COASTAL LANDSCAPES AND CHANGE
What is the littoral zone and why is it dynamic?
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The littoral zone (beach) � it is the boundary between the land and the sea.
It is divided into 4 zones:
1. Backshore
2. Foreshore
3. Nearshore
4. Offshore
It is always changing, and is dynamic due to processes that operate in seas, oceans and on
land. Some changes can occur rapidly.
Short-term processes include:
▪ Tides
▪ Longshore drift
Long-term processes in include:
▪ Sea level rising/falling (climate change)
What is the coastal system?
Inputs
Geology
People
Waves
Storm surges
Tides
Solar
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Processes
Erosion
Weathering
Mass movement
Outputs
Depositional landforms
Erosional landforms
Different classification of
coasts
Transportation
Deposition
The inputs to the systems are altered by processes to become outputs.
How are coasts classified?
According to the geology:
Rocky coasts, for example Bedruthan Steps, Cornwall. Older resistant rock such as slates and
sandstones can withstand winter storms without suffering from rapid erosion.
Sandy coasts, for example Holkham Beach, Norfolk. Low-lying beaches are inundated at high tide
but the vegetated dunes are not and prevent erosion. Sediment is supplied from different
terrestrial and offshore sources.
Estuarine coasts, for example Lymington in Hampshire. Extensive mudflats are exposed at low
tide but inundated at high tide with a salt marsh behind. Sediment is supplied from different
terrestrial and offshore sources.
Cliffed coasts, for example Flamborough Head, Yorkshire. The transition from land to sea is abrupt
and a wave-cut platform is exposed at low tide.
Concordant coasts, for example Lulworth Cove, Dorset. Different rock bands run parallel to the
coast.
Discordant coasts, for example Studland Bay, Dorset. Different rock bands run at right angles to
the coast.
According to the level of energy:
High-energy coasts, for example Cornwall. The waves are powerful for much of the year.
Low-energy coasts, for example Lincolnshire. The waves are less powerful or the coast is sheltered
from large waves.
According to the balance between erosion and deposition:
Erosional coasts, for example Holderness, Yorkshire. Erosion is the dominant process.
Depositional coasts, for example Dungeness, Kent. Deposition is the dominant process.
According to changes in sea level:
Emergent coasts, for example the west coast of Scotland. A fall in sea level exposes land
previously covered by the sea.
Submergent coasts, for example south-west England. A rise in sea level floods the coast.
No classification system is definite – Cornwall’s high energy coast is mainly rocky but also has long
stretches of sand and some estuaries!
What are concordant and discordant coasts?
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Concordant coasts have different rock bands that run parallel to the coast.
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Discordant coasts have different rock bands that run at right angles to the coast.
How has The Isle of Purbeck’s concordant and discordant coasts resulted in different landforms?
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Lulworth Cove to Durlston Head is concordant
Lulworth Cove – over time, the sea gradually eroded the resistant Purbeck limestone at the
entrance to Lulworth Cove. Then, rapid erosion of the less-resistant clays behind the limestone
led to the formation of a cove.
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Durslton Head to Studland Bay is discordant
The Bagshot and Tertiary beds consist of unconsolidated (loose) sands and clays. They are less
resistant to erosion and, where exposed to the sea at Studland, have formed a large bay as a
result.
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The chalk is strong and resistant to erosion, so it has formed cliffs and a headland at the coast
(The Foreland).
Long-term changes to a discordant coast
1. Unsurprisingly, more resistant rock (such as chalk or limestone) tends to form headlands along
discordant coastlines, whilst weaker rocks (such as clay) are eroded to form bays.
2. However, over time the coastline becomes straighter again.
3. Process happens all over again.
How the discordant coastline straightens up
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Headlands force the incoming waves to refract or bend – concentrating their energy at the
headlands. This increases the waves’ erosive power, which leads to a steepening of the cliffs and
their eventual erosion into arches and stacks.
By contrast, when waves enter a bay, their energy is dissipated (spread out) and reduced. This
leads to the deposition of sediment (sand or shingle) – forming a beach.
More concordant coasts
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Dalmatian type concordant coasts have valleys and ridges that run parallel to each other. When
the valleys flood due to a rise in sea level, the tops of the ridges remain above the surface of the
sea as a series of offshore islands that run parallel to the coast.
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A Haff type concordant coast consists of long sand spits and lagoons aligned parallel to the
coast.
How does geological structure affect coastal morphology, erosion rates and coastal recession?
Geological structure (jointing, dip, faulting and folding) is an important influence on coastal
morphology (shape), erosion rates and coastal recession (landwards). It also affects the formation of
cliff profiles and the occurrence of micro-features such as caves, as well as determining whether
coasts are concordant or discordant.
How does geological structure influence erosion rates and the formation of cliff profiles?
Jointing – the division of
rocks into blocks
Dip – the angle of rock strata
(layers) caused by tectonic
processes
Faulting – creation of major
weaknesses in rocks
Folding – compresses the
Earth’s crust and often
results in joints and fissures
(small cracks)
Cliff profiles
Cliffs develop a blocky
structure
Dramatic impact on cliff
profiles
Rocks are heavily fractured
and broken either side of a
fault line
Forms anticline folds (convex
A shape) and syncline folds
(concave U shape)
Erosion rates
Faster along the joints
between blocks
Cliffs with a seaward dip are
less stable than those with a
landward dip
Vulnerable to erosion –
weaknesses are exploited
Joints, fissures and exposed
soft rock are eroded quickly
Anticline – top of the fold
Syncline – bottom of the fold
Cliff profiles
How does bedrock lithology affect rates of erosion and coastal recession?
− Bedrock � underlying rock type
− Lithology � relative hardness, permeability and solubility of the rock
Bedrock lithology
Igneous rock
● Igneous rock – solidified lava
Metamorphic rock
● Metamorphic rock – sedimentary rock
that has been changed by heat and/or
pressure
Rates of erosion and coastal recession
Very slow coastal recession rates as
interlocking crystals make for strong,
resistant rock. There are few joints and
faults so there are limited weaknesses that
erosion can exploit.
Show coastal recession rates as interlocking
crystals make for strong, resistant rocks.
However, these rocks are often folded and
heavily fractured, which creates weaknesses
that erosion can exploit. Additionally, if
foliation (when bits of a rock peel off) is
present the crystals are all oriented in one
Sedimentary rock
Sedimentary rock – impressed layers of
sediment
Unconsolidated rock
● Unconsolidated rock – loose sediment
direction, which produces further
weaknesses.
Moderate to fast rates of erosion as joints
and faults are vulnerable to erosion.
Very fast coastal recession rates as
unconsolidated, sediment such as sand,
gravel, clay and silt is loose and easily
eroded.
Types of rocks
● Igneous rock – solidified lava (strongest)
● Metamorphic rock – sedimentary rock that has been changed by heat and/or pressure
● Sedimentary rock – compressed layers of sediment
● Unconsolidated rock – loose sediment (weakest)
Complex cliff profile reflecting different alternating lithology
Lyme Regis
Strata with jointing
therefore vulnerable to
erosion.
Sedimentary rock
(limestone).
Scree (bits of rock that
have fallen off due to
mass movement) is
collected at the bottom
of the cliff; therefore, a
lot of weathering and
erosion has occurred to
loosen the rock.
Bridport
Scree is present, therefore
weathering and erosion
has occurred. Faulting has
occurred.
Bude
A syncline and anticline are
present therefore folding
has occurred. Scree is also
present so weathering and
mass movement have taken
place.
CONCLUSION:
Geological structure is a very important influence on coastal landscapes. However, other factors play
a key role too, for instance: wave type, tides, storms, human activity (including management),
vegetation and sea level change.
What are the different types of waves?
Wavelength – the distance between the crests of two waves
Swash – water flowing up the beach
Backwash – water flowing back down the beach
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Constructive waves
Strong swash, weak backwash
Beach gets bigger – hence constructive (as beach gaining)
Usually occur on, and help to create, gently sloping beaches
Low, surging waves with a long wavelength
The waves break with a frequency of about 6-8 per minute so the swash isn’t interrupted
(therefore swash is strong)
The energy of the backwash is reduced as water percolates through the beach material due to
the relatively gentle beach sediment profile
The swash of a constructive wave deposits larger material at the top of the beach creating a berm
(a ridge/bump on the beach)
Destructive waves
Weak swash, strong backwash
Beach gets smaller – hence destructive (as beach loss)
Usually found on, and help to create, steep beaches
The wave frequency is about 13-15 per minute so the backwash of the previous wave makes the
swash of the wave that follows it weaker
The backwash erodes material as it runs off the relatively steep beach sediment profile
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Strong backwash transports sediment offshore and deposits it as offshore bars
- More deposition of sand
- Constructive waves dominate in the
summer leading to more deposition of sand
creating a berm
- Destructive waves cause berm erosion
leading to a steeper gradient
- Destructive waves drag more sediment out
to sea and deposit this offshore creating a
bar
How does marine erosion create distinctive coastal landforms?
Erosion – the wearing away and removal of material by a moving agent of erosion (in this case, the
sea).
Different types of erosion:
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Hydraulic action – when a wave advances, air can be trapped and compressed (either in joints in
the rock forming the cliff or between the breaking wave and the cliff). Then, when the wave
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retreats, the compressed air expands again. This continuous process weakens joints and cracks
in the cliff – causing pieces of rock to break off.
Abrasion (corrasion) – when waves advance, they pick up sand and pebbles from the seabed.
Then, when they break at the base of the cliff, the transported material is hurled at the cliff foot
– chipping away at the rock.
Corrosion – when cliffs are formed from alkaline rock (e.g. chalk & limestone), solution by weak
carbonic acid in seawater can dissolve them.
Attrition – the gradual wearing down of rock particles by impact and abrasion, as pieces of rock
are moved by waves, tides and currents. This process gradually reduces particle size and makes
stones rounder and smaller. Rocks can also be broken down when they bump into each other.
Flamborough Head, Yorkshire
Wave-cut notch
Cave
Wave-cut platform
Wave-cut notches and wave-cut platforms
When waves break against the foot of a cliff, erosion tends to be concentrated close to the high tide
line. This creates a wave cut notch, which will begin to undercut the cliff. As the wave-cut notch gets
bigger, the rock above it becomes unstable and eventually the upper part of the cliff collapses.
As these erosional processes are repeated, the notch migrates inland and the cliff retreats, leaving a
remnant feature behind – which is known as a wave-cut platform. Wave-cut platforms have gentle
slopes and dissipate wave energy.
West Wales
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Arch
Stack
Stumps
Caves arches, stacks and stumps
Caves, arches, stacks and stumps are all connected as part of a sequence of a coastal landform
development.
1. Erosion of rocks like limestone and chalk tends to exploit any lines of weakness – joints, faults
and fissures.
2. When joints and faults are eroded by hydraulic action and abrasion, caves can be created.
3. If two caves are on either side of a headland, an arch is formed. This gap is further enlarged
by erosion and weathering – becoming wider at the base.
4. Eventually the top of the arch will become unstable and collapse – leaving an isolated pillar
of rock, called a stack. The stack itself continues to be eroded by the sea, and as it collapses
and is eroded further, a stump is created.
How do sediment transport and deposition create distinctive coastal
landscapes?
What is longshore drift?
● Longshore drift is the movement of material along the coast by wave action
● Waves are caused by the friction between water and wind, with some energy from the wind being
transferred into the water
● The amount of energy gained by a wave is affected by:
1. Fetch (– length of open sea over which a winds blow to generate waves)
2. Strength of wind
3. Duration of wind
4. Depth of water
Prevailing wind direction determines the direction of swash, and backwash occurs under the
influence of gravity. This results in a zigzag motion as sediment is transported along the
coastline.
Tides and currents
The angle at which waves approach a beach is a major factor in coastal sediment transport. However,
tides and currents also affect the transportation of sediment.
● Tides are changes in the water level of seas and oceans. These are caused by the
gravitational pull of the moon and, to a lesser extent, the sun. The UK coastline
experiences two high and two low tides each day.
● The relative difference in height between high and low tides is called the tidal range. A
high tidal range creates relatively powerful tidal currents, as tides rise and fall. Tidal
currents can become particularly strong and fast in estuaries and narrow channels, and
are important in transporting sediment.
Deposition
Sediment is deposited when the force transporting sediment stops. For example:
● Gravity settling occurs when the energy of transporting water becomes too low to move
sediment; large sediment will be deposited first.
● Flocculation is important for clay particles which are so small they remain suspended in
water. Clay particles clump together due to electrical or chemical attraction and become
large enough to sink. Salt causes flocculation, so the process is common at estuaries and
deltas.
Berms and storm beach on Holy Island, Northumberland
Shingle beach
Berm
Storm beach
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Beaches are landforms where
there is an accumulation of sediment
which is reworked by the action of
waves and tides.
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Berms are formed by
constructive waves.
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Storm beaches are formed by
swash under extreme conditions.
Ridges and runnels at Watergate Bay, Cornwall
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Runnels are depressions in
sand between ridges left as tidal
scour causes sediment to be
removed (runnels are dips and
ridges are bumps).
Hurst Castle spit, Hampshire
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Spits are long, narrow
ridges of sand or shingle that are
attached to the land at one end
known as proximal end.
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Spits are formed where the
line of the coast changes, but
longshore drift carries on. They form
where constructive waves dominate
and there is a surplus of sediment.
The distal end of the spit is in the
sea.
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An estuary is a good
example of a change in direction of
the coastline. An estuary is where a river meets the sea. The end of the spit has
curved round due to wave refraction at its tip, so it is known as a recurved spit.
Double spit at the entrance of Poole Harbour, Dorset
● Two spits
extend from
different ends of
the bay.
Offshore bare at Hordle, Hampshire
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Line of sediment
caused by destructive
waves.
Stuart Bay barrier beach and Slapton Ley lagoon
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Where a spit extends across a bay
to join two headlands, it forms a barrier
beach or bar with a lagoon behind.
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Where a beach becomes separated
from the mainland, it is referred to as a
barrier island.
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The river currents are too weak to
prevent the spit forming across the bay.
Tombolo linking St Ninian’s Isle to the
south-west Shetland mainland
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A tombolo is a beach that has
formed between a small island and the
mainland.
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Deposition occurs where waves lose
their energy and the tombolo begins to
build up.
Cuspate foreland at Dungeness, Kent
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This is a triangular-shaped headline
that extends out from the mainland.
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Occurs when a coast is exposed to
longshore drift from opposite directions.
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Sediment is deposited at the point
where the two meet.
Why is vegetation important in stabilising coastlines?
Coastal Succession:
● Successional development refers to the changing structure of a plant community over
time, as an area of initially bare sediment is colonised by plants. On a coast, where
deposition occurs, certain very specialised plants will begin to grow in the bare sand or mud.
These are called pioneer species and they begin the succession. The final community is
relatively stable and best adjusted to the climatic conditions of the area; this is known as the
climatic climax community. As the succession develops over many years, the coastline is
stabilised.
● Most plants that grow in coastal environments are halophytes (can tolerate salt) or
xerophytes (can tolerate very dry conditions).
Sand Dunes:
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1. Pioneer species:
Sand is unstable, salty, dry and lacks
nutrients. Therefore, only highly
specialised pioneer species such as sea
rocket may colonise.
2. Mobile dunes:
Incursion of rainwater results in
slightly less salt substrate so marram
grass is able to colonise and become
the dominant species.
3. Fixed dunes:
Vegetation has formed a cover on the sand where less specialised species such as wild thyme
can grow. However, this is still a stressful environment as the soil lacks nutrients.
4. Woodland:
The climatic climax is deciduous woodland.
Salt Marsh:
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1. Eelgrass:
Eelgrass slows currents and
therefore helps to trap
sediment.
2. Cordgrass/Glasswort:
These pioneer species are
halophytes.
3. Lower salt marsh:
Further plants colonise and
more sediment is trapped.
4. Higher salt marsh:
Eventually, the land rises above
sea level as new species, such as rushes and reeds, become established. These species are
perennials (they come back every year).
As are trees such as alder and ash that appear.
5. Woodland:
The climatic climax is deciduous woodland.
How do plants protect deposited sediment?
● Plants slow currents and help to trap more sediment.
● Root systems bind sand and mud particles together.
● Plants reduce wind speed as they create friction.
● They can also provide a protective layer so the surface sediment is not directly exposed to
moving water.
● Salt marshes act as buffer zones between the sea and land to absorb coastal floods in
estuarine areas.
● Long blades of cordgrass in a salt marsh can trap sediment building up a muddy substrate,
which helps stabilise the roots of other plants.
● Marram grass establishes good root networks in bare sand which stabilises the dune, so it
can cope with gale-force winds.
● When plants die and decay, they add nutrients to the soil, which allows other species to
colonise. Therefore, the coastline is fixed and stabilised over time.
What is the sediment cell concept?
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A sediment cell is part of the coast that is linked
together by sources, transfers and sinks.
Each cell can be regarded as a closed system
because larger sediment is not transferred
between them, although finer sediment in
suspension out at sea can be transferred.
Sources � places where sediment is generated
such as cliffs or estuaries.
Transfers � move sediment along the shore
through longshore drift and out to sea through
offshore currents.
Sinks � places such as spits or barrier beaches
where deposition is the dominant process.
There are 11 sediment cells in England and
Wales, and these are determined by the shape
of the coastline, with a major role played by
peninsulas (pieces of land that are bordered by
water on three sides but connected to the
mainland). These act as natural barriers that
prevent the transfer of sediment from one cell
to another.
The amount of sediment available is the sediment budget.
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The depositional features that build up are in equilibrium with this
sediment budget.
Sediment Cell 2 Processes:
1. Due to the softer boulder clay at the source, the Holderness Cliffs,
erosion can easily take place.
2. Sediment is then transferred by longshore drift and tidal currents
southwards, and makes its way towards the sink at Spurn Head.
3. There is a low energy environment at Spurn Head, allowing for
deposition.
Negative and Positive Feedback Mechanisms:
● If a sediment cell’s equilibrium is disrupted, negative feedback
mechanisms help maintain the balance by pushing the system back
towards equilibrium. For example, during a major erosion event, a
large amount of cliff collapse may occur, but the rock debris at the
base of the cliff will slow down erosion by protecting the cliff base
from wave attack.
● Therefore, the sediment cell system attempts to balance itself and operates in a state of
dynamic equilibrium.
● On the other hand, positive feedback mechanisms tend to change the balance until a new
equilibrium is reached, e.g. increased storminess could lead to long term erosion of sand
dunes with no chance to recover between storm events.
How do subaerial processes influence coastal landscapes?
Subaerial processes – are land-based (not marine) and include weathering and mass movement.
Mass movement – movement of weathered material downslope under the influence of gravity.
Examples are below.
Landslides – slabs of rock slide over underlying rocks along a slip pane.
Blockfall – a large block of rocks falls away from the cliff as a single piece, due to the jointing of the
rock.
Rotational slumping – a section of a cliff remains intact as it moves down a cliff along a curved slip
plane.
(A slip plane is also known as a failure surface.)
Weathering – the in-situ breakdown of rocks by chemical, mechanical or biological agents. It does
not involve any movement. Examples are below.
Mechanical weathering – breakdown of rocks due to the exertion of a physical factor; it does not
involve any chemical change.
− Freeze-thaw – water expands by 9% in volume when freezing, exerting a force within cracks
and fissures. Repeated cycles force cracks open and loosen rocks.
Biological weathering – often speeds up mechanical or chemical weathering through the action of
plants, bacteria or animals.
Chemical weathering – Involves a chemical reaction and the generation of new chemical
compounds.
Rotational scars at Holderness, Yorkshire
Slumping
Slumps often occur in saturated conditions
The difference between sliding and slumping
is that there is a rotational movement in
slumping.
Slumps occur on moderate to steep slopes.
They are common where softer materials
(clays or sands) overlie more resistant or
impermeable rock, such as granite. Huge
masses of material can slowly rotate
downslope over periods lasting from days to
years.
Slumping causes rotational scars.
Terraced cliff profiles at Barton-on-Sea, Hampshire
Repeated slumping creates a terraced cliff
profile.
Talus scree slopes at Silverdale Cove, Cumbria
Blockfalls
A large block of rock falls away from the cliff
as a single piece, due to the jointing of rock.
Weathering and erosion loosen the blocks,
and undercutting of cliffs by the creation of
wave-cut notches can lead to large falls.
Blockfalls are a rapid form of mass
movement. Talus scree is formed where the
fallen blocks break against the wave cut
platform.
How does sea level change influence coasts on different timescales?
What is the difference between eustatic change and isostatic change?
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Eustatic change – involves a rise or fall in water level caused by a change in the volume of water.
It is therefore a global change, affecting all of the world’s connected seas and oceans. Eustatic
change may occur relatively quickly.
Isostatic change – is a local rise or fall in land level relative to the sea. Isostatic changes take much
longer.
Eustatic change
● Land-ice formation/melting and thermal changes cause eustatic change.
● During global periods, ice sheets form so more water is stored as ice leading to a global fall in sea
level.
● At the end of the glacial period, melting ice sheets return water to the sea causing the sea level
to rise globally.
● Warmer temperatures cause the volume of the ocean water to increase due to thermal expansion
and there is therefore a global rise in sea level.
Isostatic change
● Post glacial adjustment/isostatic recoil (see below), subsidence, accretion and tectonic activity
cause isostatic change.
● During glacial periods, the colossal weight of ice causes the earth’s crust to sag leading to a local
rise in the sea level. When the ice sheets melt, the land surface slowly rebounds over thousands
of years leading to a local fall in sea level.
Emergent coasts – a fall in sea level exposes land previously covered by the sea including a raised
beach with fossil cliffs.
Isostatic recoil along the west coast of
Scotland has caused a local fall in sea
level.
Fossil cliffs are visible behind the raised
beaches, with wave-cut notches and caves as
evidence of past marine erosion.
Raised beaches
Submergent coasts – a rise in sea level floods the coast. E.g. a ria south-west England.
Eustatic sea level rise has flooded the
lower reaches of a river valley and its
tributaries. Rias have a V-shaped
cross-section and the deepest part is
at the river’s mouth.
Fjords are also found along Submergent coasts. E.g. in New Zealand’s South Island.
Eustatic sea level rise has
flooded a glacial valley.
Fjords are long and steepsided with a U-shaped
cross-section. Unlike rias,
fjords are much deeper
inland than they are at the
coast (because this is where
glacial erosive power is
greatest). Fjords
characteristically have
steep sides and flat
bottoms.
Dalmatian coasts are submergent too. E.g. illustrated in Croatia.
Dalmatian type concordant
coasts have valleys and ridges
that run parallel to each other.
When the valleys flood due to a
rise in sea level, the tops of the
ridges remain above the surface
of the sea as a series of offshore
islands that run parallel to the
coast.
Concordant coasts have
different rock bands that run
parallel to the coast.
Why is Kiribati at risk from contemporary sea level change?
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The nation of Kiribati consists of 33 widely spaced islands, which stretch across the Pacific Ocean;
it is nearly as wide as the USA.
Kiribati’s islands are very low-lying sand and mangrove atolls.
Eustatic sea level rise is a major threat, caused by the melting of land-ice and thermal expansion
of the ocean.
However, land reclamation and aggregate mining may currently be playing a bigger role in
coastal erosion.
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Change in weather patterns with higher storm surges also contribute to an increasing risk of
coastal flooding.
Saltwater incursion (mixing with the fresh water in the island) is adversely affecting agriculture.
How does rapid coastal retreat cause threats to people at the coast?
What factors are responsible for coastal recession at Holderness?
The factors:
Subaerial processes
Waves (type, fetch, direction)
Tides
Weather systems
Seasons and occurrence of storms
Geology
Coastal management (see following section)
Subaerial processes
Slumping is the main form of mass movement affecting the boulder clay cliffs at Holderness. The
alternate wetting and drying of clay causes expansion and shrinkage, producing cracks during dry,
long periods. Subsequent rain then enters the cracked clay and percolates into the cliff, which
becomes lubricated and much heavier. The weakened cliff cannot support the extra weight, and the
clay slides downslope under gravity. The slumped material collects at the base of the cliff and then is
removed by the sea, causing the cliff line to retreat.
Waves
The main factor affecting the rate of erosion is wave energy. This depends on the fetch (how far the
waves have travelled).
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Fetch determines the power of the waves and refers to how far they have travelled.
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For example, the fetch along the Holderness coastline is typically about 800 km across the
North Sea.
However, the fetch for Cornwall is the whole width of the Atlantic Ocean 5000km, therefore
powerful destructive waves work along this coastline.
Small, almost enclosed seas often generate huge waves during storms. Waves move within
the sea but cannot disperse their energy.
The sea floor is relatively deep along the Holderness coast, so waves reach the cliff without
first being weakened by friction with shallow beaches.
Tides
Tides are changes in water level due to the gravitational attraction exerted by the moon and the
sun.
The tides flow southwards, transporting sand southwards and leaving the cliffs at Holderness poorly
protected against wave attack. Beaches south of Hornsea have reduced width, because an
imbalance exists between the input of sand (deposited by swash) and the removal of sand (by
backwash).
The Holderness Coast has a small tidal range; consequently, wave energy is concentrated across a
relatively small zone with increased erosion.
Weather systems
Low pressure weather systems and winter storms passing over the North Sea are often intense,
producing locally strong winds and waves. Low pressure air weighs less, raising sea levels, which in
turn produces much higher tides than usual. Low pressure weather systems additionally contribute
to storm surges as rising sea levels and strong winds cause water to pile up against the Holderness
Coast.
Seasons and Occurrence of Storms:
Erosion of Holderness also varies over time. Most erosion peaks occur when the biannual spring
measurement is taken. Some reasons for variations include:
1. Winter storms, which cause most erosion, especially when these coincide with high spring
tides.
2. Storms are rare in summer months, so erosion rates measured in autumn are lower.
3. North-easterly storms cause most erosion because of the long wave fetch, 1500km- from the
north Norwegian coast, but these are rare.
Geology
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Most of the Holderness coast consists of boulder clay. Boulder clay is also known as glacial
till, or drift, and is a mixture of fine clays, sands and boulders deposited by glaciers after the
last Ice Age. Boulder clay is structurally weak and has little resistance to erosion. It produces
shallow, sloping cliffs between 5 and 20 metres high.
●
The chalk band that surrounds the boulder clay has created a headland at Flamborough Head.
Erosion along fault lines and bedding planes has created features such as cliffs, arches and
stacks.
CONCLUSION:
Overall, the most important factors affecting coastal recession at Holderness are subaerial processes
and geology. Subaerial processes include rotational slumping, which may remove large sections of
cliff during a single event. Moreover, slumped material collects at the base of the cliff and then is
removed by the sea, causing the cliff line to retreat. Geology is a critical factor because this affects
the rate of mass movement and coastal erosion. For instance, Holderness’s boulder clay is prone to
slumping and offers little resistance to abrasion and hydraulic action.
Why is the Nile Delta receding?
Delta – where the river meets the sea and deposits part of its load.
The delta is a depositional landform created from sediment brought down by the Nile during annual
floods. Following construction of the Aswan High Dam on the River Nile in the 1960s, both river
discharge and sediment volume fell dramatically.
These changes were caused by:
● Water withdrawals for industry, cities and farming from the reservoir behind the Aswan High
Dam.
● Sediment being trapped in the reservoir behind the dam; water in the reservoir flows very
slowly allowing sediment to be deposited.
The effect of the Nile Delta has been dramatic. Erosion rates at the Rosetta, where one of the main
delta branches of the river meets the sea, jumped from 20 to 25m per year to over 200m per year as
the delta was starved of sediment.
Why is coastal flooding a significant and increasing risk for some coastlines?
Kiribati, Bangladesh and the UK all have coastlines at significant and increasing risk from coastal
flooding.
Why is Bangladesh at risk due to local factors?
1. Bangladesh is the world’s most densely populated country.
2. 46% of the country's population lives less than 10 meters above sea level.
3. Bangladesh also lies on the floodplains of three major rivers (Brahmaputra, Meghna and
Ganges).
4. Subsidence – some of Bangladesh’s estuarine islands have sunk by as much as 1.5 metres over
the last 50 years or so. Isostatic readjustment is partly responsible, due to the rising up of the
Himalayas. Nevertheless, the main reason for Bangladesh subsiding is the clearance and drainage
of more than 50 large islands.
5. The largest remaining tract of mangrove forest in the world is found in the Sundarbans region of
Bangladesh. The Sundarbans forest helped reduce the impact of Cyclone Sidr, but satellite
studies show that 71% of Bangladesh’s mangrove-forested coastline is now retreating by as much
as 200 metres per year.
6. The coastline narrows to a funnel shape in the Bay of Bengal, meaning that a storm surge can be
compressed into an increasingly narrow space, resulting in severe coastal flooding.
These six factors are local to Bangladesh. However, climate change is a global factor contributing to
the significant and increasing risk of coastal flooding in Bangladesh. Climate change has led to
eustatic sea level rise and is increasing the magnitude and frequency of storm surges. Moreover, the
pace and effects of climate change are uncertain.
What is a storm surge?
A storm surge is a change in sea level that is caused by a storm. They can lead to extensive flooding
and are dangerous for people living in many coastal areas.
The main cause is high winds pushing the seawater to the coast, causing it to pile up there. There is
also a smaller contribution from the low pressure at the centre of the storm “pulling” the water level
up, by about 1cm for every 1 millibar bar decrease in pressure. This is called the inverse barometer
effect, and this is similar to what happens when you drink through a straw.
What are the consequences of coastal recession and flooding for different communities?
Short-term economic
consequences
Short-term social
consequences
Cyclone Sidr 2007
Bangladesh (developing
country) (Huge storm surge
reached 6m in height.)
Cost of damage to roads,
embankments, sluices and
river bank protection (key
infrastructure) - US $29.6
million
1.8 million cattle and poultry
killed
700 Km of electricity lines
were damaged
Dead/missing - 4234
Damaged houses - 1.5 million
Some economic losses at Holderness
● Loss of businesses – e.g. Cliff House Farm
(south of Mappleton) lost agricultural land
North Sea Storm Surge 2013
UK (developed country)
(Large storm surge reached
3m in height.)
Insurers calculated the cost of
the damage at £100 million
Rail services in eastern
counties were disrupted
2 people died in the UK
At Hemsby, cliff erosion
resulted in several properties
collapsing into the sea
1400 homes flooded
Some social losses at Holderness
● It is predicted that 200 homes and several
roads will fall into the sea by 2100.
●
●
and owners had to stop rearing pigs due to
lack of access by road.
The Golden Sands Holiday park, south of
Withernsea, has lost 100 chalets to the sea
in 15 years. If they had not lost them, there
could have regularly been 400 extra people
visiting Withernsea and helping the local
economy.
Money has to be spent on coastal
management.
●
No compensation is paid out for the loss of
private property or land caused by coastal
erosion in England.
CONCLUSION:
Although economic and social losses from coastal recession are potentially devastating for some
densely populated communities, they are relatively small-scale at Holderness. Both the UK and
Bangladesh experienced serious economic and social consequences from storm surge events,
however these were more severe in Bangladesh. Finally, the consequences of contemporary sea level
rise for the nation of Kiribati are extreme. Experts predict that the islands may become uninhabitable
in the next century, and some citizens are already seeking refugee status in New Zealand. New
Zealand has opened a visa program for environmental refugees.
What are the different approaches to managing the risks associated with
coastal recession and flooding?
Hard engineering – involves building structures along a coast, usually at the base of a cliff or on the
beach.
Soft engineering – is designed to work with natural processes in the coastal system, in order to
manage erosion.
Sustainable coastal management – is a long-term approach that considers future threats such as
sea level rise and higher storm surges. However, its implementation can lead to local conflicts in many
countries.
Examples of hard engineering
● Groynes
● Sea walls
● Offshore breakwaters
● Rip-rap
● Revetments
Examples of soft engineering
o Strategic realignment / managed retreat
o Dune stabilisation
o Cliff re-grading
o Cliff drainage
o Beach nourishment
●
Hard engineering structures can remain effective for decades and provide reassuring and
“obvious” protection. However, economic costs are usually very high, and coastlines are made
visually unattractive. Moreover, defences built in one place frequently have adverse effects
downdrift. Finally, physical processes are directly altered, making hard engineering a less
appropriate choice for environmentally sensitive land.
o
Soft engineering is less intrusive at the coast and usually cheaper in the long term. Nevertheless,
in general the protection provided is not as effective.
●
Overall, hard engineering is most suitable for high value land whereas soft engineering is most
suitable for low value and/or environmentally sensitive land.
Advantages and disadvantages of hard and soft engineering
Examples of different management approaches
Hard engineering at Holderness:
●
●
●
Withernsea - In the 1990s, following a cost-benefit analysis, the straight wall was replaced by a
curved wall for £6.3 million (£5000 per metre). The waves are now nosier when they break against
the wall, and the promenade is smaller. The views from sea front hotels have also been restricted.
Some tourists find the rip-rap at the base of the sea wall unattractive. Moreover, the Golden
Sands Holiday Park is downdrift of the defences (lost chalets).
Mappleton – Two rock groynes (costing £2 million) were built in 1991, with the aim of preventing
the removal of the beach by longshore drift. As well as this, rock armour was used. At Cowden,
3km south (downdrift) of Mappleton, the resultant sediment starvation caused is argued to have
increased erosion of the cliffs – from 2.5 to 3.8 metres a year between 1991 and 2007.
Therefore, hard engineering at Holderness has led to conflict between different players
(businesses, tourists, homeowners, local authorities and environmental pressure groups).
Soft Engineering at Abbotts Hall Farm:
Location
Abbotts Hall Farm is situated on the Blackwater Estuary; this is the estuary of the River Blackwater
between Maldon and West Mersea in Essex. Abbotts Hall Farm is a good example of an area where
soft engineering has been implemented.
Abbotts Hall Farm
is located on
Maldon Road on
the opposite side
to Hillside Farm
Before the sea wall was built, there were 40,000ha of salt marsh but today only 2500ha are left. As
sea level continued to rise, it became too expensive to continue to heighten the sea wall in order to
protect the arable farmland behind. At Abbotts Hall Farm, managers chose to take a more
sustainable approach and breached the sea wall, which is called strategic realignment. This allowed
the tide to flow in and out and aimed to allow the salt marsh to redevelop on the arable land behind
the sea wall. The salt marsh potentially acts as a large sponge, absorbing seawater and reducing the
impacts a flood could have. Although many coastal landowners may resist the idea of the managed
realignment due to the fear of flooding, using nature as soft engineering is more sustainable and
also less expensive to maintain, hence strategic realignment was chosen for Abbotts Hall.
How was conflict minimised?
Solution adopted was radical:
● In 2000 Essex Wildlife Trust purchased Abbotts Hall Farm on the Blackwater
Estuary
● 4000 hectare strategic realignment scheme was implemented by creating 5
breaches in the sea wall in 2002- allowed new salt marshes to form inland
Benefits of the scheme:
● Abbotts Hall Farm owners received market price for their threatened farm
● Very high costs of hold the line policy avoided but flood risk reduced
● Water quality in estuary improved because of expansion of reeds that filter and
clean the water
● New paths and waterways were created for leisure activities
● Additional income streams from ecotourism and wildlife watching were created
● Important birds and fish nurseries enhanced
● Change in species provides evidence that successional development of the salt
marsh has occurred.
Overall the scheme shows how different stakeholders (environmentalists, landowners, coastal
managers and local residents) can all be kept happy when radical plans are adopted.
This is an example of sustainable engineering as well as being soft.
Sustainable management in the Maldives (an emerging country):
The key to the Maldives’ new strategy is renting out islands and using the money to reclaim, fortify
and even build new islands. People living on smaller lower-lying islands may then be relocated to
more flood-resistant islands when needed.
The City of Hope is being built on an artificial island called Hulhumale, near the capital Male. To build
it, a state-owned company is pumping sand from surrounding atolls and depositing it on shallow reefs
that surround the original lagoon. It is being fortified with walls 3 metres above sea level – which is
higher than the highest natural island at only 2.5 metres above the sea.
The capital city Male has also been ringed by a 3 metre sea wall (hard engineering).
However, this strategy has potential to cause conflict because:
● Money spent protecting the capital city Male and creating artificial islands such as Hulhumale
means that isolated islands are ignored.
● Sustainable management of traditional income sources (such as fishing) and resources (such
as mangroves) is overlooked in favour of protecting urban and tourism development from
coastal threats.
Sustainable management in the Mahanadi Delta, India:
The Mahanadi delta is prone to storm surges associated with tropical cyclones.
In 1999 during ‘super cyclone’ Kalina, villages that still had four or more kilometres of mangroves
recorded no deaths. However, in areas where the protective belt was less than 3km wide deaths rose
sharply.
The NGO Wetlands International, the Indian government and Odisha’s Integrated Coastal Zone
Management project are trying to reverse decades of mangrove destruction. They are helping
villagers to plant mangroves along the coast, and also on the banks of all tidal rivers along Odisha’s
coast.
This is an example of soft engineering as well as being sustainable. Research from the Australian
Institute of Marine Science concluded that the faster sea levels rise, the faster mangroves accumulate
sediment in their roots. They can keep up with a rise of 25 mm a year, further emphasising
sustainability.
Why are coastlines now increasingly managed by holistic integrated
coastal zone management (ICZM)?
Integrated Coastal Zone Management
Manage complete sections of the coastline as a whole rather than by individual towns or villages. This
takes the sediment cell concept into account and brings together all of those involved in the
management and use of the coast.
Shoreline Management Plan
A sediment cell managed as an integrated unit; part of Integrated Coastal Zone Management.
No Active Intervention
No investment in defending against flooding or erosion, whether or not coastal defences have existed
previously. The coast is allowed to erode landward and/or flood.
Strategic Realignment
Allow the coastline to move naturally (in most cases to recede) but manage the process to direct it in
certain areas.
Hold the Line
Build or maintain coastal defences so that the position of the shoreline remains the same over time.
Advance the Line
Build new coastal defences on the seaward side of the existing coastline. Usually this involves land
reclamation.
Benefits of ICZM:
● Sediment (or littoral cells) can be managed by a whole
● The entire coastal zone is managed (including ecosystems), not just the littoral zone
● Management can occur across political boundaries (such as different council areas) to ensure
a holistic approach along extended areas of coastline
● Different stakeholders are involved in decision making in order to harmonise policies and
minimise conflict
● Natural processes may be utilised rather than halted (so more sustainable)
● It is easier to adapt to changing risks.
The East Riding of Yorkshire Council’s ICZM
●
●
The ICZM was launched in 2002 and involved over 80 organisations
This ICZM was used to develop the Flamborough Head to Gibraltar Point SMP published in
2011
The Flamborough Head to Gibraltar Point SMP policy for Holderness up to 2025
-
The East Riding of Yorkshire Council worked with a number of players and stakeholders in
developing the shoreline management plan (SMP), including:
National government agencies such as the Environmental Agency
Local governments such as Lincolnshire County Council
Stakeholders in the economy such as the National Farmers Union
Environmental stakeholders such as the Yorkshire Wildlife Trust
Cost Benefit Analysis (CBA) and Environmental Impact Assessment (EIA) at Holderness concluded
that:
●
●
●
Along the undefended parts of the cost, the ‘do nothing’ policy has no direct costs. However,
there will be some economic losses (infrastructure, buildings, etc.).
The benefits outweigh the costs of continuing to protect Bridlington, Hornsea and
Withernsea.
The economic benefit of holding the line at Mapleton is similar to the cost.
●
●
●
Because of the current importance of the gas terminals at Darlington and Easington, the
benefits of ‘hold the line’ clearly outweigh the costs.
Spurn Point (nature reserve) will be allowed to evolve – requiring minimal costs and
encouraging sand dune and salt marsh succession.
Note that two rock groynes have been built at Mappleton to ‘hold the line’ despite the small
size of the village and debate over whether ‘no active intervention’ should be used.
How successful are the management approaches used at Walton-on-theNaze?
Beach profile diagrams for managed beach and wave cut platform
The diagrams show a clear difference between the beach profiles of the managed beach and wave
cut platform. The managed beach appears to be significantly higher however, statistical testing is
needed to confirm this.
Managed Beach Table 𝒙̅ =0.95
Site
Cumulative beach
height
x
Variance from
Variance from mean
mean 𝒙−𝒙̅
squared (𝒙−𝒙)̅2
Cumulative beach
height squared 𝒙2
1
0.00
-0.95
0.9025
0
2
0.70
-0.25
0.0625
0.49
3
0.71
-0.24
0.0576
0.5041
4
0.78
-0.17
0.0289
0.6084
5
0.81
-0.14
0.0196
0.6561
6
0.81
-0.14
0.0196
0.6561
7
0.87
-0.08
0.0064
0.7569
8
0.95
0
0.00
0.9025
9
1.00
0.05
0.0025
1.00
10
1.03
0.08
0.0064
1.0609
11
1.08
0.13
0.0169
1.1664
12
1.18
0.23
0.0529
1.3924
13
1.28
0.33
0.1089
1.6384
14
1.30
0.35
0.1225
1.69
15
1.34
0.39
0.1521
1.7956
16
1.40
0.45
0.2025
1.96
∑
15.24
1.7618
16.2778
Standard Deviation Formula
SD = 0.33
The standard deviation for the wave cut platform is 0.10.
Therefore, the results for the managed beach show more variance from the mean suggesting that
there is more deposition there. However, the standard deviation result may still have happened by
chance. Hence a student t-test (t) is needed to further explore statistical significance.
Student t-test Formula
Null Hypothesis: the mean cumulative beach height (m) of the managed beach and wave-cut
platform have no statistically significant difference.
Alternative Hypothesis: the mean cumulative beach height (m) of the managed beach and wave-cut
platform have a statistically significant difference.
Calculating the variance (s1^2) for the managed beach. S1^2 = sigma x^2 - (sigma x)^2 over n/ n-1
S1^2 = sigma 16.2778-15.24^2/16/15
S1^2 = 0.1174
The variance (S2^2) for the wave cut platform is 0.0110 and the mean (x bar ^2) is 0.19
= 8.48 to 2dp
n1 + n2 - 2 degrees of freedom = 30
8.48 is greater than 3.46 therefore there is only a 1% probability that the difference occurred by
chance. The null hypothesis may be rejected, but the alternative hypothesis may be accepted. In
conclusion, the management strategies have a created a significantly difference in mean beach
height.
Mean, mode and median
● The mean is calculated by adding up the total and dividing by the number of items. The
mean uses every value in the data and hence is a good representation of the data. However,
it can be influenced by any extreme values and gives no indication of data spread.
● The mode is the most commonly occurring value within a data set. It can be calculated
easily yet fluctuation in the frequency of observation is more when the sample size is small.
● The median is the midpoint value of a rank order. Where there are an odd number of data
items the median is always a whole number. Where there are an even number of data items
the median lies across two items at the midpoint. The median is not distorted by extreme
values however is not used in many statistical tests.
Mean infiltration in mm:
● Managed Beach - 85mm
●
Wave-cut platform - 29mm
The managed beach has higher infiltration as sand is permeable. Hence, more water is infiltrated in
comparison to a wave-cut platform.
Modal total sediment weight in (g):
● Managed Beach - 440g
● Wave-cut platform - 0g
This suggests that most of the sediment on the wave-cut platform is trapped due to groynes as they
are a structure which holds back material transported by longshore drift.
Range, dispersion and inter-quartile range
● The median divides the data into two halves. For a set of n ordered numbers the median is
the (n + 1) ÷ 2th value.
● Similarly, the lower quartile (LQ) divides the bottom half of the data into two halves, and
the upper quartile also divides the upper half of the data into two halves. For a set of n
ordered numbers the lower quartile is the (n + 1) ÷ 4th value and the upper quartile (UQ) is
the 3 (n + 1) ÷ 4th value.
● The difference between the upper and lower quartiles is the interquartile range.
The range in beach height is 1.4m for the managed beach whereas it is only 0.35 metres for the
wave-cut platform. This again indicates that more sediment has been deposited on the managed
beach due to the effect of the groynes.
Managed Beach Table (rearranged number in order from lowest to highest - for cumulative
beach height to calculate LQ, Median, UQ.
Distance along transect
(m)
Beach
Height
Difference in Height
(m)
Cumulative Beach Height
(m)
0 [Sea]
4.70
0.00
0.00
1
4.00
0.7
0.7
2
3.99
0.01
0.71
3
3.89
0.1
0.78
4
3.92
0.03
0.81
5
3.89
0.03
0.81
6
3.83
0.06
0.87
7
3.75
0.08
0.95
8
3.70
0.05
1.00
9
3.67
0.03
1.03
10
3.62
0.05
1.08
11
3.52
0.1
1.18
12
3.42
0.1
1.28
13
3.40
0.02
1.30
14
3.36
0.04
1.34
15
3.30
0.06
1.40
Lower Quartile: In between 0.78m and 0.81m
Answer: 0.795m, wave cut platform = 0.105m
Median: 0.975m, wave cut platform = 0.185m
Upper Quartile: between 1.18m and 1.28m
Answer: 1.23, wave cut platform = 0.27m
Interquartile Range: 1.23m - 0.795m
Answer: 0.435, wave cut platform = 0.165m
These results again confirm that the height of the managed beach is greater and more varied than
that of the wave cut platform.
CONCLUSION:
The evidence presented indicates that management has been successful at Walton-on-the-Naze.