Coastal Systems and Landscapes Flashcards
Define an open system
Inputs and outputs of sediment through a system boundary.
Define a closed system
Inputs and outputs of energy but not matter through a system boundary.
Define an isolated system
No inputs or outputs of energy or matter.
What system is the coastal system?
Open System (energy and matter can enter and leave).
Give an example of a negative feedback cycle in the coastal system
1) Sediment eroded from a beach.
2) Sediment deposited forming an offshore bar.
3) Waves forced to break earlier, dissipating their energy.
4) After the storm, waves return offshore bar sediment back to the beach.
What is a small scale coastal system?
A beach.
What is a large scale coastal system?
A sediment cell. Often bounded by headlands.
What atmospheric condition operates in the UK? (The Ferrel Cell)
The Jetstream.
How are waves created?
Friction between wind and water transfers energy to water.
What factors determine the amount of energy transferred to waves?
Direction of wind
Duration of wind
Strength of wind
Fetch
Define fetch
The distance a wave travels interrupted by land masses.
What are some characteristics of waves?
- Circular orbit
- Wave crest and trough
- Orbit becomes elliptical because of shore friction.
What are constructive waves?
- Weak backwash, strong swash.
- Low height.
- Low frequency, 6-8/min.
What are destructive waves?
- Weak swash, strong backwash.
- High wave height.
- High frequency, 10-14/min.
What is wave refraction?
Waves approach an irregular coastline, becoming more parallel to the coastline.
Where does wave refraction typically occur?
Headlands, high energy concentrated here.
Define currents.
The permanent or seasonal movement of surface water in seas and oceans.
How do longshore currents occur?
Waves approach in the coastline at an angle, swash in the direction of the prevailing wind, backwash perpendicular to the beach.
What are rip currents?
Strong currents moving away from the shoreline. The current flows parallel to the coast before flowing out.
Define upwelling
Movement of cold water from deep oceans to the surface. Colder water is more nutrient rich and is responsible for global ocean currents.
Define spring tides
Occurs twice a month when sun and moon are parallel to earth. Causes highest monthly tidal range.
Define neap tides
Occurs twice a month when sun and moon are perpendicular to earth. Causes lowest monthly tidal range.
Define the coastal sediment budget
Measures the inputs and outputs of sediment in a cell and can be used to estimate the net movement of sediment each year.
Define sub-aerial/aeolian processes.
Removal of rocks through mechanical, biological, or chemical means.
Define hydraulic action
Process by which air is forced into cracks in the rocks, mixture of acid and pressure erodes the cliff.
Define corrasion
Advancing waves picking up sediment and throwing it at the cliff face, transferring energy to the cliff.
Define solution/corrosion
Weak acids in seawater dissolve minerals such as calcium carbonate in cliffs.
Define attrition
Pieces of sediment hit against each other and become smaller, smoother, and rounder over time.
Define mechanical weathering
Processes that physically damage the cliff.
What are some examples of mechanical weathering?
- Wetting and drying
- Crystallisation.
- Freeze-thaw
Define chemical weathering
Breakdown of rocks by changing the chemical composition, Carboniferous limestone dissolved by weak carbonic acids.
Examples of chemical weathering
- Carbonation
- Oxidation
Define biological weathering
Breakdown of rocks from living organisms.
Examples of biological weathering
- Plant roots
- Birds
- Decaying material
- Marine organisms.
What is mass movement?
Sudden or gradual movement of sediment downslope due to force of gravity.
What is rockfall?
Rapid free fall of rock from a steep, bare cliff face.
What are three features that allow a mudflow to occur?
- Slopes of 10’ or more.
- Layer of top soil that can be saturated.
- Impermeable rock below to allow soil to slide as it gets heavier.
What are key features that allow rotational slumping to occur?
- Permeable rock above impermeable rock.
- Step effect.
- Undercutting.
What is soil creep?
Soil expands at right angles and increases in size and weight. When it dries out, it moves downslope. Very slow and occurs on gentle slopes.
What are the four transportation processes?
Traction
Saltation
Suspension
Solution
Define traction
Boulders and other large materials are dragged along seabed.
Define saltation
Large pebbles and gravel bounce along seabed.
Define solution (transport)
Dissolved substances are carried in the water.
Define suspension
Fine material like silt carried by the water.
What is a concordant coastline and what landform often occurs here?
Rocks are organised in bands of harder and softer rocks parallel to coastline.
Coves occur here e.g. Lulworth Cove
What is a discordant coastline and what landform often occurs here?
Rocks are organised in band of hard and soft rocks perpendicular to the coastline.
Headlands and bays occur here e.g. Isle of Purbeck.
Outline the formation of caves
- Hydraulic action and abrasion
- Wave energy concentrated on cracks that expand.
- May form an arch in the future.
Outline the formation of headlands and bays
- Harder rocks eroded more slowly, forming headlands.
- Softer rocks eroded more quickly, forming bays and beaches.
Outline the formation of Geos
- Concentrated wave energy and weathering erodes a long vertical crack.
- Geo is widened by waves over time.
Outline the formation of spits
- Caused by change in direction in coastline, prevailing wind blows sediment across a river or body of water.
- Decrease in wave energy behind spit, forming salt marshes.
Outline the formation of barrier beaches/bars
- Spit cuts off an entire body of water.
- Bar may be infilled over time and start a new cycle of headlands and bays.
Outline the formation of a tombolo
- Occurs when a spit connects an island to the mainland.
- May be eroded by marine processes or be tidal.
Outline the formation of sand dunes
- Lots of deposited sand needs to build up.
- New dunes may form in front of older ones.
What are three different types of sea level rise?
- Eustatic
- Isostatic
- Tectonic
How high has the sea level risen in the Holocene period?
120m on average.
Are we currently in a glacial or interglacial period?
Interglacial
What is the name of the current period we are in?
Holocene period - started 10,000-12,000 years ago.
What is eustatic sea level change?
- Sea level itself rising and falling.
- Global changes.
- Affected by human induced climate change (1-2m rise by 2100).
What is isostatic sea level change?
- Land rising and falling relative to the sea.
- Local change.
Define tectonic sea level change
- Tectonic activity.
- Local change.
- Juan de Fuca plate causing tectonic uplift (1mm/yr).
- Most changes reverted by large earthquake or volcanic eruption.
Define marine regression
Where the sea level drops and produces emergent coasts.
What are some examples of marine regression?
- Eustatic fall in sea level.
- Isostatic rebound of earth’s crust.
Define marine transgression
Where sea level rises and produces submergent coasts.
What has led to consistent transgression in the Holocene Period?
- Thermal expansion
- Melting ice
Define emergent coastlines
Results of local tectonic uplift or fall in sea level. Often leaves rocky coastlines.
Define submergent coastlines
Coastlines flooded due to relative sea level rise. Often river valleys flooded by ocean water.
What are raised beaches?
Isostatic rebound - Glacial ablation allows land to rise.
Can also occur because of tectonic uplift but is restricted to areas of volcanic and earthquake activity.
What is a fjord?
Carved from mountainous glaciers, usually several km thick. Abrasion of material dragged down mountain.
What key characteristics does a fjord have?
- Longer than it is wide.
- Mountains often range up to 1km above sea level around fjord.
What are rias?
Flat, low lying areas. Commonly nicknamed a ‘drowned valley’. Common in SE England where sea levels rose following deglaciation period.
What are dalmation coasts?
Forms where ridges and valleys are parallel to coastline and have been flooded. The ridges stay exposed.
Why do people manage coastal areas?
- 1 billion people live near the coastline.
- 50% of the population live within 60km of the coast.
- 75% of large cities are coastal.
- Coastlines are very economically active for shipping and trade.
Define hard engineering
Man-made structures that physically protect the coastlines.
What are two different types of management plans?
SMP - Shoreline Management Plan
ICZM - Integrated Coastal Zone Management
In the SMP in the UK, what are DEFRA’s four terms that are used for each plan?
- Hold the line
- Advance the line
- Managed retreat/realignment
- No active intervention
Describe a sea wall
Hard engineering
A solid barrier that reflects waves back out to sea. Reduces erosion against flooding.
What are the advantages and disadvantages of sea walls?
+ Reduces erosion and lowers flooding risks.
- Expensive to build and maintain.
- Stronger backwash can undercut the sea wall and erode underneath.
Describe gabions
Hard engineering
Rock filed cages usually placed at the foot of cliffs to absorb wave energy.
What are the advantages and disadvantages of gabions?
+ Relatively cheap
+ Very good temporary solution
- Can be unappealing
- Cliffs can still be eroded.
Describe groynes
Hard engineering
Fences or boulders built perpendicularly to coastline. Trap material moving by longshore drift.
What are the advantages and disadvantages of groynes?
+ Usually cheap
+ Widens beaches and reduces erosion in that area.
- Increases erosion further along coastline, beach starved of sediment.
Describe breakwaters
Hard engineering
Concrete blocks or boulders dropped off coastline, forcing waves to break earlier.
What are the advantages and disadvantages of breakwaters?
+ They can physically reduce the wave energy before it reaches coastline.
- Quite expensive
- Can be damaged by large storms.
Define soft engineering
Use of natural looking structures that improve sustainability and are less visually pollutive.
Describe beach nourishment
Soft engineering
Sand and shingle added to beaches from other areas.
What are the advantages and disadvantages of beach nourishment?
+ Cheap if done once
+ Creates wider beaches
- Often has to be repeated which can become expensive
Describe dune regeneration
Soft engineering
Sand dunes are created or repaired by readding or stabilising sand.
What are advantages and disadvantages of dune regeneration?
+ Cheap to start
+ Allows wave energy to be absorbed
- Can be difficult to encourage growth of dunes
- Expensive to maintain
Describe land use management
Soft engineering
Use of physical structure to limit the levels of activity on certain areas of coastline.
What are the advantages and disadvantages of land use management?
+ Reduces vegetation loss from specific areas.
- Can be expensive
- Requires coordination from the public.
Describe managed retreat
Soft engineering
Planting of vegetation or reducing wave power by breaching existing flood defences and flooding the area behind.
What are the advantages and disadvantages of managed retreat?
+ Created salt marsh ecosystems which are dying out.
- Requires coordination from all stakeholders, agriculture hit badly.
- Expensive to remove existing defences.
Define coastal accretion
Movement of sediment from the sea back to the foreshore/backshore. Usually occurs after submersion in stormy periods.
Define brackish water
Water with a grater salt content than fresh water but lower than sea water. Common in tidal zones and spits. Ideal for mangroves.
Define halophyte
An organism that can tolerate salt water.
