PB Coastal Systems & Landscapes

Question 1

What are the main sources of sediment?

Answer 1

• Cliff Erosion
• Rivers
• Long-shore Drift
• Wind
• Glaciers
• Offshore (Ocean)

Question 2

What are Sediment Budgets?

Answer 2

Sediment Budgets account for the gains, losses and movement within a coastal system or sediment cell. Every sediment cell should be aiming for dynamic equilibrium.

Question 3

What is a Sediment Cell?

Answer 3

A conceptual way of describing sediment movement from a source, through various transfers to a sink or output. The movement is usually cyclical.

Question 4

What is Swash?

Answer 4

Water that washes up on the beach after an incoming wave has broken.

Question 5

What is Backwash?

Answer 5

Water that washes down the beach after an incoming wave has broken.

Question 6

What determines the type of wave?

Answer 6

The energy of the Swash and Backwash.

Question 7

How are waves formed?

Answer 7

As air moves across water, the frictional drag that takes place disturbs the surface and forms ripples or waves. These waves have circular orbits. When the water becomes shallower, friction with the seabed/beach causes the orbit to become more elliptical which results in the crest of the wave rising and steepening. As the friction increases, the orbit becomes more and more elliptical until eventually the wave breaks and the water rushes up and down the beach as swash and backwash.

Question 8

What are the different types of waves?

Answer 8

Constructive and Destructive.

Question 9

What are the characteristics of a constructive wave?

Answer 9

Formation - Distant weather systems generate these waves in the open ocean.
Wave Form - Low, surging waves (with a long wavelength).
Wave Break - Strong swash, weak backwash.
Beach gain/loss - Beach gain.
Beach Profile - Usually associated with a gentle beach profile. Although, overtime, they will build up the beach and make it steeper.

Question 10

What are the characteristics of a destructive wave?

Answer 10

Formation - Local storms are responsible.
Wave Form - High, plunging waves with a short wavelength.
Wave Break - Weak swash, strong backwash.
Beach gain/loss - Beach loss.
Beach Profile - Usually associated with a steeper beach profile. Although, overtime, they will flatten the beach.

Question 11

What are wave crests and troughs?

Answer 11

Crest - The top of a wave.

Trough - The dip in water between waves.

Question 12

What are the wavelengths and wave heights?

Answer 12

Wavelength - The distance between two wave crests.

Wave Height - The height of the wave (from the crest to trough).

Question 13

What are rip currents?

Answer 13

Most commonly formed when a series of plunging waves cause a temporary build-up of water at the top of a beach. When met with resistance from breaking waves, the backwash forces the excess water below the surface. This fast flowing surge of water can drag people into deep water.

Question 14

How many tides are there in 1 day?

Answer 14

4 - 1 every 6 hours

Question 15

How do you escape rip currents?

Answer 15

Swim/surf parallel to the beach. DO NOT swim towards the beach as the surge of water is too strong and you will be pushed out to sea.

Question 16

How do tides work?

Answer 16

During a Neap Tide, the moon is at right angles to the sun in the first or last quarter (of the moon cycle). This causes the gravitational pulls of the moon and the sun to act against each other and cause low high-tides and high low-tides. During a Spring Tide, the sun and moon are in line at full moon or new moon (of the moon cycle). This causes the gravitational pulls of the moon and the sun to act together causing higher high-tides and lower low-tides.

Question 17

What are tides?

Answer 17

Tides are changes in the water levels of seas and oceans caused by the gravitational pull of the moon and to a lesser extent the sun.

Question 18

What is the tidal range?

Answer 18

The relative difference in height between high and low tides.

Question 19

What is a high energy coastline?

Answer 19

In the UK these are:

• Stretches of the Atlantic-facing coast (west) where the waves are more powerful for much of the year.
• Where the rate of erosion exceeds the rate of deposition.
• Examples are Cornwall and North-West Scotland.

Question 20

What is a low energy coastline?

Answer 20

In the UK these are:

• Stretches of the coast where the waves are less powerful, or where the coast is sheltered from large waves.
• Where the rate of deposition exceeds the rate of erosion.
• Examples are the bays and estuaries of Lincolnshire (East England)

Question 21

What is wave refraction?

Answer 21

Wave refraction causes energy to be concentrated at headlands and dissipated in bays. Due to variations in rock strength headlands and bays are formed which causes wave refraction.

Question 22

What landforms are made due to wave refraction?

Answer 22

Cliff, arches, caves, stacks and stumps at headlands and beaches at bays.

Question 23

What is weathering?

Answer 23

Weathering is the breakdown or decay of rocks in their original place, or close to the surface.

Question 24

What are the three types of weathering?

Answer 24

Chemical, Biological and Mechanical

Question 25

How do the three types of weathering work?

Answer 25

Chemical - This type of weathering can occur due to carbonation, oxidation and solution. Carbonation is when rainwater absorbs CO₂ in the air forming a weak carbonic acid. This reacts with calcium carbonate in limestone and chalk and forms calcium bicarbonate which is easily dissolved. Oxidation is when rock minerals react with oxygen e.g. iron which forms a rusty red powder making it more vulnerable to other types of weathering. Solution is the dissolving of rock minerals.

Biological - This is the breakdown of rocks by organic activity. Thin plant roots can grow in small cracks in a cliff face which then breaks as the roots grow. Water running through decaying vegetation can become acidic which leads to increased chemical weathering. Birds and animals dig into cliffs.

Mechanical - This involves the break-up of rock without any chemical changes taking place. Frost shattering or freeze-thaw occurs when water goes into cracks and joints of rocks, freeze and then expands when melted. Salt crystallisation is when salt water evaporates leaving behind salt crystals which exert stresses on the rock. Wetting and drying is when rocks (rich in clay) expand when wet and contract when dry causing cracks to form.

Question 26

What is mass movement?

Answer 26

This is the downhill movement of material under the influence of gravity.

Question 27

What are the 7 types of mass-movement?

Answer 27

Soil creep, mudflows, landslide, rockfall, landslip or slump, runoff and solifluction.

Question 28

What is soil creep?

Answer 28

This is an extremely slow form of mass movement. Terracettes are often formed due to soil creep as the freezing and thawing of the ground causes particles to move downhill.

Question 29

What are mudflows?

Answer 29

A mudflow involves earth and mud flowing downhill, usually over unconsolidated or weak bedrock such as clay. This normally occurs after or during heavy rainfall as water gets trapped within the rock, increasing the pore water pressure and forcing rock particles apart.

Question 30

What are landslides?

Answer 30

A landslide involves a block of rock moving very rapidly downhill along a planar surface, often a bedding plane that is roughly parallel to the ground surface.

Question 31

What is rockfall?

Answer 31

Rockfall involves the sudden collapse or breaking away of individual rock fragments at a cliff face. Rockfalls are often triggered by mechanical weathering (generally freeze-thaw) or an earthquake.

Question 32

What is a landslip or slump?

Answer 32

A landslip or slump differs from a landslide in that its slide surface is curved not flat. Landslips commonly occur in weak unconsolidated clays and sands.

Question 33

What is runoff?

Answer 33

Runoff is a good illustration of the link between the water cycle and the coastal system. This can be considered a type of flow that transfers both water and sediment form one store to another. (rock face to beach).

Question 34

What is solifluction?

Answer 34

This is similar to soil creep but is specific to cold periglacial environments. In the summer the surface layers of the soil thaws out and becomes extremely saturated because it lies on top of impermeable frozen ground (permafrost). Known as the active layer, this sodden soil with its blanket of vegetation slowly moves downhill by a combination of heave and flow.

Question 35

What are the 5 types of coastal erosion processes?

Answer 35

Hydraulic action, wave quarrying, corrasion, abrasion and solution (corrosion)

Question 36

What is hydraulic action?

Answer 36

This is the sheer force of the water as it crashes against the coastline. When a wave advances air can be trapped and compressed, either in joints in the rock or between the breaking wave and the cliff. When the wave retreats the air expands weakening the joints and cracks in the cliff.

Question 37

What is wave quarrying?

Answer 37

This is the action of waves breaking against unconsolidated material such as sands and gravels. The waves scoop out the loose material similar to a digger in a quarry on land.

Question 38

What is corrasion?

Answer 38

This is when waves advance and pick up sand and pebbles from the seabed, a temporary store or sediment sink. When they break at the cliff the transported material is hurled at the cliff foot which chips away at the rock.

Question 39

What is abrasion?

Answer 39

This is when waves advance and pick up sand and pebbles from the seabed, a temporary store or sediment sink. When the waves break the transported material is dragged up and down the shoreline and acts as a sandpaper affect.

Question 40

What is solution (corrosion)?

Answer 40

This is when weak acids in seawater dissolve alkaline rock (e.g. chalk or limestone) or the alkaline cement that bonds rock particles together.

Question 41

What are coastal transportation processes?

Answer 41

Traction - The rolling of coarse sediment along the seabed that is too heavy to be picked up and carried by the sea.

Saltation - Sediment ‘bounced’ along the seabed, light enough to be picked up or dislodged but too heavy to be carried by the flow of the water.

Suspension - Smaller (lighter) sediment picked up and carried within the flow of the water.

Solution - Chemicals dissolved in the water, transported and precipitated elsewhere.

Question 42

What is long-shore drift?

Answer 42

Long-shore Drift (LSD) is when waves approach a beach at an angle due to the prevailing wind. Sediment is carried up the beach at this angle by swash. Backwash then carriers the sediment back down the back perpendicular to the shore. This process continues and results in sediment moving along the beach.

Question 43

What is coastal deposition?

Answer 43

This is when the velocity of the water (or wind) falls below a critical value to carry sediment. When the velocity is lowering larger sediment moved by traction and saltation is deposited first and the finer sediment moved by suspension and solution is carried further and then deposited.

Question 44

What is an isostatic change?

Answer 44

The rising or falling of land mass relative to the sea resulting from the release of the weight of ice after the last ice age or by the weight of sediment being deposited.

This is a long-term process.

Question 45

What is an eustatic change?

Answer 45

Variations in relative sea level resulting in changes in the amount of liquid water entering the oceans (e.g. glacial melt water at the end of an ice age).

This is a short-term process.

Question 46

What are the different erosional coastal formations? And how do they form?

Answer 46

• Headlands and bays –> formed due to the difference in rock type (H = Hard, B = Soft) which causes different rates of erosion.
• Caves, Arches, Stacks & Stumps –> formed due to wave refraction at a headland. Each represent a different stage of erosion of the headland (cave has the least erosion, stump has the most).
• Wave-cut platforms –> formed as a result of erosion at the foot of a cliff (mainly hydraulic action and corrosion) which creates a wave-cut notch. As this repeats, the weight of the cliff above the wave-cut notch increases until the point of collapse.

Question 47

What is lithology?

Answer 47

The physical characteristics of rocks.

Question 48

What examples of lithology can be found along a coastline?

Answer 48

Strata - Layers of rock

Bedding planes - Horizontal breaks in the rock

Joints - Vertical fractures in rocks

Folds - Buckles and crumples in the rock formed due to tectonic activity

Faults - Fractures in the rock caused by pressure

Dip - Angle at which the rocks lie

Question 49

What are the different depositional coastal formations? And how do they form?

Answer 49

• Swash beaches –> formed when the waves are parallel to the beach (generally in bays).
• Drift beaches –> formed as a result of LSD at beaches where the waves are at an angle.
• Bars –> formed when LSD deposits sediment across a bay. This also then forms a lagoon.
• Offshore bars –> formed when destructive waves erode the coastline and then deposit the sediment offshore.
• Tombolo’s –> formed between an island and the main land. As waves wrap around the island due to wave refraction, they hit each other, lose energy and deposit sediment forming a beach.
• Spits –> formed as a result of LSD at the end of a drift beach. As LSD transports and deposits sediment along a beach, it extends out into the ocean or a river channel, away from the coastline.
• Dunes –> formed when an obstacle traps sediment in place on a beach resulting in a build up of sediment. As plants begin to grow, the dunes stabilise and more develop further in land.

Question 50

What are the different coastal formations that formed due to sea level change?

Answer 50

Emergent:
- Raised Beaches –> This is primarily due to isostatic change where former wave-cut platforms were raised above the current sea level. However sea level change can also cause this by lowering and creating new wave-cut platforms.

Submergent:
- Rias –> Common in the south-west of England, this is when valleys in a upland areas are flooded. Tides also occur here as they are connected to seas & oceans.

• Fjord –> Generally found in Norway, Chile or New Zealand, this is when deep glacial troughs are flooded by a rise in sea level. Unlike rias, fjords are further inland so do not have tides.

Question 51

What are hard engineering coastal defences?

Answer 51

Man-made coastal defences that are used to absorb wave energy to help prevent erosion and flooding.

This consists of:

• Groynes –> Timber or rock structures built at right angles of the coast to prevent LSD by trapping sediment.
• Sea walls –> Stone or concrete walls at the foot of a cliff or top of a beach. They usually have a curved face to reflect the waves back.
• Rip Rap/Rock Armour –> Large rocks placed at the foot of a cliff or top of a beach. This breaks up the wave by allowing some water through the gaps which helps to dissipate the energy.
• Revetments –> Sloping wooden, concrete or rock structures placed at the foot of a cliff or top of a beach. The angle of this helps break the waves’ energy.
• Offshore Breakwater –> A partially submerged rock barrier, designed to break up the waves before they reach the coast.

Question 52

What are soft engineering coastal defences?

Answer 52

Coastal defences that work with natural processes to help protect coasts.

They consist of:

• Beach Nourishment –> The addition of sand or pebbles to an existing beach to make it higher or wider. The sediment used is usually dredged from the nearby sea bed.
• Cliff Regrading and Drainage –> Reducing the angle of the cliff to help stabilise it and removing water to prevent landslides and slumping.
• Dune Stabilisation –> The management of dune ecosystems to create increasingly stable dunes. This can be through the planting of pioneer species such as marram grass to bind the sediment together.
• Marsh Creation –> Allowing low-lying coastal areas to get flooded by the sea, creating a salt marsh. Salt marshes can trap sediment increasing deposition in the region.

Question 53

What are SMPs and ICZMs?

Answer 53

SMP:

• Known as Shoreline Management Plans
• This is a plan put in place for the human processes that need to occur in each sediment cell along a coastline. The 4 processes are hold the line (often using hard engineering), advance the line (often using soft engineering especially beach nourishment), a managed retreat (creating salt marshes to allow the coast to retreat to a certain point) and having no intervention.

ICZM:

• Knows as Integrated Coastal Zone Management
• This is used to develop and manage the coast by bringing together all areas affected. This ensures that specific towns/cities etc do not effect others with their management strategies.
• E.g. The implementation of groynes in one region may reduce LSD in another region along the coast leading to coastal retreat. An ICZM prevents this from occurring by implementing strategies that benefit all regions.

Question 54

Holderness Coast Case Study:

Answer 54

About:

• Located on the East coast of England near Hull
• Formed as a result of deposition from ice sheets (from Scandinavia) during the last ice age
• Two distinct materials (chalk which forms the pre-glacial coastline and clay which forms the present coastline)
• Highest rates of coastal erosion in Europe
• Average of 1m lost/year (with up to 10m in some places)
• Waves come from NE resulting in a long fetch and more destructive waves
• LSD carriers sediment south to Spurn Head (a spit formed at the mouth of the river Humber)

Problems:

• High rates of erosion which can destroy settlements and force migration
• No coastal defences meaning erosion is unlikely to slow
• At risk of storm surges (due to low pressure in the North Sea) which can lead to death (1953 - 300+ deaths due to storm surges)

Solutions:

• An SMP for this sub-cell in the 2nd UK sediment cell was set up to manage the coastal processes of erosion, transportation and deposition
• The SMP covers the whole of the Holderness Coast
• At Flamborough Head, the SMP states that natural processes should continue with no intervention
• From Sewerby to Kilnsea, the SMP states that intervention should occur to sustain Bridlington, Hornsea & Withersea as towns and seaside resorts
• At Spurn Head, the SMP states that natural processes should occur with little intervention to ensure key areas such as Spurn Point are accessible

Question 55

Odisha Coast Case Study:

Answer 55

About:

• State on the East coast of India (near Bangladesh)
• 9th largest state by area, 11th largest by population
• 480km of a relatively straight coastline (few natural inlets or harbours)
• 6 major deltas along the coastline (Subarnarekha, Budhabalanga, Baitarani, Brahmani, Mahanadi & Rushikulya)
• Wide range of coastal & marine fauna & flora (including 1435km² of mangroves)
• Chilika lake is a lagoon which is a bird sanctuary and a temporary store of water during the monsoon season.
• It is a significant sediment store by providing a source and sink to this region of the Bay of Bengal
• Cultural and archaeological sites along the coast bring tourists
• Due to large fish stocks, coastal fishing and aquaculture (e.g. shrimp farms) are the highest employers
• 46.8% accreting (growing), 36.8% eroding & 14.4% stable

Problems:

• 28% of the coastline has been lost between 1990 & 2018 (28 years)
• Severe soil erosion has created undercut cliffs, which collapse and destroy the homes above
• The water supply has become more saline which has affected agriculture due to the soil becoming more saline (pH is more alkaline affecting the growth of most crops)
• Constructing ports & harbours has prevented LSD in areas further North with hard engineering practices only create more erosion in areas further along the coast due to less deposition occurring

Solutions:

• The creation of an ICZM
• Replanting destroyed mangroves (mangroves acts as a natural sea wall)
• Building cyclone shelters (to protect the population from storm surges and flooding)