Coasts Flashcards
What is the coast?
The coast is the area where land and sea meet.
What defines the shoreline?
The shoreline is the boundary of the land defined by the high water mark on a low-lying coast or the base of a steeply sloping coast.
What is the shore?
The shore is the area between the highest and lowest tide points.
How often do tides occur?
Tides are usually twice a day but vary from coast to coast and with the time of the year.
What is the tidal range?
The difference between low and high tide is known as the tidal range.
What determines the waves’ height and depth?
The tide determines the waves’ height and depth.
What affects coastal features?
The movement of waves and currents affects coastal features.
How are waves created?
Winds blowing across the sea’s surface create waves, which are marine processes that erode, move, and deposit material.
What factors determine the size of a wave?
The size of a wave depends on the speed of the wind, the fetch (distance the wind travels), and the amount of time the wind blows in the same direction.
What happens to a wave as it approaches the coast?
Friction from the seabed pushes a wave forward as it gets closer to the coast and into shallower water, where it will finally crest and crash onto the beach.
What is swash and backwash?
The movement of water up the beach is called the swash, and the return movement is the backwash.
What are destructive waves?
Destructive waves erode the beach and have a steep wave gradient, short wavelength with high height, high-frequency wave rate of 10-12 per minute, high energy, and a strong, abrasive backwash.
What are constructive waves?
Constructive waves are beach builders and have a long wavelength with low height, a low-frequency wave rate of 6-8 per minute, a shallow wave gradient, low energy, and a stronger swash.
What is the main effect of destructive waves?
Destructive waves are responsible for the majority of erosion that happens along a coast.
How do destructive waves cut into the coastline?
They cut into the coastline through hydraulic action, attrition, corrosion, and abrasion.
What is attrition?
A large, rough boulder is gradually reduced into round sand grains (quartz) the longer it remains in the ocean and the farther it travels along the shore.
What is marine transportation?
The sea transports sediment that it gets from erosion in the same way rivers do.
What are the sources of material in the sea?
Material in the sea arrives from eroded cliffs, transported by longshore drift, brought inland from offshore by constructive waves, and carried to the coastline by a river.
What are the ways material is moved in the sea?
Material is moved through traction, saltation, suspension, solution, and longshore drift (LSD).
What is longshore drift (LSD)?
Longshore drift (LSD) is the main process of transportation along the coast, where waves approach the beach at an angle due to the prevailing wind.
How does longshore drift work?
As the waves break, the swash carries material up the beach at the same angle, and the backwash carries the material down the beach at right angles (90°).
What happens if longshore drift is blocked?
If longshore drift is blocked, sediment cannot move, leading to smaller beaches and loss of natural coastal protection.
How does backwash and swash interact with sediment?
The waves carry sand or shingle as they travel; backwash carries it away, while swash carries it onto a shore.
Where is the largest material deposited during a constructive wave?
The largest material is deposited along the upper reach of the swash when a constructive wave carries sediment up the beach.
What forms a berm during a storm?
During a storm, large shingle is thrown above the usual high tide level to form a ridge at the top of the beach called a berm.
Wave Types
Long shore drift
Deposition of sediments
What are cliffs?
Cliffs are sloping or steep rocks with different profiles depending on the topography and geology.
How do geology and wave attack affect cliffs?
Geology and wave attack at the base of the cliff affect the angle of the cliff face; low-energy waves cause less damage than high-energy ones.
What is a wave-cut notch?
A wave-cut notch is a ‘knick-point’ around the high-water mark where the wave has undercut the rock.
What processes extend the wave-cut notch?
Abrasion, corrosion, and hydraulic action further extend the notch back into the cliff.
What happens when undercutting continues on a cliff?
The cliff above becomes unsupported and unstable and eventually collapses.
What is a wave-cut platform?
A wave-cut platform is left behind after the backwash of waves carries away the eroded material.
What characterizes headlands and bays?
They are found in areas of alternating bands of resistant (hard) and less resistant (soft) rocks running perpendicular to oncoming waves.
How is a bay formed?
A bay is formed when less resistant rock (e.g. clay) is eroded back.
What is a headland?
A headland projects out to sea, has cliffs along its sides, is usually longer than it is wide, and has a geology of resistant rock.
What are the characteristics of a bay?
A bay usually has a wide, open entrance from the sea, a roughly semi-circular shape, and land that is lower than the surrounding headlands.
What happens to waves as they near the shoreline?
Wave speed reduces, and the angle of the waves changes, becoming parallel to the coast, known as wave refraction.
What is the erosive effect on a headland?
The headland’s erosive effect is concentrated on all sides due to wave refraction.
How is a cave formed in a headland?
A cave is formed as a crack begins to widen due to hydraulic action, abrasion, and corrosion.
What happens to a cave over time?
The cave becomes larger and eventually breaks through the headland to form an arch.
What is a stack?
A stack is an isolated column of rock left after the roof of an arch collapses.
What is a beach?
Beaches form in sheltered places like bays due to constructive wave action.
What causes beach formation?
Beach formation typically takes place during the calmer summer months when swash is stronger than backwash.
What is a spit?
A spit is an expanse of sand or shingle that stretches from the shore out to sea.
What are the conditions for spit formation?
Spits occur when there is a change in the shape of the coastline or a river mouth stops a spit from forming across the estuary.
What is a bar?
A bar is when a spit grows across a bay and joins two headlands together.
What is a lagoon?
A lagoon is a small body of water cut off from the sea, which may form behind a bar or tombolo.
What is a tombolo?
A tombolo is formed when a spit joins the mainland to an island.
What are barrier islands?
Barrier islands form parallel to the coast and are open at one or both ends.
What are sand dunes?
Sand dunes are dynamic environments formed by strong onshore winds transporting sand.
How do sand dunes form?
Sand dunes form when sand grains are trapped and deposited against an obstacle.
What are the stages of sand dune formation?
The stages include embryo dunes, fore dunes, yellow dunes, grey dunes, and mature dunes.
What characterizes embryo dunes?
Embryo dunes are fragile, reach a maximum height of 1 metre, and are colonized by pioneer species.
What are fore dunes?
Fore dunes provide protection against wind and allow other plant species to grow.
What are yellow dunes?
Yellow dunes initially appear yellow but darken as organic material adds humus to the soil.
What are grey dunes?
Grey dunes are more stable, have less than 10% exposed sand, and support a good range of biodiversity.
What are mature dunes?
Mature dunes are the oldest and most stable, found several hundred metres from the shoreline.
Cliff and wave cut platform
Arc stack stump
Coastal landforms
Tombolo, Spit, bar
Sand dunes
How do coral reefs and atolls form?
Coral reefs and atolls form through the build-up and compression of lime-secreting polyp skeletons.
Where do living coral polyps exist in a coral reef?
Only the upper and outer parts of the coral reef contain living coral polyps.
What is necessary for corals to start growing?
For corals to start growing, there needs to be a solid surface, which could be from a shipwreck or other debris.
How do coral reefs run along the coast?
Coral reefs run parallel to the coast, with breaks where river mouths exit.
What is the geographical range of coral reefs?
Corals are found in the tropical and subtropical Western Atlantic and Indo-Pacific oceans between 30°N and 30°S.
What factors affect the distribution of coral reefs?
Four factors affect their distribution: Temperature, Light, Water depth, Salinity.
What is the optimal temperature range for coral growth?
Corals cannot tolerate water temperatures below 18°C but grow best at 22°C – 25°C.
What is the role of light for corals?
Corals need light for photosynthesis due to the algae, called zooxanthellae, that live in their tissue.
At what depth are corals generally found?
Corals are generally found at depths of less than 25 m where sunlight can penetrate.
What salinity range do corals require?
Corals need salty water to survive, ranging from 32-42% saltwater.
How does wave action benefit corals?
Wave action provides well-oxygenated, clean water which is beneficial for corals.
What happens if corals are exposed to air?
Corals cannot be exposed to air for too long or they will die.
How does sediment affect corals?
Sediment in the water blocks light and interferes with the feeding habits and photosynthesis of zooxanthellae.
What are fringing reefs?
Fringing reefs are low, narrow bands of coral running parallel to the coast and form around a land mass.
Example: Coral Coast of Fiji.
What are barrier reefs?
Barrier reefs are wide, deep lagoons below at depths at which polyps can live, separated from the coast.
Example: The Great Barrier Reef.
What are atolls?
Atolls are narrow, ring-shaped reefs consisting of a coral rim that encircles a deep lagoon.
Example: Maldives Suvadiva Atoll.
Where are salt marshes found?
Salt marshes are found all over the world and are not temperature-dependent.
What are the features of salt marshes?
Salt marshes are communities of nonwoody, salt-tolerant plants that begin as tidal mud flats.
What is succession in salt marshes?
The process of the development of vegetation over time in a salt marsh is known as succession.
What are mangrove swamps?
Mangrove swamps are ecosystems found in warm tropical waters, highly adapted to changing conditions.
What is the ideal temperature for mangroves?
Mangroves thrive in temperatures around 27° C.
What are the characteristics of mangroves?
Mangroves are trees that live on the coastline with complex root systems that trap mud and form dense thickets.
What are some opportunities that coastal areas provide?
Coastal areas offer opportunities for development including homes, shops, hotels, roads, schools, restaurants, nature reserves, swimming and sports, industry, fishing and aquaculture, tourism, agriculture, and ports and harbours.
What are coastal hazards?
Coastal hazards can be either natural or human-induced, including storms, flooding, and tsunamis.
What are the consequences of urbanisation and transport on coastal areas?
Consequences include changing land use for ports and harbours, increased traffic, and water extraction.
What are the impacts of urbanisation and transport on coastal areas?
Impacts include environmental damage, loss of species, pollution, health risks, and introduction of invasive species.
What are the consequences of agriculture on coastal areas?
Consequences include land reclamation, overuse of fertilizers and pesticides, and water abstraction.
What are the impacts of agriculture on coastal areas?
Impacts include loss of ecosystems, coastal squeeze, water pollution, and eutrophication.
What are the consequences of fisheries and aquaculture on coastal areas?
Consequences include construction of ports and harbours, fish processing, and fish farm waste.
What are the impacts of fisheries and aquaculture on coastal areas?
Impacts include overfishing, pollution, habitat damage, and changes in marine communities.
What are the consequences of industry on coastal areas?
Consequences include land use changes, natural resource extraction, and waste processing.
What are the impacts of industry on coastal areas?
Impacts include loss of habitats, water pollution, and coastal erosion.
What are the consequences of tourism and recreation on coastal areas?
Consequences include development changes, congestion, and water abstraction.
What are the impacts of tourism and recreation on coastal areas?
Impacts include loss of habitats, visual pollution, and human health risks.
What are natural coastal hazards?
Natural coastal hazards include storm surges, storm tides, tsunamis, king tides, and sea level rise.
What are tropical storms?
Tropical storms include hurricanes, typhoons, and cyclones, differing by formation location.
What are the impacts of tropical storms?
Impacts include destruction of infrastructure, loss of ecosystems, and high economic costs.
How can the risks of tropical storms be managed?
Management strategies include sea walls, evacuation plans, satellite tracking, and building resilient structures.
What happens to coastlines due to changing sea levels?
Rising sea levels create submergent coastlines, while falling levels produce emergent coastlines.
How does geology influence coastlines?
Geology shapes coastlines over time, with softer rocks eroding faster than harder rocks.
What are the characteristics of hard rock cliffs?
Hard rock cliffs are high, steep, and have bare, rugged faces.
What are the characteristics of soft rock cliffs?
Soft rock cliffs are lower, less steep, and have smoother faces with evidence of slumping.
What is coastal erosion?
Coastal erosion is the process of coastline degradation influenced by geology and wave action.
What accelerates coastal erosion?
Tourist developments and coastal constructions can accelerate erosion and damage ecosystems.
What is Integrated Coastal Zone Management (ICZM)?
ICZM aims to use a combination of methods to best reflect all stakeholders’ needs.
What are soft engineering methods?
Soft engineering works with natural processes rather than against them, is usually cheaper, and is considered a more sustainable approach to coastal protection.
What is beach replenishment?
Beach replenishment is the pumping or dumping of sand and shingle back onto a beach to replace eroded material.
Advantages include absorbing wave energy and widening the beachfront, while disadvantages include the need for regular repetition and potential impact on sediment transportation.
What is fencing, hedging, and replacing vegetation?
This method helps to stabilize sand dunes or beaches and reduces wind erosion.
Advantages include being a cheap method to protect against flooding and erosion, while disadvantages include difficulty in protecting larger areas of coastal cliffs.
What is cliff re-grading?
Cliff re-grading involves softening the angle of a cliff to reduce mass movement.
Advantages include preventing sudden loss of large cliff sections, but it does not stop erosion; it only slows it down.
What is beach re-profiling?
Beach re-profiling is the artificial re-shaping of a beach using existing beach material.
Advantages include replacing shingle after winter storms, while disadvantages may negatively affect beach habitats.
What is managed retreat?
Managed retreat involves abandoning existing coastal defenses, allowing the sea to flood inland until it reaches higher land or a new line of defenses.
Advantages include no expensive construction costs and creating new habitats, while disadvantages include disruption to people and potential high relocation costs.
What are hard engineering methods?
Hard engineering involves building concrete, wood, or rock sea defenses that work against the power of the waves.
What is a sea wall?
A sea wall is usually concrete and curved outwards to deflect the power of the waves.
Advantages include effectiveness at preventing erosion and flooding, while disadvantages include high costs and potential damage if not maintained.
What are groynes?
Groynes are wood, rock, or steel pilings built at right angles to the shore.
Advantages include effectiveness at preventing erosion and flooding, while disadvantages include starving other beaches of sand and maintenance needs.
What is rip-rap or rock armour?
Rip-rap involves large boulders piled up to protect a stretch of coast.
Advantages include being a cheaper method of construction, while disadvantages include potential erosion or dislodging during storms.
What are gabions?
Gabions are wire cages filled with stone, concrete, or sand that absorb wave energy.
Advantages include being the cheapest form of coastal defense, while disadvantages include the need for secure tying down and lower efficiency.
What are revetments?
Revetments are sloping wooden or concrete fences that break the force of the waves.
Advantages include trapping beach material, while disadvantages include ineffectiveness in stormy conditions and visual unattractiveness.
What are off-shore barriers?
Off-shore barriers are large concrete blocks, rocks, and boulders sunk offshore to alter wave direction.
Advantages include low maintenance and maintaining natural beach appearance, while disadvantages include high construction costs and potential removal in storms.
What is the purpose of early warning systems?
Early warning systems allow communities to prepare for flooding before it occurs.
What actions are included in coastal flooding prevention?
Actions include building flood defenses, establishing emergency centers, implementing early warning systems, educating locals, and planning new developments away from high-risk areas.
What are buffer zones?
Buffer zones are areas of land allowed to flood before reaching settlements, slowing down floodwater’s journey.
This may involve moving people away from the coast, which could be controversial.
What are shoreline management plans (SMPs)?
SMPs outline strategies to prevent flooding and erosion along a coastline.
What does ‘hold the line’ mean in coastal management?
‘Hold the line’ is a long-term approach involving building and maintaining coastal defenses to keep the current shoreline position.
It is the most costly approach and dominated by hard engineering.
What is ‘managed realignment’?
Managed realignment allows the coastline to move naturally, with processes monitored and directed when necessary.
It is the most natural approach to coastal defense.
What does ‘do nothing’ mean in coastal management?
‘Do nothing’ is the cheapest method where the coast is allowed to erode and retreat inland without any investment in protection.
It is also the most controversial option.
