Coastal systems and landscapes

Dorset coast landforms and geology 

Major landforms: Arch, cove, wave-cut platform, headland, beach, bays, stacks, sand dunes, spit, offshore bars

Geology: chalk, weaden clays and greensand, purbeck limestone, Portland limestone

Holderness coast - benefits and costs of management strategies 

East coast of Yorkshire, hard engineering strategies including sea wall, groynes, revetments and rip rap to protect the quickly eroding clay cliffs

Benefits- protects high value land

Costs- upset locals on intrusive defences, seen as unsustainable, expensive

Formby point management strategies

Sefton coast north of Liverpool, soft engineering strategies including planting used Christmas trees, fencing off dunes, banning off road vehicles and educating local children about protection and conservation

The Sundabans location, opportunities, challenges and responses

Located in the south of India and Bangladesh, mangrove forests that are vunrable to flooding with rising sea levels.

Opportunities: provides goods such as fuel, foods, materials and medicines, protects land, cultural value, ecologically diverse

Challenges: human eating tigers, lack of fresh water, poor accessibility, one fifth of homes have electricity, few income opportunities, high risk of natural hazards, over exploited recourses damaging habitats

Responses: NGOs training fishers and farmers on sustainable methods, extending electricity, improving roads and increasing access to clean water, promoting eco tourism to provide income, embalmers build to prevent flooding

coastal zone

a dynamic environment with distinctive landforms formed by interaction of marine, terrestrial and wind processes

examples of mass movement

rockfall

slump

landslides

creep

examples of coastal landforms

erosional:

stack, stump, arch, headland, cave

depositional:

spit, bar, tombolo

examples of coastal erosion

attrition, abrasion, saltation, hydraulic action, corrosion

examples of coastal transportation

traction, solution, suspension, saltation, longshore drift

landform

a distinctive geomorphological feature created by processes of erosion, weathering, mass movement and transportation

landscape

part of the earths surface that can be viewed at one time from one place. distinctive landforms are made up of a series of landforms

backshore

land only effected under storm conditions. cliffs, sand dunes and beaches may be present

foreshore

area lying between the HWM and the LWM. It is the most important zone for marine processes in times that are not influenced by storm activities

inshore

area between LWM and the point where waves cease to have any influence on the land beneath them

offshore

water depths are over half the wave length of the incoming waves. limited sediment movement by waves

swash zone

varies with the tide, water moves up as swash and down as backwash

surf zone

broken waves that travel towards the shore. Sediment movement may be onshore/offshore or along the shore

breaker zone

varies in width depending on the type of wave approaching the shore

wave length

the distance between the two crests of a wave

wave height

distance between the crest and trough of a wave

wave frequency

number of waves per minute

crest

the peak/highest point the wave reaches

trough

the lowest point a wave reaches between 2 waves

fetch

the distance a wave moves due to wind

swash

movement of water upwards a beach

backwash

movement of water down a beach back out to sea

ridges and runnels

Small semi-circular hollows in a beach, formed by a collection of waves reaching the same point. The sides of the U shape channel incoming swash into the center of the depression and this produces stronger backwash; dragging material down the beach from the centre.

cusp

The spreading out of wave energy across a wide area of the beach tends to produce a series of raised areas above the adjacent shore which dips it to depressions.

berm

ridges that develop at the position of the mean HWM resulting from deposition at the top of the swash.

storm beach

at the back of the beach, very strong swash during storm conditions may deposit larger material

coastal plain

a lowland area adjacent to the sea, which may have formed from marine sediments which may have been revealed by a fall in sea level

beach

an accumulation of sediment deposited by waves and longshore drift along the coast

longshore bar

a ridge of sand, gravel or mud built by the seashore by waves and currents, generally parallel to the shore and submerged by high tides

concordant coastline

a coastline with alternating bands of more and less resistant rock PARALLEL to the sea

discordant coastline

a coastline with bands of more and less resistant rock PERPENDICULAR to the sea (at a right angle)

differential erosion

erosion that occurs at different rates due to the type of rock on a coastline

coastal current

permanent or seasonal movement of surface water in the sea

longshore current / littoral drifts

Occurs as most waves do not hit the coastline ‘head on’. The angle generates a flow of water running parallel to the shore, which moves water along the surf zone and transports sediment parallel to the shore.

rip currents

Strong currents moving away from the shore. They develop when sea water piles up along the coast. Initially, current runs parallel to coast before flowing out of breaker zone at a headline where it changes direction - can be hazardous for swimmers or small boats.

upwelling

Movement of cold water from deep in the ocean towards the surface, replacing the warmer surface water creating nutrient rich cold ocean currents - forming patterns of global ocean circluation.

tides

changes in water levels of seas and oceans caused by the gravitational pull of the moon and sun

spring tide

when sun and moon align, enhancing moons pull, creating larger tides than usual

neep tide

when sun and moon are at right angles, meaning the pull from the sun takes away some from the moon, causing lower than usual high tides

tidal range

difference in height between low and high tide

sediment

natural material that has been broken down through erosion/weathering, can be transported and deposited.

sediment cell

distinct area of coastline and its nearshore area, movement of sediment is usually contained within the cells boundaries (closed system)

sediment budget

balance of sediment entering and exiting a coastal system POSITIVE= surplus sediment NEGATIVE= deficit of sediment

accretion

build up of sediment

geomorphology

study of the shape of the land

longshore drift

process of material being moved along coastline as swash carries sediment on the angle of the prevailing winds and backwash returns at a right angle to the beach

aeolian (wind) deposition

saltation= sediment repeatedly lifted by wind and dropped, causing a bouncing of particles

surface creep= similar to traction - rolling of larger particles along a surface

When does marine deposition occur

• water carrying sediment percolates (sand sinks in to surface)

• water pauses at the shore during longshore drift

• waves slow after breaking

• sand and shingle accumulate faster than removed

• low energy waves are present

5 types of transportation

solution - dissolved sediment in sea

suspension - very small sediment carried along

saltation - bouncing of particles along seabed

traction - heaviest sediment rolling along

longshore drift - sediment deposited as swash hits coast at an angle and waves retract parallel

5 types of erosion

hydraulic action - sheer force of water against cliff

wave quarrying - air trapped in a crack of cliff causing pressure

abrasion - sediment thrown against cliff in a wave

attrition - sediment hitting each other in a wave

solution/corrosion - calcium rocks being dissolved by slightly alkaline water

how rate of erosion is increased

steeper waves= more energy

breaking point of wave close to cliff

longer fetch

deeper sea level

flat + wide beaches absorb less energy

humans removing sediment - alternatively building coastal defences lowers erosion

biological weathering

animals burrowing in cliffs, plant roots in cliff, piddock (shellfish) drilling into cliff, seaweed in cliff dragging waves

chemical weathering

oxidation - oxygen in water reacts with minerals in rock

hydration - porous rock expands creating stress, weakening it

hydrolysis - acid rain dissolves rock

carbonation - calcium carbonate (in limestone) + carbonic acid=calcium bicarbonate

mechanical/physical weathering

depends on climate, freeze thaw = water enters crack, freezes overnight, melts back to water when temp rises releasing pressure exerted from the ice

mass movement

downhill movement of weathered sediment under the force of gravity, rate depends on angle of slope, saturation, cohesion and size of sediment, 5 types

landslides

rapid movement of weathered material down a straight slip plane

rockfalls

when exposed to mechanical weathering, cracks in the cliff looses support for sediment higher up causing rapid falls

mudflows

movement of earth and mud flowing downhill over impermeable rock due to saturation reducing friction, very fast-flowing

rotational slip / slumping

whole sections of rock move along a curved slip plane as sediment collapses under its own weight, rotational movement

soil creep

very slow movement of individual soil particles moving downslope due to wetting and freezing

geology

a branch of natural science concerned with the earth, the rocks of which its composed and the processes by which they change over time (earths structure and processes)

sedimentary rock

layers of small chipped off sediment compacts to form a larger rock, weakest type, e.g. mudstone, limestone and coal

metamorphic

heat and pressure from magma changes the chemical state of the rock, binding it together stronger, takes a very long time e.g. marble

igneous

rocks become so hot, they melt into a liquid (molten rock) then cools down and hardens, e.g. granite and pumice

rock cycle

the newly formed igneous rocks eventually get weathered and small sediment gets chipped off, starting the sedimentary rock process - a continuous cycle over millions of years

differential erosion

when rates of erosion occurs at different speeds due to varying rock resistance

factors that affect rate of erosion

• resistance to erosion - well-jointed rocks are more venerable to erosion

• permeability and porosity - ability to hold fluids and allow them to flow through

• orientation - discordant / concordant coastline

• dip - angle of the rock strata

rock strata

layers of rock that have formed over time

swash aligned beach

parallel to incoming waves, minimal longshore drift, irregular coastlines

drift aligned beach

parallel to direction pf longshore drift, considerable amounts f sediment, regular coastline

tombolo

a spit that joins an island to mainland

estuary

the zone were the freshwater of rivers meets the salt water of the sea and begin to interact

bar

a spit that forms two headlands, can form a lagoon

sand dune formation

sand gets transported up the beach by wind, larger sediment rests against an obstacle creating a ridge which builds up to a crest of an embryo dune. the dune becomes a new obstacle and larger and mores stable sand dunes are formed further inland

mudflats

Mudflats are created by the deposition of fine silts and clays in sheltered low energy coastal environments such as estuaries. saltmarshes

flocculation

particles in sediment like clay and silts clump together, sinking to the bed as they are heavier

halosere

tolerant of salty conditions

salt marsh structure

climate

average weather over a 30 year period

weather

the atmospheric conditions (temperature and rainfall) of each day

climate change

a long term change in the climate, could be global warming or cooling

Eustatic change

Change in the sea, global effect, caused by tectonic movements and change in climate

Isostatic change

Changes in land movements, local effects, caused by tectonic uplift or depressions, compression/decompression of the crust and subsidence of land

Sequence of sea level change

Colder climate, more water in glaciers, sea level falls, weight of glaciers compress land, sea levels rise, climate warms, ice melts, sea levels rise

Emergent landforms

Raised beaches with relic cliffs and wave-cut platforms where the sea level has dropped so a new beach has been formed

Rias

A submergent landform, a flooded river valley with a dentritic pattern

Fjords

A submergent landform, flooded glacial valley, shallower at the mouth where the ice would have lost energy as it melted, very steep sided and narrow

Dalmatian coast

Where a landscape of valleys and ridges are parallel to the coastline, the low lying parts of the valleys will be flooded when sea level rises. The exposed tops of the ridges become small offshore islands parallel to the coast. The best known example of this is the Dalmatian Coast in Croatia

Groynes

Timer or rock structures perpendicular to coast that trap sediment moved by longhairs drift

+work with natural processes, protects land, not too expensive

-starve other beaches leading to erosion, unattractive

Sea walls

Stone or concrete walls at foot of cliff or top of beach with curved face to reflect waves back to sea

+effectively prevents erosion, provided a promenade

-dosnt absorb waves energy, intrusive and unnatural looking, very expensive

Rip rap

Large rocks at foot of cliff or top of beach forming a permeable barrier to break waves

+relatively cheap and easy

-intrusive, dangerous to people climbing

Revetments

Sloping wooden/concrete/rock structures at foot of cliff or top of beach breaking waves energy

+relatively inexpensive

-intrusive, needs high maintained

Offshore breakwater

Partly submerged concrete/rock structures designed to break waves before they reach the coast

+effective permeable barrier

-visually unappealing, navigation hazard

Beach nourishment

Adding sand or pebbles to an existing beach

+cheap and easy, looks natural, makes a bigger beach

-needs constant maintained because of erosion and transportation

Cliff regrading and draining

Regrading reduces angle of cliff to stabilise it

Draining removes water to prevent landslides and slumping

+effecting on clay or loose rock, cost-effective

-causes cliff to retreat, drained cliffs and dry out and lead to collapse (rockfalls)

SMP (shoreline management plan)

Strategy for managing flood and erosion for a particular coast of coastline in the UK, aiming to provide strategic and sustainable improvements