Coastal Environments Flashcards
1
Q
Waves
A
- Waves are marine processes. They erode, transport and deposit material.
- Waves are formed by winds blowing over the surface of the sea.
- The height and strength of a wave is dependent on 3 factors:
1. The fetch
2. The amount of time the wind blows
3. The strength of the wind - The greater the strength, time and fetch of the wind, the larger the wave
- As a wave approaches the coast and enters shallower water, friction from the sea bed causes the wave to lean forward and eventually crest and break onto the beach.
2
Q
Swash
A
The movement of water up the beach.
3
Q
Backwash
A
The return of water back down the beach to the sea.
4
Q
Destructive waves
A
Swash - Weak
Backwash - Strong
Wavelength - Short, high height
Frequency - High (10-12 per min)
Type of beach - Shingle: erosional
Break down and destroy the beach with erosion from the strong backwash.
5
Q
Constructive wave
A
**Swash **- Strong
Backwash - weak
Wavelength - Long, low height
Frequency - Low (6-8per min)
Type of beach - Sandy: depositional
They build up and contruct the beach with deposition from the strong swash.
6
Q
Erosion
A
Destructive waves erode the coastline in four ways:
1. Hydraulic action
2. Attrition
3. Corrosion
4. Abrasion
7
Q
Erosion - Hydraulic action
A
The sheer force of the waves hitting the coast.
8
Q
Erosion - Attrition
A
Material are carried by the waves and bump against each other and are worn smaller and smoother. This type of erosion doesn’t really erode the coast but forms shingles and sand.
9
Q
Erosion - Corrosion/solution
A
Sea water is slightly acidic and this gradually dissolved some types of coastal rock. eg. Limestone.
10
Q
Erosion - Abrasion
A
Waves pick up material and hurl it at the coast.
11
Q
Transportation
A
material arrives from:
* Eroded cliffs
* Longshore drift
* Constructive waves
* River discharge
12
Q
Transportation - Traction
A
where large heavy material is dragged along the sea floor.
13
Q
Transportation - Saltation
A
Where smaller material is bounced along the sea floor.
14
Q
Transportation - Suspension
A
Where fine material is held in the water.
15
Q
Transportation - Solution
A
dissolved material is carried in the water.
16
Q
Longshore Drift
A
- It is the main process of deposition and **transportation **along the coast.
- The prevailing wind pushes the waves at angle to the beach.
- As the waves break, the **swash **carries material up the beach at the same angle.
- As the swash retreats, the backwash carries the material down the beach at right angles (90°) due to gravity.
- The process repeats, transporting material along the beach in a zig-zag movement in the direction of the prevailing wind.
17
Q
Weathering
A
This is the breakdown of rock in-situ. Weathering does not involve the movement of material, making it different from erosion.
Weathering weakens cliffs and makes them more vulnerable to erosion.
18
Q
Mechanical weathering
A
- Mechanical weathering physically breaks up rock:
- eg. freeze-thaw
- Water gets into cracks and joints in the rock.
- When the water freezes it expands and the cracks open a little wider.
- Over time, pieces of rock split off the rock face, whilst big boulders are broken into smaller rocks and gravel
19
Q
Chemical weathering
A
Chemical weathering occurs when rocks are broken down by a chemical process:
* Rainwater is slightly acidic through absorbing carbon dioxide from the atmosphere.
* This reacts with minerals in the rock, creating new material.
* Rock-type affects the rate of weathering; e.g. limestone chemically weathers faster than granite.
* The warmer the temperature, the faster the chemical reaction.
20
Q
Biological weathering
A
Biological weathering takes place when rocks are worn away by living organisms:
* Trees and other plants can grow within the cracks in a rock formation.
* As the roots grow bigger, they push open cracks in the rocks, making them wider and deeper.
* Over time, the growing tree eventually forces the rock apart.
* Tiny organisms like bacteria, algae and moss can grow on rocks.
* These produce chemicals that break down the surface layer of the rock.
* Burrowing animals, such as rabbits, disturb the ground. This destabilises the rock above the burrow. Increasing pressure on any cracks. Eventually, pieces fall off the rock
21
Q
Mass movement
A
The downhill movement of material under the influence of gravity.
includes: landslides, slumping and rockfalls
22
Q
Influences of mass movement type
A
- The angle of slope (steeper is faster)
- Amount and type of vegetation
- Water
- Type and structure of rock
- Human activity
- Climate
23
Q
Types of mass movement:
A
Fall: Fragments of rock break away from the cliff face due to weathering.
Slide: Blocks of rock slide downhill.
Flow: Saturated soil and rock debris flows down a slope
Slump: Saturated soil along a curved surface
24
Q
Headland & Bay formation
A
- Found in areas of **alternating **bands of resistant (hard) and less resistant (soft) rocks running **perpendicular **to oncoming waves (discordant coastline).
- Initially, less resistant rock (e.g. clay) is eroded back, forming a bay.
*A bay is an inlet of the sea where the land curves inwards, usually with a beach. *
The more resistant rock (e.g. limestone) is left protruding out to sea as a** headland**.
25
Cove
* A cove forms where the coastline has bands of resistant and less resistant rock running parallel to the oncoming waves (concordant coastline).
* There is usually a band of resistant rock facing the oncoming waves, with a band of softer rock behind.
* Wave processes of abrasion, corrosion and hydraulic action will exploit faults in the resistant rock and erode through to the softer rock.
* Further wave action will erode the softer rock quickly, which will leave behind a circular cove with a narrow entrance to the sea.
* Wave refraction within the cove spreads out the erosion in all directions, creating the typical horseshoe shape
Lulworth Cove in Dorset, UK, is a good example of a cove
26
Cliffs
* Cliffs are shaped through erosion and weathering processes.
* Less resistant rock erodes quickly and will form sloping cliff faces.
* Steep cliffs are formed where there is harder rock facing the sea.
27
Wave-cut platform
*A wave-cut platform is a wide gently sloped surface found at the foot of a cliff:*
* As the sea attacks the base of a cliff between the high and low water mark, a wave-cut notch is formed.
* Abrasion, corrosion and hydraulic action further extend the notch back into the cliff.
* The undercutting of the cliff leads to instability and collapse of the cliff.
* The backwash of the waves, carries away the eroded material, leaving behind a wave-cut platform.
* The process repeats and the cliff continues to retreat, leading to a coastal retreat.
28
Cave, Arch, Stack and Stump
* Found on a headland due to wave action and weathering.
* weaknesses in the headland are exploited by erosional processes.
* As the **crack** begins to widen, abrasion will begin to wear away at the forming **cave**.
* The **cave** will become larger and eventually break through the headland to form an **arch.**
* The base of the arch continually becomes wider and thinner through erosion below and weathering from above.
* Eventually, the roof of the arch collapses, leaving behind an isolated column of rock called a **stack.**
* The stack is **undercut** at the base by wave action and sub-aerial weathering above until it collapses to form a **stump**.
29
Depostional landforms - Beach
* Form in sheltered areas such as** bays**.
* Deposition occurs through **constructive** wave movement, where the swash is stronger than the backwash.
* Beach formation usually occurs in the summer months when the weather is calmer.
* Sometimes sand from offshore bars can blow onto the shore by strong winds.
* Blown sand can create sand dunes at the backshore of a beach.
30
Depositional Landforms - Spit
An extended stretch of sand or shingle that extends out to sea from the shore.
Spits occur when there is a change in the shape of the coastline Or the mouth of a river, which prevents a spit from forming across the estuary.
Stages of formation:
* Sediment is transported by longshore drift
* Where the coastline changes direction, a shallow, sheltered area allows for deposition of sediment.
* Due to increased friction, more deposition occurs.
* Eventually, a spit slowly builds up to sea level and extends in length
* If the wind changes direction, then the wave pattern alters and results in a hooked end.
* The area behind the spit becomes sheltered
* Silts are deposited here to form salt marshes or mud flats.
31
Depositional landforms - Bar
* When a spit grows across a bay, and joins two headlands together.
* A bar of sand is formed (sandbar)
* Sandbars can also form offshore due to the action of breaking waves from a beach.
32
Depositional Landforms - Lagoon
A lagoon is where a small body of water is cut off from the sea.
A lagoon may form behind a bar or tombolo
Lagoons do not last forever and may fill with sediment and form new land
33
Depositional Landoforms - Tombolo
A tombolo is formed when a spit joins the mainland to an island.
34
Depositional Landforms - Barrier Island
Barrier islands form parallel to the coast.
The main difference between a bar and barrier island is that a bar joins two headlands, whereas a barrier island is open at one or both ends.
35
Influence of Geology on coastlines
* A coastline made up of softer rocks (sands, clays) will be easily eroded by destructive waves to form low, flat landscapes eg. bays & beaches.
* Coastlines of more resistant, harder rock will take longer to erode and produce rugged landscapes eg. headlands.
**Hard Rock:**
* Shape of cliff = high & steep
* Cliff face = Bare rock & rugged
* Foot of cliff = Boulders & rocks
**Soft Rock: **
* Shape of cliff = Generally lower & less steep
* Cliff face = smoother; evidence of slumping
* Foot of cliff = Few rocks; some sand/mud
36
Influence of vegetation
* The longer a coastal landform has existed, the more likely it will be colonised by vegetation.
* Vegetation adaptation is important in order to survive coastal conditions.
* The largest influence of vegetation is to assist in protecting and preserving coastal landforms such as sand dunes, salt marshes and mangroves.
37
Sea levels
Rising sea levels = submergent coastlines
Falling sea levels = emergent coastlines
38
Influence of human activity on sea levels
Human activities transform the features and landscape of a coastline:
* **Settlement** - coasts have always been a place of attraction and residence for people.
**Economic Development** - exploitation through fishing, farming, trade, tourism and energy production.
**Coastal Management** - controlling the coastline to protect human interests.
39
Distribution of coral reefs
**Coral reefs are large deposits of calcium carbonate built entirely of living organisms called coral polyps.**
* Corals are scattered throughout the tropical and subtropical Western Atlantic and Indo-Pacific oceans and The Indo-Pacific ocean region.
* The Great Barrier Reef in northern Australia is renowned for its great biodiversity and size.
40
Main features of coral reefs
**Temperature **- Grow best at 23 - 29C. This is why they grow between the Tropic of Capricorn and the Tropic of Cancer.
**Light** - They need light for photosynthesis due to the algae that live in their tissue.
**Water** - Found in depths of less than 25m. Water must be clear and clean to allow photosynthesis to occur.
**Salinity** - Need salty water to survive, 32-42% saltwater.
Other factors:
Wave action
Exposure to air
41
Types of Coral reefs
**Fringing Reefs** -reefs that form around a land mass.
**Barrier Reefs** - found parallel to the shore but are separated by a channel of water eg. The Great Barrier Reef, It is the world's largest coral reef system.
**Atolls **- horseshoe-shaped rings, consisting of a coral rim that encircles a lagoon.
42
Distribution of Mangroves
* They are very adaptive to changing conditions.
* Originate from Southeast Asia and spread across the globe
* Mainly found in warm tropical waters and coastal swamps within 30° N and S of the equator.
43
Characteristics of Mangroves
**Mangroves are trees that live on the coastline. **
* They sit in water between 0.5 to 2.5 metres high.
* They range in size
* They have numerous tangled roots that grow above ground and form dense thickets.
* They need high levels of humidity (75 - 80%) and rainfall (1500 - 3000mm per annum).
* The ideal temperature is around 27° C but are adapting to more temperate climates.
* The mangrove root system is complex, with a filtration system to keep salt out.
* Some have snorkel-like roots that stick out of the mud to help them take in air.
44
Distribution of Sand dunes
* Coastal sand dunes are found all over the world.
* They are the accumulation of sand, shaped into mounds and ridges by the wind.
* Found at the back of a beach, above the maximum reach of the tide.
Develop best when:
* Wide beach + large quantities of sand
* The prevailing wind is onshore
* There is a large tidal range to allow time for the sand to dry.
* There are suitable locations for the sand to accumulate
45
Characteristics of Sand dunes
* Sand dunes can be small ridges or large hills usually found at the back of a beach.
* They can extend backwards for many miles as well as along the beach.
* They are an important ecosystem supporting unique flora and fauna that have adapted to live within the dune system.
* Dunes are vulnerable to erosion by natural processes and human activity.
46
Formation of a sand dune
* Wind-blown sand is deposited against an obstruction - pebble or driftwood.
* As more sand particles are caught, the dunes grow in size, forming rows at right angles to the prevailing wind.
* Over time, the ridges of the dunes will be **colonized** and **fixed** by vegetation in a process called **succession**.
* The first plants (pioneer species) have to deal with:
Salinity
Lack of moisture
Wind
Temporary submergence
Rising sea levels
47
Types of sand dunes
* Embryo dunes
* Fore dunes
* Yellow dunes
* Grey dunes
* Mature dunes
48
Distribution of Salt marshes
* Salt marshes are found all over the world and are not temperature dependant.
* They are an ecosystem of the intertidal zone.
* They are typically very flat, with numerous channels running through them.
They form in:
* Coastal areas that are well sheltered (inlets and estuaries)
* Areas behind spits and artificial sea defences where tidal waters can flow gently and deposit fine sediments.
* They form in brackish water
49
Features of Salt marshes
* Salt marshes are communities of salt-tolerant plant.
* begin as tidal mud flats, gaining height as more sediment is deposited.
* ensures that the soil never dries out and remains muddy and sticky.
* Pioneer species begin to colonise
* As these plants die and add nutrients to the soil, sediment builds up. This makes the conditions more favourable and other species start to develop.
* The process of the development of vegetation, over time is known as succession.
* are good coastal defences in some areas, acting as a natural buffer against coastal erosion and flooding.
50
Mangroves - nutrient cycle
Nutrient store = Mud/sand
Biomass store = plants, animals
Litter = Plants, animals
Degrades in = water
Transfers = water
51
Sand Dunes nutrient cycle
Nutrient store = Mud/sand
Biomass store = plants, animals
Litter = Plants, animals
Degrades in = water
Transfers = Land
52
Salt marsh nutrient cycle
Nutrient store = Mud/sand
Biomass store = plants, animals
Litter = Plants, animals
Degrades in = water
Transfers = water
53
Coral Nutrient cycle
Nutrient store = Sea water, Rivers
Biomass store = Coral Polyps, Seaweed, Fish, Crustaceans, Invertebrates
Litter = Dead coral polyps, Seaweed, Fish, Crustaceans, Invertebrates
Degrades in = Sea water
Transfers = Tidal and ocean currents
54
Biotic Components of a Coral reef
* Producers - seaweed, phytoplankton, Zooxanthellae
Consumers - sea turtles
Scavengers - feed on dead decaying plants and animals, crabs, lobsters
Decomposers - bacteria, sea cucumbers
55
Abiotic features of a coral reef
* Light
* Depth: 25m
* Water temp: 23-25c
* Salinity
* Air
* Water
56
Biotic components of a Mangrove
* Mangroves are their own producers
* Primary cons= small fish, crabs
* Secondary cons= larger fish
* Tertiary cons=birds, crocodiles
* Scavengers
* Decomposers
57
Abiotic features of a mangrove
* Temp= not below 19c
* Oxygen
* Salinity
* Soil
* Wave energy
* Ocean currents
58
Biotic features of sand dunes
**Producers:** Phytoplankton,seaweeds
**Primary cons:** beetles, butterflies,flies
**Secondary cons:** frogs, spiders, snakes
**Tertiary cons:** Seagulls, hawks
**Scavengers:** Crabs, rats
**Decomposers:** flies, fungi, bacteria
59
Abiotic features of Sand dunes
**Wind:** Onshore prevailing wind is needed
**Tidal range:** needs to be large
Water: mix of fresh and saline
**Sand:** Large quantities
Beach: wide
**Obstacles: **needed for sand to accumulate behind
60
Biotic features of Salt marshes
Producers - algae, seaweed
Primary consumers - fish, insects, mussels
Secondary consumers - fish, mice, frogs
Tertiary consumers - sea eagles
Scavengers - snails, rats, crows, flies
Decomposers - fungi, bacteria, worms
61
Abiotic features of salt marshes
Waves - sheltered away from the open sea & destructive waves.
Water - brackish (mix of fresh and salty)
Tidal Range - large tidal range with occasional flooding
Mud - sediment needed to build up mud flats.
Elevation - needs variation in height to build up mud flats and stabilise marshes
62
Goods provided by coastal ecosystems
* Fish
* Shellfish
* Salt
* Animal feed
* seaweed for food, medicine
* Land for building/farming
* Construction materials eg. sand, Timber
63
Services from coastal ecosystems
* Protection from; storms, flooding
* Natural shelter
* Recreation/lesiure
* Biodiversity
* Wildlife habitats
* Natural waste treatment
64
Threats to Coral reefs
* Easily stressed by **human action** such as; pollution, industrialisation causing sea level rise, rising sea level temp > coral bleaching
* **Overfihsing **
* Fertiliser runoff
* Fishing using explosives
* **Tourism** > contact with the human body is likely to kill coral immediately.
* Removal of coral reef for stone building
* Clearance of coastal forests disturbs natural flow of water leading to coral bleaching.
65
Threats to Mangroves
* Pollution
* overfishing
* Clearance for land development
* Aquaculture
* Disturbance of habitats
* Removal of trees leads to collapse of the ecosystem
* Leaves coast open to storms, flooding
* Mangrove wood is used for timber and fuel
66
Threats to Sand dunes
* Sand mining
* Destabilisation due to grazing animals
* Tourists trampling on dunes
* driving over sand dunes
* sporting events > sand surfing
* Pollution from rubbish
* Car parks
* Development of sea side towns
* Removal of trees destroys the mature dunes and allows for dune migration
67
Threats to Salt marsh
* Industrial pollution
* sites for nuclear power sites
* clearance for development
* Noise and light pollution can affect wildlife behaviour
* Cleared for farming
* Eutrophication through heavy use of fertilisers
* Pollution from pesticides/herbicides
* Roads have divided salt marshes
* Trampling by visitors
68
Conflict between coastal stakeholders
* **Wildlife** want an unpolluted, safe, quiet environment.
* **Local residents** want jobs, clean beaches, affordable housing, schools
* **Tourists** want beaches, hotels, entertainment, holiday homes, marinas
*** Employers** want building space, offices, and factories
* **Developers** want areas by the sea for tourists—hotels, duplexes, golf courses
* **Fishermen** want harbours, unpolluted waters, easy access to sea
* **Farmers** want well-drained land, sheltered from prevailing winds
* **Government and Councils** want to build offshore wind farms and coastal defences
* **Transport companies **want good road networks, well-connected ports and terminals
69
Relationship between stakeholders and Coastal Zone issues
**Agriculture:** Fertiliser/ pesticide overuse > species and habitat loss, eutophication.
**Urbanisation/Transport:** Change of land use, waste disposal > congestion, loss of habitats
**Tourism/ Recreation:** Harbours, waste disposal > Pollution, litter and fuel spills
**Fisheries and Aquaculture:** Fish processing facilities, trawlers > overfishing, pollution from trawlers, habitat damage
**Industry:** Land use change, road networks, power stations > pollution, habitat destruction****
70
Causes of Coastal flooding
* Storm surges- caused by tropical storms
* Tsunamis - underwater earthquakes
* Sea level rise - global warming
* Higher river discharge
71
Prediction of coastal flooding
* Early warning systems allow communities to prepare before flooding occurs.
Two methods are used:
1. Past records - identify areas at high risk
2. Modern technology - GIS, satellite and computer monitoring (forecasting and tracking potential hazard events)
* Both these methods of forecasting help officials to say when and where the event will occur.
* It indicates the possible strength and scale of the flooding, and the likelihood of damage and death.
72
Prevention of coastal flooding
* Flood defences
* Emergency centres placed on higher ground
* Early warms systems
* Education
* Planning
* Designing building to cope eg. elevating buildings
73
Shoreline Management Plans
*Approach to manage a coastline from flooding and erosional risk. *
* **Hold the line** - Long term approach and most costly. Build and maintain.
* **Advance the line** - Build new defences
* **Managed realignment** - coastline is allowed to move naturally.
* **Do nothing** - coast is allowed to erode and retreat landward.
**Decisions depend on: **
* Economic value of resources protected
* Engineering solutions may not be possible
* Cultural and ecological value of land
* Community pressure
* Social value of communites
74
Hard engineering Defences
**Sea wall:** A-most effective D-expensive, restricts beach access
**Groynes:** A- slows erosion, creates wider beaches D-Makes walking difficult, stops material moving down the coast
**Rip-rap:** A-cheaper, absorbs wave energy D-boulders can be eroded
**Gabions**: A- Cheapest, cages absorb wave energy D- Not as efficient
**Revetments:** A- break the force of waves D- regular maintenance, visually unattractive
**Off-shore barriers**: A-effective at breaking wave energy, low maintenance D-expensive
75
Soft engineering
**Beach replenishment:** A-beaches absorb wave energy D-repeated regularly which is expensive.
**Fencing/hedging: **A- cheap method D- harder to protect larger areas
**Cliff regrading:** A- prevents sudden loss of cliff D- doesnt stop erosion
**Managed retreat:** A - No construction costs D- disruptive to people, cost of relocation
76
ICZM
* There are conflicting views about using a particular type of engineering for coastal defence.
* Most coastal managers aim to use a range of methods depending on the value of what is being protected.
* This method is known as Integrated Coastal Zone Management (ICZM)
ICMZ aims to use a combination of methods to best reflect all stakeholder needs
