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coastal defences at dawlish
warren – are they sustainable?
by Michael White and
Paul Campbell
N
Starcross
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Or
HEADLAND
Exmouth
Direct
Cockwood
c
al
ig
in
The
Point
Exe
estuary
Spit stopped from
growing any further
due to river outlet
removing material
e
Saltmarsh created
behind spit in low
energy zone
482
ion o
f lon
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Saltmarsh
Change in shape
of land (initiation of
deposition)
re dr
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Recurved
laterals
created by
change in
wind
direction
SPIT
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lis
ar
W
Dawlish
Short-term change
in wind direction
Prevailing
wind direction
w
Da
Dawlish Warren
Langstone Rock
Figure 2: Formation of a spit
GeoActive Series 24 Issue 1
Figure 1: Dawlish Warren and the
Exe estuary in 1974
GeoActive Series 24 Issue 1
Fig 482_01 Mac/eps/illustrator v15 s/s
NELSONWARREN
THORNES PUBLISHING
DAWLISH
is a major
Artist: David Russell Illustration
spit (Figures 1 and 5) which lies at
the mouth of the River Exe, less
than 3 km north-east of the south
Devon holiday town of Dawlish.
Historically, the spit has built up
as a result of deposition of sand
at the mouth of the estuary. This
sand has been transported by
longshore drift (material carried
along the coast by the prevailing
south and south-westerly winds)
in a north-easterly direction. A
spit formed across the mouth of
the estuary, where the coastline
changed direction and wave
energy was low.
Figure 2 shows the main processes
involved in the formation of a
spit. Beach sediment is transported
along the coast by longshore drift
until it meets a change in direction
of the coastline – in this case a
As Figure 3 shows, the shape of
Dawlish Warren has changed
considerably since 1787. Evidence
from such early maps suggests
that over 200 metres of the
sandspit has been lost by erosion,
which is continuing at the rate of
1 metre a year. Dramatic losses
were experienced between 2009
and 2010, with a single storm
removing around 10 metres
of dune frontage and reducing
the beach level by more than a
metre. There is also evidence
to suggest that the sand dunes
themselves are being lost, partly
due to the loss of the marram
grass from extensive use of the
dunes by holidaymakers who
flock here in the summer. One
theory is that the breakwater at
Series 24 Autumn issue Unit 482 Coastal Defences at Dawlish Warren – Are they Sustainable? © 2012 Nelson Thornes
N
Exmouth
Exe
estuary
Saltmarsh
87
Road
Railway
Sandbanks
9
1 km
0
19
0
tid
e
Key
v15Rock
s/s has prevented
headland. The sedimentFig
is 482_03
then Mac/eps/illustrator
Langstone
THORNES PUBLISHING
deposited in the form of aNELSON
spit
sand
from
moving
onto the spit
Artist: David Russell Illustration
which grows over time. Often the
to replace the sand lost due to
area behind the spit accumulates
erosion. Other evidence suggests
sediment forming a saltmarsh.
that the spit was being eroded
Eventually the spit will stop
before the breakwater was built
growing as beach sediment runs
and that in fact this is a natural
out or it is checked by river or
process. Could global warming
coastal currents.
and consequently a sea-level
rise be partly responsible for the
increased erosion? Whatever
Changes at Dawlish Warren
Railway
line
gh
Hi
h
Hig
t id
a
em
rk
17
Sea
0
500 m
Figure 3: The shape of Dawlish
Warren in 1787 and 1990
GeoActive Series 24 Issue 1
Fig 482_04 Mac/eps/illustrator v15 s/s
NELSON THORNES PUBLISHING
Artist: David Russell Illustration
This page may be photocopied for use within the purchasing institution only.
GeoActive Online
Page 1 of 4
the cause, the sand spit is still
getting narrower and there is a
concern that should the spit be
breached and eroded away by
a major storm, then it will have
a major impact not only on the
environment but also on the
local economy.
Type of sea defence
10 years
Sea wall
£2,500
30–50 years
Concrete revetment slope
£5,000
20–35 years
£600
10 years
£1,200
10 years
None
Unlimited
Timber groynes
Managed retreat
Figure 4: Different types of coastal defence options with costs and lifespans
A cost-benefit analysis is one
way that councils and the
Environment Agency assess the
need to persist with the current
coastal management strategies or
to re-think how they will defend
a coastal environment in the
future – if at all. This involves
the Environment Agency sending
agents to the area to survey all of
the present land uses that would
be affected or lost due to coastal
flooding should nothing be done.
The value of all the properties and
land uses is calculated and assessed
against various possible scenarios.
These defences have generally
been successful and apart from
storm damage to the rock
armour they have stood the test
of time well. However, they are
now beginning to show their
age, and increasing maintenance
costs, an ever decreasing budget
and greater awareness of the
impact on the environment mean
that Teignbridge District Council
is having to rethink its coastal
management strategy. The option
of managed retreat – allowing
the sea to reclaim the land –
may well prove to be the only
economically viable option in the
future.
If the cost of building sea defences
is significantly less than the cost
of replacing the lost property and
income to the area caused by a
major flood, then the benefits will
outweigh the costs and therefore
become viable.
Another factor that all councils
have to consider is the
sustainability of defending a coastal
environment. Increased awareness
of the use of resources and the
impact this has on the environment
has become a major issue, and
councils have to ensure that any
strategies used in the future will
have a limited impact on the
environment and can be sustained
in the long term. This means that
they must consider not only the
cost of the resources but also where
they are sourced, in order to reduce
pollution by transport, energy
costs, the longevity of the strategy
(so that new natural resources are
not having to be used), and how it
affects the natural processes in that
coastal zone.
Planning for defence against
the sea
As the council seeks to make
major savings, cutting costs on
expensive engineering work is
one way it can make ends meet,
but this needs to be weighed up
against the value of the land and
property that would be lost to
coastal flooding if the present
strategies are not maintained or
replaced.
£16,000
Gabion mattresses
Research in the 1960s suggested
that major engineering work
was required, so the Teignbridge
District Council and the
Environment Agency set about
building a range of sea defences
to protect the Warren. As was
common then, the council
went for a strategy of hard
engineering, by building large,
robust sea defences including a
sea wall, rock armour, concrete
revetment, gabions and groynes.
However, these are the mostly
costly options, and will only
be effective for a limited time
(Figure 4).
GeoActive Online
Lifespan before
significant
rebuilding works
Rock armour revetment
What has been done to
protect Dawlish Warren?
Page 2 of 4
Current cost of
replacement per
metre
Some councils, including nearby
East Devon District Council, have
increasingly moved to a strategy
of managed retreat, which
essentially means doing nothing
and allowing the coastal processes
to proceed without any human
intervention.
Pennington Point, near Sidmouth,
about 15 km to the north and
east of Dawlish Warren, is part of
the Jurassic coastline. Increased
erosion has already put eleven
properties there at risk of falling
into the sea. The local council
is in favour of managed retreat
as this is the only way in which
this part of the coastline can be
managed without affecting the
natural beauty and processes
of the area. It is of course the
cheapest option, as the council
is not responsible for the
replacement of the properties.
An alternative to managed retreat
is to use more natural ways of
protecting the coastline, known
as soft engineering. These include
methods that blend in more with
the natural environment and
require less energy to build and
maintain. For example, beach
nourishment involves replacing
sand lost during storms, and a
wider beach offers protection from
destructive waves to land uses
and habitats beyond the beach.
Other strategies used at Dawlish
Warren include the planting of
marram grass on the sand dunes
to stop the sand being blown away
and destroying them. Christmas
trees have even been pegged flat
against the front of the dunes to
Series 24 Autumn issue Unit 482 Coastal Defences at Dawlish Warren – Are they Sustainable? © 2012 Nelson Thornes
This page may be photocopied for use within the purchasing institution only.
encourage sand to be trapped
within their branches, again
helping to preserve the dunes.
Why defend Dawlish Warren?
Teignbridge District Council will
reach a point in the near future
when it will have to make some
difficult decisions as to how
it intends to manage Dawlish
Warren (Figure 5). Will a costbenefit analysis allow for the
present sea defences to be updated
and maintained, or will more
environmentally friendly and
sustainable options have to be
considered? A number of factors
will need to be taken into account
before any decisions are made.
The sandspit itself is a nature
reserve and it is an internationally
valuable habitat for a wide range
of birds and plants. It has Special
Protection Area status (SPA is
designated under the European
Birds Directive) and is an
important Site of Special Scientific
Interest (SSSI), which means
that any changes planned must
not harm or disrupt the natural
processes that preserve the habitat.
There are over 40 local businesses
both on the spit itself and in the
nearby village, including cafés, gift
shops and amusement arcades.
A new pub, The Boathouse, was
built on the Warren in 2001 and
it has helped to attract even more
visitors to the area. A bike shop has
also opened recently to encourage
even more visitors to explore
the coastline. Here too there is a
range of accommodation where
tourists can stay, from grand hotels
to campsites. There are no fewer
than 5 holiday parks with more
than 300 caravans available for
tourists to use all year round. These
attractions bring millions of pounds
a year into the local economy and
provide local people with jobs.
Money paid for use of the car park
is another major source of income
for the local council.
Another consequence of losing
the spit to erosion would be the
breaching of a natural sea defence
Figure 5: Aerial view of Dawlish Warren
Source: © Teignbridge District Council
that protects the settlements
along the Exe estuary, including
Cockwood, Starcross, and the
village of Dawlish Warren itself.
The spit acts as a giant breakwater,
preventing waves and coastal
surges from flooding these lowlying villages.
What is the future for Dawlish
Warren?
Dawlish Warren has undergone
many changes and over the years
the area has been managed in
different ways. The Environment
Agency and other local
organisations such as the Exe
Estuary Management Partnership
have tried to balance the needs
of tourism to help promote local
industries and businesses whilst
maintaining the unique beauty
and habitats of the area. Special
boardwalks and designated paths
have been built from the car
park to the beach to ensure that
erosion of the sand dunes is kept
to a minimum, and marram grass
has been planted to help conserve
and protect the dunes. Signs have
been placed in key areas, and a
special Visitor Centre was built in
1985 to help promote and educate
people about conservation of the
Warren. In an attempt to allow the
conservation to be as sustainable
as possible, wild ponies have been
released on the Warren to graze
behind the sand dunes, to ensure
that the area does not become
overgrown and destroy some of
the indigenous and unique plant
life there.
However, this sustainable
approach to managing the area
does not extend to building
and maintaining sea defences.
Currently the Environment
Agency and Teignbridge District
Council are committed to
preserving and maintaining the
existing hard engineering defences,
and it seems unlikely that policy
will change at any time in the near
future.
Series 24 Autumn issue Unit 482 Coastal Defences at Dawlish Warren – Are they Sustainable? © 2012 Nelson Thornes
This page may be photocopied for use within the purchasing institution only.
GeoActive Online
Page 3 of 4
Activities
1 (a) Write a definition for each
of the following key geographical
terms:
Land
• Prevailing wind
• Swash
• Backwash
Sea
• Longshore drift.
(b) Draw a diagram to show how
longshore drift moves material
along a beach. Use arrows and
lines to annotate your diagram.
Use a copy of Figure 6 as a basic
outline for your diagram.
(c) What is the main problem
caused by longshore drift?
2 Study Figure 5. Draw
a labelled sketch of the
photograph to show the
characteristics of Dawlish
Warren spit.
• Hard engineering
• Soft engineering
• Managed retreat
(b) Look at Figure 7. Wooden
groynes like this are a key
feature seen on the beaches at
Dawlish Warren. Draw up a
table showing the advantages
and disadvantages of using this
type of hard engineering scheme
along a section of coastline.
(c) What are (i) the costs and (ii)
the benefits of hard engineering
in managing a coastline?
(d) In a recent interview (18
March 2010), Teignbridge
District Council suggested that
it may bring in sand from the
Isle of Wight. How will this help
protect the spit? Is this measure
sustainable?
5 Describe a coastal
environment that you have
studied, and explain why it
provides a suitable habitat for
the plants and animals that live
there.
8 The dilemma for government
and for local councils in the
future will be:
7 Study Figure 8, which lists
some of the groups who are
interested in the future of
Dawlish Warren. Make a larger
copy of this table. For each
person or group, mark a tick or
cross to indicate whether or not
you think they would want to
see future sea defence schemes
built at Dawlish Warren. Try to
give an explanation for your/
their decision.
4 (a) What are the meanings
of the following key coastal
management options?
GeoActive Online
Figure 7: A wooden groyne
6 Study the text in this unit
under the heading ‘Why defend
Dawlish Warren?’ Make a list of
all the land uses at risk if a major
storm were to break up the spit.
3 (a) Describe what has
happened to the shape and size
of the spit at Dawlish Warren
over time.
(b) Explain why sea level is
expected to rise in the future.
Page 4 of 4
Figure 6: Outline for diagram
showing the process of longshore drift
Source: © Evelyn Simak; licensed for reuse under the
Creative Commons Licence
Should they invest billions of
pounds in protecting our seaside
towns from rising sea levels
through engineering, or should
they work with nature?
Working in pairs or small groups,
outline a management plan,
setting out what you think should
be done in the future to protect
the spit at Dawlish Warren.
Want more
sea defence
schemes
√ Yes X No
Reason
Hotel owners
Bird watchers
Teignbridge District Council
Tourists
Amusement arcade owner
Figure 8: Why some people may or may not want the Warren to be protected
Series 24 Autumn issue Unit 482 Coastal Defences at Dawlish Warren – Are they Sustainable? © 2012 Nelson Thornes
This page may be photocopied for use within the purchasing institution only.