Coasts Flashcards
Littoral?
Coastal zone
What are the 4 main zones between the land and sea boundary?
Backshore
Foreshore
Nearshore
Offshore
What are the 4 input processes operating at the coast?
Marine- waves and tides
Atmospheric- climate change
Land- rock type
People- human activity
What are the 3 main processes operating at the coast?
Weathering
Erosion
Transport
What are the 3 main outputs operating at the coast?
Erosional landforms
Depositional landforms
Different types of coasts
What 4 ways can coasts be classified?
Via:
Geology- is the geology resistant to the erosive forces of the sea, wind and rain or not?
Energy- is the coast exposed to powerful waves or sheltered?
Balance- does erosion exceed deposition or vice versa? Is the coast retreating or advancing?
Sea level- does the coast have emergent or submergent features?
What are the main features of a high energy coastline?
Destructive waves
Storm conditions
Longer fetches
What are the main features of a low energy coastline?
Constructive waves, calmer, short fetches, sheltered
Why might it be difficult to classify some coasts?
Changes in space
Seasonality change
Local geology can produce rocky areas within coastal plain landscapes
Along fetches + destructive waves in bays
Geological structure?
The arrangement of rocks in layers, or folds and joints + bedding planes within them
Lithology?
Rock type and their general characteristics
Bedding planes?
Horizontal breaks in the strata, causes by gaps in time during periods of rock formation
Dips?
The angle at which the rock strata lie. Can be horizontal. vertical, towards the sea or inland
Faults?
Formed when the stress or pressure to which a rock is subjected exceeds its internal strength causing it to fracture
Folds?
Formed by pressure during tectonic activity, which makes rock buckle and crumble
Joints?
Vertical cracks caused by contraction (shrinking) as sediments dry out, or by earth movements during tectonic uplift
Strata?
Layers of rock
Coastal morphology?
Shape
What type of coastline to caves form on?
Concordant coastline- waves exploit weaknesses or faults
What type of coastline to headlands and bays form?
Discordant coastline
What is a concordant coastline?
Where rock is eroded at the same rate
What is a discordant coast?
Rock is eroded at different rates due to the different layers of softer vs harder rock
Cliff profile?
Height and angle of cliff face
What does horizontal strata of a cliff produce?
Steep cliffs
What does strata of a cliff that dips seaward produce?
Unstable cliffs- gravity causes mass movement ie rock fall
What does strata of cliff that has a landward dip produce?
Steep, stable cliffs
Igneous rock?
Formed from cooling of lava eg basalt + granite
Sedimentary?
Formed when layers of sediment deposited in lakes and sea are cemented together
Metamorphic?
Formed from other rocks that are chemically changed by intense pressure from surrounding rock, or by heat from near magma
What is glacial till?
A type of unconsolidated rock found in much of eastern england: it’s a mixture of sand clay and stones left behind by glaciers as they retreated at end of ice age
Prosity of igneous rocks?
Non-porous
Tightly fit together
Permeability of igneous rocks?
No water can be absorbed. No bedding planes of joints.
Resistance of igneous rock?
Very resistant to erosion and weathering
Prosity of sedimentary rocks?
Very porous due to rounded crystals
Permeability of sedimentary rocks?
Able to absorb water- permeable
Resistance of sedimentary rocks?
Less resistant to marine erosion and chemical weathering
Prosity of of metamorphic rock?
Non-porous- heat and pressure flatten rounded crystals in sedimentary rocks
Permeability of metamorphic rock?
Impermeable- no bedding planes or joints
Resistance of metamorphic rock?
Hard but some rocks are prone to mass movement
Example of sedimentary rock
Chalk
Example of metamorphic rock
Slate
Example of Igneous rock
Granite
What are the 4 coastal ecosystems?
Salt marsh
Coral reef
Sand dune
Mangrove forest
Why are salt marshes and sand dunes important?
They stabilise soft sediment (mud and sand) which is deposited in low energy coastal environments
Plant succession?
Evolution of plant communities at a site over time
Coastal plain?
Low land
What do sand dunes need?
A plentiful supply of land
Large area for the sand to dry out
Onshore winds to blow sand towards the land
Sand dunes?
Known as psammosere where drought-tolerant or xerophytic plants can survive with little fresh water
Porous?
Sedimentary rocks often contain small holes called pores which can contain water or other fluids. If the holes are connected, then the rock is permeable and fluids can flow through the rock.
Dune slack?
Area of the dunes which is lower than the water table
Water table?
Level of the soil that is saturated with water
What type of dunes tend to be the highest?
Yellow dunes
What type of grass is found on yellow dunes?
Marram grass
What type of plant is located on grey dunes?
Gorse
Salt marshes?
Are known as haloseres where salt tolerant or halophytic plants can survive in brackish (salty) conditions. Are common in the low energy environments of estuaries and sheltered bays
Where are salt matches commonly located?
Low energy environments of estuaries and sheltered bays
Why is coastal vegetation important?
Stabilises sediment in low energy coastlines allowing coasts to advance
In also provides a buffer between the land and the sea acting as long term flood and storm defence
Wave period?
The time interval from crest to crest in seconds. Sea waves have intervals of 1 and 20 seconds
5 key features of constructive waves
Strong swash Weak backwash Forward spilling breaker 6-8 mins frequency Deposition
ie build up beaches
5 key features of destructive waves
Weak swash Strong back wash Downwards plunging breaker 15per min frequency Erosive
How are beaches formed?
By deposition of rounded sand and shingle
What do beach profiles (gradient) have a close relationship with?
The dominant wave type
What are the features of a beach that have constructive waves as a dominant wave type?
Strong swash and weak backwash pushes material up the beach. The main feature is a large berm near the high water mark
What are the features of a beach that have destructive waves as a dominant wave type?
When backwash is stronger than swash it removes material from the beach and creates large bars. The beach is steeper at the very back above the high water mark
SWELL waves?
Waves generated during storms in the middle of oceans and maintain their energy for thousands of miles.
What is the distance of open water swell waves move travel called?
The fetch- the longer the more destructive the wave
What is the main form of transport at the coast?
Long shore drift or litoral drift
Long shore drift?
The offshore movement of sediment along the coast
What pulls sediments back off of a beach?
The backwash
When is long shore drift strongest?
When waves approach the coast at an angle of 30 degrees to the beach
What is the sediment cell concept?
The idea that sediments move along the coast in sediment cells.
What do sediment cells act as?
Closed systems with inputs, outputs and transfers
What is the main transfer of sediment cells?
Long shore drift
What is the main sink of sediment cells?
Depositional landforms
Sediment budget?
Amount of available sediment within a sediment cell
Inputs?
Sediment sources
Transfers?
Sediment transport
Sinks?
Sediment stores
Negative feedback?
Balancing out the system: as one increase the other increase
Dynamic equilibrium?
The way in which natural systems attempt to balance this way
Equilibrium?
Depositional landforms build up which are in line with the sediment available
What are sediment cells always in a state of?
Equilibrium
Closed systems?
Physical barrier between 3 processes- self contained system
What are the two ways in which deposition can occur?
Gravity settling
Flocculation
Gravity settling?
Energy becomes too low to move sediment. Large sediment is deposited first followed by smaller sediment (sand silt)
Flocculation?
Very small particles of sediment such as clay, which are usually suspended in water, clump together through electrical or chemical attraction and become large enough to sink
Sub areal processes?
Processes that affect coastal land above sea level
ie weathering and mass movement
Weathering?
Breakdown of material in situ. This means that the rock wares away without any movement
Tree main types of weathering?
Physical/mechanical
Chemical
Biological
Mass movement?
The movement downslope of rock, sand, clay, glacial till or soil. It is caused by gravity once slope has become unstable.
When can mass movement occur?
When waves undercut resistant rocks or when rainwater enters unconsolidated rocks and forces particles apart so that they no longer cohere (stick together)
Four main types of mass movement?
Rock fall
Block fall
Flow
Rotational Slumping
How does weathering affect the rate of coastal erosion?
Accelerates the rate of coastal recession because weak rocks can fall and contribute to attrition etc
What does rotational slumping involve?
A section of the cliff that remains intact as it moves down the cliff. Vegetation layer onto of slump usually
What does flow involve?
Lobe of clay and mud- cliff material tumbled to create a talus slope. Mudflow may result
Where do rock fall and block fall occur?
On a steep slope as a cliff face is weakened. which loosens blocks, and when wave erosion has created a wave cut notch so that a section of a cliff is no longer supported. Found on rocky coastline (resistant lithology)
What affects the rate of physical weathering?
Climate- hot or cold? ie precipitation is
What affects the rate of chemical weathering?
Temp and precipitation ie climate
Lithology and geological structure
What affects the rate of biological weathering?
Climate
Lithology
What are the 2 main types of sea level change?
Eustatic and Isostatic change
What is eustatic change?
Are the dropping of sea levels when water is locked away as ice, and it’s rising as it melts
What is isostatic change?
The process by which land rises out of the sea due to tectonic activity. It occurs when a great weight is removed from the land eg melting of ice
What is an emergent coast?
A stretch along the coast that has been exposed by the sea due to relative falls in sea levels
What is a submergent coast?
A relatively flat, horizontal or gently inclined surface of marine origin, mostly an old abrasion platform to which has been lifted via wave activity
What are the two landforms that can be located on emergent coastlines?
Raised beaches
Fossil cliffs
What are the three landforms that can be located on submergent coastlines?
Ria
Fjord
Dalmatian coast
What is a raised beach?
Originating from the sea, raised beaches are platforms formed out of coastal erosion. While sea level remains the same, land that was once at sea level is eroded. This leave the adjacent land further above sea level
What is a relic/fossil cliff?
A steep slope found at the back of a raised beach exhibiting evidence of formation through marine erosion but now above tide level
What is a ria?
A funnel shaped estuary that occurs at a river mouth and is formed by the submergence of an un-glaciated river valley
What is a fjord?
Is formed when glaciers retreat, after carving a typical u shaped valley, and the sea fills the resulting valley floor
What is a dalmatian coast?
Is formed where the geology creates valleys parallel to the coast so that when sea level rises, a series of elongated island remains offshore
What is isostatic rebound or decompression?
The melting of ice, the rising of land and the falling of sea levels
What stage is the world currently in?
An inter glacial period
With the earths warming atmosphere, what does this lead to?
Causes glaciers to melt- water enters rivers and oceans
Water warms up in seas etc which has a larger volume (thermal expansion)
Results in flooding due to rise in sea levels
What are six factors which explain why the rates of coastal recession vary?
Geology Fetch Waves Wind direction Season Weather systems
What are three human factors which explain why the rates of coastal recession vary?
Climate change
Groyne development
Dredging sediment
Where will the most rapid rates of coastal recession occur?
Where there are softer rocks, destructive waves, large scale mass movement, constant weathering and submergence
Where do the slowest rates of coastal erosion occur?
Where there are harder rocks, constructive waves, small scale mass movement, limited weathering and emergence
What is terminal groyne syndrome?
The upper coast is starved of material, cliffs are exposed to wave attack
Why is flooding a significant risk for some coastlines?
An increased risk and global concern because so many people have settled in lowland coast
The formation of a storm surge:
A low pressure system such as a depression or tropical cyclone develops offshore
Rising air within the low pressure system draws the sea upwards in a dome
Large storm waves develop on top of the dome due to the strong winds associated with low pressure systems
Onshore winds drive the dome of seawater towards the coastline. The increased height in sea level allows waste to surge onto the land.
What are climate change migrants?
Currently trying to migrate due to climate change
Hard engineering?
Involves building structures along the coast, usually at the base of a cliff. A wide variety of these types of defences are used across the uk
What are the 6 main types of hard engineering?
Sea walls Rip rap Revetments Off shore breakwaters Gabions Groynes
What are the five main types of soft engineering?
Beach nourishment Cliff regrading Cliff drainage Dune stabilisation Managed retreat
Groynes?
Commonly wooden walls in a beach at right angles to the coast to slow down long shore frost movement.
Advantages and disadvantages to groynes
Maintain the size of a beach
Enhance the beach for recreational amenity
Expensive
Narrower beaches further down coast- terminal groyne syndrome
Advantages and disadvantages to sea walls
Made of long lasting concrete
Can be used a promenades
Most expensive
May make beach access difficult
Rip rap?
Usually boulders that are resistant to erosion with a large surface area to break up waves
Advantages and disadvantages to rip rap
Long lasting and flexible in use
May look unsightly
Difficult to climb over creating difficulties
Revetments?
Sloped walls that are able to take the force of breaking waves thus protecting the back shore
Advantages and disadvantages to revetments
Absorb wave energy and trap sediment behind them reducing removal via backwash
Reduce access up and down beach
Wood may require constant maintenance
Offshore breakwaters?
Rock boulders to absorb wave energy and dissipate
Advantages and disadvantages to offshore breakwaters
Proved effective in protecting vulnerable areas of the coast
Very costly
Unsightly
Gabions?
Pebbles in wire which can break up waves and energy
Advantages and disadvantages to gabions
Relatively cheap
Not very strong so not suitable for high energy locations
Beach nourishment?
Replaces beach sediment that may have been eroded or transported via long shore drift
Advantages and disadvantages to beach nourishment
Natural looking
Provides amenity for recreation
Does not last long especially under winter conditions
Costly
Cliff regrading?
Lithology of cliff may be prone to collapse so engineers calculated a stable slope angle based on rock characteristics then the slop is artificially cut back to the stable angle
Advantages and disadvantages to cliff regrading
Creates a natural looking slope
Brings confidence to property owners
Expensive
Some land and property can be lost
Cliff drainage?
Drains with gravel can be inserted into a cliff to drain water out quickly to stabilise cliff
Advantages and disadvantages to cliff drainage
Looks natural once completed, engineering not visible
Reduces mass movement
Difficult to implement along the whole coastline
Only reduces mass movement- not stopped
Dune stabilisation?
Replanting grasses will help keep the dune in place
Advantages and disadvantages to dune stabilisation
Looks natural and is an effective barrier to high tide and waves
Many need to be fenced off during work which reduces amenity value
Managed retreat?
Accepted that there is little that can be done to stop high sea levels changing the coast, areas can be set aside for the sea to flood or erode ie former salt marshes
Advantages and disadvantages to managed retreat
Allows natural processes to take place un disturbed
Doesn’t prevent land from being lost
Needs agreement from property and land owners
What is an example of a type of vegetation that stabilises the coastline against erosion?
Mangroves
Hard engineering?
Involves building structures along the coast, usually at the base of a cliff
Soft engineering?
Where the natural environment is used to help reduce coastal erosion and river flooding.
What are the 6 main types of hard engineering structures?
Gabions Rip-rap Groynes Sea walls Revetments Offshore breakwaters
What are the 5 main soft engineering methods?
Beach nourishment Cliff regrading Cliff drainage Dune stabilisation Managed retreat
Gabions?
Theses are pebbles in wire which when tied together can make a wall of great surface area to absorb wave energy.
Offshore breakwaters?
Artificial offshore structure protecting a harbour, anchorage, or marina basin from water waves. Breakwaters intercept longshore currents and tend to prevent beach erosion.
Rip rap?
Absorbing and deflecting the impact of a wave before the wave reaches the defended structure. Usually boulders.
Revetments?
Wooden, steel, or concrete fence-like structures that allow sea water and sediment to pass through, but the structures absorb wave energy.
Groynes?
Creates and maintains a wide area of beach or sediment on its updrift side. It reduces erosion on the other downdrift side. It is a physical barrier to stop sediment transport in the direction of longshore drift
Sea wall?
A wall or embankment erected to prevent the sea encroaching on or eroding an area of land
What is a positive and negative of gabions?
Relatively cheap and easy to maintain
Not very strong so not suitable for high energy coastlines
What is a positive and negative of sea walls?
Made of long lasting concrete
Very expensive and doesn’t fit the natural surroundings
What is a positive and negative of groynes?
Maintains the size of the beach
Can increase erosion down drift- beaches can be starved
What is a positive and negative of rip rap?
Long lasting and flexible
May look unsightly and can contrast with the local geology
What is a positive and negative of revetments?
Traps beach sediment behind them so reduces removal via backwash or longshore drift
May require constant maintenance (wooden)
What is a positive and negative of offshore breakwaters?
Proved effective in protecting vulnerable sections of the coast
Very expensive
Beach nourishment?
Or replenishment is the artificial placement of sand on an eroded shore to maintain the amount of sand present in the foundation of the coast, and this way to compensate for natural erosion and to a greater or lesser extent protect the area against storm surge
Cliff regrading?
Where the gradient of the cliff is reduced so that damage of coastal erosion is reduced as the destructive waves with just go up the cliff and just back again.
Cliff drainage?
Steel barriers and drains put into a cliff to intercept the water movement through the cliff which causes mass movement.
Dune stabilisation?
Marram grass planted on sand dunes stabilises the dunes and helps to trap sand to build them up.
Managed retreat?
The controlled flooding of low-lying coastal areas. If an area is at high risk of erosion, managed retreat could be an option. It usually occurs where the land is of low value, for example farm land.
What is a positive and negative of beach nourishment?
Uses natural sediment so beach looks natural
Does not last long, especially in winter conditions
What is a positive and negative of cliff regrading?
Creates a natural looking slope
Very expensive and Some land and property may be lost if slope is changed
What is a positive and negative of cliff drainage?
Looks natural once completed as engineering is generally not visible
Difficult to implement along the whole coast without disturbing cohesion rock layers
What is a positive and negative of dune stabilisation?
Looks natural and is an effective barrier
Powerful storms may mean that this approach only works for a short while
What is a positive and negative of managed retreat?
Allows natural processes to take place
Does not prevent land from being lost
Amenity value?
Are the characteristics that influence and enhance people’s appreciation of a particular area. These values are derived from the pleasantness, aesthetic coherence and cultural and recreational attributes of an area.
Environmental impact assessment (EIA)?
Are carried out to find out what effects coastal management might have: > Water movement and sediment flow >Water quality >Changes to marine ecosystems >Air quality, noise pollution
What is the cause of mangrove deforestation?
They were uprooted to make way for shrimp ponds (aquaculture)
How effective are mangroves in terms of coastal protection?
They can absorb wave energy and help dissipate tsunamis dues to their dense roots and branches
How sustainable are mangroves?
They are cost effective and act as carbon sinks- prevent the global problem that causes sea levels to rise ie positive especially in the long term
How effective are mangroves in terms of protecting the population?
Areas that had mangrove forests suffered less devastation that those who had their mangroves uprooted- there were fewer casualties
What are the 2 main reasons as to why coasts flood?
Isostatic rebound
Storm surges
What 2 ways can we reduce the flooding effects?
Prediction ie when will it flood? and prevention ie stopping flood water from reaching properties
What are the 2 organisations that are involved in the prediction of flooding?
1- Storm tide forecasting service
2- MET office
What are the 2 organisations that are involved in the prevention of flooding?
1- Environment agency
2- DEFRA
What are the effects of rotational slumping?
Heavy rain is absorbed by unconsolidated material making up the cliff (often glacial till, or boulder clay). The cliff face becomes heavier and eventually it separates from the material behind at a rain-lubricated slip plane.
