RAC PAPER
Shoreline Protection
May 2011
Document Version 2 Final
Client:
Province of PEI
Prepared by:
M. Davies, Ph.D., P.Eng.
Coldwater Consulting Ltd.
5510 Canotek Rd., Suite 203,
Ottawa, Canada
K1J 9J4
Tel: 613 747-2544
www.coldwater-consulting.com
Shore Protection
Climate Change Adaptation
Contents
1
Introduction ...............................................................................................................................1
2
Coastal Hazards ..........................................................................................................................1
3
PROCESSES .................................................................................................................................3
3.1
Climate Change................................................................................................................................................................5
3.2
Sea level change ..............................................................................................................................................................6
3.3
Storminess..........................................................................................................................................................................6
3.4
Erosion.................................................................................................................................................................................7
3.5
Coastal Flooding .............................................................................................................................................................8
3.6
Coastal Squeeze ...............................................................................................................................................................9
4
Options .................................................................................................................................... 10
5
Protection ................................................................................................................................ 10
5.1
Hard protection and ongoing shoreline retreat ........................................................................................... 11
5.2
Soft protection .............................................................................................................................................................. 12
5.3
Hybrid techniques ....................................................................................................................................................... 13
5.4
Regional Sediment Management ......................................................................................................................... 14
5.5
Coastal Resilience ........................................................................................................................................................ 14
6
Challenges ................................................................................................................................ 15
6.1.1
The seawalls of Northwest Arm, Halifax, NS ................................................................................. 15
6.1.2
The Cow Bay Causeway, Cole Harbour, NS .................................................................................... 16
6.1.3
Crowbush Golf Course, Lakeside, PEI ............................................................................................... 17
6.1.4
Panmure Island causeway, PEI ........................................................................................................... 18
6.1.5
Salt Marsh Trail, Cole Harbour, NS .................................................................................................... 19
7
What to do? ............................................................................................................................. 20
7.1
Data ................................................................................................................................................................................... 20
7.2
Research........................................................................................................................................................................... 21
7.3
Planning ........................................................................................................................................................................... 21
7.4
Public Involvement ..................................................................................................................................................... 21
7.5
Implementation of Best Practices ........................................................................................................................ 21
8
Current Activities / Links ........................................................................................................... 22
9
Bibliography ............................................................................................................................. 23
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Shore Protection
Climate Change Adaptation
1 Introduction
Canada’s Maritime Provinces are developing adaptation strategies for dealing with the effects of climate
change. A key requirement of this work is developing an understanding of the effects of climate change
on coastal areas. This includes the response of shorelines, wetlands and estuaries to changing water
levels and storm conditions, as well as the effects that climate change will have on coastal infrastructure
and the communities that live on or near the coast.
Over the past century, much of the Maritimes have observed a 30cm increase in relative sea level.
Climate change is expected to at least double this rate in the coming century. Coastal erosion increases
dramatically with sea level rise. The past 100 years has seen the elimination of the safety margin (the
safe set-back distance) that many Maritime communities and their infrastructure originally had. To
weather the next 100 years a new and different approach will be required. Difficult decisions will have
to be made: In some instances, the natural processes of erosion will have to be allowed and retreat from
the shoreline will be the only option. In other instances, the societal costs of retreat will be too large and
a defence strategy will be required.
Defending the shoreline does not simply mean a hardened, armoured shore. Development regulations,
sand management, dune restoration and beach nourishment are key elements in ensuring that the
natural beauty and touristic value of the shore is retained. This paper examines climate change
adaptation as it applies to shore protection and coastal hazards.
2 Coastal Hazards
The power of the sea is indisputable. Recent events such as the Japanese tsunami, Hurricane Katrina,
Hurricane Juan, and Hurricane Igor have reinforced this. The coast is continuously shaped and defined
by the actions of tides, storm waves, and extreme water level events such as storm surges and tsunamis.
In the absence of human development, the effect of these events on the shore is simply part of the
natural processes by which our shores and the coastal environment respond to the forces of nature. It is
when human development occurs in the coastal zone that these natural processes lead to problems.
Mankind is drawn to the sea for both aesthetic and practical reasons. People want to live near the water
for the vistas, the air, the shoreline. Communities, businesses and industry value the waterfont for all
that it can provide: Access to docks and shipping, and to process water. Economies built on the
resources that coastal waters offer (fishing, oil and gas, aquaculture, tourism) result in the development
of communities along the coast.
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The challenges faced in living near the coast include: coastal flooding, erosion, sedimentation, and storm
damage to infrastructure. From a planning and engineering perspective, these challenges are referred to
as ‘coastal hazards’.
The presence of communities, developments and industry in the coastal zone has led to the construction
of protection works. Often termed ‘coastal defences’, these works include infilling, re-shaping and
armouring of the shoreline in order to provide protection against coastal hazards. In a sense,
development is the enabler for coastal protection: When erosion occurs along undeveloped shorelines,
the cost of the shore protection often exceeds the value of land lost – shore protection is not
economically viable. With development, the resulting increase in land value and the value of the
infrastructure justify and, in some cases, necessitate, the expense of shore protection.
Broadly speaking, coastal development is driven by an
economic need or desire to establish facilities or dwellings
near the coast. The forces of nature along the coast push
back. Building too far from the coast dilutes the benefits –
communities and industry don’t establish themselves
kilometres away from water’s edge but as close as
practical. How close? In one sense, the severity of the
coastal climate defines how close – It is often simply
impractical to build expensive, durable structures right at
the water’s edge on an exposed coast. Sheltered areas are
naturally preferred. Hence coastal development in the
Maritimes, for example, has historically been concentrated
around select areas – those stretches of the coast that
provide shelter from storms, deep water access for boats
and ships, and relatively flat, developable land. Estuaries,
fjords and deep, natural bays have therefore been the
logical starting points for coastal development.
The edge of the sea is a strange and
beautiful place. All through the long
history of Earth it has been an area of
unrest where waves have broken
heavily against the land, where the
tides have pressed forward over the
continents, receded, and then
returned. For no two successive days is
the shore line precisely the same. Not
only do the tides advance and retreat
in their eternal rhythms, but the level
of the sea itself is never at rest… Today
a little more land may belong to the
sea, tomorrow a little less. Always the
edge of the sea remains an elusive and
indefinable boundary.” From the
opening of The Edge of the Sea by
Rachel L. Carson
In Canada, coastal development started as early as the
1700s; defining the fabric of our communities. As such our
coastal communities have tremendous historic and
societal value. Over time infrastructure has grown and
anchored itself against the waterfront. In erosional areas (e.g. Souris, PEI), what were originally
reasonable setbacks from the water’s edge have been eroded, leaving many communities with difficult
decisions – maintain or abandon? Protect or retreat? These questions apply to key infrastructure such
as roads, bridges, and water works, not just residential properties.
The scale of change that Maritime shorelines such as shores of Prince Edward Island have experienced in
the past few decades is profound. Both PEI and New Brunswick have experienced the dramatic losses to
the dune systems of their shores (e.g. Brackley Beach and Buctouche). Increased vulnerability to storm
surges and the related flooding and erosion damage (e.g. the winter storms of 2001/02 and more
recently December 2010), and ongoing bluff erosion endangering homes and infrastructure are
indicative of a coast that is under stress. To develop a proper adaptive management strategy for living
with the coast and for responding to the effects of climate change, a strong understanding of coastal
processes is needed.
Within the context of climate change – which in coastal terms results in changing ice cover, increasing
water levels and increasing storminess – the term ‘adaptation’ is frequently used. The
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Climate Change Adaptation
Intergovernmental Panel on Climate Change (IPCC) defines adaptation as the "adjustment in natural or
human systems in response to actual or expected climatic stimuli or their effects, which moderates
harm or exploits beneficial opportunities" (IPCC, 2007). As described in Burton et al (2006) adaptation
can be either proactive or reactive. This distinction is in part based on the stimulus behind the
adaptation: Is it in reaction to observed climate change; or is it in anticipation of future climate change?
It can also be distinguished based on the form of the action: Proactive if the actions aim to reduce future
risks, reactive if they alleviate impacts once they have occurred.
In the context of this paper, we will focus on proactive adaptation measures that can moderate the risks
of future climate change. Elements of which include:



Integrating climate change into policy and planning with respect to coastal zone management,
Adopting strategies to moderate harm caused by coastal hazards (retreat, defend…), and
Developing and adopting standards and codes of practice that allow planners, engineers and
architects to ensure that our built environment is capable of withstanding increasingly severe
coastal hazards.
Figure 1 Eroding bluffs at Souris, PEI (photo credit: M. Davies)
3 PROCESSES
Some of the physical processes of concern along the coast are as follows:
Erosion – Existing erosion problems around the Maritimes are likely to worsen under climate change the first step to developing appropriate responses is understanding of the relationships between erosion
processes, rising sea levels and changing storm conditions.
Coastal flooding due to rising sea levels and storm surge – mapping of the extent of potential inundation
under various combinations of sea level rise and storms is key to developing infrastructure, developing
appropriate planning policies and to building community awareness.
Salt marsh migration – as sea levels rise, salt marshes need to migrate inshore in order to survive –
understanding the location and extent of existing salt marshes and the factors influencing their potential
retreat is key to developing appropriate adaptation measures.
The mechanisms that affect these processes are:


Waves
Currents (due to tides, river flow, wind-driven currents, surges and ocean circulation)
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
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Water levels (including tides, surges, seiches and relative sea level rise)
Ice cover
Sediment budgets
Waves, river flows and tidal currents are generally the main driving forces for coastal erosion. Ice and
wave action are jointly the two largest forces to be reckoned with in the design of coastal structures.
Water levels and wave action are the controlling factors for coastal flooding. Sediment budgets affect all
of these mechanisms in a more indirect manner: The physical condition of the shore has an enormous
influence on the effects of a given wave, water level or ice condition. For example, the presence of a
wide sand beach provides a buffer to keep wave action away from coastal properties. It can encourage
the development of shore-fast ice thereby protecting infrastructure from ice forces. It can cover and
protect the toe of eroding bluffs to limit bank erosion. It is the sediment budget; the balance of supply
and removal of sediments from the shore – that controls the health of the beach.
The coastal enigma: Of these mechanisms, water levels have an all-pervasive influence. In open waters
wave conditions are controlled by the wind speed, direction, duration and fetch. On the Atlantic coast
wave heights of 10m or more commonly occur during storms. At the coast, waves start to break when
they reach a depth equal to twice their height. Inshore of the surf zone, wave heights are limited to
roughly ½ the water depth. Out in deep water a 30cm increase in water levels has a relatively small
influence on a 10m high storm wave. At the shore, however, it is a different matter altogether. A typical
shore protection scheme, for example, might be built at or above the ordinary high water mark. Day-today waves won’t reach such a structure but severe storms (and their associated storm surge) will,
bringing breaking waves with them. These waves increase in size in direct proportion to the amount of
sea level rise.
Figure 2 The road at Queensland Beach after Tropical Storm Noel
http://gsc.nrcan.gc.ca/coast/storms/noel/images/impact10.jpg
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Figure 3 Storm surge from Hurricane Juan (2003) washed rail cars into Halifax Harbour. Photo: Roger Percy and
Andre Laflamme http://www.ec.gc.ca/ouragans-hurricanes
3.1 Climate Change
Climate change poses the following challenges for the coast and for coastal protection:




Increasing water levels: While relative sea levels have risen roughly 30cm over the past century,
the consensus of climate change experts is that relative sea level rise will be as much as 60 to
120cm over the coming century.
Changing storminess. While some of the science is still under debate, there is growing evidence
that climate change will result in changes in storm patterns with a real risk of increased storm
frequency and severity.
Changing winters. Warmer temperatures mean less winter ice. Shorelines that are generally
protected from wave action by shore-fast ice over the winter months will become exposed to
more winter wave action due to reductions in ice cover.
In the far north, warmer weather also means the melting of permafrost resulting in dramatic
increases in shoreline erosion.
The effects of climate change are cumulative: Many of our coastal areas are already under stress,
already suffering from coastal erosion, flooding and development pressures. Climate change threatens
to intensify these concerns.
While there continues to be debate in the science and engineering communities about the actual
magnitude and timing of predicted climatic changes, one defining characteristic of the problem is clear:
We are moving into a period of increased uncertainty – predicting future conditions on the basis of
historic observations is no longer sufficient. Regardless of the final numbers used in our analyses, we
have to adapt our design and decision-making processes to this climate of increased uncertainty.
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3.2 Sea level change
Since 2006, the federal government has undertaken several extensive assessments of the effects of
rising sea levels (e.g. Prince Edward Island (CCAF A041 Project Team, 2001), New Brunswick (Buctouche),
and Halifax, NS (Forbes, Manson, Charles, Thompson, & Taylor, 2009). These studies have been funded
by the Canadian Cimate Change Action Fund and were led by staff from Natural Resources Canada
(NRCAN) at the Atlantic Geoscience Centre in Dartmouth, NS.
As these studies show, shorelines throughout the Maritimes are experiencing long-term sea level rise
due to the combined effects of crustal subsidence and rising sea levels. There is a general consensus in
the scientific community that this rate of sea level rise will increase in coming years due to the effects of
climate change and global warming. Figure 4 shows long-term records of mean sea level at
Charlottetown, showing how sea level has risen steadily over the past century at an average rate of
3.2mm/year or 0.32m (1 foot) per century (CCAF A041 Project Team, 2001).
Figure 4 Long-term sea level rise at Charlottetown (Forbes et al, 2004).
The Intergovernmental Panel on Climate Change (IPCC) (Intergovernmental Panel on Climate Change,
2007) provides a range of predicted sea level rise over the next century. Amidst considerable
uncertainty, future rates of sea level rise in much of the Maritimes are estimated to be between 0.6 and
0.76m/century (including both the effects of sea level rise and crustal subsidence).
3.3 Storminess
Changing climate means changing weather patterns, and with that comes the potential for changes in
the intensity of storms to which a shoreline is exposed. Changes in storm intensity have already been
clearly recognized in terms of rainfall events with climate change bringing more frequent, more intense
rainstorms. It appears that changes are occurring in our offshore wave climate as well. The following
figure shows analysis of storm conditions offshore of Halifax. Plotting the annual maximum significant
wave height measured each year from 1970 to 2010 shows a trend of increasing wave height. This could
partially reflect improvements in wave measurement technology but this data does support the
common perception that severe storms are becoming more frequent and more intense offshore of
Halifax.
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Annual maximum wave conditions
(combined MEDS037, C44258 dataset)
12
10
Hs (m)
8
6
4
y = 0.0582x + 5.9306
R² = 0.2328
2
2008
2006
2004
2002
2000
1998
1996
1994
1992
1990
1988
1986
1984
1982
1980
1978
1976
1974
1972
1970
0
Figure 5 Annual maximum wave conditions offshore of Halifax. (Data source: ISDM, Fisheries & Oceans Canada,
analysis by M. Davies)
3.4 Erosion
Shorelines respond gradually to the water level and wave climate to which they are exposed. This
happens through erosion of the land within a vertical band extending from the highest vertical elevation
that the action of waves, tides and storm surges can reach down to the lowest elevation at which wave
action can move sediments.
For sandy shores, the interaction of waves and sediments results in an equilibrium profile. The beach
profile adjusts in response to the wave action, reforming until it obtains a shape that results in a near
uniform rate of dissipation of wave energy (Wang, 2005). Out near the wave breaker line, the large wave
heights flatten out the beach slope and beach slope increases gradually as you move shoreward and as
wave heights decrease. The result is a concave-upward beach shape where the local slope generally
steepens from offshore to inshore.
This equilibrium is a dynamic condition, beaches are continually adjusting to the ever-changing wave
conditions to which they are exposed. Steep winter storm waves tend to pull material offshore to the
break point where bars form, steepening the beach face. Milder summer conditions tend to push
material onshore resulting in wider, milder beach slopes.
For a beach in equilibrium, the forces acting to move sand onshore (wave-generated currents) are
balanced against the offshore forces of gravity and offshore flows such as undertows. Generally,
beaches that are in equilibrium have the following characteristics:




They are concave upward in shape
Slopes are milder when they are composed of finer sediments
Slopes tend to be flatter for steeper waves
Sediments tend to sort such that the finest materials are found offshore and the coarsest
materials are onshore
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An increase in water level will disrupt this equilibrium. Due to the shape of the beach profile, the depth
at a particular distance from the new shoreline will now be greater than it was before the increased
water level. If the equilibrium profile had been a straight line, then the increase in water level would
not change the depth at a distance from the new shoreline and there would be no disequilibrium. As
shown in Figure 6, without the introduction of additional sediment into the system, the only way in
which the profile can re-attain equilibrium is to recede, thus providing sediment to fill the bottom to a
depth consistent with the equilibrium profile and the new (elevated) water level (CEM, 2002). This
widely accepted conceptual model for the response of the beach profile to changing water levels is
commonly referred to as the Bruun rule (Bruun, 1962), (Bruun, 1988). A key element of this rule is that
the rate of shoreline recession is proportional to both the rise in sea level and the local beach slope. This
slope dependency means that, for typical sandy shores, the shoreline retreat is some 50-200 times the
sea level rise (this ratio is highest for mild beach slopes and high energy wave conditions) (CEM, 2002)
Figure 6 Beach profile response to sea level rise according to the Bruun rule (CEM, 2002)
Regardless of the uncertainty in trends for future sea levels, much of the infrastructure of the Maritimes
including roads and lighthouses were positioned some 100 years ago. As was shown in Figure 4, sea
levels have risen about 0.3 m since then. Simple application of the Bruun Rule would account for some
15m of recession due to this sea level rise alone. It should be emphasized here that the actual
prediction of shoreline recession is much more complex than the simple Bruun rule. The balance of
supply and movement of sediments, the effects of wave transformation, wave-generated currents and
their interaction with the tides make the prediction of coastal processes remarkably complex, as is
evidenced by the complexity of coastal shorelines themselves, with bars, bays, estuaries, and a
seemingly infinite variety of coastal landforms. The Bruun rule does, however, provide a conceptual
framework to assist us in understanding the response of the beach profile to sea level rise.
3.5 Coastal Flooding
For coastal flooding, the effect of sea level rise is similarly compounded. Coastal flooding is largely
driven by the processes of wave runup and overtopping. Water levels at the shore reduce the freeboard
of the land or shore protection (measured as the vertical difference from the still water level to the top
of the structure/land). At the same time, the wave height is increased by virtue of the water being
deeper.
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Figure 7 Sea level rise increases the frequency of occurrence of extreme water levels
3.6 Coastal Squeeze
Sea level rise and shoreline hardening on the inland side (revetment, roads, communities, etc.) confine
the natural habitats (both in estuaries and in sheltered coasts). This can prevent the natural landward
migration of habitat as sea levels rise. This phenomenon is commonly referred to as ‘coastal squeeze’.
Typically a rising relative sea level results in a landward migration of estuaries and salt marshes.
However, this migration is blocked when the landward boundaries have been hardened and fixed
through development, resulting in a squeeze that reduces the space available for estuarine and marsh
lands.
Figure 8 Illustration of the process of 'Coastal squeeze' (source: Linham & Nicholls, 2010)
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4 Options
At its simplest, the response to coastal hazards is to make a decision to either defend the shoreline or to
retreat and abandon the infrastructure. The altruistic viewpoint is that abandonment and renaturalization of the coast is the only ‘correct’ approach. A more pragmatic approach is that there
always will be coastal infrastructure – whether as an inherited legacy or as part of new development.
Here the role of coastal zone management comes into play. Society needs to make informed, strategic
decisions about how to live with our coasts. Rather than simply viewing the problem as one of protect
or abandon, the approach to the problem can be considered as a broader range of choices to address
coastal hazards (DEFRA 2008):
1. Hold the Line – implement or maintain shore protection works along the existing
waterfront/coastline to preserve existing infrastructure and development.
2. Advance the Line – undertake bold initiatives to move the first line of defence further offshore,
creating sheltered waters that can reduce coastal hazards while creating recreational and
environmental benefits.
3. Managed Realignment – make strategic decisions about where and how to retreat from the
shoreline. Regulating building development, implementing coastal flood zones and erosion
hazard delineation are used here. Coastal setback regulations are used to define retreat
distances.
4. No Active Intervention – Make a conscious decision to not intervene along the coast.
The process of implementing an adaptation strategy is not a once-off task. It is an ongoing process
involving evaluation and prioritization of hazards and opportunities. Ongoing monitoring and analysis
are essential to this process.
In a review of US coastal adaptation strategies, Titus et al (2008) propose that, in the short term, retreat
is more socially disruptive than protection; however, in the long term, protection may turn out to be
more disruptive than retreat. But this is highly dependent on the nature of the protection scheme.
Issues of coastal erosion and sedimentation relate to the overall flows of sediment and to land
management issues. It is the net balance of sediment inflows and outflows that defines the generally
erosional/depositional characteristics of a shoreline. Land use, farming practices, and development
along the shorelines of rivers and estuaries can greatly reduce the supply of sediment to the coast. The
erosion of a shoreline can be as much due to local land use practices as it can be to storm action or sea
levels.
Poorly designed and poorly built shore protection can offer only a short-term defence against erosion
and inundation and can, in some instances, actually worsen conditions. If an area is experiencing longterm erosional pressures, abandonment and retreat may be preferable to shoddy shore protection
works. Titus et al state: “Short-term shore protection projects can impair the flexibility to later adopt a
retreat strategy. By contrast, short-term retreat does not significantly impair the ability to later erect
shore protection structures inland from the present shore.”
5 Protection
Coastal defences and shore protection can take on many forms ranging from policy initiatives (setbacks,
building code requirements, through to coastal structures). Adaptation will require using a wide range of
technologies each suited to a particular situation. Limnoff and Nicholls (2010) provide the following
chart that summarizes some of the available adaptation technologies and showing where those
measures are complementary, and where they are competing.
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Figure 9 A portfolio of coastal adaptation technologies (source: Linham & Nicholls, 2010).
The following section describes some of the structural approaches for protection against coastal
hazards.
5.1 Hard protection and ongoing shoreline retreat
Hard protection – the armouring of the shoreline – is what comes to mind when many people think of
coastal protection. The basic concepts of this type of sea defense are relatively simple. Replace or cover
the eroding, low-lying shoreline with a man-made structure that is both large enough and strong enough
to provide protection against storm damage and flooding.
Hard protection can take the following forms:


Shoreline armouring: Seawalls or bulkheads built of armour stone, concrete, or piling.
Flood protection works: Dikes, tide gates, storm surge barriers to prevent flood waters from
entering reaches of an estuary.
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Super-elevation: Raising the elevation of flood prone lands to allow development, or raising the
elevation of the development itself to be out of harm’s way.
Examples of hard protection in the Maritimes include the seawalls at Northwest Arm in Halifax, the
causeway at Cow Bay Road, and the numerous seawalls that surround urban coastal communities.
Figure 10 Residential shore protection along the west shore of Cape Breton. Gabion baskets (foreground left),
concrete retaining wall (centre) and armour-stone revetment (far distance).
Note that the term ‘shoreline protection’ is often itself a misnomer. When an eroded natural shoreline is
replaced with armour stone the shoreline has not been protected. The shoreline has been replaced and
the shoreline position has been protected. True shoreline protection is more likely to be accomplished
through the use of hybrid and soft protection techniques as described in the following.
5.2 Soft protection
In many ways, the best protection that can be provided for an eroding shoreline is to build a beach in
front of it or to use some other measure to reduce the damaging effects of storms. Often, this takes the
form of re-establishing a beach that used to exist, but it can also involve building a beach where none
existed before.
Soft protection typically involves one or more measures that lessen the damaging effects of storms
while improving nearshore sediment stability or abundance.
Beach nourishment is a key component of many soft protection initiatives. In the southern US, beach
nourishment is often undertaken by itself. Suitable sand sources are located either offshore on on land
and sediments are dredged or trucked in place to re-establish the beach. The effectiveness and longevity
of such measures is largely controlled by the amount of sediment introduced and by the sequence of
storms that follow.
Re-establishment of dunes and offshore reefs can also provide increased protection against coastal
hazards without placing structures in the littoral zone.
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For dune systems, plantings, sand fences and traffic control are proven measures to help establish and
maintain a healthy dune system. The dunes can then offer a sacrificial protection against storm events.
5.3 Hybrid techniques
Control structures can act as artificial headlands to form embayments that maintain beach sediments.
These can be constructed in various ways such as groynes, detached offshore breakwaters, or artificial
reefs.
If there is a sufficient supply of sediments to the shoreline, construction of artificial headlands or other
control structures can, by itself, be an effective defence against coastal hazards. Combining beach
nourishment with control structures often proves to be a more reliable and cost-effective means of soft
protection.
Figure 11 Hybrid protection at Basin Head, PEI. Buried revetment covered with sand dune and marram grass.
Figure 12 Typical beach nourishment operation - a dredge pumps sand onshore while bulldozers distribute the
new sand. (Photo courtesy USACE)
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Figure 13 Examples of hybrid shore protection from Portugal using beach fill conained by artificial headlands
and offshore detached breakwaters (Coastal Actions, Spain, 1988).
5.4 Regional Sediment Management
When it comes to protecting shorelines, there are many lessons to be learned from around the world
and there are new and innovative strategies being developed and implemented. A growing
understanding is being developed of the importance of regional sand management. In much the same
way that the study of water resources takes the entire watershed into consideration, regional sand
management looks at all the factors that influence the movement of sand onto and off the beach. This
includes erosion from upland sources, sediment transport through streams and rivers to estuaries, the
migration of sand along the shore and its onshore-offshore movement. Precipitation, runoff, freezethaw cycles, bluff erosion, sediment transport and the actions of tides and waves are the driving
processes behind regional sediment management. Climate change and sea level rise have a pervasive
influence on these processes.
5.5 Coastal Resilience
In developing strategies for shoreline development and management issues, “coastal resilience” is a
useful concept that is gaining acceptance (e.g. Beatley, 2009, Nature Conservancy, 2009, NOAA, 2010,
Kamphuis, 2009). Resilience is the capacity of a system to absorb changes while still retaining its basic
structure and function. Applied to coastal areas, building coastal resilience requires a broad perspective
– it affects land use planning, infrastructure, and the socio-economic fabric of a community. The
underlying themes are flexibility, adaptability and durability – all of which are needed to create coastal
communities that are well-suited to adapting to, and surviving, the various hazards to which the coast is
susceptible. Building coastal resilience means:

Building resilient infrastructure – infrastructure that does not collapse under extreme loading
events but continues to provide partial protection and can be repaired,

Building governmental resources to support coastal communities – this includes research and
development, advance warning systems, regulations, zoning and permitting, communication
and transportation networks, utilities and emergency response systems,
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Developing a resilient socio-economic system – this involves open communication with
communities and stakeholders to understand the risks presented by coastal hazards and
enlisting their cooperation.
6 Challenges
The challenges faced when implementing a coastal management strategy are multi-faceted. Decisions
have to be made about which shorelines require protection and which don’t. For those that require
protection, what level of protection can be environmentally, socially or economically justified? For areas
to be left unprotected, how should this be handled? Should existing infrastructure be disassembled?
How should it be relocated to ensure that similar problems won’t occur in the future? In evaluating the
present and future conditions for coastal developments, one must consider the behaviour of the entire
coastal system, not just a selected property or structure. This includes considering changes to sediment
budgets, estuary constrictions, shoreline hardening, dredging and disposal practices, etc.
Coastal structures and shore protection systems are susceptible to failure through one or more of the
following processes:
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Overtopping – high waves and water levels carry excessive flows over the structure damaging
the crest of the structure and landward facilities,
Structural damage – the structure itself breaks or unravels from storm loading,
Flanking – excessive erosion at either end of the structure triggers instability,
Scour – a erosion at the base of the structure leading to structural failure, or
Geotechnical instability – failure of the structure through sliding, overturning or other
geotechnical failures.
To illustrate the challenges inherent in working along the shore, and to illustrate the various factors that
need to be considered in the design of coastal structures, we will now examine some successes and
failures along Maritime coasts.
6.1.1 The seawalls of Northwest Arm, Halifax, NS
The stone walls lining Northwest Arm at the Dingle, and Horseshoe Island Park in Halifax have required
frequent repairs over the past 10 years following Hurricane Juan, Tropical Storm Noel and numerous
other storm events. Studies were conducted to determine the wave and water level conditions to which
these seawalls are exposed, the present condition of the seawalls and the future outlook for the walls
under conditions of climate change.
The combined effects of storm surge and waves were shown to cause frequent overtopping and
structural damage to the walls. Some of the original walls at Horseshoe Island are now almost 100 years
old: Built when sea levels were 30cm lower than they are today. Clearly, as sea levels continue to rise
these walls will need to be rebuilt to a higher elevation to afford the same level of protection that they
were originally designed to provide. At the same time the walls need to be made stronger to withstand
future wave conditions. The key questions being: How much higher? How much stronger? A statisticallybased optimization process was developed that, for a given sea level rise scenario, computes the capital
and maintenance costs for a given wall design over the next 50 years. Using climate change scenarios
developed by the International Panel of Climate Change and adapted to the Halifax region by scientists
at NRCan in Dartmouth, we were able to develop optimized wall designs that incorporate climate
change scenarios into the design process. This is an example of proactive adaptation; the effects of
future climate change have been anticipated in the design process and the design of the infrastructure
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has been adapted accordingly. Detailed design work for the first section of wall repairs (at Sir Sanford
Fleming Park) is presently underway and construction will be completed in 2011.
Figure 15 Seawall damage, Northwest Arm, Halifax.
Figure 14 Typical high tide conditions, Northwest
Arm, Halifax.
6.1.2 The Cow Bay Causeway, Cole Harbour, NS
Heading east out of Cole Harbour toward Osborne Head, the Cow Bay Road crosses a 500 m long
causeway built over a cobble barrier beach. Protected by an armour stone revetment, this causeway has
become a maintenance problem over the past decade. Storm waves frequently overwash the road
carrying with them stones and debris. The asphalt road surface has been ripped up by waves on several
occasions and the frequency of storm damage has been increasing. Two factors are at play here: Rising
relative sea levels have reduced the causeway’s freeboard, increasing the frequency and severity of
damage; Storm conditions directly offshore have been intensifying over the past decade bringing larger
waves to shore.
Analysis was undertaken to evaluate the relative merits of building a more effective armour stone
barrier or raising the roadbed. Using a similar approach to that used at Northwest Arm, an optimized
design has been developed for this causeway that minimizes total costs (combined capital and
maintenance costs) over the next 30 years. In the long term it is likely that the causeway will eventually
have to be abandoned and the road routed further inland. The analysis showed that re-building the
protective barrier to withstand higher water levels and bigger waves was, however, the most costeffective approach for the next 30 years.
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Figure 16 Cow Bay Causeway after Noel (http://gsc.nrcan.gc.ca/coast/storms/noel)
6.1.3 Crowbush Golf Course, Lakeside, PEI
The north shore of Prince Edward Island has taken a severe hammering over the past twenty years. This
is evidenced by the disappearance of the dunes at Brackley Beach and widespread erosion. The defining
characteristic of the golf course at Crowbush Cove is its ‘links’ setting. A style of golf course popular in
Scotland, the focus of a links course is the coast: the dunes, the vistas and the winds. Severe winter
storms in 2001 washed away a significant portion of dune that protected two brackish ponds at the 6 th
and 8th tees. Storm waves, carrying with them sandstone cobble, devastated the fairways and tee boxes.
The layout of the course and bounding properties precluded the option of retreat. A coastal protection
scheme was needed that would protect course infrastructure during severe events but not detract from
the links character of the course. The dunes in front of the two ponds were rebuilt using a low-lying
armourstone core which was buried in a reconstructed sand dune. Following construction, planting the
dune with marram grass helped stabilize the dune and ensured a natural appearance. The exposed
north shore of PEI is a large-scale erosional system. Nothing about the dune restoration changes the
overall erosional nature of this entire shoreline. Severe storms such as those of December 2010 can
wash away the dune, but the underlying armoustone remains in place to protect landward
infrastructure. Maintenance is required from time to time to replenish the dune and there will
eventually come a time when it is no longer feasible to hold this position. But in the meantime, a
valuable tourism resource continues to serve the community.
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Figure 17 Marram grass established on re-built dune (over buried revetment) at Crowbush GC.
Figure 18 Fairway view with protection works hidden from view, Crowbush GC 4 years after construction.
6.1.4 Panmure Island causeway, PEI
The causeway to Panmure Island on PEI’s east coast is built over a sand spit. This spit is a natural
formation built by sand moving along the shore from Panmure Island Provincial Park northward to
Panmure Island and beyond where it deposits in a large shoal at the entrance to Georgetown Harbour.
Over the years the eastern shore of Panmure Island has eroded tens of metres. The iconic Panmure
Lighthouse has been relocated landward several times as part of a coastal retreat strategy. The island
forms a headland that controls the position of the Panmure Spit. As the headland erodes it becomes less
effective at intercepting the northward transport of sand. More sand ends up in the Georgetown
Harbour shoal and the Panmure Spit becomes narrower, resulting in the loss of sand dunes and the
erosion of the roadbed. To protect this important road link, a buried revetment was placed along the
edge of the road. Again sand was built up over top and planted with marram grass to encourage dune
re-stabilization. The protection works have been successful and the road has remained open through
increasingly frequent and severe winter storms. The second phase of this project is to restore the beach
in front of this protection. This is contingent upon the beach’s sediment budget – the balance of sand
entering and leaving this coastal system. While there haven’t been substantial changes to the supply of
sediment to this beach, the erosion of the headland at Panmure Island has resulted in an increase in the
amount of sand leaving the beach. The result being that the net supply of sediment to the beach has
diminished, leading to increased erosion. Works to re-establish the headland at Panmure Island using an
armour stone spur and reef construction are under consideration.
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Figure 19 Panmure causeway May 2009 showing some armour stone exposure and erosion of the re-built dune.
6.1.5 Salt Marsh Trail, Cole Harbour, NS
The Cole Harbour estuary just east of Halifax allows a fascinating examination of human influence on a
tidal estuary. Prior to the 1700s Cole Harbour was an unobstructed estuary. The arrival of the Acadians
around 1750 brought with it the diking of the upper marshlands of the estuary to farm marsh hay. As
documented in M. Kuhn’s “A Tale of Two Dikes”, the late 19th century saw more ambitious efforts to
harness the marshlands for agriculture with construction of a dike near the mouth of the estuary. Heavy
flapper gates would close during ebb tide, leaving much of the marsh dry for pasture and haying. Around
1912, the Musquodoboit railway built a causeway across the marshland of the upper estuary, effectively
bisecting it. When the dike was dynamited in 1917 in efforts to restore trout and salmon runs to the
estuary, the salt marshes re-flooded but remained obstructed by the presence of the rail causeway
which restricted circulation in the upper estuary through four small bridges. The lingering obstruction at
the mouth of the estuary caused by the remains of the dike resulted in the sea has carving a new
entrance to the estuary further to the east. The Trans-Canada trail now follows the path of the
abandoned railbed providing a popular recreational resource.
The causeway is now a century old, and sea levels are some 30cm higher now than when the causeway
was first built. Maintenance of the causeway is on ongoing job that’s getting more challenging as the
years go by. Regularly damaged by high water levels and storm waves, the causeway needs to be rebuilt
at a higher elevation if it’s going to survive. Three alternatives were examined in our analysis:
1. Maintain the present trail alignment by rebuilding in a way that will minimize ongoing
maintenance costs.
2. Take an adaptive management approach that maintains the trail while using culverts and
innovative design features such as fords to restore natural circulation patterns and improve
water quality and aquatic habitat.
3. Start the planning process to abandon the causeway in favour of a new land route to the north.
As with so many coastal issues, the decision-making process can be more complicated than the technical
analysis. The decision to make a fundamental change to the way a coastal feature/development is used
is more than simple economics; it is a societal one that must consider historical values and must respect
the community effort that has gone into maintaining the status quo. One of the biggest challenges
facing coastal planners and policy makers in coming years is how to be proactive in adaptation to
climate change. It is in some ways easier to make a decision not to rebuild a structure after a storm
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destroys it, than to decide on a course of action based on evolving climatic conditions – even though in
many cases the best decisions may arise from the latter.
Figure 20 1966 air photo of the Cole Harbour estuary
Figure 21 Flooding and erosion of Salt Marsh Trail,
January 2010. Photo credit: Cole Harbour Parks and
Trails Association
7 What to do?
Adapting to climate change along our coasts requires an understanding of our coasts and how they
respond to the action of tides, waves and water levels. We need improved detail in defining future
climate scenarios. We need practical research into the design of coastal defences. We need to adapt our
policies and planning methods to ensure that the effects of climate change are incorporated in decisionmaking. We need public involvement in the development and implementation of new strategies. We
need to develop and implement new and higher standards for both decision-making and action in the
coastal zone.

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Data
Research
Planning
Public involvement
Implementation of Best Practices
7.1 Data
To properly understand the path ahead we need measurements of the past and present-day conditions.
A key element in this is the measurement of waves and water levels. At present there are only a handful
of permanent water level gauging stations operating in the Maritimes. The present mandate of Fisheries
and Oceans is to collect water level data for the purposes of navigation. The national permanent
gauging network is very sparse in the Maritimes. For example, there is just one permanent gauge in
Prince Edward Island (at Charlottetown). Interpretation of storm surge and extreme water levels along
the north, east and west shores of the island must rely on gauges located 100s of kilometres away.
While computer models and remote sensing data are of increasing use in interpreting and predicting
water levels, there is an underlying need for reliable, long-term measurements.
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Data on offshore wave conditions is even more sparse. Again, regional wave climate models and remote
sensing data are making great strides in improving our understanding of our nearshore waters but they
themselves depend upon wave measurements for calibration and validation.
7.2 Research
A significant effort has been (and continues to be) placed on understanding the science of climate
change. Comparatively little effort, however, has been spent to date on improving our understanding of
how to respond to climate change. One of the biggest challenges is our ability to predict the long-term
and large-scale response of shorelines to climate change; including the interactions between the natural
and built environments.
At INRS in Quebec City, a new flume is being built to allow very large scale evaluation of the effects of
waves and water levels on coastal infrastructure. Scientists and engineers will use this facility to conduct
basic and applied research into the processes of wave-structure interaction and coastal flooding. With a
cross-section of 5m x 5m and a length of 120m, this flume will be large enough to overcome many of the
scaling issues that plague existing facilities.
7.3 Planning
Planning is the key step in implementing a rational response to the coastal impacts of climate change.
Integrated coastal zone management initiatives have been underway in Canada for the past decade
under the Oceans Act. Originating from within Fisheries and Oceans Canada, this initiative has a focus on
marine resources (fisheries) and the factors that affect them. In other countries, the term integrated
coastal zone management is used to identify a strategic approach to planning coastal protection.
At the provincial level, several Maritime Provinces have recently released ‘state of the coast’ reports.
HRM has taken a lead role in integrating climate change issues into their planning processes. Coastal
hazards and the effects of climate change (notably relative sea level rise) are becoming an integral
element of their municipal planning processes.
These exciting developments are starting to provide a framework for adapting to the coastal
impacts of climate change.
7.4 Public Involvement
There is a high level of public awareness of climate change and the threat it poses for our coastal areas.
From the devastation of Hurricane Juan through to the coastal damage and flooding experienced during
last December’s winter storms, there is little doubt in the public’s mind that our coasts are vulnerable
and that the issue of climate change needs to be addressed. Planners and policy makers need to ensure
that public involvement is an integral aspect of developing an adaptation response to coastal climate
change.
7.5 Implementation of Best Practices
Moving forward, we need to ensure that government and the public are informed by the best available
research and data, and that best practices are developed and implemented to allow informed and
responsible management of our coastal regions.
The long-term goals for the Maritimes should be the development of integrated shoreline management
plans that will provide the technical and managerial framework, as well as the tools needed, for
implementing an adaptive response to the effects of climate change on the coastal zone. The success of
an integrated shoreline management plan stems from a focus on integration: covering not only the
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technical aspects of the plan but also the vital human factors involving the community that lives, works
and plays in our shore zones.
Public awareness of the critical state of our shorelines and of their vulnerability to climate changes is
remarkably high. The opportunity exists to use this planning process as a way of successfully connecting
with diverse stakeholders on significant issues and opportunities. The ISMP offers a vehicle to establish
close relationships with those who share an interest in the long-term management of our coasts. The
design of an effective stakeholder engagement process is the cornerstone for an ISMP that properly
identifies the issues and opportunities at hand. The process needs to be seen as evolutionary and longterm.
The development of this plan needs to be an inclusive process, one that spans governmental and
jurisdictional divides and one that gets everyone engaged in planning the future of our coasts.
The development and implementation of an informed policy for coastal management goes hand-in-hand
with the development of new ways to design, evaluate and build coastal protection works. New
approaches are needed that view coastal protection as an integral part of shoreline management: not
piecemeal armouring of individual properties. When a larger scale perspective is employed, it becomes
easier to adopt and integrate elements of hybrid and soft shore protection along with sediment budget
remediation to restore the shoreline rather than to just armour it.
One of the key challenges in implementing these ‘best
practices’ is cost. Generally speaking it takes more time,
more effort and more money to implement a
sustainable coastal protection scheme than it does to
build a simple revetment. Few of these ‘soft engineered’
responses can be expected to be built without a policy
framework in place that ensures that sustainability is a
built-in component of coastal works.
To paraphrase the late Prime Minister
MacKenzie-King: “Shore protection if necessary,
but not necessarily shore protection.”
8 Current Activities / Links
Looking beyond our borders there are some interesting initiatives being undertaken in the US, Europe
and elsewhere. The following list points to further reading on this subject.
Within Atlantic Canada:
Guide to Considering Climate Change in Environmental Assessment in Nova Scotia
Guide to Considering Climate Change in Project Development in Nova Scotia
Prince Edward Island and Climate Change: A Strategy for Reducing the Impacts of Global Warming
The State of Nova Scotia’s Coast Report: http://www.gov.ns.ca/coast/
Newfoundland and Labrador’s Climate Change Action Plan (2005) :
http://www.env.gov.nl.ca/env/climate_change/
Nationally:
NRCan e.g. http://gsc.nrcan.gc.ca/coast/storms
Environment Canada: http://www.ec.gc.ca/sc-cs/
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Internationally:
IPCC: Climate Change 2007: Working Group II: Impacts, Adaption and Vulnerability (www.ipcc.ch)
http://www.unesco.org/csi/
UNESCO: Sea Level Rise and Variability – A summary for policy makers:
http://unesdoc.unesco.org/images/0018/001893/189369e.pdf
US EPA Background Documents Supporting Climate Change Science Program Synthesis and Assessment
Product 4.1: Coastal Elevations and Sensitivity to Sea-Level Rise. Edited by James G. Titus and Elizabeth
M. Strange. 2008. Washington, D.C.: U.S. Environmental Protection Agency. EPA 430-R-07-004.
http://www.epa.gov/climatechange/effects/coastal/background.html
USACE Guidance and Policy for Sea Level Change Adaptation, Engineering Circular 1165-2-211 (2009)
Coastal zone management initiatives related to climate change adaptation can be found at NOAA’s
website: http://coastalmanagement.noaa.gov/climate/adaptation.html
In the UK, the Department of Environment, Food and Rural Affairs (DEFRA) has responsibility for
national responses to flooding and coastal erosion. http://ww2.defra.gov.uk/environment/flooding/
contains many links to relevant studies.
Finally, one of the most comprehensive assessments of the challenges faced in the coastal zone and of
the technologies available to address coastal erosion and flooding along is presented in a report
prepared for UNEP’s RISO centre and funded by the Global Environment Facility (GEF)
(Linham & Nicholls, 2010). Available online at:
http://tech-action.org/Guidebooks/TNAhandbook_CoastalErosionFlooding.pdf.
9 Bibliography
Bruun, P. (1962). Sea-level rise as a cause of shore erosion. Journal of Waterways and Harbour Division ,
88, 117-130.
Bruun, P. (1988). The Bruun rule of erosion by sea-level rise: A discussion of large-scale two- and threedimensional usages. Journal of Coastal Research , 4 (4), 627-648.
CCAF A041 Project Team. (2001). Coastal impacts of climate change and sea-level rise on Prince Edward
Island. Dartmouth, Nova Scotia: Climate Change Actoin Fund project CCAF A041.
CEM. (2002). Coastal Engineering Manual. US Army Corps of Engineer, Coastal and Hydraulics Lab.
CIRIA. (2007). The Rock Manual - The use of rock in hydraulic engineering (2nd ed). C683, London.
Coldwater. (2009). Point Pleasant Park Shoreline Restoration Study Technical Report. Ottawa: Coldwater
Consulting Ltd.
Direccion general de puertos y costas. (1988). Actuaciones en la costa / Coastal actions. Costa del Sol,
Malaga, Spain: MOPU; Servicio du publicidad.
FHWA. (2008). Highways in the Coastal Environment, Second Edition, FHWA NHI-07-096. U.S.
Department of Transportation Federal Highway Administration.
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Forbes, D., Manson, G., Charles, J., Thompson, K., & Taylor, R. (2009). Halifax Harbour Extreme Water
Levels in the Context of Climate Change: Scenarios for a 100-year Planning Horizon. Geological Survey of
Canada Open File 6346.
Halifax Regional Municipality. (2008). Point Pleasant Park Comprehensive Plan. NIP Paysage and Ekistics
Planning and Design.
Intergovernmental Panel on Climate Change. (2007). Climate Change 2007: Synthesis Report Summary
for Policymakers.
Kamphuis, J. (2000). Introduction to Coastal Engineering and Management. World Scientific.
Linham, M., & Nicholls, R. (2010). Technologies for Climate Change Adaptation: Coastal Erosion and
Flooding. Roskilde, Denmark: UNEP Riso Centre on Energy, Climate and Sustainable Development.
Pilarczyk, K. (1990). Coastal Protection. Rotterdam: Balkema Press.
Reis, M., Hedges, T., Williams, A., & Keating, K. (2007). Discussion: Specifying seawall crest levels using a
probabilistic method. Proc. of the Institution of Civil Engineers, Maritime Engineering 160, June 2007,
Issue MA2 , 87-90.
Rosen, P., & Vine, D. (1995). Evolution of seawall construction methods in Boston Harbor,
Massachusetts. Proc. Inst. Civil Engineers, Structs. & Bldg.s , 110, Aug., 239-249.
Swail, V. R., Cardone, V. J., Ferguson, M., D, G., Cox, E. T., Harris, E. L., et al. (2006). The MSC50 wind and
wave reanalysis. 9th International Wave Worskhop on Hindcasting and Forecasting, Sept. 25-29 2006.
Victoria, BC.
The SWAN Team. (2009). SWAN User Manual. Delft, NL: Delft University of Technology.
van der Meer, J. (1993). Conceptual design of rubble mound breakwaters. Delft, NL: Delft Hydraulics.
Wang, P. a. (2005). Beach profile equilibrium and patterns of wave decay and energy dissipation across
the surf zone elucidated in a large-scale laboratory experiment. Journal of Coastal Research , 21 (3), 522534.
About the author:
Mike Davies holds a Ph.D. in coastal engineering from Queen’s University and is President of Coldwater
Consulting Ltd., a Canadian consulting engineering firm specializing in coastal and river engineering. He
has been involved in the Canadian coastal scene since the early 1980s and has conducted research and
engineering works throughout North America and overseas.
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