Topic 4: Coastal Environments

Constructive

Strong

Weak

Builds beaches

Destructive

Weak

Strong

Erodes beaches

Hydraulic action

Force of water traps air in cracks, breaking rocks apart

Abrasion (corrasion)

Rocks hurled against cliffs – sandpaper effect

Attrition

Rocks smash into each other → smaller, rounder

Solution (corrosion)

Seawater dissolves rock (limestone, chalk)

1

Waves approach shore at angle (prevailing wind)

2

Swash carries sediment up beach at angle

3

Backwash carries sediment straight back (gravity)

4

Zig-zag movement of sediment along coast

1

Waves erode base of cliff (hydraulic action, abrasion)

2

Wave-cut notch forms at base

3

Notch deepens → cliff above unsupported

4

Cliff collapses due to gravity

5

Cliff retreats inland

6

Smooth, gently sloping rocky surface left = wave-cut platform

7

Platform exposed at low tide, covered at high tide

1

Coastline has alternating bands of hard rock and soft rock

2

Soft rock (clay) erodes faster → forms bay

3

Hard rock (chalk, granite) erodes slower → remains as headland

4

Bays have beaches (low energy, deposition)

5

Headlands have cliffs (high energy, erosion)

1

Waves erode weakness (crack/joint) in headland → cave

2

Cave eroded through headland → arch

3

Arch roof collapses → stack

4

Stack eroded at base → collapses → stump

1

Waves bend as they approach headland

2

Wave energy concentrated on sides of headland (more erosion)

3

Wave energy reduced in bays (less erosion, more deposition)

4

This further deepens bays and sharpens headlands

What they are

Accumulation of sand, shingle, or pebbles at coast

How they form

Waves deposit material where energy is low

Sandy beaches

Gentle slope, fine material

Shingle beaches

Steeper slope, larger material

1

Longshore drift transports sediment along coast

2

Coastline changes direction (river mouth or bay)

3

Longshore drift continues out to sea

4

Waves lose energy in deeper, sheltered water → deposition

5

Sediment builds up as ridge = spit

6

End may curve landwards (recurve) due to wind changes

7

Sheltered area behind spit becomes salt marsh

Bar

Spit that grows across a bay, trapping lagoon behind

Tombolo

Spit connecting island to mainland

1

Embryo dunes

Pioneer plants (sea rocket), low height, unstable, closest to sea

2

Yellow dunes

Marram grass dominates (traps sand, deep roots), sand visible, growing

3

Grey dunes

Soil forming (humus), more plant variety, more stable

4

Dune scrub/grassland

Shrubs (gorse, brambles), even more stable

5

Mature dunes (climax)

Trees (pine, oak), full soil, fully stable, furthest inland

Coastal protection

Absorb wave energy, prevent flooding

Habitat

Home to rare plants (marram grass) and animals

Carbon storage

Trap and store carbon in soil

Trampling

Walkers destroy vegetation → dunes erode

Development

Building on dunes removes them

Climate change

Sea level rise floods dunes

Tourism

Beaches, scenery, water sports – jobs and income

Fishing

Food and employment

Ports and trade

Harbours for imports/exports

Renewable energy

Wind, wave, tidal power

Habitat

Mangroves, coral reefs, salt marshes

Coastal erosion

Cliffs retreat, land lost, property damaged

Flooding

Storm surges, sea level rise

Tropical storms

High winds, waves, flooding

Tsunamis

Giant waves from earthquakes

Sea level rise

Permanent flooding of low-lying areas

Sea wall

Concrete barrier reflects waves

Strong protection

Expensive, ugly, reflects energy

Groynes

Wooden/rock fences trap sediment

Builds beaches, cheap

Starves beaches downdrift, ugly

Rock armour (riprap)

Large boulders absorb wave energy

Absorbs energy, cheaper than sea wall

Expensive, ugly

Gabions

Wire cages filled with rocks

Cheap, easy to install

Rust, ugly, short lifespan

Beach nourishment

Adding sand to replace eroded beach

Natural look, good for tourism

Expensive, needs repeating

Dune regeneration

Planting marram grass, fencing off dunes

Natural, habitat creation, cheap

Takes time, fragile

Managed retreat

Allowing coast to flood naturally

Cheapest, creates salt marsh habitat

Land lost, compensation

Warm ocean

Sea temperature >26.5°C (provides energy)

Latitude

Between 5° and 20° north/south of equator (Coriolis effect)

Deep water

At least 60m deep

High humidity

Moist air rises and condenses

Low wind shear

Wind does not change direction with height

Atlantic/Caribbean

Hurricane

Pacific (Asia)

Typhoon

Indian Ocean

Cyclone

Before

Monitoring (satellites), early warning systems, evacuation plans, building regulations

During

Evacuation to shelters, emergency services

After

Search and rescue, aid (food, water, medicine), rebuilding

Salt tolerance

Excrete salt through leaves or exclude salt at roots

Prop roots (stilt roots)

Anchor tree in unstable mud, trap sediment

Pneumatophores (breathing roots)

Stick up out of mud to get oxygen

Vivipary

Seeds germinate while still on tree

Coastal protection

Absorb wave energy, reduce erosion and flooding

Habitat

Nursery for fish, shrimp; home to birds, crabs

Carbon storage (blue carbon)

Store more carbon per hectare than rainforests

Fisheries

Support 80% of tropical fish catch

Deforestation

Cleared for shrimp farms, tourism, development

Pollution

Oil spills, sewage, agricultural runoff

Climate change

Sea level rise

Overharvesting

Timber and charcoal extraction

Replanting

Growing seedlings in nurseries, planting in degraded areas

Hydrological restoration

Reconnecting mangroves to tidal flow (digging channels)

Community management

Local people given responsibility for protection

Legal protection

Designating mangrove areas as protected

Community involvement

Locals protect what they help restore

Right species

Native species suited to local conditions

Tidal flow

Mangroves need natural water flow

Long-term monitoring

Ensure restoration is working

Mikoko Pamoja

Kenya

Community-led mangrove restoration funded by carbon credits

Warm water (>18°C)

Coral polyps require warm temperatures

Clean water

Sediment blocks sunlight and smothers coral

Shallow water

Sunlight needed for algae (zooxanthellae)

Salt water

Cannot survive in freshwater

Oxygenated water

Waves and currents bring oxygen

Biodiversity

25% of marine species live in coral reefs

Fisheries

Provide food and income for millions

Coastal protection

Absorb wave energy, reduce erosion

Tourism

Snorkelling, diving – brings revenue

Medicine

Source of compounds for drugs

Marine Protected Areas (MPAs)

Legal protection – fishing banned or restricted

Fishing restrictions

Banning destructive fishing (dynamite, cyanide)

Tourism management

Limits on visitors, mooring buoys (no anchoring)

Pollution control

Treating sewage, reducing agricultural runoff

Coral nurseries

Growing coral fragments and transplanting to degraded reefs

Coral bleaching

Warmer water → corals expel algae → turn white → die

Ocean acidification

CO₂ absorbed by seawater → harder for corals to build skeletons

Pollution

Sediment, chemicals, sewage smother or kill coral

Overfishing

Removes key species (parrotfish) → algae overgrows coral

Physical damage

Boats, anchors, tourists, dynamite fishing

Coral polyp

Provides shelter and CO₂

Zooxanthellae (algae)

Lives inside polyp; provides food via photosynthesis (90% of coral's energy)

Temperature rise

Polyps expel zooxanthellae (bleaching) → no food → starve

Acidification

Harder for polyps to build skeletons → reefs grow slowly

Pollution

Sediment smothers polyps; chemicals poison them

Disease

Stressed polyps more vulnerable to disease

1

Water temperature rises >1°C above normal for weeks

2

Coral polyps expel zooxanthellae (algae)

3

Coral loses its colour (turns white) = bleached

4

Without algae, coral has no food source

5

If conditions don't improve, coral dies

Name

Gardens of the Queen (Jardines de la Reina)

Country

Cuba

Location

Southern coast of Cuba

Sea

Caribbean Sea

Length

Stretches over 150 km

Protected since

1996

Type

Marine Protected Area (MPA)

Fishing

Completely banned in core zone

Tourism

Strictly controlled, limited visitors

Enforcement

Full-time park rangers patrol the area

Fishing ban

Fish populations recovered; top predators (sharks, groupers) abundant

Strict eco-tourism

Only licensed guides; limited number of divers

No anchoring

Boats use mooring buoys (no reef damage)

High fish biomass

10x more fish than surrounding areas

Healthy coral cover

Coral cover much higher than Caribbean average

Climate change

Coral bleaching (warming water) – cannot be stopped locally

Ocean acidification

CO₂ absorbed → harder for corals to grow

Ocean pollution

Plastic and chemicals carried by currents from other countries

Illegal fishing

Rare but occurs (poachers from outside)

Marine Protected Area

Legal protection since 1996

Strict visitor limits

Only a few thousand tourists per year

Licensed dive guides

All visitors accompanied

Mooring buoys

No anchoring on reefs

Scientific monitoring

Regular surveys of reef health

Park rangers

Full-time enforcement against illegal fishing

One of Caribbean's best-preserved reefs

Still threatened by global climate change

Fish biomass 10x higher than surrounding areas

Local management cannot stop ocean acidification

Successful eco-tourism model

Illegal fishing still occurs (rarely)

Community support (local fishermen as rangers)

Requires ongoing funding for enforcement