Coasts Flashcards
Coastal system
- Coasts - where land meets the sea
- Coastal systems are in dynamic equilibrium - inputs and outputs are balanced
Positive feedback - when a chain of events amplifies (increases) the impacts of the original event
Examples:
- Beach starts to form —> slows down waves —> causes more sediment to be deposited —> size of the beach increases
Negative feedback - when a chain of events nullifies (reduces or stops) the impacts of the original event
Examples:
- As a beach is eroded —> the cliffs behind it are exposed to wave attack —> sediment from cliffs is deposited on the beach, causing it to grow in size
Coasts are systems:
Inputs:
- Energy and sediment coming into coastal system e.g. energy inputs come from waves, wind, tides and currents
Stores (stores of sediment):
- Erosional landforms e.g. cliffs
- Depositional landforms e.g. spits, beaches, dunes
Outputs:
- Energy and sediment moving out of the coastal system e.g. sediment carried out to sea via backwash, sediment removed by longshore drift
Flows/transfers (sediment moves from one store to the next):
- Erosion, deposition, transportation, weathering, mass movement
Sources of energy in coastal systems
Wind:
- Winds are created by air moving from areas of high pressure to areas of low pressure. During events such as storms, the pressure gradient (the difference between high and low pressure) is high and winds can be very strong
- Strong winds can generate powerful waves. If wind consistently blows from the same direction (prevailing wind) — this causes higher-energy waves than winds that change direction frequently
Waves:
How are waves formed?
1. Waves are created by the wind blowing over the surface of the sea. The friction between the wind and the surface of the sea creates small waves which gives the water a circular motion
2. When waves approach the shore they break. Friction with the sea bed slows the bottom of the waves (makes their motion more elliptical - squashed and oval shaped). The crest of the wave (top of wave) carries on moving - rises up and collapses
What is wave energy affected by?
The taller a wave, the more energy it carries —> wave height is affected by wind strength, duration and fetch of the wave
- Wind strength (link to pressure gradient)
- Wind duration
- Fetch of the wave (the maximum distance of sea the wind has blown over)
- Sea bed —> gently sloping sea bed — waves experience friction with the sea bed and slow down —> waves lose energy —> less erosion// steeply sloping sea bed —> less friction with the sea bed —> waves won’t lose as much of its energy —> more erosion
2 types of waves and characteristics:
Constructive:
- Low frequency —> 6-8 per minute
- Low and long
- Strong swash, weak backwash —> carries material up the beach and deposits it
Destructive:
- High frequency —> 10-14 per minute
- High and steep
- Strong backwash, weak swash —> removes material from the beach
- Constructive waves tend to deposit material —> size of beach increases
- Destructive waves cause erosion —> size of beach decreases
Anatomy of a wave (search up diagram):
- Crest - highest point of wave
- Trough - lowest point of wave
- Wave height - different in height between crest and trough
- Amplitude - half the wave height
- Wave length - difference between 2 crests/2 troughs
- Frequency - number of waves per minute
Tides:
- Tides - the periodic rise and fall of the level of the sea, caused by the gravitational pull of the moon and the sun
- Spring tide - when the moon, earth and sun are in a line, the combined gravitational pull creates the highest high tides and the lowest low tides —> greatest tidal range
- Neap tide - when the sun and moon are perpendicular to each other, their gravitational pulls interfere with one another, giving the lowest high tides and the highest low tides —> smallest tidal range
- Tides affect erosion and lead to the formation of different landforms
Currents:
- Currents - general flow of water in one direction
3 types of currents:
Longshore currents (littoral drift)
- Flow of water parallel to the coastline —> move material along the coast
Rip currents
- Strong currents moving away from the beach
- Waves cause a build up of water at the top of the beach —> eventually the waves finds a route back out to sea —> creates a strong current
Upwelling
- Winds drive water across the ocean surface, allowing cold, nutrient-rich water from the deep ocean to rise to the surface
High and low energy coastlines
- High-energy coasts receive high inputs of energy in the form of large, powerful waves. These can be caused by strong winds and long fetches. High-energy coastlines tend to have rocky landforms e.g. cliffs, caves, stacks and arches. The rate of erosion is often higher than the rate of deposition
- Low-energy coasts receive low inputs of energy in the form of small, gentle waves. These can be caused by gentle winds and short fetches. Low-energy coastlines often have saltmarshes and tidal mudflats. The rate of deposition is often higher than the rate of erosion
Sediment
Sources of sediment in coastal systems:
- Rivers carry eroded sediment into the coastal system
- Sediment is eroded from cliffs by waves, weathering and landslides
- Sediment can be formed from the crushed shells of marine organisms
- Waves, tides and currents can transport sediment into the coastal zone from offshore deposits
- Sea level rise can flood river valleys, forming estuaries (river and sea meet). Sediment in the estuary becomes part of the coastal system
Sediment budget:
- Sediment budget - difference between the amount of sediment that enters the system and the amount that leaves
- If more sediment leaves than enters, there’s a negative sediment budget and overall the coastline retreats
- If more sediment enters than leaves, there’s a positive sediment budget and overall the coastline grows
Sediment cells:
- The coast is divided into sediment cells (also called littoral cells)
- These are lengths of coastline (often between two headlands) that are pretty much entirely self-contained for the movement of sediment (sediment doesn’t move between cells). This means that each cell is a closed coastal system
Wave refraction
- Occurs when waves approach a coastline that is not a regular shape (headland and bay)
- Wave energy becomes concentrated on the headland, causing greater erosion
- In a bay, the waves lose power, causing deposition
Coastal processes
- Sub-aerial processes (operate on land)
- Marine processes (operate in the sea)
- Aeolian processes (driven by the wind)
Erosional processes
Erosional processes:
- Abrasion/corrasion - bits of rock/sediment carried by the sea are picked up by strong waves and thrown against rocks and cliffs, breaking bits off and smoothing surfaces
- Wave quarrying - energy of wave is enough to detach bits of rock
- Solution (corrosion) - soluble rocks get dissolved by the seawater e.g. limestone
- Attrition - Bits of rock in the water smash against each other and break into smaller bits
- Hydraulic action - force of water crashing into rocks, compressing air in cracks, and breaking the rock apart
Factors affecting erosion:
Wave strength (strong waves = more erosion)
- Controlled by fetch and wind strength/duration e.g. long fetches and stronger/longer winds create bigger and powerful waves —> more erosion
Bathymetry:
- Underwater topography of the seabed impacts the strength of waves
- Gently sloping sea bed —> waves experience friction with the sea bed —> waves lose energy —> less erosion
- Steeply sloping sea bed —> waves experience less friction with the sea bed —> waves won’t lose as much of its energy —> more erosion
Beaches:
- Beaches increase the distance a wave travels before it reaches the cliffs —> absorbs some wave energy before it reaches cliffs —> waves energy is reduced —> less erosion
Weathering:
- Weathering creates weaknesses in rocks which can be further exploited by the processes of erosion
- Weathering rates are high —> rates of erosion will be faster
Rock type:
- Sedimentary rocks e.g. limestone have lots of faults, making them weak and vulnerable to erosion whereas igneous and metamorphic rocks are made up of interlocking crystals, making them more resistant to erosion
Transportation
Transportation (eroded material being moved):
- Solution - substances that can dissolve are carried along in the water e.g. limestone is dissolved into water that’s slightly acidic
- Suspension - very fine material e.g. silt are carried along in the water (most eroded material is transported this way)
- Saltation - larger particles e.g. pebbles are too heavy to be carried in suspension so particles bounce along the sea bed
- Traction - very large particles e.g. boulders are dragged along the sea bed
Longshore drift:
1. Swash carries sediment up the beach in the direction of prevailing wind
2. Backwash carries sediment back down the beach at right angles
3. Overtime, sediment is moved along the beach
Deposition
Deposition (process of dropping eroded material):
- Marine deposition - when sediment carried by seawater is deposited
- Aeolian deposition - when sediment carried by wind is deposited
- Both marine and aeolian deposition happen when the sediment load exceeds the ability of the water or wind to carry it - happens because sediment increases or wind/water slows down
Wind and water slow down for similar reasons:
- Friction increases — if waves enter shallow water or wind reaches land, friction increases, which slows down the water or wind
- Flow becomes turbulent — if water or wind encounters an obstacle, flow becomes rougher and overall speed decreases
Weathering
- Weathering is a sub-aerial process (operates on land)
- Weathering - weakens rocks and makes them more vulnerable to erosion
Different types of weathering:
- Physical/mechanical - when rocks break up with no chemical changes
- Chemical - rock breakdown due to a chemical reaction
- Biological - rock breakdown due to organic activity
Salt weathering (physical/mechanical):
1. Salt water enters cracks in rocks at high tide
2. As the tide goes out the rocks dry and the water evaporates —> salt crystals are left behind in the cracks
3. As the salt crystals form they expand, exerting pressure on the rock - this causes pieces to fall off
Wetting/drying (physical/mechanical):
1. Some rocks contain clay
2. When clay gets wet, it expands, exerting pressure on the rock - this causes pieces to fall off
Freeze thaw weathering (physical/mechanical):
1. Water enters cracks in rocks
2. When temperatures drop below 0°C, the water freezes and expands which causes the crack to widen
3. The ice melts and more water fills into the cracks
4. The process repeats itself until the rock breaks
Biological weathering:
1. Plant roots growing in cracks of rock —> widens cracks —> can cause rocks to breakdown
Chemical weathering:
1. Carbon dioxide in the atmosphere dissolves in rainwater, forming a weak carbonic acid. This acid reacts with rock that contains calcium carbonate e.g. limestone and the rocks are gradually dissolved
Mass movement
- Mass movement is a sub-aerial process (operates on land)
- Mass movement - shifting of material downhill due to gravity
Types of mass movement:
- Slides - material shifts in a straight line (consolidated rock)
- Rockfalls - material breaks up and falls (consolidated rock)
- Mudflows - material flows downslope (unconsolidated rock)
- Slumps - material shifts with a rotation (unconsolidated rock)
Coastal landforms caused by erosion
Caves, arches, stacks and stumps:
1. Headlands have cracks —> abrasion and hydraulic action widen the cracks
2. Repeated erosion of cracks causes cave to form
3. Continued erosion deepens the cave until it breaks through the headland to form an arch
4. Arch is eroded until the roof collapses leaving a stack
5. A wave cut notch forms at the base of the stack, eventually causing it to topple over and collapse —> leaving behind a stump
Example: Jurassic Coast in Dorset - old harry and old harry’s wife (stack and stump)
Headlands and bays:
1. Headlands and bays form where there are alternating bands of hard and soft rock at right angles to the coast (discordant coastline)
2. The soft rock is eroded quickly, forming a bay
3. The hard rock is eroded more slowly and forms a headland which sticks out
Example: Jurassic Coast in Dorset - Swanage Bay
Wave cut platform:
1. Sea attacks base of cliff forming a wave cut notch
2. Repeated erosion causes rock above notch to become unstable and it eventually collapses
3. Collapsed material is washed away and a new wave cut notch starts to form
4. The process repeats and the cliff continues to retreat, leaving behind a wave cut platform
Example: Jurassic Coast in Dorset - kimmeridge bay
Blowhole:
1. Waves approach the bottom of the headland where there’s a crack
2. Water is forced and compressed into the cracks - wave quarrying and hydraulic action
3. Eventually water spurts out the top, forming a blowhole
Example: the world’s largest blowhole is found in Nakalele blowhole in Hawaii
Coves:
1. Formed on concordant coastlines
2. Resistant outer band rock is eventually breached
3. Erosion speeds up when waves reach the less resistant bands of rock —> erosion spreads out laterally
4. Once harder rock is reached again, erosion slows down
Example: Jurassic Coast in Dorset - Lulworth Cove
Coastal landforms caused by deposition
Spits:
- Spit - a finger of beach material extending out to sea
1. Longshore drift moves material along the coastline
2. When the coastline changes direction e.g. at a headland, longshore drift doesn’t change direction
3. Sediment builds out to sea and this creates a spit
4. A change in wind direction will cause the spit to curve at the end. This is known as a recurved end
5. Over time, several recurved ends form. A spit that has multiple recurved ends is called a compound spit
6. The area behind the spit is sheltered from the waves and often develops into mudflats and saltmarshes (sheltered area allows for the deposition of river sediment —> over time, this sediment builds up to form a mud flat —> as vegetation begins to grow on the mud flat, it transitions into a salt marsh)
- Example: Spurn Head - Holderness Coast
Bars:
1. A bar forms when a spit joins 2 headlands together
2. A lagoon forms behind the bar
- Example: Slapton Sands in Devon
Tombolos:
- If a spit joins up to an island, it creates a tombolo
- Example: Angel Road in Japan
Offshore bars:
- Destructive waves remove sediment from the beach and form the offshore bar
- Example: Scroby Sands, Norfolk, England
Barrier islands:
- Barrier islands are long, narrow islands of sand that run parallel to the shore and are detached from it
- They tend to form in areas where there’s a good supply of sediment, a gentle slope offshore (more friction with seabed —> waves loss energy —> increased deposition), fairly powerful waves and a small tidal range (if the tides don’t rise and fall too much, the water doesn’t wash over the island as often - this helps the sand build up)
- It’s not clear exactly how barrier islands form, but scientists think that they probably formed after the last ice age ended - ice melt caused rapid sea level rise - rising waters flooded land and transported sand offshore, where it was deposited
- Example: Horn Island
Sand dunes (depositional landform)
- A vegetation succession is a plant community that changes over time - from pioneer species (first plants to colonise an area of bare ground e.g. marram grass) to climax community (a community of plants which have reached a steady state over time and vegetation has evolved to the end point of succession e.g. deciduous woodland)
Conditions needed for dune formation:
- Large tidal range (large amount of sand exposed at low tide)
- Large supply of sand
- Large tidal range and large supply of sand allows the sand to dry so that it is light enough to be picked up and carried by the wind to the back of the beach
- Wind
- Obstacle
- Vegetation
Sand dune formation:
1. Sand is deposited around an obstacle e.g. seaweed and driftwood
2. An embryo dune develops which may become vegetated by pioneer species such as marram grass
3. Roots bind the sand together// marram grass help slow the speed of wind —> wind loses energy —> sediment is deposited
4. Several embryo dunes will join together to create foredunes and yellow dunes. This is the tallest of the dune succession (yellow dunes)
5. Grey dunes form as the dunes become more mature. As plants die, nutrients are added to the sand dune, so more complex plants can grow. Eventually, the climax vegetation is reached e.g. heathland or woodland
6. Areas between dunes (slacks) may be damp or even contain water
Characterises of marram grass:
- It is tough and flexible, so can cope when being blasted with sand
- It has adapted to reduce water loss through transpiration
- It has mechanisms to tolerate high salinity
Example: Sand dunes at Cape Hatteras in North Carolina
Mudflats and salt marshes
- Mudflats and saltmarshes form in sheltered, low-energy environments e.g. river estuaries or behind spits. These areas are protected from strong waves, allowing fine sediments to accumulate
- As silt and mud are deposited by the river, mudflats develop. Vegetation such as eelgrass and algae starts to grow, stabilising the sediment
- The mudflats are then colonised by vegetation that can survive the high salt levels and long periods of submergence by the tide (known as halophytes e.g. cordgrass). These plants trap more mud and silt, causing the area to build upwards over time
- As the mudflats rise and remain exposed for longer periods, they transition into a saltmarsh. Pioneer species like cordgrass are succeeded by other plants, such as sea lavender, which continue to stabilise and build the marsh
- Eventually, these species are replaced by other species. Dead organic matter improves soil fertility and helps soil to retain water. This allows taller plants to grow, adding further height to the salt marsh
- Eventually, the vegetation is replaced by trees and shrubs and the climax community forms
Example of saltmarsh: Huntington Beach State Park, South Carolina
Eustatic and Isostatic sea level change
- Eustatic sea level change is caused by a change in the volume of water in the sea, or by a change in the shape of the ocean basins (global)
Causes of eustatic sea level change:
1. Changes in climate:
- An increase in temperature causes melting of ice sheets, which increases sea level
- As water becomes warmer, it also causes water to expand, which increases sea level further
2. Tectonic movements:
- Tectonic movements of the earths crust can change the shape of ocean basins e.g. sea floor spreading increases the volume of the basin and so decreases the sea level
- Isostatic sea level change is caused by movements of the land relative to the sea (local)
- Any downward movement of the land causes sea level to rise locally, while uplift of land causes sea level to fall
Causes of isostatic sea level change:
1. Tectonic movements:
- A coastal region experiencing seismic activity (earthquakes) may experience land being shifted upwards or downwards as a result of pressures being released by an earthquake
- Subduction plate sinks under overriding plate —> lots of friction between 2 plates which causes the overriding plate to be stuck —> however, the subduction plate is still moving, which causes slow distortion of overriding plate (plate is being forced/bent upwards overtime) —> land rises so sea level appears lower
2. Subsidence of land due to shrinkage after abstraction of groundwater e.g. drainage of marshland
3. Crust is floating on the mantle —> ice sheet adds lots of weight onto crust and pushes it down into the mantle below —> results in sea level rise// if the weight is lifted e.g. ice sheet melts during interglacial period —> crust rebounds and rises —> sea level falls
Sea level changes
- During the last glacial period, water was stored in ice sheets, so sea level was lower than present. At the last glacial maximum, sea level was about 130m lower than present
- Over the last 4000 years, sea level has fluctuated around its present value
- Since about 1930, sea level has been rising
- Over the last century, global temperature has increased rapidly. This is called global warming. There’s been a sharp rise in average temperature (1.08 °C between 1900 and 2016)
- There is a consensus among scientists that the changes in climate over the last century are a result of human activities, such as deforestation and burning fossil fuels —> increased GHG —> planet warms up
- Increases in temperature are likely to cause increases in sea level, through melting of ice sheets and thermal expansion of water in oceans
- Global sea level is currently rising at almost 2mm each year. If greenhouse gas emissions remain very high during the 21st century, this is predicted to increase to 8 to 16 mm a year by 2100
Impacts of climate change on coastal areas
Impacts of climate change on coastal areas:
1. Storms are likely to become more frequent and more intense. This would cause damage to coastal ecosystems and settlements
2. If sea level rise continues as predicted, it will have major impacts on coastal areas:
- More frequent and more severe coastal flooding. Flooding of low-lying areas has increased with sea level rise and it will increase more with further rises
- Submergence of low-lying islands. Lots of low-lying islands are at risk of disappearing. For example, if the sea level rises by just 0.5 m from its current level then most of the Maldives will be submerged
- Contamination of water sources and farmland. Salt water may enter bodies of fresh water (e.g. lakes and rivers) near the coast, damaging ecosystems and making the water unsuitable for lots of uses. Salt water entering soils may damage crops and make land impossible to farm
- Changes in the coastline. As sea levels rise the coastline changes — islands are created and the area of land is decreased e.g. if the sea level rises 0.3 m from its current level, 8000 km^2 of land in Bangladesh will be lost
- Sea level rise and increased storminess will increase coastal erosion, putting ecosystems, homes and businesses at risk
Coastal management
Coastal Management:
1. The aim of coastal management is to protect homes, businesses and the environment from erosion and flooding
2. This is because flooding and erosion of the coastline can have severe social, economic and environmental impacts
3. All coastal settlements want to be defended, but the amount of money available is limited so not everywhere can be defended. Choosing which places are defended (and how) is based on a cost-benefit analysis (evaluate whether the benefits outweigh the costs). The money available is usually used to protect large settlements and important industrial sites, rather than isolated or small settlements
4 options for coastal management:
1. Hold the line - maintain the existing coastal defences
2. Advance the line - build new coastal defences further out to sea than the existing line of defence
3. Do nothing - build no coastal defences at all
4. Managed realignment - where areas are intentionally allowed to flood to protect more important places e.g. flooding farmland rather than towns
Hard engineering
- Hard engineering - involves built structures
Sea walls:
- Reflects waves back out to sea, preventing erosion at the coast
- Acts as a barrier to prevent flooding
Positives and negatives:
- Sea walls acts as promenades so people can walk across them —> promotes tourism ✅
- Expensive ❌
- Waves can erode the sea wall ❌
Revetments:
- Sloping structures that absorb wave energy —> reduce erosion
Positives and negatives:
- Beach access steps can be built into the revetment —> promotes tourism ✅
- Cost effective ✅
- Visually unappealing ❌
Groynes:
- Fences built at right angles to the coast. They trap material transported by LSD. This creates wider beaches —> less erosion
Positives and negatives:
- Builds a wider beach —> encourages tourism ✅
- Can create erosion further down coast ❌
Rock amour:
- Large boulders placed in front of a cliff or sea wall —> absorb wave energy and reduce erosion
Negatives:
- Visually unappealing —> they look different to the local geology as the rock has been imported from other areas ❌
- The rocks are expensive to transport ❌
- Can shift in storms ❌
Gabions:
- Wire cages filled with rocks —> absorb wave energy and reduce erosion
Positives and negatives:
- Cheap compared to other forms of hard engineering ✅
- Wire cages can rust —> unattractive —> less tourism ❌
- If the wire cages break then they are very dangerous —> people may trip on rocks or cut themselves with the broken wire// birds could injure themselves with the broken wires ❌
Breakwaters:
- Concrete blocks or boulders deposited off the coast. The waves energy and erosive power are reduced before they reach the shore
Negatives:
- Can be damaged in storms ❌
- Expensive ❌
Soft engineering
- Soft engineering - natural approach to manage coastal erosion and flooding
Beach nourishment:
- Beach nourishment is where sand and shingle are added to beaches from elsewhere. This creates wide beaches, which reduces erosion
Negatives:
- Very disruptive —> e.g. material delivered by trucks will cause congestion in the road and beaches might need to be closed to allow this to happen ❌
- Expensive —> has to be repeated ❌
- Taking material from places like seabed can kill organisms like sponges and corals ❌
Dune regeneration:
- Creating new sand dunes or restoring existing ones by planting vegetation to stabilise the sand —> dunes act as a barrier and absorb wave energy —> waves have less energy —> less erosion
Positives and negatives:
- Dune regeneration increases biodiversity —> when new dunes are created/existing dunes are restored, it provides habitats for a variety of plants and animals ✅
- Dunes can be easily damaged by storms ❌
- Areas have to be zoned off from the public while plants grows —> less tourism ❌
Creating marshland:
- Creating marshland from mudflats by planting appropriate vegetation. The vegetation helps to absorb wave energy. This reduces their erosive power and how far the waves reach inland, leading to less flooding
Positives and negatives:
- Increases biodiversity —> marshlands create habitats for wildlife ✅
- Required to compensate for people who lose buildings and farmland ❌
Sustainable coastal management strategies
- Coastal management has to be sustainable — this means that strategies shouldn’t cause too much damage to the environment or to people’s homes and livelihoods, and shouldn’t cost too much
- Hard engineering is often expensive, and disrupts natural processes
- Soft engineering tends to be cheaper and is designed to integrate with the natural environment
- So soft engineering is a more sustainable management strategy than hard engineering because it has a lower environmental impact and economic cost
Shoreline Management Plans:
- The coastline is split into sediment cells
- For each cell, a plan is created for how to manage different areas with the aim of protecting important sites
- For each area within a cell, authorities can decide to hold, advance or retreat the line, or to do nothing
Integrated Coastal Zone Management:
- ICZM considers all elements of the coastal system (e.g. land, water, people, the economy) when coming up with a management strategy (holistic approach)
- It is a dynamic strategy - decisions are re-evaluated if the environment or demands of the area change
- All stakeholders all involved
Holderness Coast Case Study
- The Holderness coastline is 61km long - it stretches from Flamborough Head to Spurn Head
- Most of the cliffs are made of boulder clay and the coast is exposed to powerful destructive waves from the North Sea during storms
There are a number of coastal processes operating in the area:
- Erosion - the soft boulder clay is easily eroded by wave action. In some places e.g. Great Cowden, the rate of erosion has been over 10m/year in recent years
- Mass movement - the boulder clay is also prone to slumping when it’s wet
- Transportation - prevailing winds from the northeast transport material southwards. Rapid erosion means there is always plenty of sediment to be transported
- Deposition - erosion and longshore drift have created a spit with a recurved end across the mouth of the Humber Estuary —> this is called Spurn Head. Mudflats and saltmarshes have formed behind the spit
Landforms:
- Headland - chalk is prevalent in the north of the area. The chalk is harder and less easily eroded —> headland is formed (Flamborough Head). Flamborough Head has features such as stacks, caves and arches
- Sand dunes - around Spurn Head, material transported by the wind is deposited, forming sand dunes
- Spit - erosion and longshore drift have created a spit with a recurved end across the mouth of the Humber Estuary —> this is called Spurn Head. Mudflats and saltmarshes have formed behind the spit
- Beaches - the area to the south of Flamborough Head is sheltered from wind and waves, and a wide sand and pebble beach has formed near Bridlington
Management of the Holderness Coastline:
Why does the Holderness Coast need to be managed?
- The Holderness coastline has retreated by around 4km over the past 2000 years. Around 30 villages have been lost
- Ongoing erosion could cause numerous social, economic and environmental problems, such as:
- Loss of settlements and livelihoods e.g. the village of Skipsea is at risk and 80000 m^2 of farmland is lost each year —> huge effect on farmers’ livelihoods
- Loss of Sites of Special Scientific Interest (SSSIs) - e.g. the Lagoons near Easington provide habitats for birds
- Loss of infrastructure - the gas terminal at Easington is only 25m from the cliff edge
Hard Engineering has been Used Along the Holderness Coastline:
- A total of 11.4km of the 61km coastline is currently protected by hard engineering
- Bridlington is protected by a 4.7km long sea wall
- There’s a concrete sea wall, groynes and riprap at Hornsea that protect the village
- Two rock groynes and a 500m long revetment were built at Mappleton in 1991. They cost 2 million
- A landowner in Skipsea has used gabions to help protect his caravan park
- Easington Gas Terminal is protected by a revetment
- Spurn Head is protected by groynes and riprap
Existing Schemes are Not Sustainable:
- The groynes trap sediment, increasing the width of the beaches. This protects the local area but increases erosion of the cliffs elsewhere e.g. the Mappleton scheme has caused increased erosion of the cliffs south of Mappleton. Cowden Farm, just south of Mappleton, is now at risk of falling into the sea
- Costly Maintenance – Hard engineering structures require regular maintenance and repairs due to constant erosion and storm damage. For example, the sea walls and groynes need upkeep, which is expensive over time
- Short-Term Solutions – While these structures provide temporary protection, they do not stop erosion in the long term. The coastline is retreating rapidly, and hard engineering only delays the inevitable rather than addressing the root causes
- Limited Coverage – Only 11.4 km of the 61 km coastline is protected, leaving large sections exposed to rapid erosion. This creates an unfair situation where some areas are defended while others are left to erode more quickly
Challenges:
- The SMP for Holderness for the next 50 years recommends ‘holding the line’ at some settlements (e.g. at Bridlington, Withernsea, Hornsea, Mappleton and Easington Gas Terminal) and ‘doing nothing’ along less-populated stretches. However, owners of land or property along the stretches are unhappy that nothing is being done
- Managed realignment has been suggested e.g. relocating caravan parks further inland and allowing the land they are on to erode. This would be a more sustainable scheme as it would allow the coast to erode as normal. However, there are issues surrounding how much compensation businesses will get for relocating
- Easington Gas Terminal is currently protected by rock revetments, and the SMP recommends that these defences are maintained for as long as the gas terminal is operating. However, the defences only span about 1km in front of the gas terminal, meaning that the village of Easington (with a population of about 700 people) isn’t protected
Sundarbans case study
Subdarbans Case Study:
- The Sundarbans region is in southwest Bangladesh and east India
- It is the largest mangrove forest in the world
- The land is very flat and low-lying
- The Sundarbans is home to many rare species of plants and animals, including white-bellied sea eagles
- The trees are adapted to living in salt water and grow on mud flats
Opportunities:
1. The Sundarbans region is home to more than 4 million people. The area provides a range of natural products, which can be used by the people who occupy the area or sold to bring economic benefits to the region:
- The flat, fertile land is ideal for growing crops, particularly rice
- The rich ecosystem of the mangrove forest provides the local population with fish, crabs and honey etc
- The mangrove forests provide timber for construction, firewood and furniture
- The mangrove forest provides a natural defence against flooding and coastal erosion. This makes it easier to live and grow crops
- There are opportunities for tourism - visitors are attracted by the mangroves
Challenges:
Human:
- Lack of employment – Few job opportunities exist in the region
- Deforestation – The growing population leads to mangrove loss, increasing flood and erosion risks
- Limited electricity and communication – Only 20% of households have access mains electricity, making flood warnings difficult to receive
- Poor infrastructure – Few, low-quality roads make access to healthcare and education difficult
Physical Challenges:
- Flooding and salinisation – Flooding can make the soil too salty for crops to grow
- Dangerous wildlife – Tigers, sharks, and crocodiles pose a threat to humans
- Rising sea levels – The low-lying land is at risk due to global warming
Attempts to overcome these risks:
Resilience - being able to cope challenges
Examples:
- Better roads and bridges are being built in the region, improving access for residents and visitors. However, this can lead to deforestation and other environmental damage
- Mains electricity is being extended to more areas. This will make it easier for flood warnings to reach communities
- There are efforts to decrease poverty in the region e.g. by providing farming subsidies to increase food production and provide jobs. However, there is a risk that some areas of land may be farmed too intensively, causing environmental damage
Mitigation - reducing the impacts of hazards
Examples:
- 3500km of embankments were built to prevent flooding. However, the embankments are gradually being eroded, and around 800km are vulnerable to being breached during storms and tsunamis
- Coastal management projects aim to protect existing mangrove forests and replant areas that have been removed, to protect against flooding and erosion. However, it is difficult to prevent illegal forest clearance throughout the whole region
Adaptation - adjusting behaviour to fit the environment
Examples:
- In some areas, salt-resistant varieties of rice are being grown — this could help residents cope with flooding and sea level rise. However, relying on a smaller range of crops can reduce biodiversity and may increase vulnerability to pests and diseases
- Projects are underway to increase tourism to the area, providing jobs and income. For example, lodges have been built and tour operators run boat trips on the rivers. However, if not properly managed, tourism can cause environmental damage
- People can adapt to sea level rise or flooding e.g. by building houses on stilts. However, infrastructure such as roads cannot be protected as easily
