Coastal Landscapes

Question 1

What is the littoral zone

Answer 1

The littoral zone is the area of shoreline where land is subject to wave action. It’s subdivided into offshore, nearshore, foreshore and backshore. (ONFB - OKAY NOW FRY BANANAS!)
sea - offshore - nearshore - foreshore - backshore - field with lots of cows

Question 2

What is the offshore, nearshore, foreshore, backshore

Answer 2

Offshore: The area of deeper water beyond the point at which waves begin to break. Friction between the waves and the sea bed may cause some distortion of the wave shape.
Nearshore: The area of shallow water beyond the low tide mark, within which friction between the seabed and waves distorts the wave sufficiently to cause it to break. (breaker zone) There may be a breakpoint bar between the offshore and nearshore zones.
Foreshore: The area between the high tide and the low tide mark.
Backshore: The area above the high tide mark, affected by wave action only during major storm events.

Question 3

3 types of coastline

Answer 3

Rocky, cliffed coastline
areas of high relief varying from a few metres to hundreds of metres in height
usually form in areas with resistant geology, in a high energy environment, where erosion is greater than deposition and big, stormy (not Daniels) waves. Destructive waves!
Sandy coastline
areas of low relief with sand dunes and beaches, that are much flatter.
they usually form in areas with:
less resistant geology
a low energy environment
where deposition > erosion
constructive waves
Estuarine coastline
Areas of low relief with salt marshes and mudflats (estuaries)
They form:
in river mouths
where deposition > erosion
in a low energy environment
usually in areas of less resistant rock

Question 4

Dynamic zone

Answer 4

There are constantly changing inputs, through flows, and outputs of energy and material. (short term)
There are also long-term changes, e.g. sea level variation due to climate change.
And short term changes (e.g. high and low tide variation over the lunar month; wave energy variation due to weather conditions)

Question 5

Long term criteria for classifying coats

Answer 5

Long Term Criteria

Geology
Geology is all the characteristics of land, including lithology (rock type) and structure (arrangement of rock units).
It can be used to classify coasts as rocky, sandy or estaurine.
Or, concordant and discordant.

Sea Level Change
Sea level change can be used to classify coasts as emergent or submergent.
This can be caused by:
Tectonic processes can lift sections of land up, causing local sea fall, or lead sections of land to subside, causing local sea rise.
Climate change causes sea levels to rise and fall in a 100,000 year cycle due to the change in the Earth’s orbit shape.
sea levels fall for 90,000 years during glacials as ice sheets expand and rise for 10,000 during interglacials
sea levels rise even more when the Earth emerges from an ice age and all surface ice melts

Question 6

Short term criteria for classifying coasts

Answer 6

​Short Term Criteria

Energy Inputs
Coasts receive energy inputs from waves (main input), tides (ebb and flow over a 12.5 hour cycle), currents. rivers, atmospheric processes, gravity and tectonics.
Used to classify coasts as high energy and low energy.

Sediment Inputs
Coasts receive sediment inputs from waves and wind (vary constantly with weather), tides (ebb and flow over 12 1/2 hour cycle), currents, mass movement and tectonic processes.
Sediment is added to a coastline through deposition and removed by erosion.

Where erosion > deposition there is a net loss of sediment and the coastline retreats – an eroding coastline.
Where deposition > erosion there is a net gain of sediment and the coastline advances – an outbuilding coastline.

Advancing/Retreating
Coastlines are classified as advancing or retreating due to long-term processes (emergent/submergent) and short term (outbuilding/eroding).

Question 7

Rocky coasts

Answer 7

Rocky Coasts

Rocky coasts occupy about 1,000 km of the UK’s coastline, mainly in the north and west.
Cliffs vary in height from high-relief areas,
e.g. 427 m Conachair Cliff on the Isle of Hirta in the Outer Hebrides
to low-relief
e.g. 3m cliffs at Chapel Porth in Cornwall
.
Rocky coasts usually form in areas of geology that is resistant to the erosive forces of the sea, rain and wind. Their lithology and structure means they erode and weather slowly

​See 2B.3A for how lithology affects resistance.

Rocky coastlines form in a high-energy environment where erosion > deposition.
Erosion is continuously moving transported and deposited sediment as well as slowly eroding the cliff.

Question 8

Coastal plains

Answer 8

Coastal Plains - (sandy and estuarine coastlines)

Coastal plain landscapes are relatively flat, low relief areas adjacent to the sea.
They often contain freshwater wetlands and marshes due to the poor drainage of the flat landscape.
Their littoral zone is composed of sand dunes, beaches, mud flats and salt marshes.

Coastal plain landscapes form in low-energy environments where deposition > erosion, so they experience a net accumulation of sediment. ​They form through coastal accretion (a continuous net deposition of sediment.) This comes from:
offshore sources (transported by waves, tides or current)
terrestrial sources (transported by rivers, glaciers, wind or mass movement)

Coastal plains may be
sandy coasts, composed of sands, shingles and cobbles.
estuarine (alluvial) coasts composed of mud (clays and silts)

They form most of the UK’s south and east coastline.

Coastal Plain Formation
They usually form by coastal accretion, where continuous net deposition causes the coastline to extend seawards. This is often extended biologically as plants colonise shallow water, trapping sediment and forming organic deposits when they die.
They also form by sea level change, when the falling sea level exposes a flat continental shelf. e.g. the Atlantic coastline of the USA.
Where erosion = deposition dynamic equilibrium exists as there’s a continuous flow of energy and material through the coasts, but the size of stores (beach, salt marsh, mudflat) remains unchanged.

Question 9

Concordant coasts

Answer 9

Concordant

Concordant coasts usually form where rock strata or folds run parallel to the coast.
Some concordant coasts have long, narrow islands running parallel to the coastline.
Concordant coasts are also known as dalmatian coasts, after the Dalmatian region of Croatia, or Pacific coasts, after the coastline of Chile in South America.

Question 10

Discordant coasts

Answer 10

​Discordant

These are where rock strata or structures are aligned at an angle to the coastline.
Discordant coasts have a crenellated pattern of projecting headlands and indented bays.
Discordant coasts are also known as Atlantic coasts, after the Cork coastline in the Republic of Ireland.
Discordant coasts forms where geological structure is such that different rock strata of folds are aligned at an angle to the coastline.
Rock strata that are less resistant (due to the rock unit’s lithology and structure) erode rapidly to form indented bays.
More resistant strata erode only slowly, and are left projecting into the sea as headlands.
The relative resistance of rock types influences the degree of indentation of bays.

The morphology of discordant coasts alters the distribution of wave energy and rate of erosion through wave refraction. Where the wind is blowing directly onshore and the wave front is parallel to the coastline, the section of wave approaching the headland will encounter shallow water before the wave front approaching the indented bay. The waves approaching the headland slow and wave height increases. The wave front refracts, becoming curved. Convex in bays, dispersing energy, and concave at headlands, concentrating energy. Refraction increases the rate of erosion at headlands and reduces it at bays, generally decreasing the degree of indentation.

Question 11

South Dorset coast

Answer 11

South Dorset Coast
A concordant coastline with resistant Portland Limestone forming a protective stratum parallel to the sea.
Less resistant Purbeck limestone and Wealden Clay lie behind the Portland, with resistant chalk further north.
Portland limestone erodes very slowly, retreating landwards by marine undercutting and collapse to form a straight W-E coastline.
At points where the Portland is weaker, erosion has broken through and then rapidly eroded out the softer strata laterally, creating a series of coves, e.g. Lulworth Cove and Stair Hole, with narrow openings, widening laterally parallel to the coast.
In places such as Worbarrow Bay and St Oswald’s Bay, lateral widening of coves led to them joining into a single bay, with remnants of the outer Portland left as a line of stumps parallel to the coast, e.g. Bull’s Head in St Oswald’s Bay.
Straight coastline now formed by a concordant band of constant chalk.

Question 12

Dalmation coast

Answer 12

Dalmatian Coast of Croatia
On the Adriatic Sea
A concordant coastline produced by the geological structure of folds parallel to the coast.
Tectonic forces produced by the collision of African and Eurasian plates compressed Carboniferous Limestone during the Alpine Orogeny 50 million years ago.
Created up folded ridges (anticlines) and down folded valleys (synclines) aligned parallel to the coast.
Sea level rise at the end of the Devensian Glacial overtopped the low points of the anticlines and the sea flooded synclines.
This produces lines of narrow islands parallel to the coast formed by projecting sections of anticlines.
Lines of islands separated by narrow sea channels parallel to the coast (sounds)

Question 13

Half coastline

Answer 13

Haff Coastlines
These form where deposition produces unconsolidated geological structures parallel to the coastline.
During the Devensian glacial the sea level was about 100 m lower than today as water was retained in huge ice sheets.
Meltwater rivers on land beyond the ice front deposited thick layers of sand and gravels onto outwash plains (sandurs)
In the Holocene Interglacial constructive waves pushed the ride of sands and gravel landwards as sea levels rose.
Sand ridge formed bars across some bays and river mouths, with trapped river water forming a lagoon behind (callled haffs in Poland on the Baltic Sea)
For example the Neman Haff behind the bar running from the Kaliningrad in Russia to the Lithuanian coast at the mouth of the river Neman.
Chesil Beach in Dorset was formed this way. Shingle ridge reconnected island of Portland Bill to land (a tombolo)

Question 14

Swanage bay

Answer 14

Swanage Bay
on the Isle of Purbeck in East Dorset
formed by the erosion of less resistant Wealden Clays
More resistant Jurassic Portland Limestone forms the Peveril Point headland to the south, projecting out by 1 km.
Resistant Cretaceous Chalk forms the Foreland headland, projecting 2.5 km to the north.
However, structure is not the only factor influencing the indentation of Swanage Bay, since Swanage bay faces east, and is sheltered from the prevailing south westerly wind and highest energy waves.

Question 15

Bantry bay

Answer 15

Bantry Bay
In Cork in the south west of the Republic of Ireland
Formed from less resistant Carboniferous Limestone
Beara Peninsula to the north formed from more resistant Devonian Old Red Sandstone and projects 35 km into the Atlantic Ocean.
Sheep’s Head Peninsula to the south formed from more resistant coarse sandstone, projects out 21 km.
The high degree of indentation of Bantry Bay is not solely influenced by the relative resistance of rock types, but also the orientation of strata SW-NE means that they directly face high energy Atlantic waves driven by the prevailing SW wind.
The Bay is also a product of sea level rise, since river erosion cut a low-relief river valley into Carboniferous Limestone, allowing the sea to flood inland and creating a ria at the start of the Holocene.

Question 16

Joints

Answer 16

Joints
Joints are fractures in rocks created without displacement.
They occur in most rocks, often in regular patterns, dividing rock strata up into blocks with a regular shape.
In igneous rocks, cooling joints form when magma contracts as it looses heat.
In sedimentary rocks, joints form when rock is subject to compression or stretching by tectonic forces or weight of overlying rock.
When overlying rock is removed, underlying strata expand and stretch, creating unloading joints parallel to the surface.
Jointing increases erosion rates by creating fissures which marine erosion processes such as hydraulic action can exploit.

Question 17

Faults

Answer 17

Faults
Faults are major fractures in rock created by tectonic forces, with displacement of rocks either side of the fault line. They are often large scale, extending many kilometres. It significantly increases rate of erosion, since zones of faulted rock are much more easily eroded.
Huge forces are involved in faulting and displacing them. Because of this, either side of the fault line, rocks are often heavily fractured and broken, which is easily exploited by marine erosion.

Question 18

Folds

Answer 18

Folds
Folds are bends in rocks. They are produced by sedimentary rock layers being squeezed by tectonic forces. The two main types are anticlines and synclines.
Folded rock is often more heavily fissured and jointed, meaning they are more easily eroded.

It also increases erosion rates by increasing angle of dip, and by causing joint formation as rock is stretched along anticline crests and compressed in syncline troughs.

Question 19

Dip

Answer 19

Dip
Dip is the angle of inclination of the rock strata from the horizontal. It’s a tectonic feature. Sedimentary rocks are deposited horizontally, but can be tilted by folding and faulting by tectonic forces. It can have dramatic effects on cliff profiles.

Horizontal dip produces a vertical, or near-vertical profile, with notches reflecting weathering and small scale mass movement of strata that are jointed or more easily eroded.

High angle of seaward dip (>45) produces a sloping, low-angled profile with one rock layer facing the sea; vulnerable to rock slides down the dip slope when uppermost strata are attacked by sub-aerial processes. The profile slopes corresponding to that of strata dip. Bedding planes between strata are weakly bonded and readily loosened by weathering.

Low angle of seaward dip (<45) produces a steep profile, that may even exceed 90 degrees, creating areas of overhanging rock; very vulnerable to rock falls. Frequent small-scale mass movement of material weathered from cliff face. Major cliff collapse when undercutting by marine erosion makes overhang unsustainable.

Landward dipping strata produces steep profiles on 70-80’ as downslope gravitational force pulls loosened blocks into place. Very stable profile with few rock falls.

cliff profile: the height and angle of a cliff face, plus its features such as wave-cut notches or changes in slope angle.

Question 20

Micro Features

Answer 20

​Micro-Features

Micro-features are small-scale coastal features such as caves and wave-cut notches which form part of a cliff profile.

They form in areas weakened by heavy jointing, which have faster rates of erosion, enlarging the joint to form a sea cave.

The location of micro-features found within cliffs, are often controlled by the location of faults and/or strata which have a particularly high density of joints and fissures.

Question 21

Mineral composition

Answer 21

Mineral composition
Some rocks contain reactive minerals easily broken down by chemical weathering, e.g. calcite in limestone.
Other minerals are more inert that chemically weather more slowly, if at all, e.g. quartz in sandstone.

Question 22

Rock class

Answer 22

Rock class
Sedimentary rocks, e.g. conglomerates, sandstones, limestones and clays, are clastic (made of clasts (sediment particles), cemented together)
Many cements are reactive and easily chemically weathered, e.g. iron oxide and calcite.
Sedimentary rocks with very weak cementation, e.g. boulder clay, gravels and sands, are termed unconsolidated.
Igneous rocks, e.g. granite, and metamorphic rocks, e.g. marble, are crystalline with strong chemical bonding.
Rocky coastlines vary in resistance of geology.
Granite erodes at a rate of 0.1 cm p.a.
Carboniferous limestone at 1 cm p.a.
Sandstone at 10 cm p.a.
Boulder clay at 1 m p.a.

Question 23

Structure

Answer 23

Structure
Rocks with fissures (e.g. faults and joints) or air spaces (porous) rocks, weather and erode rapidly.

Question 24

Lithology

Answer 24

Lithology is rock type.
Rate of recession is the speed at which the coastline is moving inland.
Clastic rocks are those made of sediment particles cemented together
Crystalline rocks are made of interlocking mineral crystals.

Rate of recession is influenced by bedrock lithology (igneous, sedimentary or metamorphic) and the geology unconsolidated sediment.
How reactive minerals in the rock are when exposed to chemical weathering
Whether rocks are clastic (less) or crystalline (more resistant)
The degree to which rocks have cracks, fractures, and fissures (these weaknesses are exploited by weathering and erosion)

Question 25

Igneous rock type

Answer 25

Igneous
Igneous rocks are formed from solidified lava or magma. (Lava is just magma on the surface of the Earth)
Some examples are: granite, dolerite, basalt and pumice.
They erode and weather very slowly, producing very slow rates of coastal recession, because:​
It’s composed of interlocking crystals, forming hard, resistant rock. (so less recession)
In addition, although they may contain cooling joints, they usually have fewer joints (e.g. granite) and weaknesses than other rock groups, slowing the rate of recession.
​Igneous coasts recede at less than 0.1 cm p.a.
However, there are exceptions:
​Newly formed lava and solidified ash layers (tuff) erode easily.
Newly formed volcanic islands can exhibit very rapid erosion rates of 40m p.a.​

Question 26

Metamorphic rock

Answer 26

Metamorphic
They are formed by the recrystallisation of sedimentary and igneous rocks through heat and pressure.
Some examples are: slate, schist, marble, gneiss
It’s hard and resistant because:
​It has a crystalline structure
​However, it is less resistant than sedimentary rock because:
​​Their crystals are often orientated in the same direction (foliation) making them weaker than the interlocking crystals of igneous rocks.
Often heavily folded and faulted
​Metamorphic coasts often recede slowly about 0.1-0.3 cm p.a.

Question 27

Sedimentary rock

Answer 27

Sedimentary
They are formed by the compaction and cementation of deposited material, or sediment.
E.g. sandstone, limestone, shale
Usually the sediment is fragments of other rock (clasts)
Conglomerates
Sandstones
Mudstones
​Sometimes the sediment is a chemical precipitate.
​E.g. limestone
​Sometimes the sediment is composed of dead organic matter.
​Coal
Chalk
​​
They are less resistant than metamorphic or igneous rocks, due to:
Weak bedding planes
​They’re clastic
Often heavily jointed as a result of compaction and pressure release.
Rocks like shale may have many bedding planes and fractures.

However, the rate of erosion varies from slow (0.5 cm) to fast (10 cm):
Carboniferous limestone 1 cm p.a.
Young sandstones 10 cm p.a.

This is because:
Older sedimentary rock is buried deeper and is subject to more intense compaction with stronger sedimentation - so tend to be more resistant than younger sedimentary rocks.

Question 28

Unconsolidates sediment

Answer 28

Unconsolidated Sediment​ - sediment that has not yet been cemented to form solid rock (lithification)
Drift geology is recently deposited unconsolidated sediment that usually overlies the solid geology of the bedrock.

Some examples of unconsolidated sediment are: (or sand)
Fluvial alluvium
Glacial boulder clay
Aeolian loess

They are very easily eroded, resulting in very fast rates of recession
The boulder clay of Holderness coast in Yorkshire retreats at 2-10 m p.a.

Question 29

Complex cliff profiles

Answer 29

Complex cliff profiles are produced where cliffs are composed of strata of differing lithology. Less resistant strata erode and weather quickly, being cut back rapidly, wave cut notches may be formed. Resistant strata erode and weather slowly, retreating less rapidly. They may form a ‘bench’ feature at the cliff base. Higher up, they form overhanging sections until they collapse by mass movement. However, generally the overall rate of cliff recession is determined by the resistance of its weakest rock layer.

Rocks show different levels of resistance to marine erosion in the foreshore zone.
Rocks show different levels of resistance to weathering or mass movement in the foreshore and backshore zones.

Complex cliff profiles can also be produced when there are alternating permeable and non-permeable strata.
Permeable rocks are those that allow water to flow through them. This may be because:
they’re porous (e.g. chalk)
these are rocks containing voids called pores, for example chalk and poorly cemented sandstones
they have numerous joints (e.g. carboniferous limestone)
Examples of permeable rocks are many sandstones and limestones.

Permeable rocks tend to be less resistant to weathering because water percolating comes into contact with a large surface area that can be chemically weathered.
e.g. Limestone weathered by carbonation converting calcium carbonate to soluble calcium bicarbonate.
Feldspar in granite weathered by hydrolysis into kaolin (china clay)

Impermeable rocks do not allow water to flow through them.
Clays, mudstones, and most igneous and metamorphic rocks are impermeable.

Question 30

A spring creating erostion

Answer 30

1) A spring creating erosion
Where a permeable rock overlays an impermeable stratum groundwater is unable to percolate down into the lower layer.
Water accumulates in the permeable layer, producing a saturated layer where the pores are full of water.
A spring will form on the cliff face at the top of the saturated layer.
As the stream flows down the cliff, fluvial erosion (surface run off erosion( will attack the saturated permeable bed and lower impermeable stratum, reducing the angle of the cliff profile.

Question 31

Groundwater flow

Answer 31

2) Groundwater flow removing cement
Water flows through the permeable (sands) but can’t flow through the impermable (clay), so flows along the interface. Groundwater flow through rock layers can weaken rock by removing the cement that binds them together. Weak, unconsolidated layers slump.

Question 32

Pore water pressure and saturation

Answer 32

3) Pore water pressure leads to slumping and sliding
It also produces pore water pressure:​ (the internal force within cliffs exerted by a mass of groundwater within permeable rocks)
Pore water pressure in the saturated layer pushes rock particles apart.
Reduces friction between grains in unconsolidated material
Lubricates lines of weakness, e.g. joints and bedding planes.
This affects their stability.

4) Saturation leads to slumping and sliding
Saturation promotes mass movement through lubrication and by adding weight.
Leads to slumping in unconsolidated material and sliding in consolidated strata - producing a complex cliff profile.

Question 33

Vegetation context

Answer 33

Vegetation can stabilise unconsolidated sediment and protect it from erosion.
Plant roots bind sediment together, making it harder to erode.
Plant stems and leaves covering the ground surface protect sediment from wave erosion and erosion form tidal or longshore currents when exposed at high tide.
They also prevent sediment from wind erosion at low tide.

In addition vegetation increases the rate of sediment accumulation:
Plant stems and leaves interrupt the flow of wind and water, reducing their velocity and encouraging deposition.
When the vegetation dies it adds its organic matter (hummus) to the soil.

​ Unconsolidated sand, silt and clay, freshly deposited at the coast are a very harsh environment for plants.

The coast is an incredibly harsh environment for plants because:
They’re exposed to high wind speeds at low tide.
Lack of shade produces a high diurnal (daily) temperature range.
They’re submerged in salty water for half the day.
The evaporated sea spray makes the sediment saline.
Salt is highly porous and permeable, so rain water drains quickly- so plants have little fresh water.
Submerged sediment has its pores saturated with salt water - there’s no oxygen for plant roots to respire with.
Sand lacks nutrients.

Question 34

Pioneer plants

Answer 34

Pioneer Plants
These are the first plants to colonise freshly deposited sediment.
They modify the environment:
Stabilising sediment
Adding organic matter that retains moisture, contributes nutrients and provides shade.
Reduce evaporation in sand.

Now, slightly less hardy plants can colonise the sediment. They add more organic matter, stabilise existing sediment and trap more.

Each step in plant succession is called a seral stage.

The end result of plant succession is called a (climatic) climax community.

Plant succession: the changing structure of a plant community over time as an area of initially bare sediment is colonised.
Plant succession: the process by which a series of different plant communities occupy an area over time.

Question 35

Dune successional development

Answer 35

Xerophytic plants are specially adapted to dry conditions to colonise bare sand.
Plant succession on sand is called psammosere.

Psammosere:
​Embryo dunes form when seaweed driftwood or litter provides a barrier or shelter to trap sand.
As the embryo grows, it is colonised by xerophytic pioneer plants, like sea couch grass, lyme grass, saltwort and sea rocket.
the embryo dunes alter the conditions to something other plants can tolerate, allowing other plants to colonise and forms a fore dune
Pioneer plants stabilise the sand allowing marram grass to colonise.
Marram grass is marvellous because it:
has waxy leaves to limit water loss through transpiration and resist wind-blown sand abrasion.
has roots that can grow to 3m to reach down the water table and the stem can grow 1m a year to avoid burial by deposited sand.
allows the dune to grow, rapidly forming a yellow dune
it’s called this because the surface is mainly sand, not soil
As the marram grass and sedge grass dies, it adds hummus to the sand, creating soil. A grey dune develops, with plants such as gorse.
grey dunes and dune slacks (see bottom) are fixed dunes
examples of plants are: red fescue, heather, creeping willow
The dune is now above high tide level, so rain washes salt from the soil, making it less saline.
The soil now has improved nutrients and moisture retention, allowing non-xerophytic plants to colonise the dunes until a climax plant community is reached, in equilibrium with the climate and soil conditions.
e.g. bramble, pine, birch

Question 36

Salt marsh successional development

Answer 36

Halophytic plants are specially adapted to saline conditions to colonise mud.
Halosere is plant succession in salty water.
Estuarine areas are ideal for salt marshes because:
they’re sheltered from strong waves (so sediment like mud and silt can be deposited)
rivers transport a supply of sediment to the river mouth, which may be added to by sediment flowing into the estuary at high tide

Halosere
The mixing of fresh water and sea water in the estuary causes clay particles to stick together and sink - called flocculation.
Blue-green algae and gut weed colonise mud, exposed at low tide for only a few hours.
The algae binds mud, adds organic matter, and traps sediment.
As the sediment thickens, water depth is reduced, and the mud is covered by tide for less time.
Halophytic glasswort and cord grass colonise as the next seral stage - the marsh is still low, and covered by high tide each day.
An accumulation of organic matter and sediment raises the height of the marsh until it is only covered by spring tides.
The higher marsh is colonised by less hardy plants
sea aster
sea lavender
sea thrift
scurvy grass
Rainwater washes salt out of the high marsh’s soil, allowing land plants to colonise.
This continues until climax community is reached.
In most of the UK, the climax community would be deciduous oak forest, or coniferous pine forest in north Scotland.

Question 37

Waves in general

Answer 37

Waves in general
A wave is created through friction between the wind and water surface, transferring energy from the wind into the water. This generates ripples, which grow into waves when the wind is sustained.
A wave is the transfer of energy from one water particle to its neighbour with individual water particles moving in a circular orbit
The size of the wave particle orbit decreases with depth
Wave height is the vertical distance from peak to trough
it’s determined by the energy transferred from the wind, and the water depth
Wave length is the horizontal distance from crest to crest (or trough to trough)
Wave frequency is the number of waves passing a particular point over a given period of time

Question 38

Waves in open sea

Answer 38

Waves are simply energy moving through water
The water itself only moves up and down, not horizontally
There is some orbital water particle motion within the wave, but no net forward water particle motion.

Question 39

Wave size depends upon

Answer 39

the strength of the wind
the duration for which the wind blows
water depth
wave fetch
this is the uninterrupted distance across water over which the wind blows, and therefore the distance waves have to grow in size.

Question 40

How a wave breaks

Answer 40

​When waves reaching the shore reach a wave depth of 1/2 their wavelength, the internal orbital motion of water within the wave touches the sea bed.
Friction between the sea bed begins to distort the wave particle orbit from circular to elliptical, and slows down the wave.
The wave has entered the offshore zone
The wave depth decreases further, and the wave velocity slows, wavelength shortens, and wave height increases. Waves ‘bunch’ together.
The wave crest begins to move forwards much faster than the wave trough
Eventually the wave crest outruns the trough and the wave topples forwards - breaking.
The wave breaks in the nearshore zone, and water flows up the beach as swash
The wave then losses energy and gravity pulls the water back down the beach as backwash

Question 41

Constructive waves

Answer 41

Low energy waves
Low, flat wave height (<1m)
Long wavelength (up to 100 m)
Low wave frequency (about 6-9 per minute)
This means their swash is unimpeded by previous backwash
A strong swash that pushes sediment up the beach, but a weaker backwash is unable to transport all particles back down, so they are deposited it as a ridge of sediment (berm) at the top of the beach
A backwash that percolates into the beach material
encouraged by a long, shallow nearshore, so friction slows down the wave and releases energy
Constructive (spilling or surging) waves have a stronger swash than backwash due to a low

Question 42

Destructive waves

Answer 42

High energy waves
Large wave height (>1 m)
Short wavelength (about 20 m)
High wave frequency (13-15 per minute)
They’re encouraged by a short, steep nearshore zone, quickly dropping away into deeper water, so that there is little energy loss through friction
They have strong backwash and weak swash due to the steep angle of impact
this directs most energy downwards and backwards, so the particle orbit is more circular than constructive breakers(?)
Strong backwash erodes material from the top of the beach, carrying down the beach to the offshore zone
it’s often deposited as a offshore ridge or berm

Question 43

Beach morphology

Answer 43

Beach morphology is the shape of the beach.
A beach sediment profile is the pattern of distribution of different sized or shaped deposited material.

Constructive waves alter beach morphology by causing net movement of sediment up the beach, steeping the beach profile.
They produce berms at the point where the swash reaches the high tide line. (A berm is a ridge of material across the beach)
Swash carries sediment of all sizes up the beach, but weaker backwash can only transport smaller particles down the beach.
This leads to a sorting of material in the foreshore zone, with larger, heavier shingle (pebble-sized sediment) at the back of the beach, and sand drawn back closer to the sea.
Since the backwash flows down the beach and loses energy through friction and depletion of water through percolation, sediment is further sorted as coarser sands are deposited in the middle of the beach and only fine sands are carried to the area of beach closest to the sea.

Question 44

Decadal variation

Answer 44

Decadal Variation​
Climate change is expected to produce more extreme weather events in the UK.
Winter profiles may be present for longer time over course of year
More frequent and more powerful destructive waves may reduce beach size, allowing high tides to reach further inland and increasing rate of coastal erosion in what was backshore zone.

Question 45

Seasonal variation in the UK

Answer 45

Destructive, high-energy waves dominate in the winter, lowering angle of beach profile and spreading shingle over the whole beach. Offshore ridges/bars formed by destructive wave erosion and subsequent deposition of sand and shingle offshore.
In summer, constructive, low-energy waves dominate, steepening beach angle and sorting particles by size, with larger shingle particles towards back of beach. ​​In summer, constructive waves build berm ridges, typically of gravel/shingle at high tide mark
Low channels and runnels between berms

Question 46

Monthly variation of waves

Answer 46

Monthly Variation
​Tide height varies over course of lunar month, with highest high tide occurring twice a month at spring tide and two very low high tides (neap tides)​
As month progresses from spring down to neap tide, successively lower high tides may produce a series of berms at lower and lower points down the beach.
Once neap tide passes and move towards next spring tide, berms successively destroyed as material pushed further up beach by rising swash reach.

Question 47

Daily variation of waves

Answer 47

Daily Variation
Storm events during summer will produce destructive waves that reshape beach profile in a few hours.
Calm anticyclonic conditions in winter can produce constructive waves that begin to rebuild beach, steepening profile for few days before storm. ​
Destructive waves change to constructive ones as the wind drops.
Storm beaches, high at the back of the beach, result from high energy deposition of very coarse sediment during the most severe storms

Question 48

Sea waves and swell waves

Answer 48

Sea waves and swell waves
Sea waves are produced by winds currently blowing in the local area, and vary in height and direction
When the wind drops, wave energy continues to be transferred across the ocean in the form of swell waves
As swell waves travel away from their origin they may absorb smaller sea waves and gain energy and height
They can travel long distances before they lose energy and dissipate
They produce waves at the coast even when there is no wind
Swell waves can form periodically larger waves amongst smaller, local sea waves at the coast

Question 49

4 wave erosion processes

Answer 49

There are four wave erosion processes:
Hydraulic action
Corrosion
Abrasion
Attrition
How these are influences by wave type, size and lithology
They are most effective during high energy storm events with large destructive waves.
However, even coastlines composed of soft, unconsolidated sediment (e.g. boulder clay of Holderness Coast in Yorkshire), experience little erosion under normal conditions.
Most erosion (in the UK) occurs in the winter, in high energy storms.
It’s faster when the wind is blowing directly onshore
It’s faster when the tide is high (bringing deeper water closer to the cliff so less energy is lost to friction before impact)

​The effect of erosion​
The boulder clay of the Holderness coast has retreated by 120 m in the last 100 years.
The granite of Land’s End in Cornwall has retreated by only 10 cm in the last 100 years.

Question 50

Hydrologic action

Answer 50

Hydraulic Action

Where the force of water itself breaks up rock
It can occur through:
the direct impact of the water itself
Plunging destructive waves can exert a force of 50 kg / cm^3
This is sufficient to break off material from unconsolidated material, e.g. boulder clay, or weak rocks like clay and shale.
the force of the breaking wave compressing air into cracks in rocks
when the wave energy is exhausted, the compressed air explodes outwards, causing micro-fractures in rock and expanding the main crack.
over time, small fragments of rock become weakened and break away
or, the main crack can extend until larger slabs of rock fall

The pressure forces the crack open, meaning more air is trapped and greater force is experienced in the next cycle of compression.

​It dislodges blocks of rock from the cliff face.

In hard, resistant igneous rocks, hydraulic action attacking its cooling joints may be the only effective wave erosion process.

High energy waves with a large wave height are the most effective at erosion through hydraulic action. It is also accentuated when there is no debris at the cliff foot to absorb some of the wave energy and protect the cliff base.

Question 51

Abrasion and corrasion

Answer 51

Abrasion (a.k.a corrasion)

Abrasion is where a wave picks up sediment and throws these load items against a rock. The repeated impact chips away at the rock face until small fragments break away.

Most effective: High-energy destructive waves with a large wave height hurl load items with greater force, resulting in faster rates of erosion by abrasion.

They need a supply of hard load items close to the foot, e.g. shingle from the beach.

Rocks eroded most quickly by abrasion: Soft sedimentary rock such as chalk, mudstones, and clays, and unconsolidated material, e.g. boulder clay.

Question 52

Corrosion

Answer 52

​Corrosion

Corrosion is where water in waves dissolves rock minerals. Minerals are immediately carried away by the wave in solution. They are also vulnerable to erosion by rainwater and sea spray.

Most effective waves: Constructive waves, as the force of impact is not relevant, and the spilling wave increases the time for the chemical reaction to occur. They are slow, and with a long wavelength (longer the better) it prolongs the contact of rock with the water.

Rocks eroded most quickly by corrosion: carbonate rocks like limestones (e.g. chalk, Jurassic limestone and carboniferous limestone) and sedimentary rocks with calcite sediment/cement.

Question 53

Attrition

Answer 53

Attrition is where material transported by a wave is eroded through collision with other load items. It breaks down sediment into smaller sized particles, and the repeated collision blunts any of the particles’ sharp edges, making the sediment increasingly rounded. Even harder rocks, such as quartz and granite form larger rounded shingle pebbles.

It occurs in the foreshore and nearshore zones, where sediment is moved by swash and backwash.

Rocks eroded most quickly by attrition: soft rocks (e.g. poorly cemented sandstones, chalk and clay) are broken down quickly by attrition into silt and sand grains.

Question 54

Wave cut notches

Answer 54

Wave cut notches and platforms (e.g. Kimmeridge Bay)
A wave cut notch is a curved indentation of about 1-2 m high extending along the base of a cliff. It forms between the high tide and low tide marks, where destructive waves impact against the cliff.
It’s eroded by hydraulic action and abrasion, and in some cases corrosion.
The depth of the notch varies depending upon the resistance of the rock at different points.

A wave cut platform is a flat rock surface exposed at low tide, extending out to sea from the base of a cliff.
Their formation:
Marine erosion between the high tide and low tide mark by abrasion and hydraulic action forms a wave-cut notch along the length of the cliff base.
The notch deepens by further erosion until the overlying material collapses by mass movement due to gravity, forming a cliff.
The process repeats, and the position of the cliff retreats (coastal recession)
The rock just below low tide level is always submerged, it’s uneroded as it’s never exposed to wave impact.
As the overlying material is eroded, uneroded rock at low tide level is left as flat rock surface, the wave cut platform.

Other stuff about wave-cut platforms:
They often slope seaward at 4 degrees.
Weathering attacking weaknesses in the platform surface may produce indentations, creating rock pools at low tide.
Platforms rarely extend for more than a few hundred metres.
This is because the shallow water causes the wave to begin to break as soon as it reaches the platform

Question 55

Cliffs

Answer 55

Cliffs
Cliffs are steep slopes that are usually unvegetated.
Marine erosion of land between the high tide and low tide mark by hydraulic action and abrasion forms a wave cut notch
The notch deepens until the overlying rock collapses by mass movement due to the force of gravity.
The exposed face forms a cliff.

Question 56

Cave-arch-stack-stump sequence

Answer 56

Cave-arch-stack-stump sequence
Rocks have joints, faults or vertically dipping bedding planes in their geological structure.
These are eroded more rapidly (e.g. hydraulic action), and the deepening and widening of a weak point forms a sea cave.
This is accentuated by how wave refraction concentrates energy on the sides of the headland, producing destructive waves with a very large wave height.
Where a line of weakness extends right through the headland caves form on both sides.
Marine erosion deepens the caves until they connect up, creating a complete tunnel through the headland and forming an arch.
Hydraulic action and abrasion attack the sides of the arch between low tide and high tide, forming wave cut notches.
The undercutting of the sides leads to the collapse of some overlying material by mass movement, widening the arch.
Weathering and other sub-aerial processes attack the arch roof.
Eventually, the roof of the arch will collapse by blockfall leaving the seaward end of the headland detached from the land as a tall vertical column called a stack.
Marine erosion at the base of the stack will form a notch on all sides until the stack collapses by blockfall.
Remnants of the stack base form a stump, a small projection of rock, exposed only at low tide.

However, unconsolidated and soft sedimentary or metamorphic rock won’t undergo this because it isn’t competent enough. (e.g. boulder clay, clay, shale)

Question 57

Context for costal landscapers

Answer 57

The cliff slope angle depends upon the dip of the rock strata.
Horizontal, vertical or landward dip produces steep cliffs.
Seaward dip produces a shallower slope angle - which can also be produced when the lithology is unconsolidated
​On a wide platform wave will have broken and swash lost energy before it reaches the cliff, halting recession.

Question 58

Traction, saltation, suspension and solution

Answer 58

Traction
Where large, heavy load items are rolled along the sea bed,
e.g. boulders, cobbles and pebbles
Saltation
Where lighter sediment bounces along
Sand particles are usually transported this way
Sand can be saltated by wind as well as waves
On a dry, windy day, there can be a layer of saltating sand 2-10 cm above the beach
Suspension
Where very light sediment is carried aloft within a body of water or air
E.g. silt or clay particles
Suspended clay particles, give the sea a cloudy, muddy brown colour on soft-rock coasts, e.g. Holderness
Solution
Where sediment is carried dissolved within the water

Question 59

Angle of wave attack

Answer 59

Direction (angle) of wave attack
​This is the main determinant of the direction of sediment transport (in the foreshore zone).
Where the wind is blowing directly onshore, the incoming swash transports the material direction up the beach at 90’ to the coastline.
Backwash then transports sediment perpendicularly back down to the beach to its original starting position.
Sediment is moved up and down the beach, but there is no net lateral movement.

Question 60

Longshore drift

Answer 60

Longshore drift
This is the net lateral transport of material along the coastline when waves approach the coast at an angle.
Incoming swash transports sediment up the beach at an angle (movement contains an up-beach component and a lateral component)
Gravitational backwash then transports sediment back down the beach at 90’ to the coastline.
A sediment particle comes to rest some distance along the beach from the original starting point due to net lateral movement.
Particle moves in a zig-zag fashion along the beach with each incoming wave.

A wave angle 30’ to the coastline produces the strongest longshore drift movement.
On most coastlines there is a dominant prevailing wind, so over time there is a dominant direction of longshore drift.

Question 61

Current

Answer 61

Current
This is the flow of water in a particular direction, and they can transport sediment in the nearshore and offshore zones.
They can be driven by winds, or initiated by differences in water density, temperature or salinity.
​Currents transport sediment over a variety of spatial and temporal scales:
The global thermohaline circulation connects four oceans and takes 500 years for one complete circuit.
Rip currents on the beach transport sediment a few metres out to sea for a few hours when the wind is blowing direcly onshore with the right strength.

Question 62

Tides

Answer 62

Tides
Tides are changes in sea level produced by the gravitational pull of the moon and the Sun.
The incoming and ebbing tide can create tidal currents in the nearshore and offshore zones that transport sediment

Question 63

Deposition

Answer 63

Deposition
Deposition occurs when waves no longer have sufficient energy to continue to transport material
This loss of energy might be due to:
the wind dropping, removing an energy source
resistance by obstruction, e.g. a groyne or headland
dissipation of energy through refraction
friction from extended transport across shallow angled nearshore and foreshore zone
Sediment transported down river systems to the coast or from offshore sources is also important.

Sediment is deposited when the force transporting the sediment drops. Deposition occurs in two main ways:
Gravity settling occurs when the energy of transporting water becomes too low to move sediment. Large sediment will be deposited first, followed by smaller sediment (pebbles -> sand -> silt)
Flocculuation is a depositional process that is important for very small particles, such as clay, which are so small that they will remain suspended in water. Clay particles clump together through electrical or chemical attration, and become large enough to sink.

Question 64

Bayhead beaches

Answer 64

​Bayhead beach
Bayhead beaches are curved beaches found at the back of a bay.
They’re common on swash-aligned coastlines where wave refraction disperses wave energy around the bay perimeter.
Waves break at 90’ to the shoreline and move sediment into a bay, where a beach forms. Through wave refraction, erosion is concentrated at headlands and the bay is an area of deposition.

Question 65

Spits

Answer 65

Spits
Spits are linear ridges of sand or shingle beach stretching into the sea beyond a turn in the coastline (usually greater than 30’) but connected to the land at one end
They form on drift-aligned coastlines, where the coastline changes direction, usually by more than 30’, e.g. at a bay or a river mouth
At the turn, longshore drift continues in the original direction, but its energy is dispersed, lost as the wave refracts and the current spreads, leading to deposition on the sea bed.
Over time, sufficient sediment is deposited to break the surface, extending the beach into the sea as a spit
The process continues until equilibrium is reached at the distal end (seaward end) of the spit, between deposition and erosion by waves or the existing river current.
The length of the spit is determined by the existence of secondary currents causing erosion, either the flow of a river or wave action which limits its length.

Question 66

Hooked and recurved spits

Answer 66

​Hooked/Recurved spits
A spit whose end is curved landwards, into a bay or inlet.
A hook or a recurve may form at the end of the spit.
This is because wave refraction round the distal end transports and deposits sediment for a short distance in the landward direction.
Alternatively, it could be because the wind and wave front are frequently at an opposing angle to the prevailing wind, generating short periods of longshore drift in the landward direction. (These last two can make it more pronounced)
Or, a strong incoming tidal current can also create a recurved spit.

Question 67

Double spits

Answer 67

Double spits
Double spits are where two spits extend out in opposite directions from both sides of the bay, towards the middle.
They form where longshore drift is operating in different directions on opposite sides of the bay.
E.g. in Poole Harbour the main longshore drift direction is SW-NE driven round Studland Bay by the prevailing wind, producing a spit from the south.
However, wave refraction around Durlston Head produces wave fronts from NE-SW along the coastline towards the north spit of Poole Harbour, generating a spit from the north.
2. They can also form when rising sea levels drive ridges of material onshore from the offshore zone.
3. Or, a barrier beach driven across a bay forms a bar (e.g. Haff coastlines) but a strong exiting river current may breach the bar to form a double spit.

Question 68

Offshore bars

Answer 68

Offshore bars (a.k.a. breakpoint bars)
Offshore bars are ridges of sand or shingle running parallel to the coast in an offshore zone.
They form from sediment eroded by destructive waves and carried seawards by backwash.
The sediment is deposited at the boundary of the offshore and nearshore zone, where the orbit of water particles ceases to reach the seabed, halting the transport offshore.
They are also called breakpoint bars because the offshore/nearshore boundary is where waves first begin to break.
They can sometimes be exposed by neap tide.
They are used:
to construct wind farms
e.g. Scroby Sands in Norfolk
as a source of sand for beach nourishment
for shingle dredging for construction material

Question 69

Bars and Barrier Beaches

Answer 69

Bars and Barrier Beaches (they’re the same thing)
Bars are linear ridges of sand/shingle extending across a bay and are connected to land on both sides.
It traps a body of seawater behind it, forming a lagoon.
They can form in two ways:
On drift-aligned coastlines, when longshore drift extends a spit across the entire width of the bay.
When rising sea levels cause constructive waves to drive a ridge of sediment onshore to coastlines with a gently sloping shallow sea bed. (barrier beach)
E.g. there’s a 9 km barrier beach that extends across Start Bay in Devon, slapping Slapton Ley lagoon behind it

Another definition of a barrier beach is a ridge of material emerging just offshore to form a chain of beaches parallel to the coast (barrier islands).
E.g. the Freisian islands off the North Sea coast of the Netherlands and Germany

Question 70

Tombols

Answer 70

Tombolos
Tomobolos are linear ridges (or bar) of sand and shingle connecting an offshore island to the coastline of the mainland.
Two ways they can form are:
On drift aligned coastlines, when longshore drift builds a spit out from land until it contacts with an offshore island.
On swash aligned coasts when there is wave refraction around both sides of the island.
This causes a collision of wave fronts on the landward side, cancelling each other out and producing a zone of still, calm water where deposition occurs, between the island and the coast.
Oppositional longshore currents may play a role, in which case the depositional feature is similar to a spit.
E.g. St Ninian’s tombolo on the Shetland Islands
The tombolo connecting Portland Bill to the mainland in Dorset.

Question 71

Cuspate forelands

Answer 71

Cuspate Forelands
Cuspate forelands are low lying triangular shaped headlands, extending our from a shoreline, formed from deposited sediment.
Formation (there is debate about this):
When longshore drift currents from opposing directions converge at the boundary of two sediment cells.
The sediment is deposited out into the sea by both currents creating a triangular shaped area of deposited material.
They can extend from a few metres to several kilometres.
An example is at Dungeness in Kent. It extends for 11 km in a south-easterly direction where the main west-east longshore drift meets north-south longshore drift currents produced by swell waves travelling down the North Sea into the English Channel.
Dungeness foreland is thought to have been two spits converging at distal ends with a lagoon between that infilled through salt marsh succession, wind deposition and storm beach material being thrown up during storms.

Question 72

Plant succession

Answer 72

Plant Succession (I don’t know why this is here, there’s already a section on it…)

Depositional landforms are unstable because:
They are made of unconsolidated material
They are dynamic as they loose material transported by waves, tides, currents and wind.
They are stabilised by plant succession, which binds the loose sediment together and encourages further deposition.

Plant succession on sand dunes is psammosere.
Plant succession on salt marsh is halosere.

Plants can stabilise unconsolidated material because:
Plant roots hold sediment together
​Their leaves/stems slow water and wind flow reducing erosion and encouraging further deposition

Land is built up through the addition of organic matter and increased deposition.
In shallow water, deposition occurs further out and land extends as an outbuilding coastline.

Question 73

Examples of sediment cel

Answer 73

Example:
​Flanborough head - source region
Holderness coast - transfer zone
Spurn head - sink region

The coastline of England and Wales is divided into 11 primary sediment cells, with sub-cells within each primary cell. The boundaries are formed by major headlands or large estuaries.

A sediment cell operates as a closed system, with virtually no inputs or outputs of sediment from the cell.
This system contains inputs, transfers and outputs.

Inputs
Sources are places where sediment is generated, such as cliffs or eroding sand dunes. Some sources are offshore bars and river systems and these are an important source of sediment for the coast.

Some examples of sediment inputs are:
Cliff erosion,
Onshore currents
River transport
Wind blown (aeolian) sediment from land
Subaerial processes
Marine organisms

Question 74

3 components of sediment cell

Answer 74

transfers
inputs
outputs

Question 75

Transers

Answer 75

Transfers
Places where sediment is moving alongshore through longshore drift and offshore currents. (Drift-aligned) beaches and parts of dunes and salt marshes perform this function.

Some examples of sediment transfers are:
Longshore drift
Swash
Backwash
Tidal currents
Sea/ocean currents
Wind (onshore, offshore or along shore)

Question 76

Outputs

Answer 76

Outputs
Sinks are locations where the dominant process is deposition and depositional landforms are created, including spits and offshore bars.

Some examples of sinks are:
Backshore depositional landforms
E.g. sand dunes
Foreshore depositional landforms
E.g. beaches
Nearshore depositional landforms
E.g. bars
Offshore depositional landforms
E.g. barrier islands ​​

Question 77

Dynamic systems

Answer 77

Sediment cells are dynamic because the sediment is constantly generated in the source region, transported through the transfer region and deposited in the sink region.

Dynamic equilibrium (in this instance) is reached when inputs of sediment from the source region are balanced by the amount being deposited in sinks. It’s dynamic because although it’s in balance, there’s a constant movement of sediment through the system.
(Think of a classroom during the school day - always full of (roughly) the same amount of people, but the people in it change)

With a dynamic equilibrium, the size of the landforms in the transfer zone will remain the same. (But not the ones in the source and sink regions)

They may operate as complete circulations: Sediment is eroded from the depositional sink landforms and is carried offshore, being being re-transported onshore by currents and wind action that act at the source region.
​
However, the dynamic equilibrium is itself dynamic because its constantly changing as energy and sediment inputs constantly alter. The amount of stuff moving through is changing.
E.g. climate change creating more frequent storms or erosion of the cliff line to a more resistant rock type.
The system’s equilibrium may be interrupted (e.g. during a storm event) but they tend to return to balance on average over time due to negative feedback.
Seasonal change (e.g. storms and strong winds during winter) will change the dynamic equilibrium.

Coastal management in the source region may reduce sediment supply, e.g. sea walls preventing cliff erosion. Management in transport region may reduce or halt sediment supply to sink region, e.g. groynes trapping sediment to encourage beach outbuilding.

Question 78

Negative and positive feedback

Answer 78

Negative feedback: when the change produced creates effects that operate to reduce or work against the original change.
E.g. when erosion leads to blockfall mass movement. The collapsed debris acts as a barrier protecting the cliff base, slowing or preventing erosion for a period of time.
E.g. major erosion of sand dunes could lead to excessive deposition offshore, creating an offshore bar that reduces energy, allowing the dunes time to recover.

Positive feedback: when the changed produces an effect that operates to increase the original change.
E.g. When wind erosion of a dune section during high velocity storms may removing stabilising vegetation.
Further wind erosion now occurs in later low velocity wind conditions, increasing the depletion of dune sand.

A source region may be an eroding coastline. A sink region may be an outbuilding coastline.

Question 79

Weathering

Answer 79

Weathering is the breakdown of rock in situ at or near the surface of the Earth.

Weathering and mass movement are subaerial processes.
Weathering attacks the backshore and foreshore parts of the littoral zone.
Weathering creates rock fragments that form sediment.
It’s most active in the source zone of the sediment cell.

Physical (mechanical) weathering
Mechanical weathering is the application of force to physically fragment rock into smaller pieces called clasts. It breaks down rocks by the exertion of a physical force, and does not involve any chemical change.

Some examples of it are:
Freeze-thaw weathering
Water seeps into cracks in rocks
When the water freezes, it expands in volume by 9%, exerting a tensional force that widens the rock
Thawing allows more water to enter the crack, and the process repeats until cracks are forced open large, angular pebble, cobble, or boulder-sized fragments are loosened off.
With porous rocks, water in the pores may freeze, prising off individual rock grains and producing sand sized fragments.
Any rocks with cracks and fissures are vulnerable to it, especially high on cliffs away from sea spray.
Freezing is relatively uncommon on UK coasts.
Salt Crystal Growth
This is common at coasts because the sea is salty.
The breaking force is less than that of freeze-thaw weathering
Porous and fractured rocks (e.g. sandstone) are vulnerable to it.
The effect is greater in hot and dry climates, promoting the evaporation and precipitation of salt crystalls.
It attacks the foreshore zone and backshore zone that’s reached by destructive wave spray.
Seawater penetrates small cracks or pores in rock at high tide, and evaporates at low tide, leaving precipitated salt crystals.
Repeated tidal cycles lead to growth of salt crystals until they begin to press against the sides of cracks or pores, exerting tensional pressure.
Eventually angular fragments of rock are broken off or there is granular disintegration (where individual grains break away)
Wetting and Drying
Rocks containing clay minerals, such as clays and shales
At high tide minerals on the rock surface are soaked with sea water and expand in volume.
At low tide, minerals dry and shrink.
Repeated cycles of expansion and contraction eventually cause the rock to fragment and crumble.

Chemical Weathering
Where chemical reactions attack individual minerals in the rock, breaking bonds and producing new chemical compounds.

Three examples are:
Carbonation
This attacks calcium carbonate in limestones, other carbonate rocks and sedimentary rocks with calcite sediment.
Rainwater mixed with carbon dioxide from the air to form weak carbonic acid (pH 5.6).
The acidic rain mixes with calcium carbonate to form soluble calcium bicarbonate solution.
‘Rock disappears’ as new minerals dissolve into the solution.
Only sediment left from limestone is clay particles that had formed impurities in the original rock.
Where calcite sediment is weathered, previously cemented clasts are released to form sediment.
Hydrolysis
The breakdown of minerals to form new clay minerals, plus materials in solution, due to the effect of water and dissolved carbon dioxide.
Rocks vulnerable to it are: igneous and metamorphic rocks containing feldspar and other silicate minerals
This attacks the feldspar (pinky) minerals in granite
H+ ions in water attack the feldspar minerals forming kaolin clay cement
Bonds between feldspar and quartz minerals broken, releasing quartz grains as sand sediment.
Oxidation
The addition of oxygen to minerals, especially iron compounds, which produces iron oxides and increases volume, contributing to mechanical breakdown.
This attacks iron minerals in haematite cements, e.g. Devonian sandstone
Wetting of haematite cement with seawater leads to a loss of an electron by iron, converting iron (II) oxide to red-coloured iron (III) oxide
Change in iron compound breaks cement bonds releasing previously cemented clasts as sediment
Rocks that are vulnerable to it are: sandstones, siltstones and shales that often contain iron compounds which can be oxidised
It’s much more effective in seawater or water with impurities than in pure water.

​Biological weathering
Biological weathering is the break down of rock in situ by living or once-living organisms. It often speeds up mechanical or chemical weathering through the actions of plants, bacteria or animals.

Examples are:
Tree root weathing
seeds falling into cracks in rocks can germinate, nourished by rainwater and nutrients from wind-blown sediment.
as the plant grows its roots expand and thicken
tree roots exert sufficient tensional force to widen the crack
eventually angular fragments of rock break away as cobble or boulder-sized sediment
it occurs in the backshore zone, away from the reach of the spray from destructive waves​
it’s an important process on vegetated cliff tops which can contribute to rock falls
2. Rock boring (there are many species of clams and mollusc that bore into rock, and may also secrete chemicals that dissolve rocks.
Piddocks live in the foreshore zone
piddocks drill depressions into sock rocks by rotating their shell equipped with sharp edges.
piddocks live in these circular depressions, filter feeding whilst protected from high-energy waves
they attack soft rock, like clays and shales. Vulnerable rocks are sedimentary rocks, especially carbonate rocks (limestones) located in the foreshore/inter-tidal zone

3. Seaweed acid
   Kelp contains pockets of sulphuric acid
   when the cells break sulphuric acid attacks rock minerals like calcium carbonate leading to a chemical reaction similar to carbonation.

Question 80

Mass movement

Answer 80

Mass movement (blockfall, rotational slumping, landslides) is important on some coasts with weak and/or complex geology.

Mass movement is the downslope movement of material (rock and soil) under the force of gravity. It is the umbrella term for a wide range of specific movements including landslide, rotational slumping and blockfall.
It occurs when the downslope gravitational force exceeds the resisting forces of friction and internal rock cohesion.

​The type of mass movement depends upon lithology:
unconsolidated material (like boulder clay) - slumping
consolidated rock (like carboniferous limestone and granite) - sliding
​

Blockfall (or rockfall)

This occurs on slopes >40’, where a rock fragment breaks away and either drops vertically (so it isn’t in contact with the cliff) or bounces downslope.

It’s initiated:
By mechanical weathering
freeze-thaw
salt crystal growth
which break the cohesive bonds in the rock
By marine erosion
Hydraulic action
Abrasion
Undercutting cliff by creating a wave-cut notch
Notch removed supporting material that supplied the resistive force holding up the rock

Cliffs prone to blockfall have:
a geological structure with many joints, faults or bedding planes
steep, near vertical dip of strata
they’re often also in an earthquake-prone area

Blockfall is very rapid, taking only a few seconds to occur.

They may involve the detachment of single fragments or of a whole section of cliff that breaks up as it descends (which occurs by the undercutting of a wave-cut notch).

In April 2013, there was a large blockfall in St Oswald’s Bay on the South Dorset Coast where an 80 m section of chalk cliff was detached overnight.

​Rotational Slumping

Rotational slumping involves rock failure and movement along a curved rock plane.
The slumping material usually moves intact as a single mass, without any internal deformation of material.

It’s slower than blockfall, often occurring in ‘slow motion’, and may take minutes, hours, days, or even years (for huge masses) to occur.

Rotational slumping occurs in:
​weak rocks, e.g. clays and shales
unconsolidated material, e.g. boulder clay, sands, gravels
in rocks with complex geology, e.g. where permeable rock strata overlie impermeable beds

Slumping is facilitated by the presence of water, which adds weight (increasing the gravitational force) as well as lubricating it, reducing friction.

An example of rotational slumping is at Christchurch Bay, in Barton-on-Sea, near Lymington in Hampshire, where unconsolidated sands overlie clay. The bedding plane between sand and clay dips seawards.
In dry weather, soil above sand cracks, funnelling water into permeable sand.
Increased pore water pressure along lines of percolation form lines of weakness in the sand.
Water accumulates in the lower sand as it is unable to to percolate into the impermeable clay. Pore water pressure lubricating the bedding plane encourages the movement of sand.
The weight of the water adds to the downslope gravitational force, while wave erosion created a notch at the cliff foot, removing support.
Eventually slumping occurs.

​Landslides

A landslide is the downslope movement of discrete blocks of rock down a flat/linear slip plane, maintaining contact with the cliff surface throughout.
The discrete blocks are released by mechanical weathering of well jointed rocks, (e.g. carboniferous limestone). Gravity then pulls the loosened block down the relatively flat slip plane of the joint or bedding plane, to the cliff foot.

Landslides can also be caused by marine erosion of a cliff foot undercutting blocks weakened by jointing. The removal of support allows gravity to release the block, resulting in sliding.

Rainstorm events can encourage a landslide, lubricating the slip plane, reducing the resistance.

Landslides occur in consolidated rocks with joints or bedding planes sloping seawards.

Flows (not mentioned in spec?)

Flows occur when unconsolidated fine grained sediment, e.g. silts and clays, mix with large volumes of water. They’re common in weak rocks such as clay or unconsolidated sands. They become saturated, lose their cohesion, and flow downslope.

Heavy rainfall, combined with high waves and tides can contribute to saturation.

Earthflows are more viscous than mudflows, and contain larger sediment.

In cold environments, earthflows known as solifluction occur in the unfrozen layer between the permafrost and the tundra vegetation turf.

Question 81

Rotational slumping and blockfall

Answer 81

Blockfall
The angular blockfall debris accumulates at the cliff foot to form a talus scree slope, a fan shaped mound of material.
Undercutting of cliffs by the creation of wave-cut notches can lead to large falls and talus scree slopes at their base.
A talus scree slope has a slope angle of 34-40’ (larger fragments maintain a steeper angle of rest)
In April 2013 there was a large blockfall in St Oswald’s Bay on the South Dorset Coast where an 80 m section of chalk cliff was detached overnight.
A large fan shaped talus scree slope was created at the slope foot, extending 30 m into the sea that will protect the cliff from further erosion for a decade or more.

Rotational Slumping
Rotational slumping exposes a rotational scar
A rotational scar is a fresh, curved, unweathered and unvegetated rock surface on the cliff face.
The detached slope section, often with vegetation intact on top of the slump, forms a beach or terraced cliff profile.

Question 82

Context of sea level change

Answer 82

Sea level change in general
Sea level changes constantly
Due to: tides, variations in surface air pressure, winds pushing on the water surface, creating temporary bulges of higher sea level.
Long term sea level changes occur over thousands of years.
Long term sea level change is due to eustatic and isostatic factors, and tectonics.

Question 83

Eustatic change

Answer 83

Eustatic
Eustatic change is a change in global sea level, usually due to a change in the volume of water in the oceans. ​

Climate change occurs cyclically, in Milankovitch Cycles, due to changes in the Earth’s orbit around the Sun.
Glacials are 90,000 year colder phases, which lead to the formation of ice sheets.
Water evaporated from the oceans falls as snow on the land and compresses to form ice.
Over the course of the cycle, the distribution of water within the hydrological cycle changes, with transfers from the ocean store to sheets on land.
A decrease in the volume of water in the oceans produces a global fall in sea level.
The sea bed is exposed as land - marine regression.
The most recent glacial was the Devensian, where global sea levels were 120 m lower than they are today. The English Channel, Irish Sea and most of the North Sea was dry land.
.
Interglacials are 10,000 year warmer phases that shrink ice sheets.
Water is transferred from the land store back to the oceans. increasing the volume of water in the oceans and raising global sea levels.
(Melting of sea ice has no effect on global sea levels as the floating ice mass already displaces its volume.)
Rising water temperature leads to the thermal expansion of water, increasing its volume even further.
This leads to marine transgression - rising sea levels flood low land areas.
.
Since 1750, humans are thought to be accelerating natural interglacial warming through greenhouse gas emissions.
Anthropogenic forcing
Sea levels rose by 21 cm from 1870 - 2010.
The melting of Antarctic ice sheets are predicted to raise sea levels by 50 m

Summary:
Eustatic fall in sea level
During glacial periods, when ice sheets form on land in high latitudes, water evaporated from the sea is locked up on land as ice, leading to global fall in sea level.
Eustatic rise in sea level
At the end of a glacial period, melting ice sheets return water to the sea and sea level rises globally. Global temperature increases and causes the volume of ocean water to increase (thermal expansion) leading to sea level rise.

Question 84

Isostatic sea level change

Answer 84

Isostatic Changes
An isostatic change is a change in local land level.
Rises in local land level causes a fall in local sea level. This may be due to:
post-glacial adjustment
accretion
sink regions in the sediment cell are experiencing net deposition, land is built up, leading to a fall in sea level (in delta regions accretion -> subsidence -> accretion and so on)
tectonics
A fall in local land level produces a rise in local sea level. This may be due to:
post-glacial adjustment
subsidence
subsidence of land produces a rise in sea level
the deposition of sediment, especially fluvial deposits in large river deltas, the weight of sediment deposition overcomes the threshold and leads to very slow ‘crustal sag’ and delta subsidence, e.g. Nile, Mississippi, Amazon
can also be caused by the lowering of the water table (from increased evaporation from climate change or human abstraction) can lead to settling of overlying sediment and land subsidence as pore water pressure is removed
or by heavy buildings
tectonics

Question 85

Post glacial adjustemnt

Answer 85

Post-Glacial Adjustment
During glacial periods, the weight of the ice depresses the crust in areas below the ice sheets. The solid lithosphere is forced down into the plastic asthenosphere. The rigid nature of the solid crust means that when sections of the crust are depressed by ice and forced down, adjacent areas are uplifted in a see-saw effect.
The melting of ice causes previously ice-covered crust to slowly rebound upwards whilst adjacent areas subside.

At the end of the last ice age 12,000 years ago, the UK was covered in ice as far down as Birmingham. Northern Britain is experiencing a isostatic fall in sea level as land is uplifted by 1.5 mm per annum.
Southern Britain is experiencing an isostatic rise in sea level as land is lowered by 1 mm per annum.
The UK is pivoting, with the south sinking and the north rising.

In northern Britain, sea levels are falling as isostatic rebound exceeds eustatic rise in global sea levels. However, in the south isostatic subsidence is accelerating a rise in sea level produced by global warming (eustatic). Land’s End in Cornwall is sinking isostatically by

Question 86

Tectonic eustatic and isostatic sea level change

Answer 86

Tectonics
Eustatic
Rising magma at a constructive plate margin/hot spots lifts the overlying crust, reducing the capacity of the ocean and producing eustatic sea level rise.
Uplift of crustal plate reduced Indian Ocean capacity
causing 0.1 mm eustatic rise in global sea levels.
Isostatic
Folding of sedimentary rock by compressive forces at a destructive plate margin produces an isostatic fall in sea level for anticlines and a fall for synclines. E.g. the Alpine folding at the Eurasian-African destructive plate boundary produced an isostatic fall of 60 cm in the Bakar-Vindol area of Croatia.
Lava or ash from volcanic activity produces an isostatic fall, e.g. Hawaiian hot spot island chain or Caribbean island arc.
Sea floor spreading - carries volcanic islands away from the uplifted crust at mid-ocean ridge. Colder, more dense crust subsides and sea levels rise, e.g. Tonga, Fiji, Kiribati.
FAULTING can uplift HORST blocks of crust producing
isostatic rise in land & fall in local sea level.
Subsidence of crust blocks by faulting form GRABEN
experiencing isostatic fall in land level & rise in local sea
level.
During 2004 Boxing Day Tsunami in Indian Ocean
extension of crustal plate caused isostatic fall in land on
island of Sumatra by 20 cm in Banda Aceh region.

Question 87

Emergent coastlines

Answer 87

Emergent Coastlines

During the Devensian Glacial eustatic changes lowered sea levels by 120 m.
At the start of the Holocene Interglacial (10,000 years BP) led to a rapid 100 m eustatic rise in global sea levels, as 3,000 years of ice sheets and glaciers shrank. This happened over about 1000 years, (very rapid) and submerged coastlines.
However, the post-glacial adjustment of ice-covered land (and adjacent areas) was much slower.
Previously ice-covered land gradually rose out of the sea, such as northern Britain and Scandinavia.
The Ford and Clyde valleys in the border region of Scotland are currently rising 2 mm p.a. (though initial adjustment was faster)
Areas of Northern Europe and North America that were covered by the thickest ice are rebounding fastest. Some areas rose isostatically by 300 m.

Emergent coastlines are being produced by post-glacial adjustment. These are parts of the littoral zone where a fall in sea level exposed land once part of the sea bed. They have landforms reflecting the previous sea levels.
Raised beach
A relict beach now above high tide level
A flat surface covered by sand or rounded pebbles/boulders.
Usually vegetated by plant succession (though further succession prevented due to grazing)
Fossil cliff
a steep slope found at the back of a raised beach exhibiting evidence of formation through marine erosion but now above high tide level.
they may contain wave-cut notches, caves and arches providing evidence of formation by marine erosion
episodic nature of isostatic recovery allows marine processes to erode cliffs and deposit beaches when sea levels are stable. Relatively rapid drop in sea level then leaves relict coastline abandoned above high tide and some distance inland.
E.g. the Isle of Arran has a raised beach 5 m above current sea level north of Drumadoon. Arran has three levels of raised beaches produced at different stages of post-glacial adjustment.
E.g. at Lendalfoot in Ayrshire, western Scotland, a flat raised beach surface is used as a route for the A77 main road. 40 m raised cliff at the back of the now now 200 m inland from the present-day beach.
Also raised stumps, etc.

Question 88

Submergent coastline

Answer 88

Submergent Coastlines

Submergent coastlines are sections of the littoral zone where sea level rise inundated areas that were previously part of terrestrial land. They are found in southern England and the east coast of America.
Areas of land adjacent to ice covered regions experience isostatic uplift during the Devensian due to the see-saw effect. These are now subsiding due to post-glacial adjustment - producing marine transgression and emerging coastlines.
A ria is a drowned river valley - a section of river valley flooded by the sea, making it much wider than would be expected based on the river flowing into it.
​Rias are the most common coastal landform.
They are common in periglacial areas that were adjacent to land covered by ice during the Devensian, e.g. Southern England.
Rivers eroded steep-sided V-shaped valleys into the frozen landscape giving the ria a V-shaped cross section when the valley flooded.
Rias have a sinuous plan profile reflecting the meandering river course. The plan view is dendritic as tributies are flooded by the rising sea.
Rias are a type of estuarine coastline.
E.g. Kingsbury Estuary on the south Devon coast is a 6 m long ria. Main channel is 1 m wide near its mouth at Salcombe. Two large drowned tributaries extend from the east side of the ria, with Frogmore Creek 2 km long and 500 m wide.
​​
Fjord
Fjords are drowned glacial valleys - a section of a glacially eroded valley flooded by the sea. They are common in glaciated areas that were covered during the Devensian, e.g. western Norway. Many Scottish sea lochs are fjords.
Fjords often have a relatively straight profile as glaciers truncate spurs to produce a direct downslope route.
Glacier erosion is often cut deep into the landscape, often tens of metres lower than the adjacent unglaciated land - meaning that fjords are often deeper than the adjacent sea.
Fjords often have a shallow entrance where there is a submerged ‘lip’ formed by the ridge of a terminal moraine.
Many fjords are shallowing by a few milimetres per year due to isostatic adjustment.
Sognefjord in western Norway is 205 km long, 1.3 deep and the main branch is 4.5 km wide.
Dalmatian Coast
This is composed of long, narrow islands running parallel to the coastline and separated from the coast by narrow sea channels called sounds.
They are produced by sea level rise flooding the coastline with the geological structure of folds aligned parallel to the coast.
Sea level rise at the end of the Devensian Glacial floods synclines to form sounds.
Sea overtops low points forming straits linking straits linking sounds and separating sections of anticline ridge into narrow islands parallel to the coast.
The Dalmatian region of Croatia has a limestone coastline stretching 520 km NW-SE with 1,240 islands running parallel to the coast.
Other

Isostatic rebound is episodic - long periods of little change followed by short bursts of marine regression.
Rias are economically important as they provide sheltered ports.

Barrier islands? (from revision guide)
The east coast of the USA has barrier island landforms
these may have formed as lines of coastal sand dunes attached to the shore
later sea level rise flooded the land behind the dunes forming a lagoon, but the dunes themselves were not eroded and formed islands
as sea levels continued to rise, the dune systems slowly migrated landwards
rivers and tidal flows maintain open water between islands
barrier islands supplied with sediment from longshore drift

Question 89

Contemporary sea level change

Answer 89

Climatic warming leads to eustatic sea level rise.
Warming leads to the melting of mountain glaciers (Alps, Himalaya) and polar ice sheets increasing the amount of water in the ocean store.
Melting of sea ice has no effect on sea level as the ice was already displacing the equivalent water volume to that produced by melting.
IPCC attributes 50% of sea level rise 1990-2010 to ice sheets melting (Greenland ice sheet 15%, Antarctic ice sheet 10%)

Warming also leads to the thermal expansion of existing ocean water as its temperature rises.
94% of increased heat energy in the climate system is transferred to oceans.
IPCC attributes 40% of sea level rise 1990-2010 to this

Tectonic activity caused the other 10% of sea level rise
Emission of geothermal heat into oceans by underwater volcanic activity can cause thermal expansion of ocean water
Rising magma at constructive plate boundaries produces a doming upwards of crust along mid-ocean ridges reducing the ocean basin volume
At destructive margins:
folding of plates increases ocean basin volume lowering sea levels
earthquakes along boundary can allow rebound of non-subducting margin - uplift of sea floor reduces ocean volume raising sea levels
2004 Boxing Day tsunami with moment magnitude 9.3 lifted sections of the Indian Ocean bed raising sea levels by 0.1 mm
It can also cause isostatic change:
faulting can uplift sections of crust, lowering sea levels (or vice versa), sometimes by up to 2 m
Turakirae Head near Wellington on New Zealand’s North Island uplifted 6 m in 1855 earthquake
Sea floor spreading transports volcanic islands away from the uplifted crustal zone along constructive boundaries or hotspots - to places where the ocean floor is colder, denser and lower lying - islands sink

Past Change
Sea levels have risen by 125 m since the Devensian Glacial
Sea level rise was on average 10 mm p.a. in the early Holocene Interglacial (18,000 - 6,000 BP)
The UN’s Intergovernmental Panel on Climate Change (IPCC) 5th Assessment Report suggests that sea level rise was only 0.5 mm p.a. from 6,000 BP to 1860.

Since 1870
The rate of sea level rise has increased.
The IPCC attributes this to global warming due to anthropogenic forcing through greenhouse gas emissions
Contemporary sea level rise has accelerated since 1940 reaching 3 mm p.a. between 1990 and 2000.
​Future
IPCC predicts sea level rise of 18-59 cm by 2100. (28-98 in 2013?)
US National Research Council predicts 56-200 cm
This wide variation in prediction is due to:
uncertainties in science of relationship between GHG increase and climatic warming due to complex feedback effects
uncertainties in science of relationship between climatic warming and rate of ice melting
uncertainties about rate of population growth and economic growth impacting on rate of GHG emission
uncertainty about future political commitment to introducing new measures to reduce GHG emissions
Complete melting of Greenland ice sheet would raise global sea levels by 7 m
Complete melting of Antarctic ice sheet would raise sea levels by 50 m
However complete melting of ice sheets would take many centuries even by the most rapid estimates

What coastlines are at risk?
low lying ones - coastal flooding through marine trangression
low lying volcanic islands or coral atolls set atop submerged volcanic guyots e.g. Maldives in the Indian Ocean, Kiribati Islands in the Pacific Ocean - at risk of complete disappearance
Volcanic islands at risk from both global warming and tectonic activity

Question 90

Physical factors causing coastal flooding

Answer 90

Rapid coastal erosion is caused by physical factors when geological and marine characteristics combine to promote erosion.
Geological factors include:
Lithology - soft rock type, weak cohesive bonds, porous rocks
Geological structure - well jointed rocks, rocks with seaward dipping beds, heavily faulted rocks
Marine factors include:
long wave fetch promoting large, destructive waves
strong longshore drift that quickly removes collapsed sediment allowing erosion to restart

Human activity can increase rates of coastal recession by interrupting the operation of the sediment cell. The construction of major dams of rivers can trap river sediment behind the dam wall. This then starves the coast of a sediment source, leading to serious consequences.

The construction of the Aswan High Dam on the River Nile in 1964 reduced sediment volume from 130 million tonnes to about 15 million tonnes per year. Erosion rates jumped from 20-25 m per year to over 200 metres per year as the delta was starved of sediment.

Dredging
This is the removal of sediment from a beach, sea or river.
Sands or gravels scooped/sucked up for use by construction industry
Dredging of river mouths and estuaries often to maintain navegable channel for ship transport

Question 91

Wind direction and fetch as a factor influencing coastal recession

Answer 91

Winds change direction daily as different weather systems pass across or near the UK
Rates of recession will be higher when the wind is blowing onshore
Offshore winds produce calm conditions
Dominant wind is the direction of the strongest wind
Prevailing wind is the direction of the most common wind
When wind blows from prevailing wind direction, strong winds produce large destructive waves and rapid recession
Where wind blows from a direction where there is a large fetch, even moderate strength winds can build up large destructive waves and produce rapid recession
Dominant wind direction often coincides with direction of largest fetch, as a large expanse of unobstructed open water allows wind to gain strength.
In the North Norfolk coastline the rare dominant wind from the north with a 1,600 km fetch across the Norwegian and North Seas can produce recession rates of up to 8 m p.a.

Question 92

Tides as a factor influencing coastal recession

Answer 92

Rates of recession more rapid during high tide when deeper water in the foreshore zone allows waves to maintain a higher energy when they reach the backshore. (And they reach the backshore in the first place)
Greater energy of impact on backshore increases erosion and rates of recession
High tides occur twice each day, about 12 hours apart
Twice each lunar month when the gravitational pull of the Sun and the Moon is aligned, particularly high Spring Tides occur
Higher sea level produces deeper water near the backshore and faster recession
IPCC estimates a 1 cm rise in sea level produces an average of 1 m horizontal erosion
Global warming predicted to raise sea levels by 18-59 cm by 2100

Question 93

Storms as a factor influencing coastal recession

Answer 93

Storm events are deep (very low pressure) depressions
They produce large, high energy destructive waves and fast rates of recession
Global warming is predicted to increase intensity of atmospheric circulation - more frequent storm events - higher intensity of storm events - increased rates of recession

Question 94

Seasons as a factor influencing coastal recession

Answer 94

Storm events are more likely to occur in the winter when the contrast in temperature and pressure between the tropical and polar air masses is the greatest
Consequently in the UK the rates of recession are faster in winter than summer
In Holderness, in winter 2-6 m of erosion is common when storms, combined with spring tides, increase erosion rates (although the average erosion rate is 1.25 m - but this varies from 0-6 m per year)
Number and intensity of storms affecting the UK each winter varies:
Weaker storms during El Niño events every 2-7 years and during phases of low solar output in the 11 year cycle

Question 95

Weather systems as a factor influencing coastal recession

Answer 95

UK located at the polar front between the boundary of warm tropical air of the Ferrel cell and the cold polar air of the Polar cell
Interaction between warm and cold produces high air pressure anticyclone and low air pressure depression weather systems
Anticyclones produce gentle winds and small waves - low rates of recession
Depressions - areas of rising air (low surface air pressure)
These produce strong winds - rapid rates of recession
Depressions form in the North Atlantic and take several days to pass across the UK from the SW to NE. As they pass the spiralling inflow air produces changes in wind direction

Question 96

Context of sea level rise increasing costal flood risk

Answer 96

Sea level rise affects a disproportionate number of people because:
Many low lying coastlines are densely populated as beaches and the sea attract a large number of tourists
Low lying deltas are extremely fertile and ideal for agriculture
Estuaries and deltas are ideal for trade with good navigable access inland up rivers
Many river deltas support megacities,
e.g. Shanghai, Yangtze Delta China - 24 million people
Dhaka, Bangladesh, Ganges-Brahmaputra delta - 14 million people
Karachi, Pakistan Indus delta - 23.5 million people
The IPCC predicts that by 2060 12% of the world’s population will be living in coastal regions less than 10 m above sea level

Question 97

Local factors increasing costal flooding risk

Answer 97

Local Factors
These also increase the flood risk of some coastlines
Height
Low lying coastlines are only 1-2 m high above (high tide) sea level so at risk from flooding
Temporary flood risk from storm surges, permanent flooding from global sea level rise
The Maldives archipelago in the Indian Ocean has a population of 340,000 spread across 1,200 islands
The highest point in the Maldives is only 2.3 m above sea level
Malé, the main island and capital, is protected by a 3 m sea wall
Bangladesh occupies the Ganges-Brahmaputra delta, 60% of the country is less than 3 m high above sea level
The Kiribati archipelago in the Pacific Ocean is composed of 33 coral atolls.
Most of the population lives on the island of Tarawa where the maximum height above sea level is 3 m
Subsidence
Low lying coastlines in estauries, deltas or outbuilding zones are subject to natural subsidence through the settling and compaction of recently deposited sediment
However, subsidence is usually outpaced by fresh deposition and the bioaccretion of organic matter
Deltas experience periodic isostatic subsidence when the weight of the delta sediment reaches the threshold sufficient to cause the crust to depress - leading to marine transgression and flooding
Human activity can also cause local subsidence:
Drainage of saturated sediment/soil for agriculture e.g. Fens of East Anglia, or ground water abstraction to supply cities, e.g. Venice, reduces sediment volume and causes subsidence
Weight of cities and built environment can also compress sediment, leading to subsidence (also happening in Venice)
Land reclaimed from the sea, e.g. Ijsselmeer polders in the Netherlands, subject to subsidence due to water abstraction via evapo-transpiration by agricultural crops.
Volcanic islands and coral atolls - seafloor spreading away from hotspot or mid-ocean ridge
Isostatic readjustment after ice sheet retreat (southern England)
Bangladesh:
50 large islands in the Ganges-Brahmaputra delta subsided by 1.5 m since 1960
Partly due to isostatic crustal depression and partly due to water abstraction by occupying populations, partly due to natural settling of sediment while the earth bund flood protection prevents compensation fresh sediment deposition
Vegetation Removal
Vegetation, like salt marshes and mangrove forest, reduces flood risk
Vegetation stabilises existing sediment and traps new sediment, raising the height of the land above sea level
Vegetation absorbs wave energy, reducing wave impact and erosion, and reduces the distance waves travel onshore before the energy is exhausted
An 100 m belt of mangrove forest is estimated to reduce wave height by 40%
A 1 km belt of mangrove forest reduces the height of a storm surge by 0.5 m
An estimated 50% world’s mangrove forest removed since 1950 - 1/4 of the loss for the creation of shrimp farms, and lots removed for tourist beaches
Bangladesh contains the 180 km Sundarbans, the largest mangrove forest in the world. However, 71% is experiencing some vegetation removal. Some parts are eroding at 200 m p.a

Question 98

Global sea level rise as a factor increasing flood risk

Answer 98

Global Sea Level Rise
Global sea level rise increases the risk of flooding in low lying coastlines (duh)
Mean global sea level rose by 20 cm in the 1900. 50% of the Netherland and large areas of the East Anglian Fens are now below sea level, but protected by coastal defences
IPCC predicts a further 18-59 cm rise in sea level by 2100
Bangladesh - a 40 cm sea level rise would permanently submerge 11% of Bangladesh, creating 7-10 million environmental refugees
Maldives - 50 cm sea level rise would permanently flood 77% of the Maldive Islands’ land area.

Question 99

Storm surges

Answer 99

Storm surge events can cause severe coastal flooding with dramatic short term impacts (depressions, tropical cyclones)
Depressions are areas of low air pressure generating surface winds that spiral into the centre of low pressure in an anti-clockwise direction. They occur in mid-latitutes, like the UK.
Storms are depression, areas of low surface pressure that generate strong winds (UK 90 kph, tropical regions 65 kph) They occur in areas just north and south of the equator.
Tropical cyclones are areas of very low surface air pressure (deeper depressions) generating very strong winds (118 kph +)
They’re classified on the Saffir Simpson scale into 5 categories, where the fifth has winds of over 250 km.

High air pressure depresses the ocean surface, lowering local sea level.
Low air pressure allows the ocean surface to dome upwards, raising local sea level.
A 1 millibar reduction in air pressure leads to a 1 cm rise in sea level.

A storm surge is a temporary rise in local sea level produced when a depression, storm or tropical cyclone, reaches the coast.
The rise in sea level during the storm surge is accentuated:
At high tide, particularly spring tide
Shape of coastline funnels into increasingly narrow space
Sea bed shallows towards coast

Storm surges can produce severe coastal flooding on low-lying coastlines.
Force of onshore current of storm surge water can cause rapid coastal erosion.
Impact of storm surge increased by large destructive waves whipped up by strong storm winds on top of the already higher sea level - rapid coastal erosion.

Question 100

Short term impacts of storm surges

Answer 100

​Short term impacts:
Deaths and injuries to people immediately through drowning or collapsing buildings
Subsequent deaths from hypothermia (homes destroyed), water borne diseases (sewer systems and freshwater pipe destroyed), natural causes (transport routes to medical care cut)
Destruction of infrastructure - roads, railways, ports, and airports flooded or destroyed
Damaged water pipes, electricity transmission lines and sewage systems - no power or water.
Homes destoyed - older houses worse standards, cheap in poor areas - homes on marginal low lying land (slums and shanty towns) most vulnerable - reconstruction may take several years, richer (insurance) likely to be rehoused first
Businesses destroyed - factories, offices - loss of power, interruption of raw material delivery, workers killed/injured/can’t get there - agricultural land contaminated - crop harvest lost

Question 101

Bangladesh, Tropical Cyclone Sidr 2007

Answer 101

Category 4 cyclone, air pressure 944 mb, 240 kmph and 6 m storm surges
Impact worsened by:
funnel shape of the Bay of Bengal focussing water on Bangladesh at the bay apex.
Out flowing discharge from the Ganges and Brahmaputra rivers combine with coastal flooding.
Intense rainfall from cyclone increases flooding.
Coastline from unconsolidated delta sediment - easily eroded.
Deforestation of mangrove swamps.
60% of Bangladesh low lying, less than 3 m above sea level
15,000 people killed and 55,000 injured. 1.6 million homes destroyed.
8,000 km of roads, 700 km of electricity transmission lines and 900 fresh water tube wells destoyed
Crops destroyed on 600,000 ha of agricultural land
Total damage estimated at $1.7 billion
However, the impacts of deaths were much lower than in the 1970 Bhola Cyclone where 300,000 were killed. ($90 million economic loss) Improved warnings, embankments and cyclone shelter network saves many lives.

Question 102

United Kingdom, Storm Xavier, December 2013

Answer 102

80+ mph winds
Storm coincided with spring tide
In the North Sea the coastline narrows into a funnel shape for a storm approaching from the north - storm surge funnelled - sea shallows towards coast - severe coastal flooding.
Average 3 m storm surge in East Anglia, but 6 m at Blakeney in North Norfolk
2 people killed. 18,000 evacuated. Coastal defences breached in Yorkshire and Kent and 1,400 homes flooded.
At Hemsby in Norfolk sand dunes were eroded, seven houses and a lifeboat station destroyed
East coast rail services suspended for one day
Total economic loss estimated at $100 million
Impacts much lower than the 1953 storm surge when 307 people were killed, 65,000 ha of farmland flooded and there were an economic loss equivalent to $1.2 billion today
This was prevented by: improved flood defences in 2013, including the Thames Barrier (raised during the storm), which protected 800,000 homes according to Environment Agency estimates
Improved forecasting and efficient evacuation also saved lives and mitigated in areas where flooding or erosion still occurred. United Kingdom, Storm Xavier, December 2013

Question 103

Climate change and costal flood risk

Answer 103

High Confidence
Sea level will rise by 18-59 cm by 2100
however the pace and extent of sea level within the predicted range is uncertain due to population growth, economic development, natural positive and negative feedback, political commitment to restrict GHG emissions.
it is also affected by adaption:
building sea walls, e.g. on the North Norfolk coast, 3 m sea wall on Malé.
new artificial island, Hulhamalé created by the reclamation of sediment from the sea bed between 1997-2002, which is 4 m above sea level and cost $32 million to construct.
building earth embankments, like the bunds in Bangladesh
storm surge barriers across river mouths - Thames Barrier, Eastern Scheldt Barrier in the Netherlands (part of the 2.5 billion euro project begun after the 1953 storm surge)
restoration of mangrove forest - protection belts, e.g. Sri Lanka replanting after the 2004 Indian Ocean tsunami killed 6,000 people in one coastal village where mangroves were cleared, but only 2 deaths in an adjacent village protected by a mangrove forest
mitigation - efforts to reduce magnitude of event. Reducing GHG emissions to limit level of global warming would mitigate sea level rise and cyclone intensity.
Delta flooding
The are area of the world’s major deltas at risk from coastal flooding is likely to increase by 50%

Medium Confidence
Wind and waves
Some evidence of increase wind speeds and large waves
Coastal erosion
Erosion will generally increase because of the combined effects of changes to weather systems and sea level

Low Confidence - evidence weak and uncertainty high
Tropical cyclones
The frequency is likely to remain unchanged, but there could be more larger storms
Predicted to increase in strength by 2-11% by 2100. Associated rainfall will increase by 20%.
Cyclone intensity would increase due to warmer ocean surface temperature and warmed atmosphere holding more moisture.
Number of tropical cyclones not predicted to increase - combination of factors form them, and a warm ocean temperature is only one of them.
In the North Atlantic, the number of tropical storms becoming hurricanes has risen from 6 in the 1900s to 8 per year from 2000-2016
However, this is only low confidence - no observed increase in maximum intensity in the Pacific and Indian Oceans over the last 20 years of monitoring.
The number and intensity of tropical cyclones is highly variable each year and decade - no statistically significant long term trend.
Storm surges
These are linked to depressions that are likely to become more common
More intense tropical cyclones will exhibit even lower surface air pressure producing larger temporary sea level rises as storm surges and increasing the risk of coastal flooding
Depressions
Polar front jet streams will accelerate, possibly increasing the number and intensity of depressions and storm surges in mid-latitudes

The magnitude and timing of all these changes is uncertain.

Question 104

Economic losses from recession

Answer 104

​​Economic
Loss of (or damage to) property in the form of homes, businesses and farmland, so relatively easy to quantify. The losses tend to be very localised and costs depend on the land’s use and location.

In 2015, the EA valued English agricultural land at £21,000 per ha, and industrial/business land at £500,000 per ha.
Residential land can vary from £500,000 (North Yorkshire, cold climate, boulder clay) to £2.1 million per ha (Dorset, warm climate, Jurassic coast).
Re-rerouting a two lane road can cost between £150,000 and £250,000 per 100 m. The collapse of the section of coast supporting the South Devon Main Line Railway in February 2014 cost £35 million to repair, and businesses in the South West lost £60 million.

Other consequences:
Economic losses to businesses if areas become unattractive and depopulated.
A whole village could be at risk (part social)
Falling property values, and an inability to sell property
Unexpected recession can cause localised loss:
In 1993 140 mm of rain in 2 months led to the collapse of the £2 million Holbeck Hall Hotel in Scarborough, in a slump of 1 million tonnes of boulder clay.
Loss of a major asset, and the costs of buying a new home
An inability to insure against the loss (because its a certainty, not a risk)*

*There is little help available for those who lose their homes to the sea. There is no national compensation scheme. The UK has the ‘Coastal Change Pathfinder’ projects, 15 two-year projects funded in 2010 by DEFRA which:
Gave the East Riding of Yorkshire £1.2 million, and funded relocation and demolition for 43 homes.
Cover the cost of property demolition and site restoration
Provide up to £1000 in relocation expenses (removal vans, storage…)
Provide up to £200 in hardship expenses
Have ‘rollback’ policies, giving people fast tracked planning approval to build a new home somewhere else

​The Environment Agency estimates 800 properties will be lost by 2035

Overall, though, the economic losses are small because:
Erosion happens slowly; a small number of properties are affected over decades.
Property at risk looses its value to buyers long before it is at risk from erosion
Areas of high-density population, such as towns and villages, tend to be protected by coastal defences. (which means the actual economic loss is much lower)

Question 105

social losses from recession

Answer 105

Social
Relocation
Cost (can be quantified)
Break up of community, loss of friends and activities like a football team or classes
Also stressful!
Loss of livelihoods (which can be quantified)
Source of income (can be quantified)
Financial problems and job searching leads to stress (and divorces, etc…)

​There are also losses in amenity value and economic losses to businesses if areas become unattractive and depopulated. For example, abandoned buildings, damaged roads, rerouted footpaths, loss of access to beach. (Amenity value is the value in cultural, human well-being and economic terms of an attractive environment people enjoy using.) ​
Unattractive environment - cliff collapse, failing sea defences and blocked roads/paths

Question 106

Consequences of flooding in developed countries

Answer 106

Consequences in Developed Countries
​Australia (future flooding)
The IPCC estimates a sea level rise of 28-98 cm sea level rise by 2100, with the most likely rise being 55 cm
A 1 m rise would flood:
116,000 homes causing property damage of US $72 billion;
$87 billion worth of commercial property threatened
$67 billion road and rail infrastructure.
5 power stations,
258 emergency service stations,
75 hospitals and
44 water and sewage plants.
Social costs would include the break up of communities, loss of livelihood, e.g. fishing, tourism, and amenity loss (?)
Coral reefs forming the Great Barrier Reef will die if they are unable to grow fast enough to keep up with sea level rise, leading to a loss in tourism income.

North Sea Flood, UK, 2013 (Part of the winter storms)
Storm surges reached heights of more than 5 m (e.g. in Hull)
On the 5 December 2013 a large storm surge hit the east coast of the UK causing widespread flooding along the coast.
Low pressure, high winds and high tidal pressures combined
Social
2 deaths in the UK
Hundreds of people were evacuated from Rhyl, in Denbighshire
Loss of amenity value - nature reserve damaged in Skegness
Loss of livelihood - businesses affected in Lowestoft, Suffolk as the harbour area, railway station and southern section of the town centre were flooded
Economic
The EA reported 1,400 homes flooded in England and Wales
Damage of about £1 billion over the course of the winter
All rail services cancelled in Scotland
40,000 homes in Scotland and Northern England lost power

Question 107

Consequences of coastal flooding in developing countries

Answer 107

Consequences in Developing Countries
Philippines (Emerging country, effects of flooding)
IPCC estimates a rise of 60 cm - 1 m by 2100 in the Philippines
Economic
A 1 m rise would cause $6.5 billion of property damage
San Fernando in the north of Luzon predicted to lose 123,000 m^2 beach with $95,000 p.a. tourism revenue
Fishing industry losses estimated at $168,000 p.a.
Much of the threatened area is poor shanty towns, e.g. Cavite City and Las Piñas in Manila, with low property value
Social
A 1 m rise would affect 2.3 million people, and 62% of Manila in the south of Luzon Island
Loss of livelihood - fishing, tourism
Loss of amenity value - San Fernando beach
Social cost high as alternative employment is difficult to find in the formal sector

Philippines 2013, Typoon Haiyan
One of the most powerful tropical storms ever with a 4-5 m surge
Economic
Damages of about US $2 billion, centred on the city of Tacloban
In Tacloban 90% of structures destroyed or damaged
Social
At least 6,300 deaths
30,000 injured
1.9 million homeless
6 million displaced - 20,000 fled to Manila

Question 108

Environmental refugees

Answer 108

Environmental refugees are those forced to leave their homes because of natural processes, including sudden ones such as landslides or gradual ones such as erosion or rising sea levels. It’s not a term used by the UN High Commission for Refugees. It includes refugees and internally displaced people.

IPCC predicts that climate change will produce a sea level rise of 26-82 cm by 2100, which would create environmental refugees by:
Flooding
Salt water encroachment (into groundwater, for drinking, irrigation and industry)
Coral bleaching (which acts as a sea defence)

The places most at risk from the sea level rise predicted by 2100 are the Maldives, Tuvalu, the Seychelles and Barbados.
Tuvalu’s highest point is 4.5 metres above sea level, and most land is only 1-2 m above
New Zealand grants residency to 75 Tuvalu citizens each year under the Pacific Access Category Ballot as rising sea levels decrease its land area.
In 2014 New Zealand courts granted the Alesana family permanent residence on their basis as ‘climate change refugees’
80% of people in the Seychelles live and work at the coast
Coral reefs, which act as a natural coastal defence against erosion, are being destroyed by global warming-induced coral bleaching
Water supply is limited and at risk from salt-water incursion as sea level rises and groundwater is over-used
They have small and narrow economies based on tourism and fishing, which is easily disrupted.
They have high population densities and very limited space, so no opportunity for relocation.
Developing or emerging countries lack the funds to finance coastal defences to protect huge lengths of coastline.
Maldives have an average height of 1.5 m above sea level, but the population of 400,000 is too large to be easily accommodated elsewhere. Its government is negotiating with India, Sri Lanka and Australia to buy land.

The worst-case scenario for Tuvalu and parts of the Maldives is that some, or all islands will have to be abandoned, creating environmental refugees.

Hurricane Katrina, USA, 2005
Created 1 million environmental refugees when a 7 m storm surge flooded New Orleans
Most were internally displaced within the USA but 30% did not return to New Orleans

Typhoon Haiyan, 2013
This and other possibly climate change driven storm events since 2008 have produced 6.8 million internally displaced environmental refugees

Question 109

Hard engineering for coasts

Answer 109

This is the traditional management process for erosion/flooding, encasing the coastline in concrete, stone and steel. The aim is to directly stop physical processes altogether (such as erosion or mass movement) or alter them to protect the coast (such as encouraging deposition to build larger beaches)

Advantages
It’s obvious to at-risk people that something is being done to protect them, its reassuring
A ‘one-off’ solution that could protect a coastline for decades

Disadvantages
Costs are usually very high, and there are still ongoing maintenance costs
Even very carefully designed engineering solutions are prone to failure
Coastlines are made visually unattractive and the needs of a coastal ecosystem are usually overlooked
Defences built in one place frequently have adverse consequences further along the coast

​

Question 110

Groynes

Answer 110

Vertical stone or timber ‘fences’ built perpendicular to the coast and spaced along the beach.

Their purpose is to prevent longshore movement of sediment and encourage deposition, building a wider, higher beach.

Impact on physical processes:
Deposition and beach accretion
Prevention of longshore drift, sediment starvation and increased erosion downdrift

Cost £150-250 per metre

Question 111

Sea wall

Answer 111

Concrete with steel reinforcement and deep-piled foundations; can have a stepped and/or ‘bullnose’ profile, to dissipate wave energy

A physical barrier against erosion.
They often also act as flood barriers
Modern sea walls are designed to dissipate, not reflect, wave energy

Destruction of the natural cliff face and foreshore environment
​If reflective, it can reduce beach volume

£3000-10,000

Question 112

Rip Rap (rock armor)

Answer 112

Stone, timber or interlocking concrete sloping structures which are permeable

Purpose: To absorb wave energy and reduce swash distance by encouraging infiltration
Reduce erosion on dune faces and mud banks

Reduced wave power
​Can encourage deposition and may become vegetated

Question 113

Offshore rock breakwater

Answer 113

Large igneous or metamorphic rock boulders weighing several tonnes (offshore rip-rap)

Forces waves to break offshore, rather than at the coast, reducing wave energy and erosive force
\

Deposition encouraged between breakwater and beach
Can interfere with longshore drift

Question 114

What is soft engineering

Answer 114

This attempts to work with natural physical systems and processes to reduce the coastal erosion and flood threat.
Usually less obvious and intrusive at the coast
May be cheaper in the long term
Not suitable for all coasts

Question 115

Beach nourishment

Answer 115

Beach Nourishment
Artificial replenishment of beach sediment to:
replace sediment lost by erosion,
to enlarge the beach
so that it dissipates wave energy and reduces erosion and
increases the amenity value of the beach.
£20 million per km of beach
Ongoing costs are high
Sediment must not be sources from elsewhere in the sediment cell

Question 116

Cliff regrading and drainage

Answer 116

Cliff Regrading and Drainage
Cliff slope angles reduced to increase stability
Re-vegetated to reduce surface erosion.
In-cliff drainage reduces pore-water pressure and mass movement risk.
Costs of £1 million per 100 m
Can be disruptive during construction

Question 117

Dune stabilisation

Answer 117

Dune stabilisation
Fences are used to reduce wind speeds across the dunes,
dunes are then replanted with marram and lyme grass to stabilise the surface
This reduces erosion by wind and water.
Fencing costs £400-2000 per 100 m and replanting £1000 per 100 m (1400-3000)
Can be very cost effective in the long term.

Question 118

Sustainable costal management

Answer 118

Coastal communities around the world face the dynamic nature of the coast’s everyday environment. They increasingly face threat from:
rising global sea levels, but there is uncertainty about the scale and timing of the rise
increased frequency of storms and the possibility of increased erosion and flooding

To cope with these threats, communities need to adapt and employ sustainable coastal management. to ensure the well-being of people and the coastal environment.

(Sustainable coastal management means managing the wider coastal zone in terms of people and their environment livelihood, social and cultural well-being, safety from coastal hazards, as well as minimising environmental impacts.

Sustainable coastal management:
Managing natural resources (fish, farmland, water supply) to ensure long-term productivity
Managing flood and erosion risk where possible, or relocating to safe areas
Creating alternative livelihoods before existing ones are lost to the sea
Adapting to sea level rise by relocating, alternative building methods and water supplies
Educating communities to understand why change is needed and how to adapt.
Monitoring coastal change and adapting to unexpected trends

Adopting sustainable coastal management may lead to conflict because:
coastal natural resources may have to be used to less in order to protect them - so some people lose income
relocation may be needed where engineering solutions are too costly or not technically feasible
some erosion and/or flooding will always occur, as engineering schemes cannot protect against all threats.
future trends, such as sea level rise, may change, creating uncertainty and the need to change plan.

Question 119

Littoral zones and Integrated Costal Zone Management

Answer 119

ICZM is coastal management planning over the long term, involving all stakeholders, working with natural processes and using ‘adaptive management’, i.e. changing plans as threats change.

ICZM is a holistic approach used to manage coasts. It dates from the Rio Earth Summit in 1992 and has a number of key characteristics:
The entire coastal zone is managed, not just the narrow zone where breaking waves cause erosion and flooding. This includes all ecosystems, resources and human activity in the zone.
It recognises the importance of the coastal zone to people’s livelihoods as, globally, very large numbers of people live and work at the coast - but their activities tend to degrade the coastal environment.
It recognises that management of the coast must be sustainable, meaning that economic development has to take place to improve the quality of life of people but that this means to be environmentally appropriate at equitable.

ICZM works with the concept of littoral cells, or sediment cells. These contain sediment sources, transport paths (flows) and sinks. Each littoral cell is isolated from adjacent cells, and can be managed as a holistic unit.

The coastline can be divided up into littoral cells and each cell managed as an integrated unit.
In England and Wales there are 11 sediment cells.
Each cell is managed either as a whole unit or a sub-unit.
In both cases a plan called a Shoreline Management Plan (SMP) is used.
The SMP area is further divided into sub-cells.
SMPs extend across council boundaries, so many councils must work together on an agreed SMP to manage an extended stretch of coastline.

Question 120

Policy decisions about costal management

Answer 120

In the UK, coastal management is overseen by DEFRA (Environment, Food and Rural Affairs). Since DEFRA introduced Shoreline Management Plans in 1995 there have been only four policies available for coastal management, which differ greatly in their costs and consequences.

1) 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.
2) Strategic (managed) realignment
Allow the coastline to move naturally (in most cases to recede) but managing the process to direct it in certain areas.
3) Hold the line
Build of maintain coastal defences so that the position of the shoreline remains the same over time.
4) Advance the line
Build new coastal defences on the seaward side of the existing coastline.
Usually this involves land reclamation.

Making decisions about which policy to apply to a particular location is complex. It depends upon:
the economic value of the assets that could be protected, e.g. land
the technical feasibility of engineering solutions: it may not be possible to ‘hold the line’ for mobile depositional features such as spits, or very unstable cliffs.
the cultural and ecological value of land: it may be desirable to protect historic sites and areas of unusual diversity
pressure from communities: vocal local political campaigning to get an area protected
the social value of communities that have existed for centuries.

SMPs plan for the future using three time periods called ‘epochs’. These are:
Up to 2025
2025-55
2055+
A hold the line policy applied to an area up to 2025 may become a managed realignment policy after 2025. This is because by 2025 sea level rise is likely to have made ‘hold the line’ a much more expensive policy to apply.

Question 121

Cost benefit analysis

Answer 121

Cost-Benefit Analysis

Cost-benefit analysis (CBA) is used to help decide if defending a coastline from erosion and/or flooding is economically justifiable.

An example is Happisburgh in North Norfolk:
The policy adapted in this area is ‘no active intervention’
This is because to defend the village would have an impact on the wider coastal management plan.
Happisburgh would end up as a promontory, blocking longshore drift and causing further erosion downdrift.
Longer term, the plan is managed realignment, although this would still involve property being lost to the sea by erosion.

Costs of erosion:
£160,000 could be available to Manor Caravan Park to assist in relocating to a new site
Affected residents could get up to £2000 each (a total costs of £40-70,000) in relocation expenses plus the cost to the council of finding plots of land on which to build new houses.
Grade 1 listed St Mary’s Church and Grade 2 listed Manor House would be lost.
Social costs as the village is slowly degraded, including health effects and loss of jobs.

Benefits of erosion:
By 2105, between 20 and 35 houses would be ‘saved’ from erosion, with a combined value of £4 million - 7 million
45 hectares of farmland would be saved, with a value of £945,000
The Manor Caravan Park would be saved, which employs local people.

The cost of building coastal defences at Happisburgh is around £6 million, very close to the value of property that could be saved, and much higher than the compensation cost payable to local residents.
Coastal managers argue that Happisburgh must be seen in the wider context of the whole SMP, further justifying the decision not to defend the village.

Question 122

Environmental impact assessment

Answer 122

Environmental Impact Assessment (EIA)

Coastal management usually requires an EIA to be carried out. This is quite separate from any CBA, although might inform the final CBA. EIA is a process that aims to identify:
the short-term impacts of construction on the coastal environment
the long-term impacts of building new sea defences or changing a policy from hold the line to no active intervention or managed realignment

EIA is wide-ranging and includes assessments of:
impacts on water movement (hydrology) and sediment flow, which can affect marine ecosystems because of changes in sediment load
impacts on water quality, which can affect sensitive marine species
possible changes to flora and fauna, including marine plants, fish, shellfish and marine mammals
wider environmental impacts such as air quality and noise pollution, mainly during construction

Question 123

Costal mangament confilicts

Answer 123

Coastal management decisions directly affect people’s lives. These effects can be positive or negative, producing perceived:
winners: people who gain from a decision, either economically (their property is safe), environmentally (habitats are conserved) or socially (communities can remain in place)
losers: people who are likely to lose property, their business or job, be forced to move, or see the coastline be ‘concreted over’ and see this as an environmental negative.

In some ways this is inevitable because:
coastal managers produce plans for entire SMP areas, so some areas are protected whilst others are not
local councils and governments (DEFRA) have limited resources, meaning not all places can be protected

There are examples where all stakeholders agree on a course of action. The Blackwater Estuary in Essex is an area of tidal salt marsh and low-lying farmland.
Prone to flooding and coastal erosion, the farmland was traditionally protected by flood embankments and revetments
Over the last 30 years it has become clear that building higher and more coastal defences in places such as Blackwater is not sustainable.

The solution adopted was radical.
In 2000 Essex Wildlife Trust purchased Abbotts Hall Farm on Blackwater Estuary, which was threatened by erosion and flooding.
A 4000 ha managed realignment scheme was implemented by creating five breaches in the sea wall in 2002.
This allowed new salt marshes to form inland.
The scheme has a number of benefits:
The Abbotts Hall Farm owners received the market price for their threatened farm
The very high costs of a ‘hold the line’ policy were avoided, by flood risk was reduced
Water quality in the estuary improved because of expansion of reed beds that filter and clean the water.
New paths and walkways were created for leisure activities
Additional income streams from ecotourism and wildlife watching were created.
Important bird (dunlin, redshank, geese) and fish (bass and herring) nurseries were enhanced.

The Blackwater Estuary shows that environmentalists, landowners, coastal managers and local people and businesses can all be kept happy, even when radical plans are adopted.

Coastal Management in the Developing World

In many parts of the developing world, such as the Maldives, parts of Vietnam, and the West African coast, erosion is rapid, often because of a combination of:
upstream dams reducing sediment supply to the coast and disrupting local sediment cells
rapid unplanned coastal development, urbanisation and the development of tourist resorts with piecemeal defences and no overall plan
widespread destruction of mangrove forests for fuelwood and shrimp-ponds, exposing soft sediment to rapid erosion.

In many cases the main ‘losers’ are the poorest people. Farmers and residents usually lack a formal land-title so cannot claim compensation (even if it were available).
Coastlines become more vulnerable to sea level rise, the impact of tropical cyclone storms and even tsunami.
When these disasters strike it is the poorest that lose everything.
In many cases it is individual property owners that take responsibility for coastal defences in the absence of local council or government plans.