for the year 2025 represent a relatively short time frame and are within the common
planning and budget horizons for land use development and infrastructure maintenance and
renewal. Planners and engineers can begin to prioritize upcoming infrastructure renewal and
relocation projects in consideration of their vulnerability to impact by sea level rise and increased
storm surge activity. Long-term scenarios such as the 100-year scenarios allow for the
consideration of significant changes to existing land use patterns and the development of future
major infrastructure projects.
Climate change is expected to increase sea levels primarily through thermal expansion of water
and by the accelerated melting of glaciers and land ice as the global temperature rises. The
most recent accepted projections of sea level rise come from the United Nations
Intergovernmental Panel on Climate Change (IPCC) Fourth Assessment Report (AR4). These
projections represent the international scientific consensus among climate change experts4. The
IPCC’s highest emission scenario, A1F1, indicates that thermal expansion of waters and melting
of land ice due to higher annual temperatures could lead to a projected global sea level rise of
0.26 m to 0.59 m by 20995. Work on the Fifth Assessment Report (AR5) is currently underway,
with anticipated completion by 2013/20146.
Since the AR4 report was released, the science of climate change and sea level rise has
produced new projections. Rahmstorf (2007), using observations since 1990 (base year of IPCC
projections), have shown that air temperature and sea level rise are tracking above the upper
limit of the IPCC AR4 projection. They report a projected global sea level rise between 0.50-1.40
m from 1990-2100. Concern has arisen among the scientific community that the AR4 projections
are too conservative because they do not account for the future acceleration of glacial melt and
ice sheet contributions7 – factors that have been identified as significant contributors to sea level
rise.
More recent publications by Rahmstorf and Vermeer (2009) as well as Grinsted et al. (2009)
predict even higher sea level rise than those reported in 2007. These scientific reports include
glacial melt in estimating sea level rise scenarios and are considered to present the most up to
date sea level rise projections at this time. Each calculates sea level rise based on different
assumptions and presents slightly varying scenarios; however, they are consistent in reporting
global sea level rise as higher than 1.00 m over the next 100 years. The upper and lower global
3
Rahmstorf, 2007; Rahmstorf and Vermeer, 2009.
Forbes et al., 2009.
5
IPCC, 2007.
6
IPCC, 2010.
7
IPCC, 2007.
4
1
mean sea levels from the IPCC AR4 Report8 and Rahmstorf (2007) and Rahmstorf and Vermeer
(2009) are shown in Table 1.
In light of the recent findings of Rahmstorf (2007), Ramstorf and Vermeer (2009) and Grinsted
et al. (2009) and concerns about under-estimating the extent of sea level rise, we do not use
the IPCC AR4 projections in developing scenarios for our work. We use the latest scientific
projections from Rahmstorf and Vermeer (2009) to generate sea level rise scenarios for the
Town and District of Yarmouth. Each of the global sea level rise prediction used in this study is
based on a scenario developed by the IPCC.
IPCC Emission Scenarios:
Established in 1988 by the United Nations Environment Programme (UNEP) and the World
Meteorological Organization (WMO), the IPCC is the leading international body for the
assessment of climate change and its impacts. The IPCC reviews and assesses the most recent
scientific, technical and socio-economic information relevant to the understanding of climate
change. It does not conduct any research of its own9. Its primary purpose is to provide a clear
scientific view on the current state of knowledge regarding climate change and its potential
environmental and socio-economic impacts10. The IPCC provides regular Assessment Reports
on the state of climate change knowledge. The latest was the Fourth Assessment Report (AR4),
completed in 2007. Thousands of scientists and experts from all over the world contribute to the
preparation of IPCC reports as authors, contributors; review editors and expert reviewers, None
of them are paid by the IPCC and thus operate at arm’s length from the organization.
The IPCC Emission Scenarios explore alternative greenhouse gas emission pathways, using a
wide array of demographic, economic and technological driving forces11.
A1 Scenarios: The A1 story line assumes rapid global economic growth, global population
growth that peaks mid-century and the rapid introduction of new and more efficient technologies.
The A1 scenario is divided into three groups that describe alternative directions of technological
change: fossil fuel intensive (A1FI); non-fossil energy resources (A1T); and a balance across all
sources (A1B)12. A1FI is the worst case scenario. In this report the worst case scenario is used
when possible. Only the 2025 global sea level rise scenario uses the A2.
A2 Scenario: The A2 Scenario describes a very heterogeneous world, with an underlying theme
of self-reliance and preservation of local identities. The scenario also predicts high population
growth, but differs from A1 in that it predicts slow economic development and slow technological
change13.
B1 and B2 Scenarios: Scenario B1 describes a convergent world, with similar population
growth to A1 but with more rapid changes in economic structures towards a service and
information economy. B2 describes a world with intermediate population and economic growth,
focused on local solutions to economic, social and environmental sustainability14.
8
IPPC, 2007.
IPCC, 2010.
10
Ibid.
11
IPCC, 2007.
12
Ibid.
13
Ibid.
14
Ibid.
9
2
Rationale and Objectives
Sea level rise and more extensive storm surge flooding are two critical impacts of climate
change on coastal communities. Knowing how high and how far flood waters will reach is
essential information for local governments when developing strategies to protect critical and
valued infrastructure and otherwise adapt land use practices in preparation for climate change
impacts. The primary objective of this project was to develop and map a series of plausible
future sea level rise and storm surge predictions for the Yarmouth area coastline by combining
information on global sea level rise predictions, land subsidence, extreme tides and extreme
storms. We selected two time frames: the year 2025 represents a modern, near- to mid-term
scenario for infrastructure maintenance and renewal planning purposes while the year 2100
represents a long-term planning scenario for major changes in lands use patterns.
The intent of these outputs is to generate understanding of what information can be combined to
generate a plausible scenario. The authors do not endorse the use of specific scenario without
consideration of the social or economic consequences as well as consideration of political and
public considerations. As new information and the science of climate change changes there will
be an ongoing need to update the scenarios.
Methodology and Approach
The Nova Scotia Environment Act. 1994-95, c. 1, s. 1, in maintaining the principles of
sustainable development, adopts “the precautionary principle in decision making so that where
there are threats of serious or irreversible damage, the lack of full scientific certainty shall not be
used as a reason for postponing measures to prevent environmental degradation”15. In keeping
with the precautionary principle, the Yarmouth flood scenarios use the upper limit estimate from
scientific sea level rise projections for various contributing factors. This practice follows other
studies in Nova Scotia such as the work done for Halifax Regional Municipality16.
The figures presented in Table 1 represent projected global mean sea level rise estimates for
varying time periods and therefore required modification in order to provide global mean sea
level rise projections for 2025 and 2100. In the worst case sea level rise can range between 0.59
(IPCC 2007) and 1.79 (Rahmstorf and Vermeer, 2009) metres depending on which report is
used. All water level data presented in this report for Yarmouth are referenced to the Canadian
Geodetic Vertical Datum (CGVD28) and the sea level rise scenarios come from various sources.
The range of sea level rise scenarios is used to bring awareness to the fact that there is no
single “right” or “best” scenario.
Atlantic Canada climate change impacts researcher R. J. Daigle has prepared sea level rise
scenarios for coastal Nova Scotia.17 Daigle presents an upper estimate sea level rise of 0.14 m
by 2025 based on predictions by Rahmstorf, 2007 as shown in Table 2. Daigle, 2011 is uses the
A2 IPCC scenario. More recent projections by Rahmstorf and Vermeer in 2009 are for the year
2100. All other internationally published sea level rise scenarios are also for 2100. In the 2100
scenarios the AlFL, worst case scenario issued.
The IPCC (2007) projections represent the difference between the projected global mean sea
level for 2090-2099 and the observed mean sea level for 1980-1999. Assigning a time interval
from the mid-point of 1980-1999 (1990) to the mid-point of the last decade of the 21st century
15
Province of Nova Scotia, 2003.
Forbes et al., 2009.
17
Daigle, 2011.
16
3
(2095), the duration is 105 years18. Consequently, some adjustment is required in order to
develop estimates for sea level rise over the next 100 years. The IPCC AR4 projections are
normalized and adjusted to account for the non-linear trend of future sea level rise (an
adjustment of -0.02 m). A maximum value of 0.57 m is obtained for the IPCC projection19.
Rahmstorf (2007) and Rahmstorf and Vermeer (2009) provide projections from 1990 to 2100
(110 year period). Forbes et al. (2009), for their work in Halifax Harbour, calculated that a -0.10
m adjustment is required to obtain levels for a 100 year time scale. A maximum value of 1.3 m is
obtained for the Rahmstorf 2007 projection and a maximum value of 1.69 m for the Rahmstorf
and Vermeer 2009 projection (see Table 2).
The impacts of sea level rise are not uniform across Nova Scotia, but rather vary locally and
regionally due to factors such as post-glacial uplift and subsidence of land (isostatic adjustment),
local geology, ocean relief and coastal morphology. In Nova Scotia, sea levels have risen by
roughly 0.32 m during the twentieth century - a rate twice as fast as the global average20. The
change observed is due to the combination of an increase in the global mean sea level and
regional subsidence of the Earth’s crust. In some parts of Nova Scotia, subsidence rates are
estimated to be as high as 0.20 m/century21. According to Daigle (2011) the subsidence rate is
expected to be 0.03 m by 2025 and 0.10 m by 2100 in Yarmouth (See Table 3). The
combination of sea level rise due to increasing water volume and the change in land elevation
due to isostatic adjustment is referred to as relative sea level rise. The projected relative mean
sea level rise by 2100 ranges from 1.40 m to 1.79 m in Yarmouth, higher than the predicted
global increases of 0.57 m to 1.69 m.22
Sea level rise increases the vulnerability of coastal property and infrastructure to flood damage
from storm surge. This is true even where property is at an elevation that is safe from permanent
inundation. Major storms in Nova Scotia are increasingly producing extreme water levels beyond
what has previously been experienced in the area, and are expected to increase in intensity and
frequency in the future due to climate change23. Scientists use additional sea elevations such as
Higher High Water at Large Tide levels (HHWLT), water levels based on varying storm surge
return periods, and storm surge water levels generated during benchmark storms to determine
the greatest reach of water under the severest conditions imposed on a rising sea level. The
combination of a high tide and high storm surge is referred to as an extreme water level 24.
Daigle (2011) estimated HHWLT for Yarmouth at 2.75 m and a 100 Year Return Period Storm
Surge Water Level for Yarmouth of 0.97 m (Table 4). Appendix A provides more frequent and
probable storm surge levels that could have been used in creating scenarios based on Daigle
(2011). The worst-case scenario sea level rise and storm surge projections used in this study
are in keeping with the precautionary principle; the intent is to encourage planners and
engineers to design resilient community and infrastructure plans.
Storm surge levels produced during benchmark storms are also used in developing scenarios,
characterising the impacts of an extreme historical event recorded in, or close to, the study
areas. The 1976 Groundhog Day Storm recorded storm surge of 1.49 m25 is used for Yarmouth.
Using storm surge levels from these extreme historical events assists policy makers, engineers,
18
Forbes et al., 2009.
Ibid.
20
Ibid.
21
CBCL Limited, 2009.
22
IPCC, 2007; Rahmstorf, 2007; Rahmstorf, 2009.
23
Nicol, 2008.
24
Forbes, 2009.
25
Daigle, 2011.
19
4
and residents of the study areas in visualizing the inundation and flood levels used in climate
change and sea level rise adaptation planning.
The levels provided in this report do not account for seiche and wave run up, or changes in the
Earth’s tilt due to melting of polar ice caps26. These factors have the potential to increase or
decrease reported flood levels.
The elevation data in this report is from Light Detection and Ranging (LiDAR), an optical remote
sensing technology. LiDAR is considered one of the best available technologies for accurate,
remote topographic mapping of large areas. A LiDAR device is attached to a helicopter or
airplane and flown along a flight path. During the flight, ground control stations are established.
The ground control information is compared to the LiDAR information to determine the remote
mapping accuracy. There is horizontal and vertical error in all elevation mapping and for LiDAR
the vertical error is about +/- 15cm, however this error is not accounted for in the sea level rise
scenarios (Webster et al. 2011). The LiDAR Vertical Datum is the Canadian Geodetic Vertical
Datum (CGVD28).
The creation of digital elevation data from LiDAR is costly, and therefore the input elevation map
in this study does not cover the entire jurisdictional boundary. The coastline of the Town of
Yarmouth is included in the coverage, but there is only partial coverage for the District of
Yarmouth extending from Chebogue Point peninsula and Clements Island north to Port Maitland
(See Part 1 Introduction and Background of this report series). Where LiDAR information is not
available, the existing provincial contour dataset can be used (See, for example, Environmental
Planning Studio 2008, Dalhousie University – “Land Use Planning and Risk as a Result of
Climate Change and Sea Level Rise in St. Margaret’s Bay, Nova Scotia”.)27 The nearest
mapped contour line above the extreme sea level rise and storm surge scenario should be
selected for application of the precautionary principle. The sea level rise and storm surge
scenario maps presented at the end of this report are based on LiDAR information used to
create a digital elevation model. The data were collected and processed under the direction of
Dr. Tim Webster, Applied Geomatics Research Group, Nova Scotia Community College.
Results and Findings
25-Year Sea Level Rise and Extreme High Water Level Scenarios and
Mapping
The following section presents 25-year sea level rise and extreme water level scenarios
developed for the Yarmouth study area (Y1-A25, Y1-B25 and Y1-C25). Figure 1 illustrates the
derivation of the three scenarios. Map 1 shows impacted locations within the study area.
In order to characterize future relative sea level rise and the additional impacts that storm surge
may have, we developed 3 scenarios. All sea level rise predictions as well as other information
outcomes were based on a draft report by Daigle (2011). His work made an interpolation of sea
level rise for 2025, 2055, 2085 and 2100 based on the 2100 year sea level rise prediction of
Rahmstorf (2007) using the A2 IPCC scenario. The input information for each scenario is as
follows:

26
27
Scenario A25 scenarios combine the local subsidence value with a predicted
incremental global sea level rise from Rahmstorf (2007).
Mitrovica et al., 2009.
Brown, et al., 2009.
5

Scenario B25 scenarios combine the predicted relative sea level rise in Scenario A25
with local Higher High Water at Large Tides and 100 Year Return Period Storm Surge
Water Level.

Scenario C25 scenarios combine the predicted relative sea level rise in Scenario A25
with local Higher High Water at Large Tides and benchmark extreme storm surge levels
recorded in, or close to, the study areas.
Scenario Y1-A25, Y1-B25, & Y1-C25
Scenario Y1-A25 is based on Rahmstorf (2007) levels generated by Daigle (2011) that projects
a relative sea level rise upper limit of 0.17 m (includes subsidence and Global Sea Level Rise
(GSLR)). Scenario Y1-B25 includes the predicted total change of 0.17 m, Higher High Water
Level at Large Tide (HHWLT) of 2.75 m and a 100 Year Return Period Storm Surge Water Level
of 0.97 m (100 YR SS) for a future extreme water level of 3.89 m. Scenario Y1-C25 includes the
predicted total change of 0.17 m, HHWLT of 2.75 m and the 1976 Ground Hog Day Storm Surge
of 1.49 m for a future extreme water level of 4.41 m.

Scenario Y1-A25:
0.03 m Subsidence + 0.14 m GSLR = 0.17 m

Scenario Y1-B25:
0.03 m Subsidence + 0.14 m GSLR + 2.75 m HHWLT + 0.97 m 100 YR SS = 3.89 m

Scenario Y1-C25:
0.03 m Subsidence + 0.14 m GSLR + 2.75 m HHWLT + 1.49 m 1976 Ground Hog Day
Storm Surge = 4.41 m
100-year Sea Level Rise and Extreme High Water Level Scenarios and
Mapping
The following section presents 100 year sea level rise and extreme water level scenarios
developed for Yarmouth (Y1-A, Y1-B, Y1-C, Y2-A, Y2-B, Y2-C). Figure 2 illustrates the
derivation of the six scenarios. Map 2 shows impacted locations within the study area.
These scenarios include a number of assumptions associated with sea level rise trends (the full
effects of glacial melt and changes in the earth’s gravitational field), the rate of regional
subsidence, and the frequency and intensity of storm events. The input information for each
scenario is as follows:

Group A scenarios combine the local subsidence value with a predicted incremental
global sea level rise from Rahmstorf (2007) and Rahmstorf and Vermeer (2009).

Group B scenarios combine the predicted relative sea level rise in Group A with local
Higher High Water at Large Tides and 100 Year Return Period Storm Surge Water Level.

Group C scenarios combine the predicted relative sea level rise in Group A with local
Higher High Water at Large Tides and benchmark extreme storm surge levels recorded
in, or close to, the study areas.
Scenarios Y1-A, Y1-B, & Y1-C
Scenario Y1-A is based on research completed by Rahmstorf (2007) that projects a Global Sea
Level Rise (GSLR) due to thermal expansion of the oceans of up to 1.30 m. Added to the 1.30 m
projection is regional subsidence of 0.10 m for a relative sea level rise of 1.4 m by 2100.
6
Scenario Y1-B includes the predicted relative sea level rise of 1.40 m, Higher High Water Level
at Large Tide (HHWLT) of 2.75 m and a 100 Year Return Period Storm Surge Water Level of
0.97 m (100 YR SS) for a future extreme water level of 5.12 m. Scenario Y1-C includes the
predicted relative sea level rise of 1.40 m, HHWLT of 2.75 m and the 1976 Ground Hog Day
Storm Surge of 1.49 m for a future extreme water level of 5.64m.

Scenario Y1-A:
0.10 m Subsidence + 1.30 m GSLR = 1.40 m

Scenario Y1-B:
0.10 m Subsidence + 1.30 m GSLR + 2.75 m HHWLT + 0.97 m 100 YR SS = 5.12 m

Scenario Y1-C:
0.10 m Subsidence + 1.30 m GSLR + 2.75 m HHWLT + 1.49 m 1976 Ground Hog Day
Storm Surge = 5.64 m
Scenarios Y2-A, Y2-B, & Y2-C
Scenario Y2-A is based on research completed by Rahmstorf and Vermeer (2009) that
combines expected sea level rise with glacial melt and ice sheet contributions and projects a
GSLR upper limit of 1.69 m. Added to the 1.69 m projection is regional subsidence of 0.10 m by
2100 for a relative sea level rise of 1.79 m. Scenario Y2-B includes the predicted relative sea
level rise of 1.79 m, Higher High Water Level at Large Tide (HHWLT) of 2.75 m and a 100 Year
Return Period Storm Surge Water Level of 0.97 m (100 YR SS) for a future extreme water level
of 5.51 m. Scenario Y2-C includes the predicted relative sea level rise of 1.79 m, HHWLT of 2.75
m and the 1976 Ground Hog Day Storm Surge of 1.49 m for a future extreme water level of
6.03m.

Scenario Y2-A:
0.10 m Subsidence + 1.69 m GSLR = 1.79 m

Scenario Y2-B:
0.10 m Subsidence + 1.69 m GSLR + 2.75 m HHWLT + 0.97 m 100 YR SS = 5.51 m

Scenario Y2-C:
0.10 m Subsidence + 1.69 m GSLR + 2.75 m HHWLT + 1.49 m 1976 Ground Hog Day
Storm Surge = 6.03 m
Conclusion and Recommendations
The results from this study provide a range of sea level rise scenarios. In their development an
important question arose through discussion with municipal planners, “which scenario to select?”
Our review of other reports on sea level rise scenarios from North America shows this topic is
not considered. Appendix B in this report speaks to the issue of probability of an extreme water
level occurring. However it does not answer the question of how to select a scenario.
Information on sea level rise predictions will change with time and potentially the return storm
events used in this study will need to be adjusted as the climate shifts. This can mean that
municipalities may have to reconsider any policy that includes the vertical or horizontal extents
of sea level rise and flooding. For this to happen, information on sea level rise will need periodic
review and translation into meaningful information that can be used for policy adjustment.
7
Even with information updating we will also need a culture of learning about and accepting
uncertainty. The rate at which new information on sea level rise is being generated is increasing
but there are also uncertainties that may not be resolved. How to efficiently and coherently
provide information that can inform coastal communities, including the public and local
government, needs to be addressed. An approach may be needed that distinguishes between
information that simply informs or educates and information that is taken into policy. Level of
detail might be a distinguishing characteristic between the two. Hollings’ (1973) adaptive
management concept, a practice of learning and experimenting, is accepted in the natural
resources management community. This practice may be a suitable framework for local
communities to consider when establishing a policy around sea level information gathering and
scenario selection (see Parkinson (2010) as an example).
The researchers conducted informal interviews with climate change and planning practitioners in
five municipalities in Canada and the United States seeking insight to sea level rise scenarios for
planning purposes. A common theme among the consultees was that any scenario brings with it
political, social and economic ramifications. These concerns and dynamics need be taken into
consideration when selecting the level that will guide planning decisions. Furthermore,
practitioners in municipalities currently managing or accounting for future sea level rise said that
political barriers are the main challenge to overcome in defining a sea level elevation for setting
policy direction. A change in political will usually requires education but changes may also
emerge incrementally or may shift in the event of a major storm and impacts. Converging
scientific knowledge and opinion will also move decision-makers along. Regardless, how to
approach scenario selection and what scenario to choose are critical for advancing adaptation
planning. Further investigation is needed on how to select the appropriated sea level rise and
storm surge scenarios and how to adopt them into policy.
8
References
Brown, J., Brown, G., Church, C. Fedak, M., Hood, S., MacIntosh, J., Sturtevant, G., Tanner, O.,
and Manuel, P. (2009). Land Use Planning and Risk as a Result of Climate Change and
Sea Level Rise in St. Margaret’s Bay, Nova Scotia. Environmental Planning Studio 2008,
School of Planning, Dalhousie University. Halifax, NS.
CBCL Limited. (2009). The 2009 State of Nova Scotia’s Coast Report - Coastal Development.
Government of Nova Scotia, Halifax, NS.
Clean Nova Scotia. (2009). Sea Level Rise. Retrieved June, 2011 from
http://www.clean.ns.ca/content/Content_Sea_Level_Rise
Daigle, R. (2011). Scenarios and Guidance for Adaptation to Climate Change and Sea-Level
Rise - NS and PEI Municipalities (DRAFT REPORT). Atlantic Climate Adaptation
Solutions Association. DRAFT from
http://atlanticadaptation.ca/acasa/sites/discoveryspace.upei.ca.acasa/files/Climate%20C
hange%20Scenarios%20NS%20and%20PEI%20-%20Final.pdf
Environment Canada. (2010). Atmospheric Hazards - Atlantic Region: Storm Surge Return
Period Maps. Retrieved July, 2011 from
http://atlantic.hazards.ca/maps/background/StormSurgeReturn-e.html
Fisheries and Oceans Canada. (2003). Tides, Currents and Water Levels - Glossary. Retrieved
July, 2011, from http://www.lau.chs-shc.gc.ca/english/glossary/H.shtml
Forbes, D., Manson, G., Charles, J., Thompson, K., and Taylor, R. (2009). Halifax Harbour
Extreme Water Levels in the Context of Climate Change: Scenarios for a 100 Year
Planning Horizon. Natural Resources Canada. Dartmouth, Nova Scotia.
Grinsted, A., Moore, J. and Jevrejeva, S. (2009). Reconstructing sea level from paleo and
projected temperatures 200 to 2100 AD. Climate Dynamics. 10p.
ftp://ftp.soest.hawaii.edu/coastal/Climate%20Articles/Grinsted%20Jevrejeva%202009%2
0SLR.pdf
Hollings, C.S. (1973). Resilience and stability of ecological systems. Annual Review of Ecology
and Systematics. Vol 4. Pp.1-23.
Intergovernmental Panel on Climate Change. (2007). Climate change 2007: Impacts Adaptation,
and Vulnerability - Summary for Policy Makers. Intergovernmental Panel on Climate
Change Fourth Assessment Report. United Nations, Brussels.
Intergovernmental Panel on Climate Change. (2010). Understanding Climate Change - 22 Years
of IPCC Assessment. IPCC Secretariat. Geneva, Switzerland.
Mitrovica, J.X., Gomez, N. and Clark, P.U. (2009). The sea-level fingerprint of West Antarctic
collapse. Science, Vol. 323 (5915) p. 753.
Natural Resources Canada. (2008). Canadian Spatial Reference System - Height Reference
System Modernization Glossary. Retrieved July, 2011, from
http://www.geod.nrcan.gc.ca/hm/gloss_e.php
Nicol, A (2008). Adapting to climate change in coastal areas: Six steps local land use planners
can take. Nova Scotia, Canada: Plan Canada. Spring. Pp. 17-20.
9
Parkinson, R. W. (2010). Municipal Adaptation to Sea-Level Rise: City of Satellite Beach, Florida
Report. RW Parkison Consulting, Inc. Melbourne Florida.
http://spacecoastclimatechange.com/documents/100730_CSB_CRE_Final_Report.pdf
Province of Nova Scotia. (2003). Towards a Sustainable Environment. Nova Scotia.
Rahmstorf, S. (2007). A semi-empirical approach to projecting future sea-level rise. Science.
Vol. 315 (5810). Pp. 368-370.
Rahmstorf, S. and Vermeer, M. (2009). Global sea level linked to global temperature.
Sustainability Science. PNAS. Espoo, Finland.
Statistics Canada. (2006). 2006 Community Profiles. Retrieved from:
http://www12.statcan.ca/census-recensement/2006/dp-pd/prof/92591/index.cfm?Lang=E
Webster, T., McGuigan, K. and MacDonald, C. (2011). LiDAR Processing and Flood Risk
Mapping for Coastal Areas in the District of Lunenburg, Town and District of Yarmouth,
Amherst, Count Cumberland, Wolfville and Windsor. Atlantic Climate Adaptation
Solutions Association.
http://atlanticadaptation.ca/sites/discoveryspace.upei.ca.acasa/files/Flood%20risk%20in
%20ACAS%20municipalities_0.pdf
10
Tables, Figures, and Maps
Table 1. Global sea level rise projections based on different assumptions such as
inclusion or exclusion of the full effects of glacial melt. The ranges in sea level rise
shown for each projection are based on the United Nation International Panel on Climate
Change Emissions scenarios.
IPCC (2007)
Rahmstorf (2007)
Global Sea Level by
2090-2099 (excludes accelerated
Glacial Melt)
Global Sea Level rise from
1990-2100 (excludes
accelerated Glacial Melt)
0.26 - 0.59 m
0.50 - 1.40 m
Rahmstorf & Vermeer
(2009)
Global Sea Level rise from
1990-2100 (includes
accelerated Glacial Melt)
1.13 - 1.79 m
Table 2. Sea level rise upper limit projections adjusted to 25 and 100 year time frame and
based on different assumptions such as inclusion or exclusion of glacial melt.
IPCC (2007)
Rahmstorf (2007)
Rahmstorf (2007)
Global Sea Level by 2100
Global Sea Level
by 2025 (Daigle,
2011)
Global Sea Level
by 2100
Global Sea Level by 2100
0.14 m**
1.3 m
1.69 m***
0.57 m*
Rahmstorf & Vermeer
(2009)
* Estimate does not include glacial melting.
** Prorated non-linear (polynomial) increase of Rahmstorf (2007) 100-year global sea-level rise
*** The melting of polar ice caps is predicted to reduce the gravitational pull on the nearby ocean
resulting in water migrating away from the poles, potentially changing the earth’s tilt (Mitrovica,
2009). This change could lead to some areas of the globe experiencing sea levels higher or
lower than projected. These impacts are not included in the estimates.
11
Table 3. Local subsidence projections for Yarmouth by 2025 and 2100.
Local Subsidence by 2025 (Daigle 2011)
Local Subsidence By 2100 (Daigle 2011)
0.03 m*
0.10 m
* Linear increase of local subsidence (25% of 0.10 m/century)
Table 4. Water levels for Yarmouth.
Higher High Water at Large
Tide (HHWLT)
100 Year Return Period
Storm Surge Water Levels
Storm Surge Recorded During
Benchmark Storms
2.75 m
0.97 m
1.49 m - 1976 Groundhog Day
Storm recorded in Yarmouth
12
Figure 1. Yarmouth 25-Year Sea Level Rise & Extreme Water Level Scenarios (in meters
CGVD28)
*Total Change includes linear increase of subsidence (25%) + prorated non-linear (polynomial)
increase of Rahmstorf (2007) 100 year global sea level rise.
13
14
Figure 2. Yarmouth 100 Year Sea Level Rise & Extreme Water Level Scenarios (in meters
CGVD28)
15
16
APPENDIX A –Sea level rise and extreme water level scenarios for
2025, 2055, 2085 and 2100.
Extreme Water Level Estimates for Yarmouth (CGVD28) for Storm Surge Return Periods
of 25, 50 and 100 years for Years 2025, 2050, 2085, and 2100. Return Period Surge Heights
Extracted from Yarmouth Tide Gauge Database).
Storm Surge
Return Period
Storm Surge
Height
Extreme Water
Level 2025*
Extreme Water
Level 2055*
Extreme
Water Level
2085*
Extreme
Water Level
2100*
10 Year Storm
Surge
0.78 m
3.70 m
4.08 m
4.66 m
4.93 m
0.85 m
3.77 m
4.15 m
4.73 m
5.00 m
0.91 m
3.83 m
4.21 m
4.79 m
5.06 m
0.97 m
3.89 m
4.27 m
4.85 m
5.12 m
Return Period
25-Year Storm
Surge
Return Period
50 Year Storm
Surge
Return Period
100 Year Storm
Surge Return
Period
(Note: This table may not correspond to the final report by. Please see Richards, W. and Daigle,
R. 2011. Scenario and Guidance for Adaptation to Climate and Sea Level Rise – NS and PEI
Municipalities. Atlantic Climate Adaptation Solutions Association. Website:
http://www.gov.pe.ca/photos/original/ccscenarios.pdf)
17
Appendix B – Realistic Scenarios and Probability
Presented here is advice, based on expert opinion, on the construction of scenarios which could
be considered appropriate for planning. Mr. Gavin Manson, a coastal geosciences specialist with
the Bedford Institute of Oceanography - Natural Resources Canada, provides an opinion on
developing a realistic sea level rise scenario. He is a co-author on the study that developed sea
level rise and extreme water level scenarios for Halifax Harbour (Forbes, et al., 2009). He
advised against basing all the scenarios on a combination of higher high water at large tide and
extreme storm surge because they have a very low probability of occurrence. He suggested that
a storm surge occurring at the same time as higher high water at large tide (HHWLT) provides a
plausible upper limit but the probability of a large storm surge occurring at the same time as
HHWLT is extremely low. Mr. Manson cautioned that only providing the most extreme water
levels with extremely low probability is not a helpful approach for those involved in coastal
planning and suggested that a planning water level lies somewhere in the middle.
Scenarios can be developed by combining the information of sea level rise and extreme storms
for different purposes. Important infrastructure and services such as emergency facilities would
be a priority for protection from any level of flooding and might call for using the most extreme
events with low probability to try to avoid the impacts of any storm event even on low probability
conditions. Three water levels were developed as example scenarios that might be used in
identifying development zones and imposing development limitations based on probability of
flooding and type of flooding. Three water levels were developed as example scenarios that
might be used in identifying development zones and imposing development limitations based on
probability of flooding and type of flooding.
Low Water Level Scenario (L) - This scenario combines global mean sea level rise and local
subsidence identifying areas with permanent inundation from sea level rise, without storm
events. This scenario identifies areas that have high probability of being permanently inundated
by relative sea level rise. A suitable recommendation is that no future development or assets
should be allowed in this area. An effort should be made to move or protect infrastructure that is
currently located in it.
Medium Level Scenario (M) – This scenario includes relative sea level rise and high probability
extreme water levels, identifying areas with permanent inundation from sea level rise and
additional impacts from a high probability storm surge event. Limited development should be
allowed in this area, potentially imposing restrictions requiring a development agreement. New
or alterations to existing development in the identified areas should demonstrate how sea level
rise and storm surge has been considered. For existing land use, effort should be made to raise
awareness amongst property owners on the potential impacts of storm surge and ways to
mitigate impacts. A suitable recommendation is that critical infrastructure be removed from this
area.
High Level Scenario (H) – This scenario includes relative sea level rise, Higher High Water at
Large tide and the water level recorded during a benchmark storm surge. The scenario presents
a plausible upper limit to sea level rise and extreme water levels inundation and flooding.
However, at the same time there is very low probability of a large storm surge event coinciding
with Higher High Water at Large Tide. A suitable recommendation is that development can occur
in the impacted areas; property owners should be made aware, however, of potential impacts of
storm surge events.
All critical, response, and hazardous infrastructure should be located outside of all three of these
zones.
18
Yarmouth Sea Level Rise & Extreme Water Levels – 25-Year
Scenarios
The following section presents 25-year sea level rise and extreme water level scenarios
developed for Yarmouth. Figure B1 illustrates the derivation of the nine scenarios. Map B1
shows impacted locations within the study area.
Scenario Y1-L25, Y1-M25, & Y1-H25
Scenario Y1-L25 is based on Rahmstorf (2007) levels generated by Daigle (2011) that projects a
relative sea level rise upper limit of 0.17 m (includes subsidence and Global Sea Level Rise
(GSLR)). Scenario Y1-M25 includes the relative change of 0.17 m and a 100 Year Return Period
Storm Surge Water Level of 0.97 m (100 YR SS) for a future extreme water level of 1.14 m.
Scenario Y1-H25 includes the predicted total change of 0.17 m, HHWLT of 2.75 m and the 1976
Ground Hog Day Storm Surge of 1.49 m for a future extreme water level of 4.41 m.

Scenario Y1-L25:
0.03 m Subsidence + 0.14 m GSLR = 0.17 m

Scenario Y1-M25:
0.03 m Subsidence + 0.14 m GSLR + 0.97 m 100 YR SS = 1.14 m

Scenario Y1-H25:
0.03 m Subsidence + 0.14 m GSLR + 2.75 m HHWLT + 1.49 m 1976 Ground Hog Day
Storm Surge = 4.41 m
19
Figure B1. Yarmouth 25-Year Sea Level Rise & Extreme Water Level Scenarios (in meters
CG VD28).
*Total Change includes linear increase of subsidence (25%) + prorated non-linear (polynomial)
increase of Rahmstorf (2007) 100 year global sea level rise.
20
21
Yarmouth Sea Level Rise & Extreme Water Levels – 100-Year
Scenarios
The following section presents 100 year sea level rise and extreme water level scenarios
developed for Yarmouth. Figure B2 illustrates the derivation of the six scenarios. Map B2 shows
impacted locations within the study area.
Scenarios Y1-L, Y1-M, & Y1-H
Scenario Y1-L is based on research completed by Rahmstorf (2007) that projects a Global Sea
Level Rise (GSLR) due to thermal expansion of the oceans of up to 1.30 m. Added to the 1.30 m
projection is regional subsidence of 0.10 m for a relative sea level rise of 1.4 m by 2100.
Scenario Y1-M includes the predicted relative sea level rise of 1.40 m and a 100 Year Return
Period Storm Surge Water Level of 0.97 m (100 YR SS) for a future extreme water level of 2.37
m. Scenario Y1-H includes the predicted relative sea level rise of 1.40 m, HHWLT of 2.75 m and
the 1976 Ground Hog Day Storm Surge of 1.49 m for a future extreme water level of 5.64m.

Scenario Y1-L:
0.10 m Subsidence + 1.30 m GSLR = 1.40 m

Scenario Y1-M:
0.10 m Subsidence + 0.97 m 100 YR SS = 2.37 m

Scenario Y1-H:
0.10 m Subsidence + 1.30 m GSLR + 2.75 m HHWLT + 1.49 m 1976 Ground Hog Day
Storm Surge = 5.64 m
Scenarios Y3-L, Y3-M, & Y3-H
Scenario Y2-L is based on research completed by Rahmstorf and Vermeer (2009) that combines
expected sea level rise with glacial melt and ice sheet contributions and projects a GSLR upper
limit of 1.69 m. Added to the 1.69 m projection is regional subsidence of 0.10 m by 2100 for a
relative sea level rise of 1.79 m. Scenario Y2-M includes the predicted relative sea level rise of
1.79 m and a 100 Year Return Period Storm Surge Water Level of 0.97 m (100 YR SS) for a
future extreme water level of 2.76 m. Scenario Y2-H includes the predicted relative sea level rise
of 1.79 m, HHWLT of 2.75 m and the 1976 Ground Hog Day Storm Surge of 1.49 m for a future
extreme water level of 6.03m.

Scenario Y3-L:
0.10 m Subsidence + 1.69 m GSLR = 1.79 m

Scenario Y3-M:
0.10 m Subsidence + 1.69 m GSLR + 0.97 m 100 YR SS = 2.76 m

Scenario Y3-H:
0.10 m Subsidence + 1.69 m GSLR + 2.75 m HHWLT + 1.49 m 1976 Ground Hog Day
Storm Surge = 6.03 m
22
Figure B2. Yarmouth 100 Year Sea Level Rise & Extreme Water Level Scenarios (in meters
CGVD28).
23
24