Coasts And Rivers Flashcards
Antecedent
Weather conditions proceeding an event
Evapotranspiration
Water which is evaporated/ transpirated from plants
Water abstraction
The removing of water from aquifers
Lag time
Time between peak rainfall and peak discharge
Discharge
Water that is in a river
What is a river regime
A river regime shows how the discharge of a river varies over a longer period of time ( usually a year) being aware of factors that change the speed and amount of precipitation that reaches the river.
Thinking of a river as a system with stores transfer inputs and outputs
How are carbon and water linked in a reaction ship
Weathering, ocean warming, volcanoes, decomposition, ocean acidification, photosynthesis and respiration
What % of the worlds population now live within 100 miles of the coast
Around 50%
Factors affecting the coast
Weathering, wave type , rock types, currents/ tides, sea level , human activity, fetch, chemical acidity
Sources of energy in coastal systems- wind
Winds created by air moving from high pressure to low pressure.
Strong winds generate powerful waves. Prevailing winds causes higher energy waves than winds that change direction frequently
Sources of energy in coastal systems- waves
Waves are created by wind blowing over the surface of the sea, creating friction giving water a circular motion
The effect of the wave on shore depends on its height which is affected by wind speed and fetch of wave.
When waves reach shore they break creating friction slowing waves , creating elliptical wave.
What is the swash
Water washing up the beach
Backwash
Water washing back down towards sea
Constructive waves
Low frequency, low and long, which gives elliptical cross profile, powerful slash so deposits sediments
Destructive waves
High and steep, circular cross profile, higher frequency, strong backwash removes material from beach
Sources of energy in coastal systems- tides
Tides are the periodic rise and fall of the oceans surface, cause by gravitational pull of the moon and sun.
Tide effects the position at which waves break ( at high tide they break higher up shore)
The area between maximum high tide and low tide is where most landforms are created and destroyed
Sources of energy in coastal systems- currents
A current is the general flow of water in 1 direction
It can be caused by wind or by variation in water temp/ salinity . Currents move material along the coast
High energy coasts
Receive high inputs of energy in The form of large powerful waves- these can be caused by strong winds, long fetches and steeply shelving offshore zones.
Tend to have sandy coves and rocky landforms
The erosion rate is higher than the rate of deposition
Low energy coasts
Receive low inputs of energy in the form of small gentle waves
Often have salt marshes and tidal mudflats
Rate of deposition is often higher than rate of erosion
Inputs of sediment into coastal system
Rivers, sea level rise, eroded cliffs, offshore deposits , crushed shells of marine organisms
Waves in England
Largest waves in sw
Most erosion takes place along Yorkshire coast meaning wave type must not be leading factor of erosion in England
What ratio of wave height to wavelength does the wave break
7:1
What is energy proportional to
Wavelength x wave height is proportional to energy
Factors affecting wave strength
Wind strength , fetch, wind direction, coast configuration, wind duration
Where do waves break on smash aligned beaches
Waves break parallel with the coats
Where do waves break on drift aligned beaches
Waves break at an angle, so material is transported along the beach via longshore drift
Wave refraction at headlands
High energy waves, depth of waves decreases, waves get higher + steeper, velocity decreases, shorter wavelength, wave crest converge on headland , increasing energy therefore erosion
Refraction in bays
Low energy waves, waves reach shallower water later, waves crests diverge = lower energy= deposition , wave refraction influences rate of marine erosion like this
Wave refraction
Waves breaking into an irregularly shaped coastline ( eg headland)
Why does the ocean move
Currents, upwellings, winds.waves,tides,conveyor belt
Global ocean conveyor belt
Constant motion in the ocean. Winds drive ocean currents in the upper 10% of surface, but this also effects deep ocean currents
These deep ocean currents are driven by differences in the waters density which. Is controlled by temp and salinity, this process is thermohaline circulation.
5 types of geomorphological processes
Weathering, mass movement, erosion, transportation, deposition
Weathering
When rocks are broken down by mechanical and chemical processes caused by the weather
What does in situ mean
Not moving
Mass movement
Rock Loosened by weathering, move down slope under influence of gravity.
Chemical weathering
Acids in rain ( eg co2) can chemically dissolve rocks ( especially chalk/limestone) nitrogen and sulphur oxide can also produce acid rain
Biological weathering
Plants roots can get into tiny cracks as they grow they open these gaps wider
Dying plants also produce acid a
Burrowing animals also erode rocks
Physical ( mechanical) weathering
Water freezes in cracks as it freezes it expands this creates pressure which enlarges cracks eventually rock fall off
Rockfall
Rocks are broken down by freeze thaw weathering, this loosened material is vulnerable to the elements. Of rock is at the top of a steep cliff face it can fall directly to the shore
Mudflow
Occurs on very steep slopes along the coast line where there is limited vegetation to under the soil together and the ground is very saturated heavy rain can produce sheet flow over the upper cliff surface, the soil eventually flows over the cliff face
Landslide
When rocks and unconsolidated material on the cliff face are saturated with water and slide down slope , they occur on steep gradient and very similar to slumps
Rotational slip/ slumping
Heavy rain is absorbed by material the cliff becomes heavier and eventually sperartes from the material behind at a slip plane . Occurs on a concave cliff face
Soil creep
Movement of soil particles down a slope . The slowest type of downhill soil movement.
Gravity pulls the water contained in soil downwards which pulls soil with it . The slope may appear rippled
Igneous rock
Formed when magma solidifies
Contains a lot of minerals crystals
Eg basalt , granite
Metamorphic
Formed when either igneous or sedimentary rocks are changed
Highly resistant to erosion
Eg marble , slate
Sedimentary Formed from build up of sediments over time Built up in layers Often contains fossils Eg limestone p, sandstone
Abrasion
Rocks hitting the side of cliff, wearing it away
Hydraulic action
The force of the water hitting the cliff
Cavitation
Wave hitting cliff forces air in and out faults in a cliff, causing erosion
Wave quarrying
Same as cavitation ( change in pressure actually causing the erosion )
Attrition
Bits of sediment hitting into each other ( makes round rocks )
Solution
Rocks dissolve in the water
Factors affecting the rate of erosion
Coastal configuration, beach presence, geology, sea depth, human activity
How does coastal configuration affect rate of erosion
headlands attract wave energy through refraction
How does beach presence affect rate of erosion
Beaches absorb wave energy and can therefore provide protection against marine erosion. Steep, narrow beaches easily dissipate The energy from flatter waves, but flatter beaches spread it out and are best at dissipating waves
How does human activity affect rate of erosion
People may remove protective materials from beaches, which may lead to more erosion
How does sea depth affect rate of erosion
A steeply shelving seabed at the coast will create higher steeper waves
How does geology affect rate of erosion
Lithology= refers to the characteristics of the rock structure = describes the layout of rock in relation to the sea
Dip
The angle at which the rock faces the sea
Saltation
Rocks bounce along bottoms quicker than traction
Traction
Rocks slowly rolls along the floor
Formation of wave cut platforms
The sea attacks base of the cliff forming wave cut notch
Weather weaken the top of the cliff
The notch increases in size causing cliff to collapse
The backwash carries the rubble towards sea forms it. A wave cut platform
What is a geo
A long narrow steep sided cleft formed by erosion in cliffs they are created along faults and bedding planes . Eg narrow bay, wales
Mudflats
Are coastal wetlands that form in intertidal areas where sediments have been deposited by tides or rivers, very susceptible to erosion
Salt marshes
Are coastal wetlands that are flooded and drained by saltwater brought in by tides they are colonised by salt tolerant plants called halophytes which stabilise the marsh
What conditions are needed for mudflats and subsequently salt marshes to be formed
Found at low energy coastlands, often at estuary’s , submerged at high tide and exposes at low , sheltered areas
What’s a creek
Basically a small stream but without branches or tributaries
What’s a salt pan
Salt pans are formed when pools of seawater evaporate at a rate faster than is replenished by rainfall, as water evaporates it leaves behind the minerals from the salt ions dissolved in the water
What is CARR woodland
It’s a largely undisturbed wildness - a tangle of woods species . A type of waterlogged wooden terrain that represents a succession stage between reedy marsh and the formation of a forest
Step by step formation of salt marsh
Pioneer( first flowering plants like glasswork)
Establishment( mud flat height increase with species growing, salt marsh grass)
Competition( plants need light,co2,space.. to grow so competition happens eg oak )
Stabilisation(competition continues but now dominant/successful species)
Climax phase ( marsh only occasionally gets covered 1/2 Annually )
Longshore drift
Prevailing wind hits the beach so sediment is deposited cause swash , however cause gravity some sediment pulled out to sea at 90 angle, then prevailing wind again transports the sediment back to land and the process repeated
What factors affect beach profiles
Wave energy= high energy= shingle beach, low= sandy beaches
Wave type- destructive = steeper, constructive = shallower
Sediment type- shingle beaches= steeper p, geological reasons too
Longshore drift- hard to have steep beach
Barrier beach
An elongated bank of deposited sand laying parallel to coastline and not submerged by incoming tides. Often become lagoon or coastal marsh. Eg the lido in Venice.
May be formed by the breeching of a spit or constructive waves pushing a bar towards land
Tombolo
1 on drift aligned coastline when lsd builds a spit out from land to an island
2 on swash aligned coastline when there is wave refraction around both sides of the island causes collision of waves , cancelling each other out producing a zone of calm water where deposition occurs
Bar
If a spit develops across a bay where there is no strong flow of water from the landward side . The 2 headlands attach
Formation of a spit
Prevailing winds and maximum fetch allows material to be transported along coast via longshore drift . When the sediment reaches the end of the headland it is deposited when the water looses its capacity to transport it. The sediment builds up and forms a spit. It curves at the end as wave refraction carries round into more sheltered water,
Eg spurn head, holderness coast
Ecstatic change
Movement of water, global scale , slow, sea levels rise
Eustatic change in glacial periods
in glacial period sea level fall precipitation falls as snow forms ice sheets Less water in seas as its now on land
Eustatic change in interglacial period
Sea levels rise as the ice sheets melts so water now being put back into the sea
Isostatic change
Movement of land, local, slow
Isostatic change in a glacial period
Land is squashed by pressure of ice
Isostatic change in and interglacial period
Now no longer under pressure the land would push back up ( glacial rebound)
How does tectonic activity cause a change in sea level
Causes 10% of sea level rise
The em is on of geothermal heat into oceans by underwater volcanoes can cause therma, expansion of ocean water. Rising magma at constructive boundaries produces a doming upwards of crust mid-ocean ridges reduces ocean basin volume. At destructive margins the folding of plates increases ocean basin vol lowering sea levels. Earthquakes allows rebound of non-subducting margin- uplift of sea floor reduces ocean vol raising sea levels. Eg Boxing Day tsunami with mag of 9.3 lifted sections of Indian Ocean by 0.1mm. Turakirae head New Zealand unplifyed 6m in 1855
East coast flooding in uk
5th December 2013. Gale force winds of up to 10mph , 2 deaths. 800 000 homes and been prepared for flooding , Thames barrier raised . Thousands evacuated , rats , urged to remain vigilant. 7 cliff tops homes collapsed in hemsby, 1400 homes flooded
Submerged coastlines
One which has a rising sea level , where the land is drowned. Eg Ria, Dalmatian coast, Fjord
Emergent coastlines
One which has a falling sea level, where the land is revealed. Eg raised beach, wave cut platform, relict cliff
Rias
Long section and cross profile typical of a new valley and usually a dendritic system of drainage.
Rias are created by rising sea levels drowning river valleys, leaving only the high land visible.
Eg river Fal in south west uk - here sea goes 18km to Truro then it deposits sediments due to balance rejuvenation
Dalmatian coast
Drowned river valleys parallel to the coast
Islands and peninsulas are aligned parallel too, but just offshore from the mainland
Fjords
Submerged glacial valleys
Steep, cliff like sides and the water is uniformally deep ( often 1000km)
Formed when glaciers eroded below sea level and then when the ice melted the valleys were flooded
U shaped valleys
Raised beaches
As the land rose former wave cut platforms and beaches were raised above the waves . There are this on the Isle of Arran. Another example Portland bill, Dorset
Relict cliffs
An old cliff displaying features such as caves, arches, stacks
Smps
Shoreline management plans are where all local governments of each sediment cell work together to create a coastal management plan
Introduced in 1995. 4 options include do nothing, advance the line, hold the line, managed retreat
Iczm
Intergtated coastal zone management considers all elements of the coastal system. national, regional and local authorities have input on the plan. Introduced to protect coastline and appease all stakeholders
Work with smps
Differences between Smps and ICZMs
Smps look closely at coastal defences whereas iczm look at more sustainability.
What stakeholders would need to be consulted before the smp gets approval
People living there
Farmers
Gas terminal
Tourist attachments
How many Smps are there
22 Smps around England and Wales in 11 sediment cells
Where are sundarbans located
Located in southern Bangladesh and in north eastern India, I’m centre all Asia, above the equator
Natural challenges in the sundarbans
Coastal flooding , cyclones, high levels of salinity in soils, instability of the islands , accessibility and remoteness , human-eating tigers
Human challenge in the sundarbans
Over exploitation of coastal resources from vulnerable habitats , conversion of wetlands to intensive agriculture and settlements , destructive fishing techniques, resource-use of coastal issues by decision makes
What’s tidal action
The primary natural process that shapes this distinctive coast landscape
What is the tide
The periodic rise and fall of the level of the sea
What’s a spring tide
A tide just after a new or full moon, when there is the greatest difference between high and low water
What’s a near tide
A tide just after first or third quarter of the moon when there is least difference between high and low water
What’s tidal range
The difference between high and low tide
Where are tidal ranges high or low in Europe
High= UK , low= Mediterranean
Why is having a high tidal range bad
Wider range means wider zone affected by erosion
Negative feedback loop in carbon cycle
Deforestation, Increase in atmospheric co2, more plant growth, reduced atmospheric co2
Positive feedback In the carbon cycle
More co2 in atmosphere, temp rise, increased ocean temps. Warmer water absorbs less co2 , so more co2 in atmosphere
