Coastal systems and landscapes

Inputs and Outputs

Inputs → refer to material or energy inputs into a coastal system

• marine inputs: waves, tides

• human inputs: pollution, recreation

• atmosphere: sun, wind

• biological: living organisms

• geological: rock type, tectonic activity

Outputs → refer to material or energy outputs

• ocean currents

• riptides

• evaporation

Flows/transfers and stores/components

Flows → processes that link the inputs, outputs and stores in a system

• deposition: flocculation, gravity settling

• longshore drift

• erosion: hydraulic action, attrition

• transportation: traction, suspension

Stores → refers to the stores of sediment or material in a system

• beaches

• caves

• wave-cut platforms

Energy and Dynamic equilibrium

Energy → the power and driving force behind the flows and transfers

• wind

• gravity

• flowing water

Dynamic equilibrium → when outputs and inputs are in balance

• the processes of positive and negative feedback adjust the system, bringing it to DE

Positive feedback loop

When changes in a coastal system are exaggerated , making it unstable and moving it away from dynamic equilibrium

• When humans walk along sand dunes, destroying vegetation

• vegetation no longer binds the sand together, exposing it to further erosion

• over time erosion continues until the sand dune is removed, taking the beach further away from its original state

Negative feedback loop

When changes in a coastal system are lessened, bringing it back to dynamic equilibrium

• After a large storm, destructive waves lose energy and deposit sediment

• a bar is created which reflects wave energy, reducing erosion on the coastline

• eventually the bar gets completely eroded, reverting the system back to dynamic equilibrium

Landform and landscape

Landform → A natural feature of a land surface created by physical processes

• cave

• wave-cut platform

• beaches

Landscape → a collection of landforms and man-made features that make the visible parts of an area

• human - infrastructure, buildings

• natural - mountains, valleys

• changeable elements - weather

• biological - wildlife, vegetation

How processes create landforms

Mass movement and weathering:

• mass movement can remove sediment to create landforms e.g., rotational slumping that removes weaker geology

• weathering involved sediment production which allows landforms to be created further along a coast

Deposition and transportation:

• deposition and transportation involve the transfer of sediment, creating distinctive landforms e.g., spits, barrier beaches

Energy sources: winds

Wind → air that moves from an area of high pressure to an area of low pressure.

• strength of the wind: the larger the difference in pressure between 2 areas (pressure gradient), the stronger the wind and the more powerful the waves.

• the duration of the wind: wind that is active for longer has more time to build up and increase.

• the size of the fetch (the distance over which the wind blows): the larger the fetch the more powerful the waves.

Energy sources: constructive and destructive waves

Constructive waves:

• long wavelength

• 6-9 waves per minute

• swash > backwash - deposit sediment, increase size of beach

• low waves, occur on gently sloped beaches

Destructive waves:

• short wavelength

• 11-16 waves per minute

• backwash > swash - erode sediment, decrease size of beach

• high waves, occur on steeply sloped beaches

Energy sources: currents

Rip current → a strong flow of water running from the beach back into the ocean:

• occur when the backwash is forced under the surface due to resistance from breaking waves, forming an underwater current.

• this flows away from the shore more quickly due to beach features e.g., gap in a sandbar, forming a rip current.

• responsible for 80% of rescues on US beaches, but can be escaped by swimming parallel to the coastline.

Energy sources: tides

Tide → a shallow water wave caused by gravitational interactions between the sun, moon & earth

Spring tide → the highest high tide & lowest low tide:

• when the sun & moon are in alignment, they work together to pull the oceans towards each other, causing the highest high tide.

• on the other side of the planet, the lowest low tide is created.

• this tide creates the largest possible tidal range.

Neap tide → the highest low tide & lowest high tide.

• when the sun & moon are perpendicular, their gravitational forces work against each other, creating the highest low tide.

• this tide creates the smallest possible tidal range.

Low and high energy coasts

Low energy coasts:

• less powerful waves

• occur in sheltered and sandy areas, where constructive waves prevail

• have depositional landforms as rates of deposition > rates of erosion

High energy coasts:

• more powerful waves

• occur in areas with a large fetch, where destructive waves prevail

• have rocky landforms as rates of erosion > rates of deposition

Sediment sources: rivers

• high-rainfall environments allows the river to be eroded easily.

• sediment is deposited & can be transferred into estuaries - where the river meets the ocean.

• waves, tides & currents transfer sediment into the coastal system.

Sediment sources: cliffs

• occur when cliffs are unstable & have unconsolidated material, allowing them to erode very easily.

• some cliffs can retreat 10m / year, creating significant sediment output.

• most erosion occurs in winter months, where storms and rainfall are more common.

Sediment sources: wind and glaciers

Wind:

• wind can cause sand to be blown up / along a beach

• most common on coastline with sand dunes or in desert environments.

Glaciers:

• sediment can be held within glaciers.

• they can be deposited when they calve (ice breaking off the glacier) or when they melt, transferring sediment into the ocean.

Sediment cells

A self-contained unit of erosion, deposition & transportation.

• a section of a the coast, which is a closed system - there is no sediment transfer between other cells.

• they are determined by the shape or topography of the coast e.g., estuaries or bays.

• within a singular cell are sub-cells with little to no movement of sediment.

• although they are not thought to be fully closed - variations in wind direction and tidal currents can transfer sediment between cells.

Sediment budget

Refers to the balance of sediment added & sediment removed from a coastal system.

• they are assessed by using data of inputs, outputs, stores & transfers to see any gains or losses.

• however, human input & natural variations can disrupt the state of equilibrium.

Geomorphological processes: weathering

Weathering → the physical disintegration and chemical decomposition of rock.

• physical weathering:

  • freeze-thaw weathering, where cracks in the rock fill with water.

  • in areas where temperatures reach below freezing, the water in the cracks freeze and expand.

  • this process repeats as ice melts when temps are above freezing, and freezes again.

• chemical weathering:

  • acidity in rainwater reacts with the rock, causing them to disintegrate.

• biological weathering:

  • when the roots of some species of plant are embedded inside the rock.

  • over time, the plants will grow and expand causing the rock to form cracks and split apart.

Importance in weathering shaping a coastline

Important:

• freeze-thaw and salt crystallisation contribute to the disintegration of rock - responsible for the creation of sediment, allowing other processes to takeover e.g., erosion by abrasion.

• e.g., seen in the Jurassic Coast, where chemical weathering by rainwater reacts with chalk cliffs, breaking them down.

Not important:

• dependent on the climate and seasonal patterns - as sub-aerial weathering is more powerful during storm seasons with heavy rainfall, but areas with hotter climates, may not experience much rain at all.

• biological weathering is time dependent - plant roots in the rock have gradual growth and take time to cause the rock to expand.

• e.g., the White Cliffs of Dover made up of chalk and soft limestone, where evidence shows plant vegetation taking decades to grow.

Geomorphological processes: mass movement

Mass movement → the movement of weathered material downhill, in response to gravity.

• mudflows:

  • an increase in the water content of soil and limited vegetation to bind the soil, reducing its friction.

  • produces sheet flow over the upper cliff surface, and eventually flows over the cliff face at high speeds as the soil continues to be lubricated.

• rockfall:

  • when rocks are broken down by weathering e.g., freeze-thaw, creating rock fragments (scree) to build up at the base of a slope, causing them to collapse.

• rotational slumping:

  • when heavy rain is absorbed by unconsolidated material that makes up the cliff.

  • the cliff face becomes heavier and eventually separates from the material behind.

  • a large area of land then moves down the slope in once piece, leaving behind a curved indented surface.

• runoff:

  • runoff is a link between the water cycle and coastal system.

  • as the water, in the form of overland flow, may erode the cliff face and coastal area.

  • or the water may pick up sediment, that then enters the littoral zone, when it’s transported in the water via suspension.

  • it may also be responsible for increasing pollution in coastal areas if it picks up waste or excess chemicals.

Importance in mass movement shaping a coastline

Important:

• has influence over the eroded and deposited material in a certain area - mass movement is a source of sediment, as well as the removal of material from a slope exposes the surface to erosion.

Not important:

• some aspects of mass movement are quite slow e.g., soil creep - although soil creep can be influenced by moisture content and freeze-thaw cycles, the stronger forces from waves and tides exceed the slow movement by soil creep.

• e.g., the Cliff of Moher have experienced a large amount of soil creep, but the most impactful shaping of the cliff has come from wave action.

Geomorphological processes: erosion

Erosion → the removal of sediment from a coastline by geological agents e.g., wind, waves, rivers or ice.

• abrasion:

  • a low energy process of sediment moving along the shoreline, causing it to be worn down over time.

• attrition:

  • wave action causing rocks and pebbles to hit against each other, allowing the sediment to become smoother and smaller.

  • attrition is an erosive process within the coastal environment, but has little to no effect on the coastline.

• corrasion:

  • sand and pebbles that are picked up by the sea from an offshore sediment sink, are hurled against the cliffs at high tide.

  • the sediment wears pieces of the cliff away, with the shape, size and quantity of sediment affecting the erosive power.

• hydraulic action:

  • air forced into cracks of rock from a wave crashing onto a cliff face, creating cracks / faults in the rock.

  • the high pressure causes the rock to force apart and widen as air expands. Leads to rock fractures over time.

  • cavitation - bubbles found within the water may implode under the high pressure, creating tiny jets of water that, over time, erode the rock.

• solution/corrosion:

  • the acidity in the seawater reacting with alkaline rock e.g., limestone, disintegrating and eroding the rock.

• wave quarrying:

  • a process similar to hydraulic action but acts with more pressure.

  • when breaking waves hit a cliff, exerting a pressure of up to 30 tonnes per m^2.

  • the force of the wave hammers the rock surface, shaking and weakening it, exposing it to further attacks from hydraulic action and corrasion.

Importance in erosion in shaping a coastline

Important:

• erosion is both responsible for breaking down and building up a coastline - erosive processes can wear away sediment, but that sediment will be transferred elsewhere to build up a new area of coast.

• erosion can be the most powerful - through wave quarrying, involves exertions of strong forces on rock in a short period of time.

Not important:

• some areas e.g., sheltered areas are less vulnerable to erosion - they experience higher deposition rates due to having large amounts of sediment present.

• e.g., formation of Wadden Sea, which is characterised by barrier islands and tidal flats, due to low erosion rates and higher deposition rates.

• human interventions mean that erosion can be significantly reduced - groynes ensure that a coastline experiences higher deposition than erosion, rendering the process as weaker e.g., Birling Gap

Geomorphological processes: transportation

Transport → movement of sediment, influenced by angles of waves, tides and currents.

• traction:

  • large boulders of rock rolling along the seabed by a push from currents.

• saltation:

  • smaller sediment bouncing along the seabed, as the sediment is too heavy to picked up by the flow of water.

• suspension:

  • small sediment carried within the flow of water.

  • the Hjulstrom curve shows how greater velocities of water are able to suspend large / heavier pieces of rock.

• solution:

  • dissolved material that is carried within the water, in a chemical form.

• LSD:

  • waves hit the beach at an angle, which is determined by the direction of the prevailing wind.

  • the waves push sediment in this direction on to the beach – known as swash.

  • gravity causes the wave to carry sediment back down to the beach at a 90^o angle – known as the backwash.

  • process repeats, moving sediment along the coastline over time.

Geomorphological processes: deposition

Deposition → when sediment becomes too heavy for water to carry or if the wave loses energy.

• tends to be a gradual and continuous process – a wave won release all of its sediment at the same time.

• gravity settling:

  • when the water’s velocity decreases, so sediment begins to be deposited.

• flocculation:

  • when clay particles clump together due to chemical attraction, and then sink due to their high density.

• resistance by obstruction e.g., groyne.

Importance in deposition shaping a coastline

Important:

• has direct impacts on the creation of new landforms - sediment is deposited when it hits a coastline, and this continuous process can change the entire outlook of the coastline by reshaping / extending it.

Not important:

• a long process - as deposition only occurs when a wave loses energy, so deposition is unlikely to occur rapidly in areas where there are many storms or high energy waves.

• the rate of deposition is dependent on the availability of sediment in an area - leaves some areas with more dominant processes, such as erosion, making deposition reliant on sediment sourced processes e.g., weathering.

Origin and development of landforms and landscapes of coastal erosion: wave cut platforms

• a sequence that occurs at steep cliffs.

• waves erode a cliff, concentrating the erosion around the high-tide line.

• processes of hydraulic action and corrasion create a wave-cut notch, by undercutting the cliff, leaving an overhang.

• as the notch becomes deeper, sub-aerial weathering weakens the cliff from the top  eventually the cliff face becomes unstable and collapses under its own weight, through mass movement.

• this leaves behind a platform of unaffected cliff base beneath the wave-cut notch.

• over time the process repeats, leading to the formation of a wave-cut platform. Which is normally exposed at low-tide.

  • e.g., the Seven Sisters in Sussex

Origin and development of landforms and landscapes of coastal erosion: caves, arches and stacks

• initially, faults in the headland are eroded by hydraulic action and abrasion - creating small caves.

• the overlying rock in a cave may collapse forming a blowhole → the blowhole spurts water when a wave enters at the base, forcing sea spray and air out of the top.

• marine erosion widens faults in the base of the headland - overtime creates a large cave.

• both marine erosion and sub-aerial processes will continue to widen the cave, eroding through to the other side of the headland - creating an arch.

• the arch will eventually collapse through mass movement as the force of gravity makes it unable to support itself - leaves a stack as one side of the arch becomes detached from mainland.

  • e.g., Azure Window in Malta  where marine erosion attacked the base of the stack, which will eventually collapse into a stump.

Origin and development of landforms and landscapes of coastal deposition: beaches

Swash-aligned beaches:

• wave crests approach perpendicular to the coast, meaning there’s limited LSD.

• sediment doesn’t travel far along the beach.

• wave refraction may reduce the speed of high energy waves, leading to the formation of a shingle beach with larger sediment.

  • e.g., Chesil Beach, Dorset

Drift-aligned beaches:

• waves approach at a significant angle, so LSD causes sediment to travel far along the beach.

• this can lead to the formation of a spit at the end of a beach.

• generally, larger sediment is found at the start of the beach.

• and weathered material moves further down the beach through LSD, becoming smaller – so the end of the beach is likely to have smaller sediment.

  • e.g., Orford Ness, Suffolk

Origin and development of landforms and landscapes of coastal deposition: spits

Simple spits:

• dominant waves push material along the coast as LSD.

• the coast turns inwards and material continues to be deposited in line with the coastal trend.

• finer materials are deposited in the sheltered side of the spit.

• marshes can build up, forcing the river to other side of the estuary.

  • e.g., Spurn Head, Yorkshire

Compound spits:

• spits build further into deeper water, and require more sediment to build above the high-water mark.

• the waves have greater energy to attack the distal end (the end of the spit that juts out into the water), turning it inwards.

• sometimes, the curves are due to the changing predominant wind direction, causing waves to change direction, therefore deposition occurs on a different angle.

• these recurves are sheltered by the spit and become prominent features.

  • e.g., Hurst Castle, Keyhaven.

Origin and development of landforms and landscapes of coastal deposition: tombolos

• LSD occurs as waves push sediment towards the coastline at an angle (from the direction of the prevailing wind).

• instead of landing on the beach, the sediment begins to build up between the beach and an island.

• this drift is influenced by wind direction

• this creates a bar which ties the island to the mainland, which is known as a tombolo.

  • e.g., Bennett Island, Russia

Origin and development of landforms and landscapes of coastal deposition: offshore bars

• formed when sand is deposited in a region, as waves don’t have enough energy to carry sediment to shore.

• this can happen when waves break early, instantly depositing its sediment as a loose-sediment offshore bar.

• waves may pick up sediment from an offshore bar, which provides an important sediment input into the coastal zone.

• they can also be formed by backwash from destructive waves, removing sediment from a beach.

• offshore bars may also absorb wave energy, reducing erosion in some areas.

  • e.g., Loe Bar, Cornwall

Origin and development of landforms and landscapes of coastal deposition: barrier beaches / islands

• when a ridge of sand extends to join 2 headlands, on either side of a bay, together.

• it’s due to LSD transporting sediment along the coastline.

• behind barrier beach, a lagoon is created where water has been trapped.

• the lagoon is where a salt marsh may develop over time, due to it being a low energy zone, which encourages deposition.

• barrier islands form when a barrier beach becomes separated from the mainland.

  • e.g., Padre Island, Texas.

Origin and development of landforms and landscapes of coastal deposition: sand dunes

• when prevailing winds blow sediment to the back of the beach.

• embryo dune → where sand begins to accumulate around a small obstacle e.g., driftwood in the upper beach area.

• yellow dune → the dune grows as sand continues to accumulate, allowing vegetation to develop on the upper and back dune surfaces, therefore stabilising it.

• grey dune → the sand develops into soil, containing lots of moisture and nutrients. This enables varied plant growth as the vegetation dies.

• dune slack → when the water table rises closer to the surface, allowing the development of moisture-loving plants e.g., willow grass.

• heath and woodland → sandy soils develop as there is a greater nutrient content. Trees can also grow e.g., willow, birch, oak trees, with the coastal woodland becoming a natural windbreak to the mainland.

  • e.g., The Great Sand Dunes, Colorado.

Estuarine mudflat/saltmarsh environments and associated landscapes; factors and processes in their development: saltmarsh succession

• algal stage → gut weed and blue green algae establish as they grow on bare mud, helping their roots to bind together.

• pioneer stage → cord grass and glasswort grow, with their roots beginning to stabilise the mud, allowing the estuarine to grow.

• establishment stage → salt marsh grass and sea asters grow, creating a carpet of vegetation, so the height of the salt marsh increases.

• stabilisation → sea thrift, scurvy grass and sea lavender grow, and so salt rarely ever gets submerged beneath the marsh.

• climax vegetation → rush, sedge and red fescue grass grow since the salt marsh is only submerged once or twice a year.

Estuarine mudflat/saltmarsh environments and associated landscapes; factors and processes in their development: estuarine mudflats and saltmarshes

• deposition occurs in river estuaries because of the flow of water from the river meeting the incoming tides and waves from the sea.

• this causes water flow to virtually stop, so the water can no longer carry its sediment in suspension.

• deposition may also occur in sheltered areas e.g., behind a spit, where there are no strong tides or current that prevent sediment accumulation / deposition.

• since the sediment is small, a build-up of mud occurs, which over time continues to build until above the water level.

• deposition occurs as a result of flocculation.

• pioneer plants colonise the area, leading to more trapped sediment.

• a meadow forms as sections of the salt marsh rise above the high tide level, leading to the climatic climax of the vegetation succession – where trees begin to colonise.

  • e.g., Blakeney, Norfolk.

Eustatic sea level change

Eustatic changes → worldwide variations of sea level resulting from climate change.

• causes of eustatic change:

  • thermal expansion → water expanding as it gets warmer, leading to a large volume, therefore rising sea levels.

  • melting of ice caps → more water stored as liquid form in the ocean, rather than as solid forms e.g., ice on land.

  • e.g., In the last ice age, sea levels were over 100m lower than they are currently – as water was stored in large ice caps, and the majority of precipitation was snowfall.

Isostatic sea level change

Isostatic change → a change in the level of land relative to the sea.

• causes of isostatic change:

  • isostatic rebound → the slow rise of areas that were once covered by ice during the last ice age, as glaciers would weigh down the land beneath.

  • e.g., Scotland is rising at 1.5mm a year as it was previously covered by glaciers.

  • tectonic activity → a short-term shift in the level of land due to seismic activity.

  • e.g., 2004 Indian Ocean earthquake – caused the city of Bandeh Aceh to sink permanently by 0.5m.

Major changes in sea level in the last 10,000 years

Eustatic sea level change:

• the current rate of eustatic sea level rise is about 3.3 mm per year. This is higher than the average rate of the past several thousand years.

Isostatic sea level change:

• during the last ice age (10,000 years ago), large areas of the earth’s surface were covered by ice sheets – which were several km thick.

• as these ice sheets melted, the land beneath them began to rebound, causing a gradual rise in sea level.

General changes:

• global sea level rose very quickly up to 6000 years ago.

• it flooded the North Sea, English Channel and Irish Sea.

• it flooded former river valleys to give the distinctive indented coastline of SW England (rias).

• since then, sea levels have remained largely consistent, with a slight rise recently due to climate change.

Coastlines of emergence

Coastlines of emergence → where the land has been raised in relation to the coastline.

Landforms of this coastline:

• raised beaches

• marine platforms (wave cut platforms).

Coastlines of submergence

Coastlines of submergence → where the sea level rises of the coastline sinks in relation to the sea.

Landforms of this coastline:

• rias

• fjords

• dalmatian coasts

Origin and development of associated landforms: raised beaches

• landforms, made by coastal processes, that are stranded above the high tide mark when sea levels fall.

• this leaves them in a raised location inland e.g., beaches.

• raised features are sometimes described as fossil landforms – they were formed by processes in the past.

• during the Pleistocene, ice sheets were much thicker, with the mass of the ice depressing the crust.

• isostatic rebound has created a distinctive line of raised sea cliffs.

  • e.g., King’s Cave, Scotland.

Origin and development of associated landforms: rias

• during the Pleistocene, sea levels were at least 100m lower than today, so rivers eroded V-shaped valleys in response to the lower sea level.

• when the ice melted, sea levels rose and the lower parts of river valleys were drowned, creating rias.

• from the air, rias have a branched / dendritic form.

  • e.g., Kingsbury Estuary, South Devon.

Origin and development of associated landforms: fjords

• fjords are U-shaped troughs that were carved by glacial erosion during the Pleistocene, when sea levels were lower.

• they are formed when rising sea levels flood deep glacial valleys to create natural inlets and harbours.

• they are deeper in the middle section than they are at the mouth, with the shallower section identifying where the glacier left the valley.

  • e.g., Sognefjord, Norway.

Origin and development of associated landforms: dalmatian coasts

• dalmatian coasts have a concordant structure.

• they’re formed where sea level rise have flooded old river valley that were roughly parallel to the coastline.

• the old river valleys are submerged, leaving former mountain ridges as series of islands, parallel to the new coastline.

  • e.g., Coast of Dalmatia, Croatia.

Recent and predicted climate change and potential impact on coasts

Pattern 1:

• since 1880 and the industrial revolution, sea levels have increased by around 235mm.

Impact 1:

• enough of a rise to overwhelm some sea defences, when combined with higher-than-expected storm surges.

• the rise also affects the drainage system in coastal cities, increasing the flood risk.

Pattern 2:

• the international Panel on Climate Change (IPCC) predicts sea levels may rise between 0.3 – 1.0 m by 2100.

Impact 2:

• could cause aquifers to be polluted in low-lying atoll islands (coral reefs protruding from the sea), affecting residents who live in them.

• may inundate many coastal cities and significantly increase risks of tropical storms and tsunamis.

• however, in some areas, turning the coastal area into recreational land as a method of adaptation to climate change, is proving to be a popular opinion.

Pattern 3:

• average surface temperatures are likely to pass 1.5^oC in the early 2030’s and 2^oC by the 2060’s.

Impact 3:

• global warming from increased ocean warmth, may increase the frequency and intensity of storms, affecting the severity of flooding. Although, these are only predictions.

Hard engineering coastal management

Hard engineering → working to change natural processes.

Examples:

• groynes

• sea walls

• revetments

• rock armour

• offshore breakwater

Hard engineering: groynes

Advantages:

• they work with natural processes to build up the beach, increasing tourist potential.

• relatively cheap, so can be a quick solution.

• build-up of sediment can protect the land behind it, preventing risk of damage to buildings and homes.

Disadvantages:

• interrupts the process of LSD, increasing rates of erosion elsewhere.

Hard engineering: sea walls

Advantages:

• contains a promenade that can be walk upon, creating social and tourist opportunities.

Disadvantages:

• sea walls create a strong backwash, which can erode under the wall.

• remains fairly expensive to construct and maintain.

• can cause increased erosion further along the coast.

Hard engineering: revetments

Advantages:

• cheap construction, so not financially impactful if need replacing.

Disadvantages:

• intrusive and very unnatural, driving away visitors from that section of coast.

• although cheap, costs begin to add up as they need constant maintenance.

Hard engineering: rock armour

Advantages:

• rocks form a permeable barrier which breaks up sea waves, reducing impacts of erosion.

• can have recreational purposes – fishing, sunbathing.

Disadvantages:

• rocks most likely sourced elsewhere, not fitting with the local geology.

• potentially hazardous if people climb upon them.

Hard engineering: offshore breakwater

Advantages:

• effective permeable barrier by breaking waves before reaching the coast, reduces the power of erosive forces on the coast.

• the rock barrier can act as a natural habitat for marine life.

Disadvantages:

• potential navigation hazards for boats.

• disrupts LSD and sediment cell circulation, as the redirection of wave energy can cause the beach to disappear entirely, further down the coast.

Soft engineering coastal management

Soft engineering → working with natural processes.

Examples:

• beach nourishment

• cliff regrading and drainage

• dune stabilisation

• marsh creation

Soft engineering: beach nourishment

Advantages:

• relatively cheap and easy process – low risk method.

• looks very natural and blends in with the original beach, increasing tourist potential.

Disadvantages:

• doesn’t prevent natural processes e.g., LSD, not a long-term strategy.

• disrupts the natural flow of sediment as material is removed from another area.

Soft engineering: cliff regrading and drainage

Advantages:

• drainage removes water through pipes to prevent landslides and slumping

• drainage is cost-effective, so can be a long-term strategy.

Disadvantages:

• drained cliffs can dry out leading to collapse through mass movement e.g., rock falls.

• regrading cliffs effectively causes the cliff to retreat.

Soft engineering: dune stabilisation

Advantages:

• increases biodiversity as the vegetations creates important wildlife habitats.

Disadvantages:

• growth of planting vegetation is time consuming, so not suitable as a quick, temporary strategy.

• maintaining the vegetation means restricted access and people may respond negatively to being kept off certain areas.

Soft engineering: marsh creation

Advantages:

• a natural defence that provides an effective buffer to the power of waves.

• provides wildlife habitats.

Disadvantages:

• agricultural land is lost, creating costs for compensating farmers / landowners.

• can be quite expensive as it’s land dependent, which is considered costly, especially in the UK.

Sustainable approaches to coastal flood risk and coastal erosion management: shoreline management plans

SMPs → identify both natural and human activities which occur within the coastline of each sediment cell.

• SMPs are extremely detailed documents which are based on the sediment cell principle – that intervention will be largely self-contained within each cell, having little / no knock-on effects elsewhere.

• 4 options are considered for each stretch of coastline:

  • 1. hold the line → maintain the level of protection provided by defences.

  • 2. advance the line → build new defences seaward of the existing defence line, to extend the shoreline.

  • 3. managed retreat / strategic realignment → allowing the retreat of the shoreline with management, and create its own defences e.g., salt marshes.

  • 4. do nothing / no active intervention → decision to not invest, provide or maintain defences, exposing coastline to natural processes.

Sustainable approaches to coastal flood risk and coastal erosion management: integrated coastal zone management

ICZM → where large sections of coastline are managed with one integrated strategy.

• the ICZM recognises the importance of the coast for people’s livelihoods.

• this means that sections of the coast are managed as a whole, rather than individual towns / villages.

• this is because:

  • human actions in one place affect other areas along the coast.

  • transfers (flows) within the sediment cell, meaning sediment moves from one place to another.

  • what is eroded in one location, eventually becomes a protective beach somewhere else.

  • erosion stopped in one place, means sediment is starved somewhere else.

• therefore, the problem is not so much solved as shifted.

• e.g., in 2013, the EU adopted a new initiative to promote the use of ICZM’s across all of Europe’s coastlines.