Coastal systems and landscapes Flashcards
What is a trough?
The low area between two waves
What is a crest?
The top of a wave
What is the wavelength?
The distance between 2 crests or 2 troughs
What is wave height?
The distance between the crest and the trough
What is wave frequency?
The number of waves per minute
What is velocity?
The speed that a wave is travelling
What is swash?
The movement of water and load up the beach
What is backwash?
The movement of water and load back down the beach
What are the 3 factors that affect the size and energy of waves?
-How long the wind has been blowing.
-The strength of the winds
-The length of the ocean over which the wind blows (fetch)
Decribe the relationship between global wind patterns and global wave energy:
The stronger the winds are, the more energy that waves will have. There are stronger winds towards the North and South poles, so the waves there are more powerful.
What is a swash aligned beach?
Where waves break parallel to the coast. Swash and backwash move up and down the beach.
Creates different features: Ridges, Runnels, Berms.
What is a drift aligned beach?
Where waves break at an angle to the coast. swash occurs at an angle, backwash occurs perpendicular.
LSD carries material along to create different features: Spits, bars and tombolos.
Describe how waves are formed:
Waves are caused by frictional drag between the surface of the sea and the lowest layer of wind. Higher layers of the wind then move faster over lower levels, dragging this along helps the waves form.
What 3 factors determine the height of the wave?
-Fetch (distance travelled)
-Duration
-Strength of wind (stronger wind = bigger wave height)
Describe what happend when a wave approaches the shore:
1) As wind blowsover the surface of the ocean friction forces water up and down.
2) Creates cicular orbits of water within the wave. In deep water the orbits are small.
3) As the waves move into shallow water, friction with seabed distorts circular motion.
4) Water molecules are now moving in an elliptical shape.
5) Waves slow due to friction with seabed, top of waves move faster, waves increase in height.
6) Wave tilts and topples over breaking onto the beach.
7) As water travels back up the beach its called swash and as it travels backwards = backwash.
What are the characteristics of a constructive wave?
-Long wavelength
-Low height
-Strong swash
-Lower energy
-Lower wave frequency
What are the characteristics of a destructive wave?
-Short wavelength
-High wave height
-Strong backwash
-Higher energy
-Higher wave frequency
What are tides?
Changes in water level of seas and oceans.
High tides = Where sea surface rises to its highest
Low tides = Where sea surface is at its lowest point.
What causes tides?
The gravitational pull of the moon and sun, gravity pulls tides towards the moon.
-The area on the opp side of the Earth to a high tide will also have a high tide due to inertia and centrifugal force as the gravitational pull is weaker here so ocean bulges out.
What is a spring tide?
When the moon, earth and sun are in alignment it causes teh gravitational pull to increase more than usual and creates a high spring tide.
What is a neap tide?
Lower than normal tides and they occur when the sun and moon are at right angles to the earth so gravitational pull from both has a reduced impacts
What are tidal surges (storm surges)?
Occasions when weather conditions create stronger winds which can produce higher water levels than those at high tide.
What are tidal bores?
When tide comes back in ans water is funnelled up an estuary, causes big waves to form.
What is an ocean current?
Current = Seasonal or permanent movement of surface water in the ocean.
Located on the surface and in deep water.
**Caused by: **Tides, winds, thermohaline circulation.
What is a longshore current?
Currents that run parallel to the shore
What is a rip current?
Fast moving, narrow channels of water where waves break on the beach.
What are upwellings?
Cold currents from the deep ocean are brought to the surface (due to wind and earth’s rotation).
What is thermohaline circulation/ (global conveyor belt)?
Oceans are mostly composed of warm salty water near the surface over cold, less salty water in the ocean depths. These 2 regions don’t mix except in certain areas, which creates a large slow current.
Describe refraction on a straight coastline:
-Most waves usually arrive at an angle to the shoreline, this angled approach can change the direction of wave travel.
-One end of the wave hits the seabed and slows down whilst the rest of the wave continues at it’s deep water speed.
-As more of the wave comes into contact with the sea floor, more slows down.
-As the wave slows along its length, the crest changes direction and becomes parallel to the shoreline.
Describe refraction on an irregular coastline (headlands and bays):
-Wave refraction occurs when waves approach an irregular coastline they curve and distort.
-As each wave nears the coast, it drags in the shallow water.
-This causes the wave to become higher and steeper with a shorter wavelength.
-That part of the wave in deeper water moves faster, causing the wave to bend.
-Overall effect is that wave energy becomes concentrated on the headland, causing greater erosion.
-Where the waves diverge, they lose power and drop sediment.
What is a sediment cell?
A strech of coastline, usually bordered by prominent headlands, where the movement of sediment is more or less contained. (Closed coastal sub-systems)
Describe the main sources of sediment
**Rivers **= Accounts for large majority of sediment, sediment is deposited in river mouths and esturaries where its re-worked by waves, tides etc.
Cliff erosion = In some areas of soft rock, erosion can reach 10m a year.
LSD = Sediment transported from other coastlines.
Wind = In glacial or hot environments, wind-blown sand can be deposited in coastal regions (sand dunes).
Glaciers = Chunks of ice shelves can break off into the sea and deposit sediment trapped in the ice.
Offshore = Transferred into ocean zone by waves, currents, tides. Storm surges can also input sediment.
What is a sediment budget?
Balance between changes in volume of sediment held within the system and the volume of sediment entering or leaving the system.
What is a positive sediment budget?
More inputs than outputs
What is a negative sediment budget?
More outputs than inputs
What factors can alter the sediment budgets?
Input changes = Volume of fluvial material deposited into coastal system + impact of human intervention (coastal defences) + rising sea levels causing increased erosion may add more sediment.
Output changes = Human intervention (removing large amounts of sand for industrial or coastal protection use). Sea level rise can change currents and material being removed from cells.
What are some characteristics of a sediment cell?
-Discreet and function separately from each other.
-Sediment is stored, sourced, and transferred within the cell.
-Amount of sediment available to the cell is the sediment budget.
How many major sediment cells are in the UK?
11
How has human activity impacted sediment cells?
-Can interfere with processes in a sediment cell by disrupting sediment budget.
-Groynes, jetties, harbour walls block movement of sediment.
-Sediment input supply can also be disrupted by dams, which cut down the amount of fluvial material entering the coastal.
-Protecting soft cliffs can prevent cliff flass and reduce sediment entering system.
What are sub-aerial processes?
Land based processes which shape the coastline. They come under the general headings of weathering and mass movement.
What is weathering?
The disintegration of rocks in situ
What is chemical weathering +examples?
Both rain and seawater contain chemcials that can react with chemical compounds in the rock, altering its structure.
-Oxidation: Rocks containing iron compounds experience oxidation when exposed to O2 and water from the air and sea - causes disintegration.
-Carbonation: Coastlines composed of chalk or limestone are dissolved by acidic rain and seawater.
What is physical/mechanical weathering + examples?
Internal pressure are exerted on rock as a result of changes in the physical structure within its mass.
-Freeze thaw: Common where temps fluctuate below freezing and there is a ready supply of water - water freezes in cracks and expands, enarging cracks.
-Exfoliation: Rock may expand as its heated by the sun and contracts when it cools. Causes cracks to form in rock.
-Wetting and drying: Rock alternates between wet and dry, rocks such as shale expand when wet and contract when dry, formign cracks.
What is biological weathering +examples?
Living organisms can contribute to the weathering of coastal rocks throught the activity of plants and animals.
-Roots of plants can create and expand tiny fissures, seaweed can attach to rocks and weaken them during movement.
-Animals can excavate nesting burrows in cliffs. Some marine organisms have adpated shells that enable them to drill into rock. Algae can secrete chemicles promoting solution.
What is mass movement?
Movement of consolidated material (rock) and unconsolidated material (clay, soil) due to gravity.
What is rockfall?
(Most rapid)
Occurs from cliffs undercut by the sea, or on slopes affected by mechanical weathering.
What are landslides?
Occur on cliffs made from softer rocks or deposited material, which slips as a result of failure in the rock when lubricated, usually following heavy rain.
What is runoff?
When heavy rain washes material from the surface of a cliff over the edge and down onto the shore.
What are mudflows?
Heavy rain can cause large quantities of fine material to flow downhill. Here the soil becomes saturated and if excess water can’t percolate, surface layers become fluid and flow downhill. Nature of flow depends on saturation.
What is slumping?
Soil or rock debris moves downhill along a concave or curved plane in a rotational manner
What is soil creep?
(Slowest movement)
Occurs when there is very slow but continuous movement of individual soil particles downhill.
What is longshore drift?
The movement of material along the shore by wave action. It happens when waves approach the beach at an angle.
What is traction?
Method of transportation
Large particles e.g. boulders are pushed along the seabed by water.
What is saltation?
Method of transportation
Pebble-sized particles bounce along the seabed by the force of water.
What is suspension?
Method of transportation
Small particles like silt and clay are carried along the water
What is solution?
Method of transportation
Soluble materials dissolve in the water and are carried along.
What is marine deposition?
(Where waves drop material they have been carrying)
-Takes place where waves are low energy or where rapid erosion provides an abundant supply of material.
What are aeolian processes?
Aeolian processes refer to the transport and deposition of sediment by wind.
Surface creep = Wind rolls or slides sand across surface.
Saltation = Wind temporarily lifts the grains into the airflow.
What are some causes of deposition?
-Energy source altering - low energy cuases deposition.
-Changes in flow direction - 2 currents meeting can increase deposition.
-Interruptions to flow
-Increased load - New sediment without increased energy causes deposition.
-Increased friction.
What is a discordant coastline?
A coast where bands of different rock types run perpendicular to the coast. The differing resistance to eroison (differential erosion) leads to the formation of headlands and bays.
What is a concordant coastline?
A coast where mostly one rock type runs parallel to the coast. The outer hard rock provides a protective barrier to erosion. Coves 9small sheltered bay) and wave-cut platforms form.
How do coves form?
Erosion focuses on area of weakness in hard rock and continues to erode through to the soft rock which erodes faster, creating a cove. Eventually rate of erosion will slow at hard rock again.
How are headlands and bays formed?
Different geologies in a discordant coastline mean that there is differential erosion, hard rock erodes slower, soft rock erodes faster, this creates headlands and bays.
How is a wave cut platform formed?
1) Sea attacks base of cliff forming a wave-cut notch through abrasion, hydraulic action, quarrying.
2) Weather weakens the top of the cliff.
3) The notch increases in size causing the cliff to collaps as it has no support underneath.
4) Backwash carries the rubble towards the sea leaving behind a wave-cut platform.
5) Process repeats and the cliff continues to retreat.
Describe the erosion of a headland:
1) Rock fractures at intertidal zone become enlarged due to hydraulic action, abrasion and solution. They are widened further by weathering processes.
2) Crevice enlarge to form caves. The larger the SA exposed to weathering and erosion processes = increase in rate of rock removed.
3) Wave refraction leads to erosion along the side of the headland forming at a very large cave. Concentration of hydraulic action on the cave roof can form blow holes when small sections of the roof collapse.
4) Caves developing on opp sides of a headland may erode deeper due to erosion until they meet and form an arch.
5) Arch roof becomes narrower as its weathered. Becomes thinner until collapses, leaving a stack.
6) Resultant stack is weathered by sub-aerial processes at its top and marine processes at its base. Reduces in height leaving a stump.
7) Stump is eventually eroded and foundations form the wave cut platform.
What is a spit, and what are the 2 types?
Depositional landform
A long, narrow beach of sand or shingle with one end attached to the shore and the other end extending into the sea.
Simple spit = Extends in a straight line.
Compound spit = Curved spit - has a wide recurved distal end with a series of barbs.
Describe the process of spit forming:
1)Spits are created due to longshore drift
2)Sediment is transported by waves along a coastline
3)When the coastline changes direction the waves no longer have the energy to carry the sediment and it is deposited
4)The build up of deposited sediment out to sea, often into an estuary, is called a spit
5)The spit often has a curved end or hooks due to a secondary prevailing wind
What is a tombolo?
Forms when a spit connects an island to the mainland or another island, usually due to wave refraction and sediment deposition in a sheltered area.
What is a bar?
Forms when a spit extends across a bay, connecting two headlands and trapping a body of water behind it, creating a lagoon
What is a barrier island?
Long, thin, sandy strech of land parallel to the ainland. Barrier island is detached from the mainland.
What is a sand dune?
Small ridges or hills of sand at the back of a beach, above usual maximum reach of waves.
Occurs when there is enough exposed sand at low tide to dry out and be blown inland.
What conditions are needed for a sand dune to form?
-Wide, flat beach
-An obstacle for sand to accumulate around
-Large supply of sand
-Onshore wind.
What is a psammosere?
Sand dune ecosystem
What is climax vegetation?
The final, stable stage of ecological succession
Describe the formation of sand dunes:
Wind blows sand which is trapped on obstacle on beach:
1)Embryo dune - 1m high, 80% exposed sand, Pioneer species (prickly saltwort)
2)Fore dune - Little organic matter e.g. sand couch grass.
3)Yellow dune - 5m high.
4)Grey dune - 8-10m, organic matter, grey soil.
5)Mature dune - Climax vegetation is reached.
What is succession?
The change in species in an ecosystem over time
What is a salt marsh?
-Area behind spits and barrier beaches that is very sheltered, where tidal currents and river currents meet leading to lots of deposition.
Salt-tolerant species colonise these sheltered, flat muddy areas.
Covered at high tide and exposed at low tide
Process of sediment accumulation and plant colonization creates a positive feedback loop, where the plants further enhance the accumulation of sediment, leading to the continuous growth of the salt marsh.
What are the inputs and outputs in a beach?
Inputs: Beach nourishment, cliff and dune erosion, fluvial sediment, longshore transport.
Outputs: Offshore transport, humans, longshore transport, storm events.
beach features
What are ridges and runnels and how are they formed?
Series of ridges and troughs running parallel to the coast, near the low water mark.
Formed by deposition during backwash and runnels are formed when water runs back to ocean.
beach features
What are ripples and how are they formed?
Small elongated ridges.
Formed when waves and currents flow across loose sand which is dragged along the bottoma dn is piled up.
beach features
What are Berms and how are they formed?
Series of small ridges that form near the high tide mark.
Formed by sediment deposited by constructive waves.
beach features
What is a storm beach and how is it formed?
Rdige found near the back of the beach composed of larger sediment.
Deposited by waves during storm events.
What is isostatic change?
Rising or falling of land mass relative to the sea resulting from the release of weight of the ice after the last ice age.
What is eustatic change?
Variations in relative sea level resulting from changes in the amount of liquid water entering the oceans.
What is an emergent coast?
Coastlines created when there has been a relative fall in sea level.
What is a submergent coast?
Coastlines created when there has been a rise in the relative sea level.
What are emergent landforms?
Appear towards end of an ice age, occur when isostatic rebound takes place faster than a eustatic rise in sea level (land height rises faster than sea).
emergent landform
Describe how a raised beach is formed?
Former wave cut platforms and their beaches were raised above present sea level due to land rising from isostatic recovery .
emergent landform
Describe how a relict cliff is formed?
Found at back of a raised beach, steep slope formed by marine erosion thats now above sea level.
E.g. = Raised beach in West Isle of Arran north of drumadoon.
What is a submergent landform?
Opposite of emergent landforms, form when eustatic rise takes place faster than isostatic rebound after an ice age.
submergent landform
Describe a fjord:
+example
Drowned glacial valleys, have steep valleys and are fairly steep and narrow.
-Have a u-shaped cross section and a glacial rock basin with a shallow section at the end.
E.g. - Milford sound Fjord - New Zealand
submergent landform
Describe a Ria:
+example
Created by rising sea levels drowning river valleys, floodplain vanishes beneath rising waters.
Only middle and upper course valleys are filled with seawater, leaving higher land dry.
E.g. - Fowey estuary in cornwall
submergent landform
Describe a dalmation coast:
+example
Found when topography of land runs parallel to coastline and becomes flooded by sea level rise, flooded valleys run parallel to coast.
E.g. - Croation coast in Adriatic
Describe the stages of sea level change:
Stage 1 (Eustatic sea level fall) = More water stored in ice, less returned to sea,climate gets colder.
Stage 2 (Isostatic sea level rise) = Sea level rises in relation to land, weight of ice causes land surface to sink, affects only some coastlines.
Stage 3 (Eustatic sea level rise) = Produces submergent features, climate warms, ice masses on land melt, floods lower parts of land.
Stage 4 (Isostatic sea level fall) = Emergent features, ice melts, land rises to previous levels.
Describe the impacts of sea level change:
Agriculture - Different crops need different conditions, if sea levels rise low lying farm land will be lost - impacts on global trade.
Flooding - Amplifies frequency and intensity of weather events e.g. hurricanes and floods.
Wildlife - Sea level rise has already led to loss of 5 vegetated reef islands (Solomon islands).
Displacement of people - Climate refugees - India, China, Bangladesh, NZ among those most at risk, Thought some pacific island nations will be complately submerged by end of 21st century, Jakarta - home to 10 mill people - dubbed fastest sinking city.
hard engineering
What are groynes ?
Structures built perpendicular (at right angles) to the shore. Sediment is trapped as it is transported by longshore drift. The beach builds up which absorbs wave energy .
What are the advantages and disadvantages of groynes?
adv = Not as expensive as other hard engineering structures, Builds up the beach which improves tourist potential.
disad = Causes sediment starvation further along the coast, Can be unattractive, Need lots of maintenance to ensure sediment isn’t getting through any holes or cracks.
hard engineering
What are Sea walls?
Walls with a curved or stepped surface that absorb and reflect wave energy
What are the advantages and disadvantages of sea walls?
adv = Highly effective, Can have tourism benefits as walkways are created.
disad = Very expensive to build and maintain - £6000 per metre, ugly and intrusive to the landscape.
hard engineering
What are gabions?
Wire cages filled with rocks or pebbles, stacked to form a barrier along the coast.
They absorb wave energy and reduce erosion, similar to rock armour.
What are the advantages and disadvantages of gabions?
adv = Flexible and can be molded to fit the contours of the coastline, relatively inexpensive and can be installed more quickly.
disad = May not last as long as rock armour and can be damaged by strong waves or vandalism.
hard engineering
What is rock armour?
Large concrete or granite boulders at the foot of a cliff. The spaces in between the boulders cause waves to bounce between many surfaces, reducing the energy of the wave
What are the advantages and disadvantages of rock armour?
adv = Cheaper than sea walls, Used for recreation such as fishing.
disad = Dangerous when people are on them, Rocks from elsewhere are intrusive to local geology.
soft engineering
What is beach nourishment?
Adding sand or shingle to a beach to widen it - creates more surface area to absorb wave energy
What are the advantages and disadvantages of beach nourishment?
adv = Looks very natural, Bigger beaches are good for tourism, Relatively inexpensive.
disad = Material is constantly subject to erosion and longshore drift so lots of maintenance and monitoring are needed, Dredging the seabed can have impacts on local ecosystems.
soft engineering
What is Cliff Regrading and Drainage?
Reducing the angle of the cliff to stabilise the slope. Drainage of water also stabilises the cliff against mass movement
What are the advantages and disadvantages of Cliff Regrading and Drainage?
adv = cost-effective
disad = Can look unnatural as the cliff is unnaturally flatter, This effectively creates a cliff retreat, Dried-out cliffs can collapse.
soft engineering
What is marsh creation?
This is a form of do-nothing or managed retreat. The land is allowed to be flooded by the sea and then left to become a salt marsh. This absorbs wave energy and also creates a buffer to rising sea levels and projects higher-value land.
What are the advantages and disadvantages of marsh creation?
adv = A cheap option, Creates important and unique wildlife habitats.
disad = Agricultural land is lost which creates a need for compensation.
Sustainable approaches to coastal management
Describe shoreline management plans (SMPs)
DEFRA overseas coastal management of the UK, and it was them who introduced SMPs. There are 4 policies SMPs have to decide from how a section of coastline should be managed:
1)No active intervention = Letting nature take its cours - chosen when cost of aid > economic benefit.
2)Hold the line = Maintaining current position of coastline, to reduce or stop the retreat of the coastline.
3)Managed retreat = Allowing coast to retreat in a managed way e.g. creating salt marsh environments.
4)Advance the line = Extending the coastline out to sea by encouraging the build-up of a wider beach.
Sustainable approaches to coastal management
Describe Integrated Coastal Zone Management (ICZM)
Means complete sections of coasts are managed as a whole, rather than individual towns or villages.
A key aim is to co-ordinate all potential conflicts of interest and handle them fairly e.g. following sustainable strategies, identifying stake holders, monitoring and recording of what is taking place at the coast.
