coastal management has 3 aims: protect coastline from erosion. protect coast from
seawater flooding. conserving fragile ecosystems
sustainable coastal management has to consider the 3 main aspects of sustainable
development: environmental, economic and social sustainability.
implies that the strategies involved should work in the present and the future with
minimum maintenance costs.
Shoreline management plans
drawn up for every coasting England and wales. based on sediment cells and subcells so future impacts of any new management strategy can be considered to
protect the whole sediment cell.
objectives: define flooding and erosion risks to people and the environment over
the next century. identify the best policy for managing those risks. identify impacts
of those policies. inform planners, developers and others of these risks when
considering future developments of the shoreline. comply with international and
national nature conservation laws. highlight areas where current knowledge is
inadequate. provide an action plan for the implementation of the SMP and to
monitor its progress.
four coastal defence options for the SMP…
hold the line: maintain and repair the current defences so coastline is protected for
the future and risk of flooding isn’t increased. expensive when there’s rising sea
levels and frequent coastal storms. usually the minimum strategy communities will
accept.
advance the line: build new defences. involves reclaiming land from sea and very
expensive for future with global warming.
managed realignment: allowing shoreline to move forwards/backwards but with
use of management strategies to control movement. works on low-lying coastlines
to create salt marshes
no active intervention: do nothing, no further investment. popular with taxpayer
not with locals
Cost-benefit analysis
used when deciding on the management strategy. benefits > costs
costs = how much it’ll cost to build or implement?
benefit = what’s the value of the land that are being protected and that would be
destroyed/damaged if nothing was done?
Hard engineering
type description advantages disadvantages
vertical
sea wall
solid wall of concrete.
deep foundations needed
to maintain stability
structure that can
withstand severe wave
action.
maintains line of
coastline.
socially re-assuring.
high initial and maintenance costs.
waves deflected downwards so
basal scour can undermine
foundations and wall can collapse.
reduced access to beach, steps
provided at intervals.
re-curved
sea wall
concrete wall with curved
lip at top. waves reflected
back to sea and don’t
cause basal scour. ramp
and steps at base of wall
to absorb wave energy.
as above.
shape avoids over-topping
by waves.
basal scour is reduced.
very expensive to buy and maintain.
reduces access to beach.
concrete isn’t eye pleasing.
groynes wood barrier of stout cheap but cost depends only last 20 years.
timber piles/planks built at
right angles to shore.
control LSD and
encourage deposition. can
be stones – rip-rap lasts
longer
on length and spacing.
deposition makes a wider
beach which absorbs
wave energy and
encourages tourists
high maintenance/replacement
costs.
visually unappealing.
dangerous to walk on.
can starve beaches from sediment
and encourage erosion further
down.
breakwat
er
solid structure made of
masonry with concrete
cap. foundations go down
to bedrock. deflect waves
and provide sheltered
environment behind.
protects area behind from
wave action, reducing
erosion.
slows LSD and encourages
sediment build up.
very expensive as broad and deep.
not cheap maintenance.
pascal scour is a problem and can
undermine lower sections.
down-drift starvation encourages
erosion.
gabions wire cages filled with
stones. wired to make any
shape or structure
cheap to build.
very flexible.
short lifespan so high maintenance
costs.
unsightly.
dangerous when rusts.
if used as a sea wall reduces beach
access.
revetment sloping wall running along
coast parallel to sea. can
be made of varied
materials. slatted wooden
revetments are known as
wave baffles and are built
in front of cliff to absorb
wave energy.
sloping ramp dissipates
wave energy.
very little wave reflection
and no basal scour.
cheap but cost depends
on materials used.
over-topping by waves is a problem
in storms at high tide.
erode very quickly if breached or
damaged, needs regular
maintenance.
wood doesn’t last long.
make beach access hard
rip-rap large blocks of
rock/concrete placed as
ramp in front of cliff or sea
wall
dissipate wave energy
effectively.
quite cheap.
natural look and low
maintenance costs.
big enough blocks to resist wave
movement.
significant costs if material not
sourced locally.
restrict access to beach and
dangerous to walk on.
Soft engineering
type description advantages disadvantages
beach
nourishmen
t
artificial addition of
beach material from
another location.
brought by lorry or
dragged from offshore
builds up the build to make it a
big buffer to absorb wave
energy.
low initial costs – depends on
how far.
bigger beach attracts tourists.
natural and aesthetically
pleasing.
requires constant maintenance
and if LSD is removing the
sediment.
needs groins-built downdraft to
reduce sediment loss.
considerate local disruption
during construction stage.
sand dune
conservatio
n
sand dunes are
important ecosystems
and they provide areas
inland from the dunes
with protection from
erosion and flooding.
protects important ecosystem
and enhances protection dunes
provide.
well-managed systems allow
access to dunes and beach
beyond without trampling.
high initial costs.
required maintenance.
damaged dunes areas may
need to be fenced off, denying
public access,
managed
retreat
current defences
breached to allow sea
to access low-lying
land. salt marsh
develops and protects
land.
land sacrificed is low cost
agricultural land.
cheaper than strengthening
defences.
settlements inland provided with
effective protection.
provides feeding ground for
new sea wall may need to build
further inland.
costly and disruptive initial
works.
compensation for those who
have lost farmland
cliff
drainage
drainage pipes inserted
into the cliff face when
cliff is made of soft or
unconsolidated
material. removes
water from cliff,
lessening the potential
for mass movements.
cliff becomes drier and less
prone to slumping. very little
environmental impact apart
from construction phase.
maintains natural appearance
and recreational value of beach.
can be expensive.
disruptive and unsightly during
the construction phase.
cliff regrading
vertical cliff turned into
a more gently sloping
cliff by removing
material from cliff top
and adding it to bottom
of cliff. works on
soft/unconsolidated
cliffs.
cliff becomes more stable and
less prone to unexpected
movements.
once naturalised the cliff isn’t
unsightly.
maintains natural appearance
and recreational value of beach.
can be expensive.
disruptive and unsightly during
the construction phase.
removes natural cliff line.
major ecological impacts.
planning
controls
planning permission for
new developments in
at risk areas is refused
cheap as planning authorities
already exist.
ensures future problems don’t
arise. links into long term aims
outlined in SMP’s.
people who are refused feel
alienated. appeals can be long
and costly. doesn’t solve
current problems related to
existing buildings
do nothing changes in coastal
system allowed to take
their natural course
no direct costs.
unprotected coastline is eroded
to provide material down drift.
beach remains natural
compensation of eroded land
properties.
socially unacceptable as house
are lost.
politely unpopular for local
council.
Barrages
solid, hard engineering scheme to prevent flooding
acts as a dam across an estuary and prevents invasion of seawater on
temp/permanent basis.
only work when combines with building of extensive embankments on sea ward
side, so high seas can’t go around the side of them
very expensive to build
permanent barrages create a freshwater lake behind and encourage reclamation of
land from lank, encouraging economic development (stop movement of ships to
ports further up estuary). major environmental impacts — changing the of water,
destroy feeding grounds of migrating bird. rare. e.g. Cardiff bay barrage UK.
temporary barrages raised at time of danger. more expensive but more flexible.
better for wildlife. allow passage of ships. e.g. Thames barrier, UK
future barrages — Severn estuary barrage, extend from Weston-Super-Mare to
Penarth. protect and generate tidal energy. high cost and environmental impacts
means it’s been rejected.
Embankments
Are often made of earth with rubble fill and more common outside the town centre
where there is more room. If set back from the channel, they can provide storage
for excess floodwaters while inhabited areas remain unaffected.
Shelters
cheaper alternative. flood proof shelters for locals in a flood. built of concrete and
raised above flood level on stilts. has to be a reliable flood warning system. can
save people but not land and livestock. death is reduced but economic and social
disruption is still considerable.
Case study: Coastal management of the Holderness coast, UK
Holderness coast in east Yorkshire, UK stretches from resistant chalk headland
(Flamborough head) to delicate spit (spurn point) which has grown out across the
mouth of the Humber estuary.
most of its length consists of bolder clay coast. erasing at rate of 2m per year. one
of fastest coastal erosion rates in EU. erosion occurs in bursts, mainly during
storms. 29 villages lost to sea in last 1000 years.
(places move from north to south)
Flambourgh head: area of chalk rock, harder than boulder clay so forms a
headland, sticking out into sea. slow erosion rates and few houses at risk. coastal
management isn’t a major issue so management schemes are in place.
Barmston: boulder clay, high average erosion rates. slumping is common. holiday
homes are being lost to the sea often. value of holiday homes are low and no
management schemes in place.
Mappleton and great Cowden farm: main road of Mappleton at risk, threatened.
road and village protected with rip-rap and 2 rock groynes. groynes stopped LSD.
great Cowden farm has less sand on beach, so erosion rates have increased.
disappeared into sea, 45 years earlier than expected.
Withernsea: small seaside resort, many tourist industry buildings. wooden groynes
used to widen beach. sea wall with splash back been built to further protect
settlement. rip-rap laid at sea wall base to break wave power.
Easington: gas terminal for 25% of UK. when it was built gas was expected to last
for 20 years, lasted much longer than expected and gas terminal at risk for coastal
erosion. rip-rap built at bottom of cliff. Future, gas brought from Norway and will
come ashore at Easington.
spurn head: spit at the end. sand supply been restricted by coastal management
methods used further up. getting thinner and could break through and turn spurn
point into an island. make life difficult. would destroy salt marsh and nature
reserve behind spit, redoing migrating bird habitat. no management plans.
Case study: Managed retreat on south coast of UK
in 2014 winter, UK environment agency completed UK’s largest coastal realignment scheme at Medmerry in west Sussex.
why was the scheme needed: coastline faces south-west so hit first by prevailing
winds. low-lying area is protected by a shingle embankment, but it was overtopped by storms and flooded. many salt marsh areas have disappeared because
of coastal developments and other areas are at threat because of rising sea levels.
scheme will create 180 hectares of salt marsh, providing a habitat.
what has the scheme involved: managed re-alignment means building new
defences inland from current coastline and allowing a new intertidal area form on
what was once farmland. old embankment will be breached and 7km of new
defences have been constructed 2km inland. drainage ditches and ponds have
been built to facilitate the creation of a new salt marsh habitat, covered by sea
water at high tide. features constructed to encouraged tourism. community
members and locals were involved in all decision making and planning. scheme
cost £28 million.
what has been the outcome: 2 holiday parks, a main road, water treatment and
350 homes have been protected from flooding. high level of protection, enough to
protect from 1000-year flood. homes are worth £60million at 2015 prices so the
cost-benefit analysis shows that its economically worthwhile. 180 hectares of
wetland will provide a habitat. tourism will be boosted.
has the scheme worked: during winter 2013/14, UK south coast suffered worst
weather for 20 years with a sustained period of high tides, strong winds and stormy
seas. new defences have held firm and are working as planned. large number of
birds are using the area. seals spotted at high tide. owner of holiday village was
sceptical about proposals. after storms he was planned.