2 - Coastal environments

Waves

Waves

Marine processes

Erode, transport + deposit material

Formed by winds blowing over surface of sea

Factors affecting wave strength

• Wind strength - stronger wind = bigger waves

• Wind duration - longer period of time = bigger waves

• Fetch (distance of open sea that wind travels across) - longer fetch = bigger waves

What causes a wave to break?

• Wave moves into shallow water

• Base of wave has increased friction, causing it to slow down

• Top of wave continues at same speed

• Wave becomes unstable and collapses

Swash

Incoming water pushed up the beach, at the same angle as the waves (transfers energy up the beach)

Backwash

Water moving back down beach, perpendicular to beach due to gravity (returns energy down beach)

Constructive wave

• Low energy

• Strong swash + weak backwash

• Causes sediment to be deposited on beach

• Low frequency, 6-8 per min

• Low wave height but long wavelength

• Deposit sand so they create flat beaches

Destructive wave

• Lots of energy

• Strong backwash

• Causes coast to be eroded away

• High frequency, 10-12 per min

• High wave height

• Can remove sand from beaches making them steep

Transportation

Material in sea arrives from many sources:

• Eroded from cliffs

• Transported by LSD along coastline

• Brought inland from offshore by constructive waves

• Carried to coastline by river

Traction

Large, heavy material dragged along sea floor

Saltation

Smaller material is bounced along sea floor

Suspension

Fine material is held in water

Solution

Dissolved material carried in water

Longshore Drift (LSD)

• Main process of deposition + transportation along coast

• Influenced by prevailing wind, waves approach beach at an angle

• As waves break, swash carries material up the beach at same angle

• As swash dies away, backwash carries material down beach at right angles (90°)

• Process repeats, transporting material along beach in zig-zag movement

Weathering

Breakdown of rock in-situ

Doesn’t involve movement of material

Weakens cliffs and makes them more vulnerable to erosion

Sub-aerial weathering

Coastal processes not linked to action of sea

Mechanical weathering

Physically breaking rock

• Example is freeze-thaw weathering

• Water gets into cracks + joints in rock

• When water freezes, it expands and cracks widen

• Over time, pieces of rock split off rock face

• Big boulders are broken into smaller rocks + gravel

Chemical weathering

Rocks broken down by chemical process

• Rainwater is slightly acidic through absorbing CO₂ from atmosphere

• Reacts with minerals in rock creating new material

• Rock-type affects rate of weathering e.g. limestone chemically weathers faster than granite

• Warmer temp → faster chemical reaction

Biological weathering

Rocks worn away by living organisms

• Trees + other plants grow within cracks in rock

  • As roots grow bigger they push open cracks in rock making them wider + deeper

  • Over time, growing tree prizes rock apart

• Tiny organisms like bacteria, algae and moss grow on rocks

  • They produce chemicals that break down surface layer of rock

• Burrowing animals like rabbits disturb the ground

  • Destabilises rock above burrow

  • Increasing pressure on cracks

  • Pieces fall off rock

Mass movement

Downhill movement of material under influence of gravity

Factors influencing type of mass movement

• Angle of slope (steeper = faster)

• Nature of regolith (weathered material)

• Amount + type of vegetation

• Water

• Type + structure of rock

• Human activity

• Climate

Sliding

Several different terms: rockslides, landslides, debris slides

Rockslides will be large blocks of solid rock, while landslides may consist of solid rock along with soil + fragments of weathered rock (regolith)

• Rocks that are jointed or have bedding planes roughly parallel to slope/cliff surface are susceptible to landslides

• An increase in amount of water can reduce friction, causing sliding

• In a rock or landslide, slabs of rock/blocks can slide over underlying rocks along a slide or slip plane

Slumping

Similar to slide + also occurs when stress acting on slope overcomes ability of slope to support own weight + resist movement

• Often occur in saturated conditions

• Rotational movement (not in sliding)

• Occur on moderate to steep slopes

• Common where softer materials (clay/sands) overlie more resistant/impermeable rock, e.g. limestone/granite

• Causes rotational scars

• Repeated slumping creates terraced cliff profile

Influence of geology on coastal environments

• Geology shapes coastline over time, place and space

• Coastline made of softer rocks (sands/clays) is easily eroded by destructive waves to form low, flat landscapes such as bays and beaches

• Coastlines of more resistant, harder rock take longer to erode + produce rugged landscapes such as headlands

• Differences between hard/soft rocks impact shape + characteristics of cliffs

• Geology shapes coastline vertically through height + profile of cliff and horizontally with bays + headlands

Influence of vegetation on coastal environments

• The longer a coastal landform has existed, the more likely it will be colonised by vegetation

• Over time, vegetation will ‘fix’ a feature (e.g. sand dune)

• Vegetation adaptation important to survive coastal conditions

• Vegetation has to cope with high levels of salt in air and soil

• Largest influence of vegetation is to assist in protecting + preserving coastal landforms such as sand dunes, salt marshes, mangroves

Influence of people on coastal environments

• Human activities transform features + landscape of coastline:

  • Settlement - coasts have always been place of attraction + residence for people

  • Economic development - exploitation through fishing, farming, trade, tourism, energy production

  • Coastal management - controlling coastline to protect human interests

Influence of sea-level changes on coastal environments

• Rising sea levels produce submergent coastlines, with rias + fjords

• Falling sea levels produce emergent coastlines, with relic features e.g. raised beaches, cliffs with caves

• Sea levels have risen + fallen many times in past

• During last Ice Age, sea levels fell as water locked up in glaciers + ice sheets, rising again as ice melted

• Sea levels link to global warming, will have significant effect on many low-lying coasts + islands

• Many Pacific islands, e.g. Kiribati, Tuvalu are at risk of being completely submerged by rising sea levels

• Issue is worsened as many of world’s densely populated areas are on coastal lowlands

• New York + Miami are major cities vulnerable to sea-level rise as cities are built at sea level

Headland and bay

• Found in areas of alternating bands of resistant (hard) + less resistant (soft) rocks running perpendicular to oncoming waves (discordant coastline)

• Initially, less resistant rock (e.g. clay) eroded back, forming a bay

• Bay = inlet of sea where land curves inwards, usually with beach

• More resistant rock (e.g. limestone) is left protruding out to sea as headland

Cove

• Forms when coastline has bands of resistant + less resistant rock running parallel to oncoming waves (concordant coastline)

• Usually band of resistant rock facing waves, with band of softer rock behind

• Wave processes exploit faults in resistant rock + erode through to softer rock

• Further wave action erodes soft rock quickly, leaving circular cove with narrow entrance to sea

• Wave refraction within cove spreads out erosion in all directions, creating typical horseshoe shape

• e.g. Lulworth Cove, Dorset, UK

Cliff

• Cliffs shaped through erosion + weathering processes

• Less resistant rock erodes quickly, forming sloping cliff faces

• Steep cliffs formed where harder rock faces sea

Wave-cut platform

Wide, gently-sloped surface found at foot of cliff

• As sea attacks base of cliff between high and low water mark, wave-cut notch forms

• Abrasion, corrosion, hydraulic action further extend notch back into cliff

• Undercutting of cliff → instability + collapse of cliff

• Backwash of waves carries away eroded material, leaving wave-cut platform

• Process repeats + cliff continues to retreat, leading to coastal retreat

Cave, arch, stack and stump

• Found on headland due to wave action + sub-aerial weathering

• Weaknesses in headland are exploited by erosional processes of hydraulic action, abrasion, corrosion

• As crack widens, abrasion wears away at the forming cave

• Cave becomes larger and eventually breaks through headland to form arch

• Base of arch continually becomes wider + thinner through erosion below + weathering above

• Eventually, roof of arch collapses, leaving isolated column of rock called stack

• Stack is undercut at base by wave action + sub-aerial weathering above until it collapses to form stump

Beach

• Form in sheltered areas such as bays

• Deposition occurs through constructive wave movement, where swash is stronger than backwash

• Beach formation usually occurs in summer when weather is calmer

• Sometimes sand from offshore bars can blow onto shore by strong winds

• Blown sand can create sand dunes at backshore of beach

Spit

• Extended stretch of sand/shingle that extends from sea to shore

• Spits occur when there is change in shape of coastline

• Or the mouth of a river, which prevents spit from forming across estuary

• Spit may/may not have ‘hooked’ end, depending on opposing winds + currents

• e.g. Spurn Point, Humber Estuary, England

Spit formation

• Sediment transported by LSD

• Where coastline changes direction, a shallow, sheltered area allows for deposition of sediment

• Due to increased friction, more deposition occurs

• Eventually, spit slowly builds up to sea level + extends in length

• If wind changes direction, wave pattern alters, resulting in hooked end

• Area behind spit becomes sheltered

• Silts are deposited here to form salt marshes/mud flats

Bar

• When spit grows across bay and joins two headlands together

• Bar of sand is formed (sandbar)

• Sandbars can form offshore due to action of breaking waves from beach

Coral reef distribution 🪸

• Generally between 30ᵒ N and S of equator

Examples:

• Great Barrier Reef (high biodiversity) - off coast of Queensland, AU

• Maldives - Indian Ocean

• Red Sea - Egypt

Coral reef global features 🪸

• Temperature (min: 18ᵒC, optimum: 23-29ᵒC)

• Shallow water (25m or less depth) because…

  • Closer to light

  • Coral can’t grow deeper than 25m because need light for zooxanthellae to photosynthesise

• Clear water because…

  • Need light to pass through for PSN

  • Sediment blocks normal feeding patterns by reducing light availability

• Salinity (between 32-42 PSU) because…

  • Coral are marine animals

  • so need salty water to survive

Coral reef local features 🪸

• Wave action

  • Coral need well-oxygenated, clean water, which wave action provides

• Exposure to air

  • Corals need oxygenated water but can’t be exposed to air for too long or will die

Mangrove distribution 🌳

• Similar distribution to coral reefs

• Mostly between 30ᵒ N and S of equator

• Most common in SE Asia

Mangrove features 🌳

• Mangroves are trees that live on coastline

• Sit in water between 0.5-2.5m high

• Range in size from small shrubs to trees 60m+ high

• Have tangled roots that grow above ground and form dense thickets

• Need high humidity (75-80%) and rainfall levels per annum (1500-3000mm)

• Ideal temp = 27ᵒC

Sand dune distribution 🏖

• Found all around the world

• They are accumulation of sand, shaped into mounds and ridges by wind

• Found at back of beach, above max reach of tide

• Large dunes are less likely in tropical + sub-tropical areas because…

  • Lower avg. wind speeds

  • Damper sand

Sand dune features 🏖

• Can be small ridge or large hills usually at back of beach

• Can extend backwards for many miles as well as along beach

• Are an important ecosystem, supporting unique flora + fauna that have adapted to live in dune system

• Vulnerable to erosion by natural processes + human activity

Salt marsh distribution 🧂

• Found all over the world, not temperature dependent

• An ecosystem of intertidal zone, like mangroves

• Typically flat, with numerous channels running through them

• They form in:

  • Well-sheltered coastal areas, such as inlets/estuaries

  • Areas behind spits and artificial seas defences

  • Brackish water (partly salty, partly fresh)

Salt marsh features 🧂

• Communities of nonwoody, salt-tolerant plants

• Begin as tidal mud flats, gaining height as more sediment is deposited

• This builds up to and above the level, and frequency of tidal flooding ensures that soil never dries out, remains muddy + sticky

• Pioneer species of halophyte plants begin to colonise

• As plants die and add nutrients to soil, sediment builds up, making conditions more favourable and other species develop

• Process of development of vegetation over time = succession

• Lower marshes are flooded daily by rising tide

• Good coastal defences in some areas, acting as natural buffer against coastal erosion + flooding

• However, in many areas they’ve been reclaimed for agriculture/development, and are threatened by human activities

Abiotic characteristics of coral reefs 🪸

• Light - need sunlight to survive:

  • Too little = zooxanthellae can’t photosynthesise to produce food for corals

  • Too much = corals may expel zooxanthellae, causing bleaching

• Depth - need light, so are typically found at approx. 25m

• Water temp - corals thrive in warm tropical waters

• Salinity - need salty water

• Air - can survive out of water for short periods

• Water - need clean, clear water that doesn’t block light

Biotic characteristics of coral reefs 🪸

• Coral reef is well-organised food web comprising of:

  • Producers

  • Consumers

  • Scavengers

  • Decomposers

• Producers in coral reef include seaweed, seagrass and phytoplankton

• Consumers are organisms that eat other organisms for energy
  There are three main types of consumers in food web: primary (e.g. sea turtle eating seagrass), secondary (e.g. stingrays, octopuses), tertiary (help maintain balance of ecosystem, e.g. sharks, dolphins)

• Scavengers feed on dead + decaying plants and animals - e.g. crabs + lobsters

• Decomposers bring nutrients back into ecosystem for another cycle - e.g. bacteria, fungi

Value of coral reefs 🪸

• Biodiversity - Great Barrier Reef has 700 coral species, 1500 fish species and 4000 mollusc species

• Protection to low-lying coasts from tropical storms

• Rich fish stocks - supply basic food requirements of developing countries

• Appeal to tourists + recreational opportunities, such as snorkelling + scuba diving - over 150m people each year take holidays in areas with coral reefs

How industry threatens coral reefs 🪸

• Coral reefs are easily stressed by human action
  If stress persists, death of reef soon follows

• Pollution, overfishing and quarrying of coral for building stone

• Industrialisation responsible for rising sea temp + sea-level rise, putting coral under threat

• Rising sea temps increase levels of coral bleaching

How agriculture threatens coral reefs 🪸

• Overfishing reduces number of grazing fish that keep coral clear of algae

• Fishing using explosives that damage coral reefs

• Commercial farming

• Fertiliser runoff

• Pesticide overspray

How tourism threatens coral reefs 🪸

• Tourism is biggest threat globally and locally to coral reefs

• 58% of all coral reefs are at threat from human activity

• Any contact with human body will likely kill coral immediately around point of contact

• Propellers + anchors directly damage coral from boat tours

• Pollution through diesel spills

How deforestation threatens coral reefs 🪸

• Clearance of coral forests + mangroves disturbs natural flows of water + nutrients, leading to stress + coral bleaching

• Removal of coral reef for stone building/tourist sales

• Any destruction of coral reef leaves coastline open to coastal flooding + storm surges

Value of mangroves 🌳

• Nurseries for fish + crustaceans; rich in wildlife

• Roots, exposed at low tide, trap silt and help create new land

• Timber provides fuel + building material

• Protection from storm surges

How industry threatens mangroves 🌳

• Pollution, overfishing and deforestation for aquaculture

• Clearance for land development, particularly in developing countries

How agriculture threatens mangroves 🌳

• Aquaculture - intense fish + shrimp farms

• Pesticide use

• Antibiotics used in aquaculture practices

• Clearance for farm development, particularly in developing countries

How tourism threatens mangroves 🌳

• Clearance of mangroves to build hotels + other tourist attractions

• Diversion of fresh water to hotels etc.

• Disturbance of habitats

• Collection of souvenirs by tourists

• Tours in waterways + pollution through spills of boat fuel

How deforestation threatens mangroves 🌳

• Removal of trees leads to collapse of ecosystem

• Leaves coast open to storms, flooding and coastal retreat

• Mangrove wood used for timber + fuel

• Cleared to reduce malaria - unsupported evidence that this works

Value of sand dunes 🏖

• Coastal protection from flooding

• Recreational activities e.g. trail biking + horse riding

How industry threatens sand dunes 🏖

• Least threatened at global level (value is mainly tourism + leisure)

• Local level, biggest threat is sand mining

How agriculture threatens sand dunes 🏖

• Destabilisation due to animals grazing on dunes

How tourism threatens sand dunes 🏖

• Largest threat to sand dunes due to trampling of delicate, unfixed dunes

• Driving using 4×4/quadbikes over dunes

• Sporting events - sand surfing etc.

• Collecting shells + driftwood

• Pollution from rubbish left by tourists

• Car parks

• Sand mining to build hotels

• Development of seaside towns

How deforestation threatens sand dunes 🏖

• Removal of trees destroys mature dunes and allows for dune migration

• Leaves coast open to storms + flooding

Value of salt marshes🧂

• Collectors of silt + organic matter

• Nursery areas for fish + crustaceans

• Protection against wave erosion + sea-level rise

How industry threatens salt marshes🧂

• Industrial pollution

• Ideal sites for nuclear power stations

• Clearance for development - commercial + private

• Development can lead to increased noise + light pollution, may affect wildlife behaviour + nesting

How agriculture threatens salt marshes🧂

• Drained + cleared for farming

• Eutrophication through heavy use of fertilisers

• Pollution from pesticides + herbicides

• Slurry run-off from cattle

How tourism threatens salt marshes🧂

• Tourism limited to local level + nature reserves

• Roads have divided salt marshes, cutting off parts of it

• Trampling by visitors

• Dog walkers letting dogs roam + disturb wildlife

• Noise from local tourist areas may disturb wildlife

Uses of coastal environments

• Development

  • Homes

  • Shops

  • Hotels

  • Roads

  • Schools

  • Restaurants etc.

• Nature reserves

• Industry

• Fishing + aquaculture

• Tourism

• Agriculture

• Ports + harbours

Conflict between Coastal users

• Wildlife want unpolluted, safe and quiet environment

• Local residents want jobs, clean beaches, affordable housing, schools

• Tourists want beaches, hotels, B&Bs, entertainment, holiday homes

• Employers want building space, offices, factories

• Developers want areas by sea for tourists - hotels, duplexes, golf courses

• Fishermen want harbours, unpolluted waters, ease of access to sea

• Farmers want well-drained land, sheltered from prevailing winds

• Govt. + councils want to build offshore wind farms, coastal defences

• Transport companies want good road networks, well-connected ports and terminal

Issues with Agriculture in coastal zone

Consequences

• Fertiliser and pesticide overuse

• Increased livestock density

• Overwater abstraction

• Animal waste disposal

• Land reclamation

Outcomes

• Species and habitat loss

• Eutrophication

• Water pollution

• Coastal squeeze

Issues with Urbanisation and Transport in coastal zone

Consequences

• Change of land use (car parks, ports etc.)

• Waste disposal

• Pollution

• Water abstraction

• Hard road surfaces

Outcomes

• Increased flooding

• Congestion

• Pollution

• Loss of habitats

• Increase in weeds + invasive species

Issues with Tourism and Recreation in coastal zone

Consequences

• Harbours, marinas

• Waste disposal

• Fuel spillages

• Change of land use

• Water abstraction

• Effluent disposal

Outcomes

• Congestion + pollution (noise, light, visual, aroma)

• Loss of habitats

• Loss of species

• Litter + fuel spills

Issues with Fisheries and Aquaculture in coastal zone

Consequences

• Ports

• Fish processing facilities

• Trawlers

• Road networks

• Lorries

• Fishing gear

• Fish farm pollution

• Water abstraction

Outcomes

• Overfishing

• Pollution on beaches

• Habitat damage

• Water pollution

• Aroma, visual and noise pollution from trawlers

• Increased seagull activity

Issues with Industry in coastal zone

Consequences

• Land use change

• Change in tidal range

• Power stations (nuclear + gas)

• Natural resource extraction

• Road networks

• Cooling water/abstraction

• Waste pollution - chemical, biological, nuclear etc.

Outcomes

• Thermal pollution

• Habitat destruction, change and loss

• Water eutrophication

• Water pollution

• Visual eyesore

Causes of coastal flooding

• Storm surges - rapid rise in sea level caused by very low-pressure storms

• Storm tides - occur when there’s combination of high tide + low-pressure storm

• Tsunamis - large sea waves due to underwater EQs, closer to coast = bigger impact

• Climate change - causes rising sea levels

Prediction of flooding

• Early warning systems allow communities to prepare before flooding occurs

• Past records (diaries, newspapers etc.) - identify areas at high risk of flooding and their frequency

• Modern technology (GIS, satellite and computer monitoring, weather stations) - allow for forecasting + tracking potential hazards, i.e.

  • Tropical storms - track storm’s path + associated storm surge

  • EQs - size + position if underwater and possible tsunami outcome

• These methods indicate possible strength + scale of flooding, and likelihood of damage + death

Prevention of flooding

• Flood defences

  • Built along high-risk stretches of coast

• Emergency centres

  • Centrally placed on higher ground where people can be safe from flooding

• Early warning systems

  • Allows for preparation/evacuation of an area

• Education

  • Informing locals on what to do if/when flood occurs

• Building design

  • Planning new development away from high-risk areas

  • Designing buildings to cope with low-level flooding

    • Elevating buildings so flood water can pass underneath

    • Floodproof buildings with raised foundations

    • Reinforced barriers

    • Dry floodproofing - sealing property so floodwater can’t enter

    • Wet floodproofing - allows some flooding of building

• Buffer zones

  • Areas of land are allowed to flood before reaching settlements

  • Allows energy in surge to dissipate, reducing the distance floodwater travels

  • Can mean moving people away from coast (could be controversial)

Shoreline Management Plans

• Shoreline Management Plans (SMP) set out approach to managing coastline from flooding + erosional risk

• Plans aim to reduce risk to people, settlements, agricultural land and natural environment

Hold the line (approach to coastal mgmt)

• Long term approach + most costly

• Build + maintain coastal defences so current position of shoreline remains same

• Hard engineering is most dominant method used, with soft engineering used to support

Advance the line (approach to coastal mgmt)

• Build new defences to extend existing shoreline

• Involves land reclamation

• Hard + soft engineering used

Managed realignment (approach to coastal mgmt)

• Coastline allowed to move naturally

• Processes monitored + directed when and where necessary

• Most natural approach to coastal defence

• Mostly soft engineering with some hard engineering to support

Do nothing (approach to coastal mgmt)

• Cheapest method, but most controversial

• Coast is allowed to erode + retreat landward

• No investment made in protecting coastline or defending against flooding, regardless of previous intervention

Factors affecting which coastal mgmt approach to apply

• Economic value of resources to protect e.g. land, homes etc

• Engineering solutions - might not be possible to ‘hold the line’ for moving landforms such as spits

• Cultural + ecological value of land - historic sites + areas of unusual diversity

• Community pressure - local campaigns to protect region

• Social value of communities - long-standing, historic communities

Hard engineering

• Involves building some form of sea defence, usually from concrete, wood or rock

• Structures and expensive to build and need to be maintained

• Defences work against power of waves

• Protecting one area can impact regions further along coast, resulting in faster erosion + flooding

• Used when settlements + expensive installations (power stations etc) are at risk - economic benefit greater than cost of building

Groynes

Hard engineering method

Wood, rock or steel piling built at right angles to shore, trapping beach material being moved by LSD

• Slows down beach erosion

• Creates wider beaches

• Stops material moving down coast where material may have been building up + protecting base of cliff elsewhere

• Starves other beaches of sand

• Wood groynes need maintenance to prevent wood rot

• Makes walking along shoreline difficult

Revetments

Hard engineering method

Sloping wooden/concrete fence with open plank structure

• Work to break force of waves

• Traps beach material behind them

• Set at base of cliffs/in front of sea wall

• Cheaper than sea walls but not as effective

• Ineffective in stormy conditions

• Can make beach inaccessible for people

• Regular maintenance is necessary

• Visually unattractive

Sea wall

Hard engineering method

Wall, usually concrete, curved outwards to deflect power of waves

• Most effective at preventing erosion + flooding (if wall is high enough)

• Very expensive to build + maintain

• Can be damaged if material isn’t maintained in front of wall

• Restricts access to beach

• Unsightly

Gabions

Hard engineering method

Wire cages filled with stone, concrete, sand etc

• Cheapest coastal defence

• Cages absorb wave energy

• Can be stacked at base of sea wall/cliffs

• Wire cages can break + need to be securely tied down

• Not as efficient as other coastal defences

Rip-rap

Hard engineering method

Large boulders piled up to protect stretch of coast

• Cheaper method

• Works to absorb wave energy from base of cliff + sea walls

• Boulders can be eroded/dislodged during heavy storms

Soft engineering

• Works with natural processes rather than against them

• Usually cheaper + don’t damage appearance of coast

• Considered to be more sustainable appraoch to coastal protection

• Not as effective as hard engineering

Beach replenishment

Soft engineering method

Pumping/dumping sand + shingle back onto beach to replace eroded material

• Beaches absorb wave energy

• Widens beachfront

• Must be repeated regularly - expensive

• Can impact sediment transportation down coast

Cliff regrading

Soft engineering method

Angle of cliff reduced to reduce mass movement

• Prevents sudden loss of large sections of cliff

• Regrading can slow down wave cut notching at base of cliffs as wave energy is slowed

• Doesn’t stop cliff erosion

Fencing, hedging, revegetation

Soft engineering method

Helps stabilise sand dunes/beaches + reduces wind erosion

• Cheap method against flooding + erosion

• Hard to protect larger areas of coastline cliffs

Managed retreat

Soft engineering method

Existing coastal defences are abandoned, allowing sea to flood inland until it reaches higher land or a new line of defences

• No expensive construction costs

• Creates new habitats, such as salt marshes

• Disruption to people where land + homes are lost

• Cost of relocation can be expensive

• Compensation to people + businesses may not be paid

Coastal problems in developed country (Abbotts Hall Farm, Essex, UK)

• Essex coast in SE England is flat + low-lying

• Abbotts Hall Farm = 282 hectare nature reserve and head office of Essex Wildlife Trust

• Area was previously defended by 3km stretch of sea wall.
  By 1990s, needed repairing, at considerable expense.

Coastal management in developed country (Abbotts Hall Farm, Essex, UK)

• Decision was made to breach section of wall and allow 80 hectares of agricultural land behind wall to flood.

• Aim was to allow nature to build up new coastal defence in form of new area of salt marsh.

• Because relatively low-value land was targeted, and with sea level rise likely in future, this was sensible + cost-effective decision.
  Essex Wildlife Trust very supportive, as salt marsh is valuable habitat for wading birds + important fish nursery.

• New walls created to protect farmland on either side of the site prior to section of old sea wall being breached in 2002.

Coastal problems in developing country (Guyana)

• Country largely covered by tropical rainforest, though much of coastal lowlands have been clear to make way for plantations, especially sugar

• Much of coastal zone is below sea level.

  Coastline densely populated - 90% of country’s pop. live below sea level.

  75% of Guyana’s economic activities, including almost all agriculture, are found below sea level.

  Protection against coastal flooding is essential.

  In past, Dutch settlers built network of coastal defences, with dykes + sea walls as barriers against sea and canals, pumps and sluices to drain low-lying areas.

• More than half of old coastal defences are beyond repair, but coastline is threatened by sea level rise due to climate change.

  As well as impacts of coastal flooding, salt water could ruin agricultural land + contaminate freshwater supplies.

Coastal management in developing country (Guyana)

• Repairing existing hard defences, constructing new ones and paying cost of maintaining defences is too expensive for Guyana.

• Restoring mangrove forests + wetland swaps to coastline and adding small earth dams is more cost-effective.
  Restoring mangroves will have environmental benefit as they provide habitats for diverse range of wildlife.

• Education emphasising need to preserve mangroves, protect marine life (e.g. sea turtles) and refrain from dumping waste + litter should help make Guyana’s coastal management more sustainable.