Coastal systems & landscapes Flashcards
What are the 2 landforms of coastal erosion?
Cliffs and wave cut platforms
Cliff profile features
What are the 3 factors affecting the development of cliffs and wave cut platforms?
Rock type
Wave energy
Coastal morphology
What landforms form on coastlines of emergence?
Raised beaches
Wave cut platforms
What are marine features that are left above the high tide level called?
Relict features
Why may raised beaches appear as grassy terraces?
Once above the high tide line they are subject to vegetation succession
What landforms form on coastlines of submergence?
Rias and fjords
Dalmatian coasts
How do fjords form?
Glaciers erode to create steep-sided U-shaped valleys.
Sea level rises relative to the land, flooding the glacial valleys.
Why are fjords often shallower at the mouth than further inland?
Glaciers can overdeepen their valley
What are the 2 different types of sea level change?
Isostatic
Eustatic
What is isostatic sea level change?
Changes in sea level as a result of the changing level of the land.
What is eustatic sea level change?
Changes in sea level as a result of the changing level of water in the oceans.
On what scale does isostatic sea level change occur?
Local/regional
On what scale does eustatic sea level change occur?
Global
How quickly are sea levels rising?
3.2mm per year
What is the main reason for current sea level rise?
Thermal expansion
What are the 3 causes of isostatic change?
Tectonic activity
Glaciation
Post-glacial readjustment
What are the 2 factors affecting the development of mudflats and saltmarshes?
Energy of coastlines
Tidal range
What type of energy coastline do estuarine landforms form on?
Low energy coastlines
What kind of succession is the formation of saltmarshes?
Halosere
How do mudlfats form?
- Saltwater flowing into an estuary at high tide brings large amounts of fine sediments.
- This meets the slow river which is carrying fine silts and clays.
- Flocculation occurs when the two flows meet, resulting in large clay particles sinking to the bed.
- At low tide this mud is exposed in the intertidal area with water flowing in channels between the mudflats.
How do mudflats develop into saltmarshes?
Low lying vegetation begins to grow on the mudflats.
This slows currents leading to further deposition.
Pioneer species colonise the area.
Gradual colonisation by other plants forms a dense mat of vegetation up to 15cm high.
Vegetation growth slows currents further, leading to more mud and silt accumulation.
The mudflats are submerged for an increasingly shorter period of time so become a saltmarsh.
Give an example of a pioneer species on mudflats.
Spartina
What is flocculation?
Where fine particles settle out of suspension
Why are sand beaches gently sloped?
Sand grains are small and easily compacted so little water percolates through. The majority of water moving up the beach therefore also returns through backwash which smooths and flattens the beach.
Why does shingle tend to be at the top of the beach?
It takes high energy storm waves to deposit the larger material.
What are the 2 classifications of beaches?
Swash-aligned
Drift-aligned
What type of system is the coast?
Open system as it receives inputs from outside the system and transfers outputs away from the coast and into other systems.
What are the main 3 types of coastal inputs?
- Marine
- Atmosphere
- Humans
What are flows/transfers?
The processes that link inputs, outputs & stores of a system
What’s the littoral zone?
Part of sea that is close to the shore
Landforms of coastal deposition [8]
- Beaches
- Spits
- Barrier beach/bars
- Tombolo
- Offshore bars
- Coastal vegetation
- Sand dunes
- Estuarine Mudflats and Saltmarshes
What are systems made up of?
- Inputs
- Outputs
- Stores
- Flows
- Boundaries
What are inputs?
When matter/energy is added to the system
What are outputs?
When matter or energy leaves the system
What are stores?
Where matter or energy builds up
What are flows?
When matter or energy moves from one store to another
What are boundaries?
The limits of the system
What is negative feedback?
When a change in a system causes the opposite effect, nullifying the effects
What is positive feedback?
When a change in the system causes other changes that have a similar effect
How does the global carbon system have an impact on the coastal system?
More carbon dioxide being emitted into the atmosphere -> contributes to global warming -> resulting in a global temperature rise -> sea temp rise
What factors influence wave energy?
The wind, wind speed, duration, and fetch.
Wind speed affects the size of the waves.
How can air create waves? [2]
- Created by air moving from areas of high pressure to areas of low pressure - during storms the pressure gradient = high & winds can be very strong
- Strong winds can generate powerful waves
What is a prevailing wind & what does it cause?
Where wind consistently blows from the same direction
Causes higher-energy waves than winds that change direction frequently
What is a dynamic equilibrium?
Where inputs and outputs are balanced
How are waves created?
Created by the wind blowing over the surface of the sea. The friction between the wind and surface of the sea gives the water a circular motion
What is wave height affected by? [2]
- The wind speed: higher wind speed = more powerful waves
- Fetch of the wave: longer fetch (distance wind has blown over) = more powerful waves
What happens as waves approach the shore?
- They break
- Friction with the sea bed slows the bottom of the waves & makes their motion more ellipitcal
- The crest of the wave rises up & then collapses
Define swash and backwash
Swash: Water washing up the beach
Backwash: Water washing back towards the sea
What are the two types of waves?
Constructive: low frequency, low & long with a powerful swash, depositional
Destructive: high frequency, steep & high with a weak swash & powerful backwash, erosional
What are tides?
The periodic rise and fall of the ocean surface, caused by gravitational pull of the Moon & Sun
What do tides affect?
The position at which waves break on the beach - the area of land between max high tide & minimum low tide is where most landforms are created + destroyed
What are currents?
A general flow of water in one direction- can be caused by wind or by variations in water temperature and salinity
What do currents move?
Currents move material along the coast
What are low energy coasts? [3]
- Recieve low inputs of energy in form of small, gentle waves -> can be caused by gentle winds, short fetches, gently sloping offshore zones
- Often have saltmarshes & tidal mudflats
- Rate of deposition higher than rate of erosion
What are some inputs into the coastal system? [2]
- Sediment is eroded from cliffs by waves, weathering & landslides
- Waves, tides & currents can transport sediment into the coastal zone from offshore deposits e.g. sandbanks
What are outputs within the coastal system? [4]
Ocean currents
Rip tides
Sediment transfer
Evaporation
Name 5 stores in a coastal system
Beaches Sand Dunes Spits Bars and Tombolos Headlands and Bays
Name 3 flows in a coastal system
Wind-blown sand
Mass-movement processes
Longshore drift
Weathering
Erosion - Hydraulic Action, Corrosion, Attrition, Abrasion
Transportation –Suspension, Traction, Solution, Saltation
Deposition - Gravity Settling , Flocculation
What is a sediment budget?
The difference between the amount of sediment that enters the system & amount that leaves.
- If more enters = positive & coastline builds
- If more leaves = negative & coastline retreats
What are sediment cells (littoral cells)? [3]
- Coast is divided into sediment cells, self-contained lengths of coastline for the movement of sediment
- 11 sediment cells in England
- Each cell is a closed system
What are the 4 ways waves erode the coastline?
Abrasion - bits of rock smash against cliffs
Hydraulic action - air in cracks in cliffs is compressed exerting pressure & breaking off rock pieces
Cavitation - as waves recede, compressed air expands violently, exerting pressure on rock & causing pieces to break off
Wave quarrying - the energy of a wave as it breaks against the cliff is enough to detach bits of rock
What are the 4 main processes of transportation? [4]
Solution: substances that can dissolve are carried along in the water
Suspension: fine material e.g. silt & clay is whipped up by turbulence and carried along in the water
Saltation: larger particles e.g. pebbles/gravel is forced by water along sea bed
Traction: very large particles e.g. boulders are pushed along sea bed by force of water
How does the processes of transportation carry sediment along the shore?
Via longshore drift:
Swash carried sediment up the beach parallel to prevailing wind & backwash carried sediment back down the beach at right angles to the shoreline
What are the types of coastal deposition?
- Marine deposition: when sediment carried by seawater is deposited
- Aeolian deposition: when sediment carried by wind is deposited
Why does marine & aeolian deposition occur? [3]
- When sediment load exceeds the ability of the water or wind to carry it due to:
Friction increases: if waves enter shallow water or wind reaches land
Flow becomes turbulent: if water/wind encounters an obstacle e.g. vegetation, overall speed decreases
What is sub-aerial weathering?
- The gradual break-down of rock by agents e.g. ice, salt, plant roots & acids
- Weathering weakens cliffs & makes them more vulnerable to erosion
What are the types of coastal weathering? [4]
Salt Weathering: caused by saline water entering cracks in rocks at high tide, as rocks dry they form salt crystals and expand causing pieces to fall off
Freeze-thaw Weathering: water enters joins & crevices in rocks, if temp. drops below 0, water in cracks freezes & expands causing pieces to fall off
Wetting and drying: Rocks containing clay getting wet expand and the pressure causes fragments to break off
Chemical weathering: breakdown of rock by changing its chemical composition
Give an example of chemical weathering [2]
- CO2 in the atmosphere dissolves in rainwater, forming a weak carbonic acid
- Acid reacts w/ rock that contains calcium carbonate, so the rocks are gradually dissolved.
Explain beaches as a depositional landform [4]
- Sand beaches = wide & flat, whilst shingle beaches = steep & narrow
- Formed when constructive waves deposit sediment on shore
- Ridges of sand & pebbles are found at high tide
- Groves in sand are formed by backwash
Explain sand dunes as a depositional landform [2]
- Formed when sand deposited by longshore drift -> moved up the beach by wind
- Dunes are colonised and can reach 10m, marram grass stabilises them
Explain spits as a depositional landform [3]
- Formed when coast suddenly changes direction e.g. across river mouths
- Longshore drift deposits material across river mouth -> leaves bank of sand & shingle sticking out
- Area behind spits are often sheltered & can form mudflats
Explain barrier islands as a depositional landform [3]
- Long narrow islands of sand/gravel that run parallel to the show & are detached
- Form in areas w/ good sediment supply, gentle offshore slope, powerful waves & small tidal range
- Probably formed after last ice age or were originally bars
Explain estuarine mudflats as depositional landforms [3]
- Formed in sheltered, low energy conditions e.g. behind spits/ river estuaries
- As silt and mud is deposited mudflats develop
- Halosere succession occurs e.g. spartina grows, plants trap more mud & silt
Explain offshore bars/tombolos as depositional landforms [2]
- Offshore bars are formed when a spit joins 2 headlands together (lagoon forms behind bar)
- Tombolos are bars that connect the shore to an island
When has sea level been rising since?
Since 1930
How much is global sea level rise predicted to increase by?
8 to 16mm a year by 2100 if greenhouse gas emissions remain very high
Give an example of the impact of sea level rise on a coastal area
- The low-lying island of the Maldives will be submerged if the sea level rises just 0.5m from its current level.
Give an example of a fjord and how deep?
- Sognefjorden in Norway is over 1000m deep in places (further inland due to deposition at the mouth)
Name 4 hard engineering defences [4]
- Sea wall
- Rip rap (boulders)
- Groynes
- Revetments (slanted slabs at foot of cliffs)
Name 4 soft engineering defences [4]
- Beach nourishment
- Dune regeneration
- Beach stabilization (reducing slope angle & planting vegetation)
- Land use management (e.g. wooden walkways & fenced off areas)
Why is soft engineering more sustainable than hard engineering?
Hard: Disrupts natural processes & expensive
Soft: Cheaper, integrates w/ natural environment
What are SMPs? [2]
- For each sediment cell a plan is devised for how to manage different areas
- Authorities decide wether to hold, advance, retreat the line or do nothing
What is an ICZM? [3]
- Considers all elements of coastal system (e.g. land, water, people, economy) when coming up with managment strategies
- Aims to protect the coastal zone in a relatively natural state, whilst allowing people to use it & develop it in different ways
- Different uses are considered e.g. fishing, industry, tourism on local regional & national scales
How long is the Holderness coastline?
61km
What type of sediment is most prevalent on the Holderness Coast?
Boulder clay
How much were the groynes at Hornsea?
Over £5.2 million
What was build to defend Mappleton in 1991, and how much was it?
2 Large rock groynes to trap wave material carried during longshore drift
A revetment of large granite boulders
Cost £2 million to protect B1242
Why was Easington protected
Lying 1km inland from the coast- only guaranteed protection when gas terminal is functioning (1/6 main gas terminals in UK)
How much does the Holderness erode?
Fasting eroding coastline in Europe- up to 2m/yr
How many sediment cells are there?
11 Sediment cells on the SMP
What is a holistic approach?
A long term approach, focused on the whole area.
What is terminal groyne syndrome?
Movement of sediment has been disrupted due to implementation of groynes.
What is a revetment?
Sloping concrete/wooden defence facing the 🌊
What are tetrapods?
Hard engineering structure able to ‘slot’ into rocks.
What is cliff regrading?
Reducing the angle of a cliff in order to stabilise it.
Natural challenges of Sundarbans (7)
- Coastal flooding
- Cyclones
- Tiger hostility (0-50 deaths/yr)
- ⬆️ salinity in soils
- Instability of islands -> Fragile equilibrium
- Accessibility and remoteness
- Top dying of Sundari trees
Human challenges of Sundarbans (6)
- Over-exploitation of coastal resources, mangroves deforestation
- Destructive fishing techniques- 🍤 pollution
- Lack of education- 55.25% primary educa
- 2% deforestation a yr of trees
- Conversion of wetlands to agriculture
- Resource use conflicts
What is the Sundarbans? (5)
- Coastal zone, worlds largest delta
- over 10,000km sq
- Tidal action shifts the landscape
- Mangrove forests w/ endangered species eg 🐯
- Equilibrium of natural processes = delicate
Opportunities in Sundarbans (2)
- Mangrove eco-village 150m away from forest
- Bottom up development- women 10km brick roads
Responses to challenges in Sundarbans (4)
- 1012 multi purpose cyclone shelters built in 2015
- 2011 -> NGOs provided solar panels, mass expansion
- 5 million electricity starved provided w/ power
- Bangladesh ICZM
