Coasts final

Fetch

the distance wind blows

Wave break ratio

the wave length cant be more then 7x the height as this is when the wave breaks (1:7)

Swash

water washed up the beach when a wave breaks -can deposit sediment.

Backwash

When water runs back into the ocean - can remove sediment with it

Constructive Waves

Adds sediment to the beach - high swash and low backwash. Longer wavelength, low height and wave frequency, and elliptical orbit.

Destructive Waves

Take sediment from the steep beach - high backwash and low swash. Shorter wavelength, higher height, more frequent wave frequency, and circular orbit.

Sediment Cell

A length of coastline which is relatively self-contained and flows of sediment act in dynamic equilibrium - so interruption to movement should not have a significant effect on adjacent ones however human impact may upset the DE in the long term

Tides

Regular rising and falling movements of the sea caused by the gravitational pull of the moon and sun

Spring Tides

Occur when the sun, moon and earth are in one straight line - so the gravitational pull is the greatest causing large tidal range (as the high is the highest and low is the lowest)

Neap Tides

When the Sun and moon are perpendicular from each other - have a smaller tidal range then spring tides

What is biological weathering - give examples

the breakdown of rock by living organisms (eg. plant roots, animals, microorganisms) which can physically or chemically alter the rock

What is chemical weathering - give examples

alteration of the rocks chemical structure - oxidation, carbonation, solution, acid rain

Examples of mass movement

Soil creep, mudflow, landslide, rockfall, landslip/slump, runoff, solifluction

Mass Movement definition and give examples

When gravity causes the downhill movement of material

Examples of things which influence the power of marine erosion

power of waves

how sandy a beach is (rock is more resistant)

geology - types of rocks and permeability

hard/soft engineering strategies

What are revetments

Concrete or wooden barriers (walls) at angles placed along the beach to take the full force of wave energy

What is Rock armour/rip-rap

Large boulders dumped in front of a cliff or sea wall to take the full force of the waves. Gabions are rocks in metal cages

What is cliff fixing

Driving iron bars into the cliff face to stabilise it and absorb some wave power - sometimes they use metal mesh netting

What do offshore barriers encourage

waves to break offshore to reduce their impact on the base of cliffs

Hard Enginering definition and examples

Man made structures use to control disruption of natural processes - groynes, sea walls, rip rap, revetments, offshore barrier.

Soft Engineering definition and examples

Natural methods to reduce erosion and stabilise coastlines - Beach nourishment, dune stabilisation, marsh creation

what does it mean if managed retreat is being undertaken - give examples

the current line of sea defences are abandoned and then the exposed land is developed in some way (eg.salt marshes to reduce wave energy, limited maintenance, attractive wetlands habitats created)

How much of Britains coastline is the Environment Agency responsible for

approx 1400km of 13,000km of Britain's coastline

How do headlands and bays form

due to varying resistances of rocks

How are caves formed

Continuous erosion (eg. hydraulic action and abrasion) on a headland can create a cave

how are arches formed

As a cave continues to erode through to the other side of the headland an arch is formed

how is a stack formed

(A cave forms, then an arch)

Over time, the top of the arch can collapse due to erosion and gravity, leaving a column of rock

how is a stump formed

(A cave forms, then an arch, then a stack)

then further erosion at the base of a stack can cause it to collapse, leaving a stump

What is a wave-cut platform and how does it form

A wide gently-sloping surface found at the foot of a cliff

how does a wave cut platform form

As a wave cut notch increases in size the cliff becomes unstable and collapses leading to the retreat of the cliff face, the backwash carries away the eroded material, leaving a wave-cut platform

what is a wave-cut notch

a dent in the cliff usually at the level of high tide caused by erosion

How does a wave cut notch form

the sea attacks the base of a cliff (between the high and low water mark) using erosional processes such as abrasion and hydraulic action

How do offshore bars form

destructive wave’s strong backwash carries sediment into the sea

over time the sediment accumulates in shallow water where reduced wave energy prevents further transport allowing a bar to develop parallel to the coastline UNDERWATER

What are berms

Ridges of sediment that form on the upper part of a beach

how are berms created

by constructive waves

swash carries sediment up the beach and as the wave energy dissipates material is deposited at the high tide mark

over time, repeated deposition during multiple high tides builds up a berm

they can increase in summer when constructive waves are more frequent

How do spits form

Longshore drift caused by prevailing winds (45) transports sediment (in a zigzag motion) along the coast

it is then deposited where the coastline changes direction

As deposition continues the spit extends out into open water

It may curve due to changes in wind direction

salt marshes can form in the sheltered area behind (eg. Spurn point, Holderness coast)

How does a barrier beach form

Offshore bars or spits accumulate enough sediment to rise above sea level

this creates elongated ridges of sand that run parallel to the coast ABOVE WATER

They’re formed by constructive waves in shallow, sheltered environments where wave energy is low, allowing deposition

Over time the barrier beach may become separated from the mainland, creating lagoons or salt marshes behind them (eg.Chesil Beach, Dorset)

What are sand dunes - what conditions do they require and and what processes form them

Mound-like landforms composed of sand blown off the beach by onshore winds

what conditions do sand dunes require to form

Dry loose sand

Wind

A flat area

what processes create sand dunes

Saltation

Depositon

Vegetation fixing (marram grass)

what is Isostatic Change

the local change in land level (eg. due to tectonic activity or post glacial rebound) which can lead to relative sea level changes

Explain post glacial rebound - example of isostatic change

During glacial periods, the weight of ice caused the land to sink, when the ice melts the land slowly rises again making the relative sea level appear to fall

Eustatic Change

A global change in sea level caused by a change in the volume of water in the oceans

usually due to ice melting or thermal expansion

What are Fjords and how do they form

A steep deep glacially-carved valley that have been filled with seawater

how do fjords form

A glacier carves out a valley through erosion

The glacier then retreats and rising sea levels flood the valley creating a narrow, deep waterway (eg Norway fjords)

what is a Ria

a drowned V shaped river valley with the higher land (the peaks) exposed

How do rias form

Rising sea levels (eustatic change) flood a river valley - usually happens after an ice age or due to global warming

As the sea levels rise the sea submerges the the lower part of the river valley while the higher land remains exposed (Rias)

An example of a ria is the Dartmouth ria in the UK.

What is a raised beach

An emergent landform of a former wave-cut platforms and beaches that are now located above the current sea level

how is a raised beach formed

as land rises due to isostatic rebound or sea level falls former wave cut platforms emerge

Dalmatian Coasts

A concordant coastline

Rising sea levels (eustatic change) cause parallel ridges and valleys to flood and become partially submerged

often leaving tops of ridges exposed

eg Dalmation coasts of Croatia

Examples of mechanical weathering

Freeze thaw

Thermal expansion and contraction

Wetting and drying

Hydraulic action

The sheer power of water hitting against a cliff causing rock to break away

• air becomes trapped in the cracks of the cliff and causes the rock to break apart

Corrasian

Sediment is thrown against the cliff face by waves which wears down the cliff face by causing material to break away

(acts like sand paper scraping and eroding the cliff)

Attrition

Sediment wearing down the surface of the shoreline through constant friction as it moves against the coast (as it moves along it smooths and erodes the sediment/rock)

Corrosion

Chemicals in sea water react with some rocks (eg chalk and limestone) as the water is slightly acidic due to dissolved CO2

example factors which effect erosion

wave intensity

beach size (eg a larger beach has more sediment to erode and dissipate energy)

Suspension

Very small particles carried in the water without touching the sea bed and stay suspended in the water column

Saltation

Smaller pebbles bounced or skipped along the sea bed in hopping/leaping motion

the waters strong enough to lift medium size sediment up but not enough to keep it suspended

Traction

stones and boulders are rolled/slid/dragged along the seabed due to the force of water (usually from waves/currents) - their weight means they stay in contact with the sea bed

Solution

Soluble minerals dissolved in water and transported in the dissolved state

primarily effects limestone and chalk containing calcium carbonate which is soluble in weak acids present in sea water

Wave quarrying

When waves break against unconsolidated materials eg sand, they can scoop out loose material

The wave’s strong upward force can dislodge rocks from the shore and drag them back when the wave retreats

Cavitation

When waves break they put pressure on the vapour bubbles in rocks

this creates an extra force causing the bubble to implode, becoming liquid

this energy can cause the rock to blast apart

Longshore drift

Prevailing winds cause waves to approach the shore at a 45 angle, swash carries sediment up the coast at this angle and backwash carries it back at a 90 angle (zig zag motion), over time sediment is deposited laterally along the shore causing the coast to get longer

How is a drift-aligned beach formed

Longshore drift causes sediment to move laterally along the beach

Swash-aligned beach

Sediment moves up and down the beach with little lateral (left/right) transfer

Swash and backwash occurs with little influence from longshore drift so waves approach head on rather then at an angle so sediment moves up/down the beach rather then along it

Often found in sheltered areas (eg bays) where energy is lower

What is a shoreline management plan (SMP)

Docs outlining the plan of intervention for a sediment cell

what are the 4 choices of shoreline management plans

hold the line

no active intervention

managed retreat/realignment

advance the line

What is hold the line

Maintaining the current position of the coastline, usually using existing defences

cheap but requires constant maintenance

What is advance the line

Extending the coastline out to sea, using new defences (eg beach nourishment)

protects natural habitats but can be expensive

What is no active intervention

Letting nature take its course - allowing the sea to erode cliffs, flood low-lying land, existing defences to collapse

cost-free but homes and farmland on land can be lost

What is Integrated Coastal Zone Management (ICZM)

the coordination of all potential pressures and conflicts of interest at the coast to manage them fairly

usually prioritises environmental protection whilst considering economic and social factors

what is a barrier island

A long narrow island made of sand that runs parallel to the mainland coast (in contrast barrier beaches are attached to the mainland)

Tombolo

A bar which connects an island to the mainland

Long shore drift causes a spit to grow out from the mainland and meet the island

Positive feedback

Where a flow/transfer leads to increase/amplifying of the original event

Negative feedback

Where a flow/transfer leads to decrease/decline/nullifying of the original event

Rip currents

A strong localised current which flows away from the shore cutting through the lines of breaking waves - can be dangerous for swimmers

What occurs at a low energy coast

More deposition than erosion

Waves aren’t very powerful

Depositional land forms (eg beaches and spits) often form

eg Lincolnshire

What occurs at a high energy coast

More erosion than deposition

Powerful waves

Erosional landforms (eg headlands, cliffs and wave-cut platforms) often form

eg Cornwall

What have the recent sea level changes been like globally (in the last 10,000 years)

There’s been global sea level rise following the end of the last glacial period

Beach zones order

Land to sea

Backshore, foreshore, nearshore, offshore

Predicted changes in sea level rise

By 2100 sea levels will have risen by 30-100 cm

how do steep cliffs form

strong resistant rock requires high energy waves to be eroded - because they erode less quickly they remain strong

any high energy waves removes debris quickly preventing a gentle slope from forming

how do gentle cliffs form

weaker rock and low energy environment means they’re more susceptible to erosion

less erosive waves allow debris to build up and act as a buffer against further erosion contributing to gentler/gradual slope

how does negative feedback effect cliff retreat

erosion causes the cliff to retreat so the fallen debris reduces further erosion by providing protection at the base

whats a halophyte

a salt tolerant plant (commonly found in mudflats and estuaries)

how do waves form

wind moves across surface of water causing frictional drag

this leads to the circular orbital motion of water

The sea bed becomes shallower towards the coastline so the water particles become elliptical

this leads to the horizontal movement of waves

The waves height increases but wavelength and velocity decreases so water backs up behind the waves until the wave breaks

3 factors affecting wave energy

strength of wind

duration of wind

size of fetch (distance wind blows)

which waves dominate in summer

constructive - due to lighter winds and longer fetch)

this may increase with climate change

what is cost benefit analysis used for

to compare the projected cost of management plans to its expected benefits

what does s DEFRA 1:1 analysis

the expected benefits must outweigh costs for the project to go ahead

What are the goals of sustainable coastal management

creating long term sustainability which manages resources for long term productivity and creates jobs

educates communities

monitor environmental changes

what is soil creep

the slow movement of soil on a slope due to the force of gravity

it’s slow as soil particles repeatedly expand and contract in wet/dry periods

what is solifluction

occurs mainly in periglacial environments when the top layers thaw during summer and flow over still frozen layers

how do mudflows occur

increased water content in soil leads to reduced friction

gravity causes the soil to surge down a slope with tremendous force

is a serious threat to life as it can be very fast flowing

what is rockfall

the abrupt movement of masses of geological material which becomes detached from steep slopes/cliffs

often due to weathering processes eg freeze thaw weathering

what is a landslide

the mass movement of material down a slope due to reduced friction caused by heavy rainfall

creates a terraced appearance

how do landslips/slumps occur

land collapses under is own weight due to pore water pressure (pressure within soil and rock layers) causing gravity to move material down the slope

in a slump the slope is curved so the land moves in a rotational manner along a curved surface (usually in a concave shape)

what is runoff

when heavy rainfall washes material from the surface of a cliff over the edge and down onto the shore

how do salt marshes form

Mud and silt is deposited along a sheltered coastline

Pioneer plants colonise the mudflat so more sediment is trapped

A meadow is formed as sections of salt marsh rise above the high tide level

how do estuarine mudflats form

fine silts and clay are deposited by the sea/tributaries in sheltered low energy coastal environment (eg estuaries)