Coastal Landscapes Flashcards

Question

Igneous rock type

Answer 1

Igneous Igneous rocks are formed from solidified lava or magma. (Lava is just magma on the surface of the Earth) Some examples are: granite, dolerite, basalt and pumice. They erode and weather very slowly, producing very slow rates of coastal recession, because: It's composed of interlocking crystals, forming hard, resistant rock. (so less recession) In addition, although they may contain cooling joints, they usually have fewer joints (e.g. granite) and weaknesses than other rock groups, slowing the rate of recession. Igneous coasts recede at less than 0.1 cm p.a. However, there are exceptions: Newly formed lava and solidified ash layers (tuff) erode easily. Newly formed volcanic islands can exhibit very rapid erosion rates of 40m p.a.

Answer 2

Metamorphic They are formed by the recrystallisation of sedimentary and igneous rocks through heat and pressure. Some examples are: slate, schist, marble, gneiss It's hard and resistant because: It has a crystalline structure However, it is less resistant than sedimentary rock because: Their crystals are often orientated in the same direction (foliation) making them weaker than the interlocking crystals of igneous rocks. Often heavily folded and faulted Metamorphic coasts often recede slowly about 0.1-0.3 cm p.a.

Answer 3

Sedimentary They are formed by the compaction and cementation of deposited material, or sediment. E.g. sandstone, limestone, shale Usually the sediment is fragments of other rock (clasts) Conglomerates Sandstones Mudstones Sometimes the sediment is a chemical precipitate. E.g. limestone Sometimes the sediment is composed of dead organic matter. Coal Chalk They are less resistant than metamorphic or igneous rocks, due to: Weak bedding planes They're clastic Often heavily jointed as a result of compaction and pressure release. Rocks like shale may have many bedding planes and fractures. However, the rate of erosion varies from slow (0.5 cm) to fast (10 cm): Carboniferous limestone 1 cm p.a. Young sandstones 10 cm p.a. This is because: Older sedimentary rock is buried deeper and is subject to more intense compaction with stronger sedimentation - so tend to be more resistant than younger sedimentary rocks.

Answer 4

Unconsolidated Sediment - sediment that has not yet been cemented to form solid rock (lithification) Drift geology is recently deposited unconsolidated sediment that usually overlies the solid geology of the bedrock. Some examples of unconsolidated sediment are: (or sand) Fluvial alluvium Glacial boulder clay Aeolian loess They are very easily eroded, resulting in very fast rates of recession The boulder clay of Holderness coast in Yorkshire retreats at 2-10 m p.a.

Answer 5

Complex cliff profiles are produced where cliffs are composed of strata of differing lithology. Less resistant strata erode and weather quickly, being cut back rapidly, wave cut notches may be formed. Resistant strata erode and weather slowly, retreating less rapidly. They may form a 'bench' feature at the cliff base. Higher up, they form overhanging sections until they collapse by mass movement. However, generally the overall rate of cliff recession is determined by the resistance of its weakest rock layer. Rocks show different levels of resistance to marine erosion in the foreshore zone. Rocks show different levels of resistance to weathering or mass movement in the foreshore and backshore zones. Complex cliff profiles can also be produced when there are alternating permeable and non-permeable strata. Permeable rocks are those that allow water to flow through them. This may be because: they're porous (e.g. chalk) these are rocks containing voids called pores, for example chalk and poorly cemented sandstones they have numerous joints (e.g. carboniferous limestone) Examples of permeable rocks are many sandstones and limestones. Permeable rocks tend to be less resistant to weathering because water percolating comes into contact with a large surface area that can be chemically weathered. e.g. Limestone weathered by carbonation converting calcium carbonate to soluble calcium bicarbonate. Feldspar in granite weathered by hydrolysis into kaolin (china clay) Impermeable rocks do not allow water to flow through them. Clays, mudstones, and most igneous and metamorphic rocks are impermeable.

Answer 6

1) A spring creating erosion Where a permeable rock overlays an impermeable stratum groundwater is unable to percolate down into the lower layer. Water accumulates in the permeable layer, producing a saturated layer where the pores are full of water. A spring will form on the cliff face at the top of the saturated layer. As the stream flows down the cliff, fluvial erosion (surface run off erosion( will attack the saturated permeable bed and lower impermeable stratum, reducing the angle of the cliff profile.

Answer 7

2) Groundwater flow removing cement Water flows through the permeable (sands) but can't flow through the impermable (clay), so flows along the interface. Groundwater flow through rock layers can weaken rock by removing the cement that binds them together. Weak, unconsolidated layers slump.

Answer 8

3) Pore water pressure leads to slumping and sliding It also produces pore water pressure: (the internal force within cliffs exerted by a mass of groundwater within permeable rocks) Pore water pressure in the saturated layer pushes rock particles apart. Reduces friction between grains in unconsolidated material Lubricates lines of weakness, e.g. joints and bedding planes. This affects their stability. 4) Saturation leads to slumping and sliding Saturation promotes mass movement through lubrication and by adding weight. Leads to slumping in unconsolidated material and sliding in consolidated strata - producing a complex cliff profile.

Answer 9

Vegetation can stabilise unconsolidated sediment and protect it from erosion. Plant roots bind sediment together, making it harder to erode. Plant stems and leaves covering the ground surface protect sediment from wave erosion and erosion form tidal or longshore currents when exposed at high tide. They also prevent sediment from wind erosion at low tide. In addition vegetation increases the rate of sediment accumulation: Plant stems and leaves interrupt the flow of wind and water, reducing their velocity and encouraging deposition. When the vegetation dies it adds its organic matter (hummus) to the soil. Unconsolidated sand, silt and clay, freshly deposited at the coast are a very harsh environment for plants. The coast is an incredibly harsh environment for plants because: They're exposed to high wind speeds at low tide. Lack of shade produces a high diurnal (daily) temperature range. They're submerged in salty water for half the day. The evaporated sea spray makes the sediment saline. Salt is highly porous and permeable, so rain water drains quickly- so plants have little fresh water. Submerged sediment has its pores saturated with salt water - there's no oxygen for plant roots to respire with. Sand lacks nutrients.

Answer 10

Pioneer Plants These are the first plants to colonise freshly deposited sediment. They modify the environment: Stabilising sediment Adding organic matter that retains moisture, contributes nutrients and provides shade. Reduce evaporation in sand. Now, slightly less hardy plants can colonise the sediment. They add more organic matter, stabilise existing sediment and trap more. Each step in plant succession is called a seral stage. The end result of plant succession is called a (climatic) climax community. Plant succession: the changing structure of a plant community over time as an area of initially bare sediment is colonised. Plant succession: the process by which a series of different plant communities occupy an area over time.

Answer 11

Xerophytic plants are specially adapted to dry conditions to colonise bare sand. Plant succession on sand is called psammosere. Psammosere: Embryo dunes form when seaweed driftwood or litter provides a barrier or shelter to trap sand. As the embryo grows, it is colonised by xerophytic pioneer plants, like sea couch grass, lyme grass, saltwort and sea rocket. the embryo dunes alter the conditions to something other plants can tolerate, allowing other plants to colonise and forms a fore dune Pioneer plants stabilise the sand allowing marram grass to colonise. Marram grass is marvellous because it: has waxy leaves to limit water loss through transpiration and resist wind-blown sand abrasion. has roots that can grow to 3m to reach down the water table and the stem can grow 1m a year to avoid burial by deposited sand. allows the dune to grow, rapidly forming a yellow dune it's called this because the surface is mainly sand, not soil As the marram grass and sedge grass dies, it adds hummus to the sand, creating soil. A grey dune develops, with plants such as gorse. grey dunes and dune slacks (see bottom) are fixed dunes examples of plants are: red fescue, heather, creeping willow The dune is now above high tide level, so rain washes salt from the soil, making it less saline. The soil now has improved nutrients and moisture retention, allowing non-xerophytic plants to colonise the dunes until a climax plant community is reached, in equilibrium with the climate and soil conditions. e.g. bramble, pine, birch

Answer 12

Halophytic plants are specially adapted to saline conditions to colonise mud. Halosere is plant succession in salty water. Estuarine areas are ideal for salt marshes because: they're sheltered from strong waves (so sediment like mud and silt can be deposited) rivers transport a supply of sediment to the river mouth, which may be added to by sediment flowing into the estuary at high tide Halosere The mixing of fresh water and sea water in the estuary causes clay particles to stick together and sink - called flocculation. Blue-green algae and gut weed colonise mud, exposed at low tide for only a few hours. The algae binds mud, adds organic matter, and traps sediment. As the sediment thickens, water depth is reduced, and the mud is covered by tide for less time. Halophytic glasswort and cord grass colonise as the next seral stage - the marsh is still low, and covered by high tide each day. An accumulation of organic matter and sediment raises the height of the marsh until it is only covered by spring tides. The higher marsh is colonised by less hardy plants sea aster sea lavender sea thrift scurvy grass Rainwater washes salt out of the high marsh's soil, allowing land plants to colonise. This continues until climax community is reached. In most of the UK, the climax community would be deciduous oak forest, or coniferous pine forest in north Scotland.

Answer 13

Waves in general A wave is created through friction between the wind and water surface, transferring energy from the wind into the water. This generates ripples, which grow into waves when the wind is sustained. A wave is the transfer of energy from one water particle to its neighbour with individual water particles moving in a circular orbit The size of the wave particle orbit decreases with depth Wave height is the vertical distance from peak to trough it's determined by the energy transferred from the wind, and the water depth Wave length is the horizontal distance from crest to crest (or trough to trough) Wave frequency is the number of waves passing a particular point over a given period of time

Answer 14

Waves are simply energy moving through water The water itself only moves up and down, not horizontally There is some orbital water particle motion within the wave, but no net forward water particle motion.

Answer 15

the strength of the wind the duration for which the wind blows water depth wave fetch this is the uninterrupted distance across water over which the wind blows, and therefore the distance waves have to grow in size.

Answer 16

When waves reaching the shore reach a wave depth of 1/2 their wavelength, the internal orbital motion of water within the wave touches the sea bed. Friction between the sea bed begins to distort the wave particle orbit from circular to elliptical, and slows down the wave. The wave has entered the offshore zone The wave depth decreases further, and the wave velocity slows, wavelength shortens, and wave height increases. Waves 'bunch' together. The wave crest begins to move forwards much faster than the wave trough Eventually the wave crest outruns the trough and the wave topples forwards - breaking. The wave breaks in the nearshore zone, and water flows up the beach as swash The wave then losses energy and gravity pulls the water back down the beach as backwash

Answer 17

Low energy waves Low, flat wave height (<1m) Long wavelength (up to 100 m) Low wave frequency (about 6-9 per minute) This means their swash is unimpeded by previous backwash A strong swash that pushes sediment up the beach, but a weaker backwash is unable to transport all particles back down, so they are deposited it as a ridge of sediment (berm) at the top of the beach A backwash that percolates into the beach material encouraged by a long, shallow nearshore, so friction slows down the wave and releases energy Constructive (spilling or surging) waves have a stronger swash than backwash due to a low

Answer 18

High energy waves Large wave height (>1 m) Short wavelength (about 20 m) High wave frequency (13-15 per minute) They're encouraged by a short, steep nearshore zone, quickly dropping away into deeper water, so that there is little energy loss through friction They have strong backwash and weak swash due to the steep angle of impact this directs most energy downwards and backwards, so the particle orbit is more circular than constructive breakers(?) Strong backwash erodes material from the top of the beach, carrying down the beach to the offshore zone it's often deposited as a offshore ridge or berm

Answer 19

Beach morphology is the shape of the beach. A beach sediment profile is the pattern of distribution of different sized or shaped deposited material. Constructive waves alter beach morphology by causing net movement of sediment up the beach, steeping the beach profile. They produce berms at the point where the swash reaches the high tide line. (A berm is a ridge of material across the beach) Swash carries sediment of all sizes up the beach, but weaker backwash can only transport smaller particles down the beach. This leads to a sorting of material in the foreshore zone, with larger, heavier shingle (pebble-sized sediment) at the back of the beach, and sand drawn back closer to the sea. Since the backwash flows down the beach and loses energy through friction and depletion of water through percolation, sediment is further sorted as coarser sands are deposited in the middle of the beach and only fine sands are carried to the area of beach closest to the sea.

Answer 20

Decadal Variation Climate change is expected to produce more extreme weather events in the UK. Winter profiles may be present for longer time over course of year More frequent and more powerful destructive waves may reduce beach size, allowing high tides to reach further inland and increasing rate of coastal erosion in what was backshore zone.

Answer 21

Destructive, high-energy waves dominate in the winter, lowering angle of beach profile and spreading shingle over the whole beach. Offshore ridges/bars formed by destructive wave erosion and subsequent deposition of sand and shingle offshore. In summer, constructive, low-energy waves dominate, steepening beach angle and sorting particles by size, with larger shingle particles towards back of beach. In summer, constructive waves build berm ridges, typically of gravel/shingle at high tide mark Low channels and runnels between berms

Answer 22

Monthly Variation Tide height varies over course of lunar month, with highest high tide occurring twice a month at spring tide and two very low high tides (neap tides) As month progresses from spring down to neap tide, successively lower high tides may produce a series of berms at lower and lower points down the beach. Once neap tide passes and move towards next spring tide, berms successively destroyed as material pushed further up beach by rising swash reach.

Answer 23

Daily Variation Storm events during summer will produce destructive waves that reshape beach profile in a few hours. Calm anticyclonic conditions in winter can produce constructive waves that begin to rebuild beach, steepening profile for few days before storm. Destructive waves change to constructive ones as the wind drops. Storm beaches, high at the back of the beach, result from high energy deposition of very coarse sediment during the most severe storms

Answer 24

Sea waves and swell waves Sea waves are produced by winds currently blowing in the local area, and vary in height and direction When the wind drops, wave energy continues to be transferred across the ocean in the form of swell waves As swell waves travel away from their origin they may absorb smaller sea waves and gain energy and height They can travel long distances before they lose energy and dissipate They produce waves at the coast even when there is no wind Swell waves can form periodically larger waves amongst smaller, local sea waves at the coast

Answer 25

There are four wave erosion processes: Hydraulic action Corrosion Abrasion Attrition How these are influences by wave type, size and lithology They are most effective during high energy storm events with large destructive waves. However, even coastlines composed of soft, unconsolidated sediment (e.g. boulder clay of Holderness Coast in Yorkshire), experience little erosion under normal conditions. Most erosion (in the UK) occurs in the winter, in high energy storms. It's faster when the wind is blowing directly onshore It's faster when the tide is high (bringing deeper water closer to the cliff so less energy is lost to friction before impact) The effect of erosion The boulder clay of the Holderness coast has retreated by 120 m in the last 100 years. The granite of Land's End in Cornwall has retreated by only 10 cm in the last 100 years.

Answer 26

Hydraulic Action Where the force of water itself breaks up rock It can occur through: the direct impact of the water itself Plunging destructive waves can exert a force of 50 kg / cm^3 This is sufficient to break off material from unconsolidated material, e.g. boulder clay, or weak rocks like clay and shale. the force of the breaking wave compressing air into cracks in rocks when the wave energy is exhausted, the compressed air explodes outwards, causing micro-fractures in rock and expanding the main crack. over time, small fragments of rock become weakened and break away or, the main crack can extend until larger slabs of rock fall The pressure forces the crack open, meaning more air is trapped and greater force is experienced in the next cycle of compression. It dislodges blocks of rock from the cliff face. In hard, resistant igneous rocks, hydraulic action attacking its cooling joints may be the only effective wave erosion process. High energy waves with a large wave height are the most effective at erosion through hydraulic action. It is also accentuated when there is no debris at the cliff foot to absorb some of the wave energy and protect the cliff base.

Answer 27

Abrasion (a.k.a corrasion) Abrasion is where a wave picks up sediment and throws these load items against a rock. The repeated impact chips away at the rock face until small fragments break away. Most effective: High-energy destructive waves with a large wave height hurl load items with greater force, resulting in faster rates of erosion by abrasion. They need a supply of hard load items close to the foot, e.g. shingle from the beach. Rocks eroded most quickly by abrasion: Soft sedimentary rock such as chalk, mudstones, and clays, and unconsolidated material, e.g. boulder clay.

Answer 28

Corrosion Corrosion is where water in waves dissolves rock minerals. Minerals are immediately carried away by the wave in solution. They are also vulnerable to erosion by rainwater and sea spray. Most effective waves: Constructive waves, as the force of impact is not relevant, and the spilling wave increases the time for the chemical reaction to occur. They are slow, and with a long wavelength (longer the better) it prolongs the contact of rock with the water. Rocks eroded most quickly by corrosion: carbonate rocks like limestones (e.g. chalk, Jurassic limestone and carboniferous limestone) and sedimentary rocks with calcite sediment/cement.

Answer 29

Attrition is where material transported by a wave is eroded through collision with other load items. It breaks down sediment into smaller sized particles, and the repeated collision blunts any of the particles' sharp edges, making the sediment increasingly rounded. Even harder rocks, such as quartz and granite form larger rounded shingle pebbles. It occurs in the foreshore and nearshore zones, where sediment is moved by swash and backwash. Rocks eroded most quickly by attrition: soft rocks (e.g. poorly cemented sandstones, chalk and clay) are broken down quickly by attrition into silt and sand grains.

Answer 30

Wave cut notches and platforms (e.g. Kimmeridge Bay) A wave cut notch is a curved indentation of about 1-2 m high extending along the base of a cliff. It forms between the high tide and low tide marks, where destructive waves impact against the cliff. It's eroded by hydraulic action and abrasion, and in some cases corrosion. The depth of the notch varies depending upon the resistance of the rock at different points. A wave cut platform is a flat rock surface exposed at low tide, extending out to sea from the base of a cliff. Their formation: Marine erosion between the high tide and low tide mark by abrasion and hydraulic action forms a wave-cut notch along the length of the cliff base. The notch deepens by further erosion until the overlying material collapses by mass movement due to gravity, forming a cliff. The process repeats, and the position of the cliff retreats (coastal recession) The rock just below low tide level is always submerged, it's uneroded as it's never exposed to wave impact. As the overlying material is eroded, uneroded rock at low tide level is left as flat rock surface, the wave cut platform. Other stuff about wave-cut platforms: They often slope seaward at 4 degrees. Weathering attacking weaknesses in the platform surface may produce indentations, creating rock pools at low tide. Platforms rarely extend for more than a few hundred metres. This is because the shallow water causes the wave to begin to break as soon as it reaches the platform

Answer 31

Cliffs Cliffs are steep slopes that are usually unvegetated. Marine erosion of land between the high tide and low tide mark by hydraulic action and abrasion forms a wave cut notch The notch deepens until the overlying rock collapses by mass movement due to the force of gravity. The exposed face forms a cliff.

Answer 32

Cave-arch-stack-stump sequence Rocks have joints, faults or vertically dipping bedding planes in their geological structure. These are eroded more rapidly (e.g. hydraulic action), and the deepening and widening of a weak point forms a sea cave. This is accentuated by how wave refraction concentrates energy on the sides of the headland, producing destructive waves with a very large wave height. Where a line of weakness extends right through the headland caves form on both sides. Marine erosion deepens the caves until they connect up, creating a complete tunnel through the headland and forming an arch. Hydraulic action and abrasion attack the sides of the arch between low tide and high tide, forming wave cut notches. The undercutting of the sides leads to the collapse of some overlying material by mass movement, widening the arch. Weathering and other sub-aerial processes attack the arch roof. Eventually, the roof of the arch will collapse by blockfall leaving the seaward end of the headland detached from the land as a tall vertical column called a stack. Marine erosion at the base of the stack will form a notch on all sides until the stack collapses by blockfall. Remnants of the stack base form a stump, a small projection of rock, exposed only at low tide. However, unconsolidated and soft sedimentary or metamorphic rock won't undergo this because it isn't competent enough. (e.g. boulder clay, clay, shale)

Answer 33

The cliff slope angle depends upon the dip of the rock strata. Horizontal, vertical or landward dip produces steep cliffs. Seaward dip produces a shallower slope angle - which can also be produced when the lithology is unconsolidated On a wide platform wave will have broken and swash lost energy before it reaches the cliff, halting recession.

Answer 34

Traction Where large, heavy load items are rolled along the sea bed, e.g. boulders, cobbles and pebbles Saltation Where lighter sediment bounces along Sand particles are usually transported this way Sand can be saltated by wind as well as waves On a dry, windy day, there can be a layer of saltating sand 2-10 cm above the beach Suspension Where very light sediment is carried aloft within a body of water or air E.g. silt or clay particles Suspended clay particles, give the sea a cloudy, muddy brown colour on soft-rock coasts, e.g. Holderness Solution Where sediment is carried dissolved within the water

Answer 35

Direction (angle) of wave attack This is the main determinant of the direction of sediment transport (in the foreshore zone). Where the wind is blowing directly onshore, the incoming swash transports the material direction up the beach at 90' to the coastline. Backwash then transports sediment perpendicularly back down to the beach to its original starting position. Sediment is moved up and down the beach, but there is no net lateral movement.

Answer 36

Longshore drift This is the net lateral transport of material along the coastline when waves approach the coast at an angle. Incoming swash transports sediment up the beach at an angle (movement contains an up-beach component and a lateral component) Gravitational backwash then transports sediment back down the beach at 90' to the coastline. A sediment particle comes to rest some distance along the beach from the original starting point due to net lateral movement. Particle moves in a zig-zag fashion along the beach with each incoming wave. A wave angle 30' to the coastline produces the strongest longshore drift movement. On most coastlines there is a dominant prevailing wind, so over time there is a dominant direction of longshore drift.

Answer 37

Current This is the flow of water in a particular direction, and they can transport sediment in the nearshore and offshore zones. They can be driven by winds, or initiated by differences in water density, temperature or salinity. Currents transport sediment over a variety of spatial and temporal scales: The global thermohaline circulation connects four oceans and takes 500 years for one complete circuit. Rip currents on the beach transport sediment a few metres out to sea for a few hours when the wind is blowing direcly onshore with the right strength.

Answer 38

Tides Tides are changes in sea level produced by the gravitational pull of the moon and the Sun. The incoming and ebbing tide can create tidal currents in the nearshore and offshore zones that transport sediment

Answer 39

Deposition Deposition occurs when waves no longer have sufficient energy to continue to transport material This loss of energy might be due to: the wind dropping, removing an energy source resistance by obstruction, e.g. a groyne or headland dissipation of energy through refraction friction from extended transport across shallow angled nearshore and foreshore zone Sediment transported down river systems to the coast or from offshore sources is also important. Sediment is deposited when the force transporting the sediment drops. Deposition occurs in two main ways: Gravity settling occurs when the energy of transporting water becomes too low to move sediment. Large sediment will be deposited first, followed by smaller sediment (pebbles -> sand -> silt) Flocculuation is a depositional process that is important for very small particles, such as clay, which are so small that they will remain suspended in water. Clay particles clump together through electrical or chemical attration, and become large enough to sink.

Answer 40

Bayhead beach Bayhead beaches are curved beaches found at the back of a bay. They’re common on swash-aligned coastlines where wave refraction disperses wave energy around the bay perimeter. Waves break at 90' to the shoreline and move sediment into a bay, where a beach forms. Through wave refraction, erosion is concentrated at headlands and the bay is an area of deposition.

Answer 41

Spits Spits are linear ridges of sand or shingle beach stretching into the sea beyond a turn in the coastline (usually greater than 30') but connected to the land at one end They form on drift-aligned coastlines, where the coastline changes direction, usually by more than 30', e.g. at a bay or a river mouth At the turn, longshore drift continues in the original direction, but its energy is dispersed, lost as the wave refracts and the current spreads, leading to deposition on the sea bed. Over time, sufficient sediment is deposited to break the surface, extending the beach into the sea as a spit The process continues until equilibrium is reached at the distal end (seaward end) of the spit, between deposition and erosion by waves or the existing river current. The length of the spit is determined by the existence of secondary currents causing erosion, either the flow of a river or wave action which limits its length.

Answer 42

Hooked/Recurved spits A spit whose end is curved landwards, into a bay or inlet. A hook or a recurve may form at the end of the spit. This is because wave refraction round the distal end transports and deposits sediment for a short distance in the landward direction. Alternatively, it could be because the wind and wave front are frequently at an opposing angle to the prevailing wind, generating short periods of longshore drift in the landward direction. (These last two can make it more pronounced) Or, a strong incoming tidal current can also create a recurved spit.

Answer 43

Double spits Double spits are where two spits extend out in opposite directions from both sides of the bay, towards the middle. They form where longshore drift is operating in different directions on opposite sides of the bay. E.g. in Poole Harbour the main longshore drift direction is SW-NE driven round Studland Bay by the prevailing wind, producing a spit from the south. However, wave refraction around Durlston Head produces wave fronts from NE-SW along the coastline towards the north spit of Poole Harbour, generating a spit from the north. 2. They can also form when rising sea levels drive ridges of material onshore from the offshore zone. 3. Or, a barrier beach driven across a bay forms a bar (e.g. Haff coastlines) but a strong exiting river current may breach the bar to form a double spit.

Answer 44

Offshore bars (a.k.a. breakpoint bars) Offshore bars are ridges of sand or shingle running parallel to the coast in an offshore zone. They form from sediment eroded by destructive waves and carried seawards by backwash. The sediment is deposited at the boundary of the offshore and nearshore zone, where the orbit of water particles ceases to reach the seabed, halting the transport offshore. They are also called breakpoint bars because the offshore/nearshore boundary is where waves first begin to break. They can sometimes be exposed by neap tide. They are used: to construct wind farms e.g. Scroby Sands in Norfolk as a source of sand for beach nourishment for shingle dredging for construction material

Answer 45

Bars and Barrier Beaches (they're the same thing) Bars are linear ridges of sand/shingle extending across a bay and are connected to land on both sides. It traps a body of seawater behind it, forming a lagoon. They can form in two ways: On drift-aligned coastlines, when longshore drift extends a spit across the entire width of the bay. When rising sea levels cause constructive waves to drive a ridge of sediment onshore to coastlines with a gently sloping shallow sea bed. (barrier beach) E.g. there's a 9 km barrier beach that extends across Start Bay in Devon, slapping Slapton Ley lagoon behind it Another definition of a barrier beach is a ridge of material emerging just offshore to form a chain of beaches parallel to the coast (barrier islands). E.g. the Freisian islands off the North Sea coast of the Netherlands and Germany

Answer 46

Tombolos Tomobolos are linear ridges (or bar) of sand and shingle connecting an offshore island to the coastline of the mainland. Two ways they can form are: On drift aligned coastlines, when longshore drift builds a spit out from land until it contacts with an offshore island. On swash aligned coasts when there is wave refraction around both sides of the island. This causes a collision of wave fronts on the landward side, cancelling each other out and producing a zone of still, calm water where deposition occurs, between the island and the coast. Oppositional longshore currents may play a role, in which case the depositional feature is similar to a spit. E.g. St Ninian's tombolo on the Shetland Islands The tombolo connecting Portland Bill to the mainland in Dorset.

Answer 47

Cuspate Forelands Cuspate forelands are low lying triangular shaped headlands, extending our from a shoreline, formed from deposited sediment. Formation (there is debate about this): When longshore drift currents from opposing directions converge at the boundary of two sediment cells. The sediment is deposited out into the sea by both currents creating a triangular shaped area of deposited material. They can extend from a few metres to several kilometres. An example is at Dungeness in Kent. It extends for 11 km in a south-easterly direction where the main west-east longshore drift meets north-south longshore drift currents produced by swell waves travelling down the North Sea into the English Channel. Dungeness foreland is thought to have been two spits converging at distal ends with a lagoon between that infilled through salt marsh succession, wind deposition and storm beach material being thrown up during storms.

Answer 48

Plant Succession (I don't know why this is here, there's already a section on it...) Depositional landforms are unstable because: They are made of unconsolidated material They are dynamic as they loose material transported by waves, tides, currents and wind. They are stabilised by plant succession, which binds the loose sediment together and encourages further deposition. Plant succession on sand dunes is psammosere. Plant succession on salt marsh is halosere. Plants can stabilise unconsolidated material because: Plant roots hold sediment together Their leaves/stems slow water and wind flow reducing erosion and encouraging further deposition Land is built up through the addition of organic matter and increased deposition. In shallow water, deposition occurs further out and land extends as an outbuilding coastline.

Answer 49

Example: Flanborough head - source region Holderness coast - transfer zone Spurn head - sink region The coastline of England and Wales is divided into 11 primary sediment cells, with sub-cells within each primary cell. The boundaries are formed by major headlands or large estuaries. A sediment cell operates as a closed system, with virtually no inputs or outputs of sediment from the cell. This system contains inputs, transfers and outputs. Inputs Sources are places where sediment is generated, such as cliffs or eroding sand dunes. Some sources are offshore bars and river systems and these are an important source of sediment for the coast. Some examples of sediment inputs are: Cliff erosion, Onshore currents River transport Wind blown (aeolian) sediment from land Subaerial processes Marine organisms

Answer 50

transfers inputs outputs

Answer 51

Transfers Places where sediment is moving alongshore through longshore drift and offshore currents. (Drift-aligned) beaches and parts of dunes and salt marshes perform this function. Some examples of sediment transfers are: Longshore drift Swash Backwash Tidal currents Sea/ocean currents Wind (onshore, offshore or along shore)

Answer 52

Outputs Sinks are locations where the dominant process is deposition and depositional landforms are created, including spits and offshore bars. Some examples of sinks are: Backshore depositional landforms E.g. sand dunes Foreshore depositional landforms E.g. beaches Nearshore depositional landforms E.g. bars Offshore depositional landforms E.g. barrier islands

Answer 53

Sediment cells are dynamic because the sediment is constantly generated in the source region, transported through the transfer region and deposited in the sink region. Dynamic equilibrium (in this instance) is reached when inputs of sediment from the source region are balanced by the amount being deposited in sinks. It's dynamic because although it's in balance, there's a constant movement of sediment through the system. (Think of a classroom during the school day - always full of (roughly) the same amount of people, but the people in it change) With a dynamic equilibrium, the size of the landforms in the transfer zone will remain the same. (But not the ones in the source and sink regions) They may operate as complete circulations: Sediment is eroded from the depositional sink landforms and is carried offshore, being being re-transported onshore by currents and wind action that act at the source region. However, the dynamic equilibrium is itself dynamic because its constantly changing as energy and sediment inputs constantly alter. The amount of stuff moving through is changing. E.g. climate change creating more frequent storms or erosion of the cliff line to a more resistant rock type. The system's equilibrium may be interrupted (e.g. during a storm event) but they tend to return to balance on average over time due to negative feedback. Seasonal change (e.g. storms and strong winds during winter) will change the dynamic equilibrium. Coastal management in the source region may reduce sediment supply, e.g. sea walls preventing cliff erosion. Management in transport region may reduce or halt sediment supply to sink region, e.g. groynes trapping sediment to encourage beach outbuilding.

Answer 54

Negative feedback: when the change produced creates effects that operate to reduce or work against the original change. E.g. when erosion leads to blockfall mass movement. The collapsed debris acts as a barrier protecting the cliff base, slowing or preventing erosion for a period of time. E.g. major erosion of sand dunes could lead to excessive deposition offshore, creating an offshore bar that reduces energy, allowing the dunes time to recover. Positive feedback: when the changed produces an effect that operates to increase the original change. E.g. When wind erosion of a dune section during high velocity storms may removing stabilising vegetation. Further wind erosion now occurs in later low velocity wind conditions, increasing the depletion of dune sand. A source region may be an eroding coastline. A sink region may be an outbuilding coastline.

Answer 55

Weathering is the breakdown of rock in situ at or near the surface of the Earth. Weathering and mass movement are subaerial processes. Weathering attacks the backshore and foreshore parts of the littoral zone. Weathering creates rock fragments that form sediment. It's most active in the source zone of the sediment cell. Physical (mechanical) weathering Mechanical weathering is the application of force to physically fragment rock into smaller pieces called clasts. It breaks down rocks by the exertion of a physical force, and does not involve any chemical change. Some examples of it are: Freeze-thaw weathering Water seeps into cracks in rocks When the water freezes, it expands in volume by 9%, exerting a tensional force that widens the rock Thawing allows more water to enter the crack, and the process repeats until cracks are forced open large, angular pebble, cobble, or boulder-sized fragments are loosened off. With porous rocks, water in the pores may freeze, prising off individual rock grains and producing sand sized fragments. Any rocks with cracks and fissures are vulnerable to it, especially high on cliffs away from sea spray. Freezing is relatively uncommon on UK coasts. Salt Crystal Growth This is common at coasts because the sea is salty. The breaking force is less than that of freeze-thaw weathering Porous and fractured rocks (e.g. sandstone) are vulnerable to it. The effect is greater in hot and dry climates, promoting the evaporation and precipitation of salt crystalls. It attacks the foreshore zone and backshore zone that's reached by destructive wave spray. Seawater penetrates small cracks or pores in rock at high tide, and evaporates at low tide, leaving precipitated salt crystals. Repeated tidal cycles lead to growth of salt crystals until they begin to press against the sides of cracks or pores, exerting tensional pressure. Eventually angular fragments of rock are broken off or there is granular disintegration (where individual grains break away) Wetting and Drying Rocks containing clay minerals, such as clays and shales At high tide minerals on the rock surface are soaked with sea water and expand in volume. At low tide, minerals dry and shrink. Repeated cycles of expansion and contraction eventually cause the rock to fragment and crumble. Chemical Weathering Where chemical reactions attack individual minerals in the rock, breaking bonds and producing new chemical compounds. Three examples are: Carbonation This attacks calcium carbonate in limestones, other carbonate rocks and sedimentary rocks with calcite sediment. Rainwater mixed with carbon dioxide from the air to form weak carbonic acid (pH 5.6). The acidic rain mixes with calcium carbonate to form soluble calcium bicarbonate solution. 'Rock disappears' as new minerals dissolve into the solution. Only sediment left from limestone is clay particles that had formed impurities in the original rock. Where calcite sediment is weathered, previously cemented clasts are released to form sediment. Hydrolysis The breakdown of minerals to form new clay minerals, plus materials in solution, due to the effect of water and dissolved carbon dioxide. Rocks vulnerable to it are: igneous and metamorphic rocks containing feldspar and other silicate minerals This attacks the feldspar (pinky) minerals in granite H+ ions in water attack the feldspar minerals forming kaolin clay cement Bonds between feldspar and quartz minerals broken, releasing quartz grains as sand sediment. Oxidation The addition of oxygen to minerals, especially iron compounds, which produces iron oxides and increases volume, contributing to mechanical breakdown. This attacks iron minerals in haematite cements, e.g. Devonian sandstone Wetting of haematite cement with seawater leads to a loss of an electron by iron, converting iron (II) oxide to red-coloured iron (III) oxide Change in iron compound breaks cement bonds releasing previously cemented clasts as sediment Rocks that are vulnerable to it are: sandstones, siltstones and shales that often contain iron compounds which can be oxidised It's much more effective in seawater or water with impurities than in pure water. Biological weathering Biological weathering is the break down of rock in situ by living or once-living organisms. It often speeds up mechanical or chemical weathering through the actions of plants, bacteria or animals. Examples are: Tree root weathing seeds falling into cracks in rocks can germinate, nourished by rainwater and nutrients from wind-blown sediment. as the plant grows its roots expand and thicken tree roots exert sufficient tensional force to widen the crack eventually angular fragments of rock break away as cobble or boulder-sized sediment it occurs in the backshore zone, away from the reach of the spray from destructive waves it's an important process on vegetated cliff tops which can contribute to rock falls 2. Rock boring (there are many species of clams and mollusc that bore into rock, and may also secrete chemicals that dissolve rocks. Piddocks live in the foreshore zone piddocks drill depressions into sock rocks by rotating their shell equipped with sharp edges. piddocks live in these circular depressions, filter feeding whilst protected from high-energy waves they attack soft rock, like clays and shales. Vulnerable rocks are sedimentary rocks, especially carbonate rocks (limestones) located in the foreshore/inter-tidal zone 3. Seaweed acid Kelp contains pockets of sulphuric acid when the cells break sulphuric acid attacks rock minerals like calcium carbonate leading to a chemical reaction similar to carbonation.

Answer 56

Mass movement (blockfall, rotational slumping, landslides) is important on some coasts with weak and/or complex geology. Mass movement is the downslope movement of material (rock and soil) under the force of gravity. It is the umbrella term for a wide range of specific movements including landslide, rotational slumping and blockfall. It occurs when the downslope gravitational force exceeds the resisting forces of friction and internal rock cohesion. The type of mass movement depends upon lithology: unconsolidated material (like boulder clay) - slumping consolidated rock (like carboniferous limestone and granite) - sliding Blockfall (or rockfall) This occurs on slopes >40', where a rock fragment breaks away and either drops vertically (so it isn't in contact with the cliff) or bounces downslope. It's initiated: By mechanical weathering freeze-thaw salt crystal growth which break the cohesive bonds in the rock By marine erosion Hydraulic action Abrasion Undercutting cliff by creating a wave-cut notch Notch removed supporting material that supplied the resistive force holding up the rock Cliffs prone to blockfall have: a geological structure with many joints, faults or bedding planes steep, near vertical dip of strata they're often also in an earthquake-prone area Blockfall is very rapid, taking only a few seconds to occur. They may involve the detachment of single fragments or of a whole section of cliff that breaks up as it descends (which occurs by the undercutting of a wave-cut notch). In April 2013, there was a large blockfall in St Oswald's Bay on the South Dorset Coast where an 80 m section of chalk cliff was detached overnight. Rotational Slumping Rotational slumping involves rock failure and movement along a curved rock plane. The slumping material usually moves intact as a single mass, without any internal deformation of material. It's slower than blockfall, often occurring in 'slow motion', and may take minutes, hours, days, or even years (for huge masses) to occur. Rotational slumping occurs in: weak rocks, e.g. clays and shales unconsolidated material, e.g. boulder clay, sands, gravels in rocks with complex geology, e.g. where permeable rock strata overlie impermeable beds Slumping is facilitated by the presence of water, which adds weight (increasing the gravitational force) as well as lubricating it, reducing friction. An example of rotational slumping is at Christchurch Bay, in Barton-on-Sea, near Lymington in Hampshire, where unconsolidated sands overlie clay. The bedding plane between sand and clay dips seawards. In dry weather, soil above sand cracks, funnelling water into permeable sand. Increased pore water pressure along lines of percolation form lines of weakness in the sand. Water accumulates in the lower sand as it is unable to to percolate into the impermeable clay. Pore water pressure lubricating the bedding plane encourages the movement of sand. The weight of the water adds to the downslope gravitational force, while wave erosion created a notch at the cliff foot, removing support. Eventually slumping occurs. Landslides A landslide is the downslope movement of discrete blocks of rock down a flat/linear slip plane, maintaining contact with the cliff surface throughout. The discrete blocks are released by mechanical weathering of well jointed rocks, (e.g. carboniferous limestone). Gravity then pulls the loosened block down the relatively flat slip plane of the joint or bedding plane, to the cliff foot. Landslides can also be caused by marine erosion of a cliff foot undercutting blocks weakened by jointing. The removal of support allows gravity to release the block, resulting in sliding. Rainstorm events can encourage a landslide, lubricating the slip plane, reducing the resistance. Landslides occur in consolidated rocks with joints or bedding planes sloping seawards. Flows (not mentioned in spec?) Flows occur when unconsolidated fine grained sediment, e.g. silts and clays, mix with large volumes of water. They're common in weak rocks such as clay or unconsolidated sands. They become saturated, lose their cohesion, and flow downslope. Heavy rainfall, combined with high waves and tides can contribute to saturation. Earthflows are more viscous than mudflows, and contain larger sediment. In cold environments, earthflows known as solifluction occur in the unfrozen layer between the permafrost and the tundra vegetation turf.

Answer 57

Blockfall The angular blockfall debris accumulates at the cliff foot to form a talus scree slope, a fan shaped mound of material. Undercutting of cliffs by the creation of wave-cut notches can lead to large falls and talus scree slopes at their base. A talus scree slope has a slope angle of 34-40' (larger fragments maintain a steeper angle of rest) In April 2013 there was a large blockfall in St Oswald's Bay on the South Dorset Coast where an 80 m section of chalk cliff was detached overnight. A large fan shaped talus scree slope was created at the slope foot, extending 30 m into the sea that will protect the cliff from further erosion for a decade or more. Rotational Slumping Rotational slumping exposes a rotational scar A rotational scar is a fresh, curved, unweathered and unvegetated rock surface on the cliff face. The detached slope section, often with vegetation intact on top of the slump, forms a beach or terraced cliff profile.

Answer 58

Sea level change in general Sea level changes constantly Due to: tides, variations in surface air pressure, winds pushing on the water surface, creating temporary bulges of higher sea level. Long term sea level changes occur over thousands of years. Long term sea level change is due to eustatic and isostatic factors, and tectonics.

Answer 59

Eustatic Eustatic change is a change in global sea level, usually due to a change in the volume of water in the oceans. Climate change occurs cyclically, in Milankovitch Cycles, due to changes in the Earth's orbit around the Sun. Glacials are 90,000 year colder phases, which lead to the formation of ice sheets. Water evaporated from the oceans falls as snow on the land and compresses to form ice. Over the course of the cycle, the distribution of water within the hydrological cycle changes, with transfers from the ocean store to sheets on land. A decrease in the volume of water in the oceans produces a global fall in sea level. The sea bed is exposed as land - marine regression. The most recent glacial was the Devensian, where global sea levels were 120 m lower than they are today. The English Channel, Irish Sea and most of the North Sea was dry land. . Interglacials are 10,000 year warmer phases that shrink ice sheets. Water is transferred from the land store back to the oceans. increasing the volume of water in the oceans and raising global sea levels. (Melting of sea ice has no effect on global sea levels as the floating ice mass already displaces its volume.) Rising water temperature leads to the thermal expansion of water, increasing its volume even further. This leads to marine transgression - rising sea levels flood low land areas. . Since 1750, humans are thought to be accelerating natural interglacial warming through greenhouse gas emissions. Anthropogenic forcing Sea levels rose by 21 cm from 1870 - 2010. The melting of Antarctic ice sheets are predicted to raise sea levels by 50 m Summary: Eustatic fall in sea level During glacial periods, when ice sheets form on land in high latitudes, water evaporated from the sea is locked up on land as ice, leading to global fall in sea level. Eustatic rise in sea level At the end of a glacial period, melting ice sheets return water to the sea and sea level rises globally. Global temperature increases and causes the volume of ocean water to increase (thermal expansion) leading to sea level rise.

Answer 60

Isostatic Changes An isostatic change is a change in local land level. Rises in local land level causes a fall in local sea level. This may be due to: post-glacial adjustment accretion sink regions in the sediment cell are experiencing net deposition, land is built up, leading to a fall in sea level (in delta regions accretion -> subsidence -> accretion and so on) tectonics A fall in local land level produces a rise in local sea level. This may be due to: post-glacial adjustment subsidence subsidence of land produces a rise in sea level the deposition of sediment, especially fluvial deposits in large river deltas, the weight of sediment deposition overcomes the threshold and leads to very slow 'crustal sag' and delta subsidence, e.g. Nile, Mississippi, Amazon can also be caused by the lowering of the water table (from increased evaporation from climate change or human abstraction) can lead to settling of overlying sediment and land subsidence as pore water pressure is removed or by heavy buildings tectonics

Answer 61

Post-Glacial Adjustment During glacial periods, the weight of the ice depresses the crust in areas below the ice sheets. The solid lithosphere is forced down into the plastic asthenosphere. The rigid nature of the solid crust means that when sections of the crust are depressed by ice and forced down, adjacent areas are uplifted in a see-saw effect. The melting of ice causes previously ice-covered crust to slowly rebound upwards whilst adjacent areas subside. At the end of the last ice age 12,000 years ago, the UK was covered in ice as far down as Birmingham. Northern Britain is experiencing a isostatic fall in sea level as land is uplifted by 1.5 mm per annum. Southern Britain is experiencing an isostatic rise in sea level as land is lowered by 1 mm per annum. The UK is pivoting, with the south sinking and the north rising. In northern Britain, sea levels are falling as isostatic rebound exceeds eustatic rise in global sea levels. However, in the south isostatic subsidence is accelerating a rise in sea level produced by global warming (eustatic). Land's End in Cornwall is sinking isostatically by

Answer 62

Tectonics Eustatic Rising magma at a constructive plate margin/hot spots lifts the overlying crust, reducing the capacity of the ocean and producing eustatic sea level rise. Uplift of crustal plate reduced Indian Ocean capacity causing 0.1 mm eustatic rise in global sea levels. Isostatic Folding of sedimentary rock by compressive forces at a destructive plate margin produces an isostatic fall in sea level for anticlines and a fall for synclines. E.g. the Alpine folding at the Eurasian-African destructive plate boundary produced an isostatic fall of 60 cm in the Bakar-Vindol area of Croatia. Lava or ash from volcanic activity produces an isostatic fall, e.g. Hawaiian hot spot island chain or Caribbean island arc. Sea floor spreading - carries volcanic islands away from the uplifted crust at mid-ocean ridge. Colder, more dense crust subsides and sea levels rise, e.g. Tonga, Fiji, Kiribati. FAULTING can uplift HORST blocks of crust producing isostatic rise in land & fall in local sea level. Subsidence of crust blocks by faulting form GRABEN experiencing isostatic fall in land level & rise in local sea level. During 2004 Boxing Day Tsunami in Indian Ocean extension of crustal plate caused isostatic fall in land on island of Sumatra by 20 cm in Banda Aceh region.

Answer 63

Emergent Coastlines During the Devensian Glacial eustatic changes lowered sea levels by 120 m. At the start of the Holocene Interglacial (10,000 years BP) led to a rapid 100 m eustatic rise in global sea levels, as 3,000 years of ice sheets and glaciers shrank. This happened over about 1000 years, (very rapid) and submerged coastlines. However, the post-glacial adjustment of ice-covered land (and adjacent areas) was much slower. Previously ice-covered land gradually rose out of the sea, such as northern Britain and Scandinavia. The Ford and Clyde valleys in the border region of Scotland are currently rising 2 mm p.a. (though initial adjustment was faster) Areas of Northern Europe and North America that were covered by the thickest ice are rebounding fastest. Some areas rose isostatically by 300 m. Emergent coastlines are being produced by post-glacial adjustment. These are parts of the littoral zone where a fall in sea level exposed land once part of the sea bed. They have landforms reflecting the previous sea levels. Raised beach A relict beach now above high tide level A flat surface covered by sand or rounded pebbles/boulders. Usually vegetated by plant succession (though further succession prevented due to grazing) Fossil cliff a steep slope found at the back of a raised beach exhibiting evidence of formation through marine erosion but now above high tide level. they may contain wave-cut notches, caves and arches providing evidence of formation by marine erosion episodic nature of isostatic recovery allows marine processes to erode cliffs and deposit beaches when sea levels are stable. Relatively rapid drop in sea level then leaves relict coastline abandoned above high tide and some distance inland. E.g. the Isle of Arran has a raised beach 5 m above current sea level north of Drumadoon. Arran has three levels of raised beaches produced at different stages of post-glacial adjustment. E.g. at Lendalfoot in Ayrshire, western Scotland, a flat raised beach surface is used as a route for the A77 main road. 40 m raised cliff at the back of the now now 200 m inland from the present-day beach. Also raised stumps, etc.

Answer 64

Submergent Coastlines Submergent coastlines are sections of the littoral zone where sea level rise inundated areas that were previously part of terrestrial land. They are found in southern England and the east coast of America. Areas of land adjacent to ice covered regions experience isostatic uplift during the Devensian due to the see-saw effect. These are now subsiding due to post-glacial adjustment - producing marine transgression and emerging coastlines. A ria is a drowned river valley - a section of river valley flooded by the sea, making it much wider than would be expected based on the river flowing into it. Rias are the most common coastal landform. They are common in periglacial areas that were adjacent to land covered by ice during the Devensian, e.g. Southern England. Rivers eroded steep-sided V-shaped valleys into the frozen landscape giving the ria a V-shaped cross section when the valley flooded. Rias have a sinuous plan profile reflecting the meandering river course. The plan view is dendritic as tributies are flooded by the rising sea. Rias are a type of estuarine coastline. E.g. Kingsbury Estuary on the south Devon coast is a 6 m long ria. Main channel is 1 m wide near its mouth at Salcombe. Two large drowned tributaries extend from the east side of the ria, with Frogmore Creek 2 km long and 500 m wide. Fjord Fjords are drowned glacial valleys - a section of a glacially eroded valley flooded by the sea. They are common in glaciated areas that were covered during the Devensian, e.g. western Norway. Many Scottish sea lochs are fjords. Fjords often have a relatively straight profile as glaciers truncate spurs to produce a direct downslope route. Glacier erosion is often cut deep into the landscape, often tens of metres lower than the adjacent unglaciated land - meaning that fjords are often deeper than the adjacent sea. Fjords often have a shallow entrance where there is a submerged 'lip' formed by the ridge of a terminal moraine. Many fjords are shallowing by a few milimetres per year due to isostatic adjustment. Sognefjord in western Norway is 205 km long, 1.3 deep and the main branch is 4.5 km wide. Dalmatian Coast This is composed of long, narrow islands running parallel to the coastline and separated from the coast by narrow sea channels called sounds. They are produced by sea level rise flooding the coastline with the geological structure of folds aligned parallel to the coast. Sea level rise at the end of the Devensian Glacial floods synclines to form sounds. Sea overtops low points forming straits linking straits linking sounds and separating sections of anticline ridge into narrow islands parallel to the coast. The Dalmatian region of Croatia has a limestone coastline stretching 520 km NW-SE with 1,240 islands running parallel to the coast. Other Isostatic rebound is episodic - long periods of little change followed by short bursts of marine regression. Rias are economically important as they provide sheltered ports. Barrier islands? (from revision guide) The east coast of the USA has barrier island landforms these may have formed as lines of coastal sand dunes attached to the shore later sea level rise flooded the land behind the dunes forming a lagoon, but the dunes themselves were not eroded and formed islands as sea levels continued to rise, the dune systems slowly migrated landwards rivers and tidal flows maintain open water between islands barrier islands supplied with sediment from longshore drift

Answer 65

Climatic warming leads to eustatic sea level rise. Warming leads to the melting of mountain glaciers (Alps, Himalaya) and polar ice sheets increasing the amount of water in the ocean store. Melting of sea ice has no effect on sea level as the ice was already displacing the equivalent water volume to that produced by melting. IPCC attributes 50% of sea level rise 1990-2010 to ice sheets melting (Greenland ice sheet 15%, Antarctic ice sheet 10%) Warming also leads to the thermal expansion of existing ocean water as its temperature rises. 94% of increased heat energy in the climate system is transferred to oceans. IPCC attributes 40% of sea level rise 1990-2010 to this Tectonic activity caused the other 10% of sea level rise Emission of geothermal heat into oceans by underwater volcanic activity can cause thermal expansion of ocean water Rising magma at constructive plate boundaries produces a doming upwards of crust along mid-ocean ridges reducing the ocean basin volume At destructive margins: folding of plates increases ocean basin volume lowering sea levels earthquakes along boundary can allow rebound of non-subducting margin - uplift of sea floor reduces ocean volume raising sea levels 2004 Boxing Day tsunami with moment magnitude 9.3 lifted sections of the Indian Ocean bed raising sea levels by 0.1 mm It can also cause isostatic change: faulting can uplift sections of crust, lowering sea levels (or vice versa), sometimes by up to 2 m Turakirae Head near Wellington on New Zealand's North Island uplifted 6 m in 1855 earthquake Sea floor spreading transports volcanic islands away from the uplifted crustal zone along constructive boundaries or hotspots - to places where the ocean floor is colder, denser and lower lying - islands sink Past Change Sea levels have risen by 125 m since the Devensian Glacial Sea level rise was on average 10 mm p.a. in the early Holocene Interglacial (18,000 - 6,000 BP) The UN's Intergovernmental Panel on Climate Change (IPCC) 5th Assessment Report suggests that sea level rise was only 0.5 mm p.a. from 6,000 BP to 1860. Since 1870 The rate of sea level rise has increased. The IPCC attributes this to global warming due to anthropogenic forcing through greenhouse gas emissions Contemporary sea level rise has accelerated since 1940 reaching 3 mm p.a. between 1990 and 2000. Future IPCC predicts sea level rise of 18-59 cm by 2100. (28-98 in 2013?) US National Research Council predicts 56-200 cm This wide variation in prediction is due to: uncertainties in science of relationship between GHG increase and climatic warming due to complex feedback effects uncertainties in science of relationship between climatic warming and rate of ice melting uncertainties about rate of population growth and economic growth impacting on rate of GHG emission uncertainty about future political commitment to introducing new measures to reduce GHG emissions Complete melting of Greenland ice sheet would raise global sea levels by 7 m Complete melting of Antarctic ice sheet would raise sea levels by 50 m However complete melting of ice sheets would take many centuries even by the most rapid estimates What coastlines are at risk? low lying ones - coastal flooding through marine trangression low lying volcanic islands or coral atolls set atop submerged volcanic guyots e.g. Maldives in the Indian Ocean, Kiribati Islands in the Pacific Ocean - at risk of complete disappearance Volcanic islands at risk from both global warming and tectonic activity

Answer 66

Rapid coastal erosion is caused by physical factors when geological and marine characteristics combine to promote erosion. Geological factors include: Lithology - soft rock type, weak cohesive bonds, porous rocks Geological structure - well jointed rocks, rocks with seaward dipping beds, heavily faulted rocks Marine factors include: long wave fetch promoting large, destructive waves strong longshore drift that quickly removes collapsed sediment allowing erosion to restart Human activity can increase rates of coastal recession by interrupting the operation of the sediment cell. The construction of major dams of rivers can trap river sediment behind the dam wall. This then starves the coast of a sediment source, leading to serious consequences. The construction of the Aswan High Dam on the River Nile in 1964 reduced sediment volume from 130 million tonnes to about 15 million tonnes per year. Erosion rates jumped from 20-25 m per year to over 200 metres per year as the delta was starved of sediment. Dredging This is the removal of sediment from a beach, sea or river. Sands or gravels scooped/sucked up for use by construction industry Dredging of river mouths and estuaries often to maintain navegable channel for ship transport

Answer 67

Winds change direction daily as different weather systems pass across or near the UK Rates of recession will be higher when the wind is blowing onshore Offshore winds produce calm conditions Dominant wind is the direction of the strongest wind Prevailing wind is the direction of the most common wind When wind blows from prevailing wind direction, strong winds produce large destructive waves and rapid recession Where wind blows from a direction where there is a large fetch, even moderate strength winds can build up large destructive waves and produce rapid recession Dominant wind direction often coincides with direction of largest fetch, as a large expanse of unobstructed open water allows wind to gain strength. In the North Norfolk coastline the rare dominant wind from the north with a 1,600 km fetch across the Norwegian and North Seas can produce recession rates of up to 8 m p.a.

Answer 68

Rates of recession more rapid during high tide when deeper water in the foreshore zone allows waves to maintain a higher energy when they reach the backshore. (And they reach the backshore in the first place) Greater energy of impact on backshore increases erosion and rates of recession High tides occur twice each day, about 12 hours apart Twice each lunar month when the gravitational pull of the Sun and the Moon is aligned, particularly high Spring Tides occur Higher sea level produces deeper water near the backshore and faster recession IPCC estimates a 1 cm rise in sea level produces an average of 1 m horizontal erosion Global warming predicted to raise sea levels by 18-59 cm by 2100

Answer 69

Storm events are deep (very low pressure) depressions They produce large, high energy destructive waves and fast rates of recession Global warming is predicted to increase intensity of atmospheric circulation - more frequent storm events - higher intensity of storm events - increased rates of recession

Answer 70

Storm events are more likely to occur in the winter when the contrast in temperature and pressure between the tropical and polar air masses is the greatest Consequently in the UK the rates of recession are faster in winter than summer In Holderness, in winter 2-6 m of erosion is common when storms, combined with spring tides, increase erosion rates (although the average erosion rate is 1.25 m - but this varies from 0-6 m per year) Number and intensity of storms affecting the UK each winter varies: Weaker storms during El Niño events every 2-7 years and during phases of low solar output in the 11 year cycle

Answer 71

UK located at the polar front between the boundary of warm tropical air of the Ferrel cell and the cold polar air of the Polar cell Interaction between warm and cold produces high air pressure anticyclone and low air pressure depression weather systems Anticyclones produce gentle winds and small waves - low rates of recession Depressions - areas of rising air (low surface air pressure) These produce strong winds - rapid rates of recession Depressions form in the North Atlantic and take several days to pass across the UK from the SW to NE. As they pass the spiralling inflow air produces changes in wind direction

Answer 72

Sea level rise affects a disproportionate number of people because: Many low lying coastlines are densely populated as beaches and the sea attract a large number of tourists Low lying deltas are extremely fertile and ideal for agriculture Estuaries and deltas are ideal for trade with good navigable access inland up rivers Many river deltas support megacities, e.g. Shanghai, Yangtze Delta China - 24 million people Dhaka, Bangladesh, Ganges-Brahmaputra delta - 14 million people Karachi, Pakistan Indus delta - 23.5 million people The IPCC predicts that by 2060 12% of the world's population will be living in coastal regions less than 10 m above sea level

Answer 73

Local Factors These also increase the flood risk of some coastlines Height Low lying coastlines are only 1-2 m high above (high tide) sea level so at risk from flooding Temporary flood risk from storm surges, permanent flooding from global sea level rise The Maldives archipelago in the Indian Ocean has a population of 340,000 spread across 1,200 islands The highest point in the Maldives is only 2.3 m above sea level Malé, the main island and capital, is protected by a 3 m sea wall Bangladesh occupies the Ganges-Brahmaputra delta, 60% of the country is less than 3 m high above sea level The Kiribati archipelago in the Pacific Ocean is composed of 33 coral atolls. Most of the population lives on the island of Tarawa where the maximum height above sea level is 3 m Subsidence Low lying coastlines in estauries, deltas or outbuilding zones are subject to natural subsidence through the settling and compaction of recently deposited sediment However, subsidence is usually outpaced by fresh deposition and the bioaccretion of organic matter Deltas experience periodic isostatic subsidence when the weight of the delta sediment reaches the threshold sufficient to cause the crust to depress - leading to marine transgression and flooding Human activity can also cause local subsidence: Drainage of saturated sediment/soil for agriculture e.g. Fens of East Anglia, or ground water abstraction to supply cities, e.g. Venice, reduces sediment volume and causes subsidence Weight of cities and built environment can also compress sediment, leading to subsidence (also happening in Venice) Land reclaimed from the sea, e.g. Ijsselmeer polders in the Netherlands, subject to subsidence due to water abstraction via evapo-transpiration by agricultural crops. Volcanic islands and coral atolls - seafloor spreading away from hotspot or mid-ocean ridge Isostatic readjustment after ice sheet retreat (southern England) Bangladesh: 50 large islands in the Ganges-Brahmaputra delta subsided by 1.5 m since 1960 Partly due to isostatic crustal depression and partly due to water abstraction by occupying populations, partly due to natural settling of sediment while the earth bund flood protection prevents compensation fresh sediment deposition Vegetation Removal Vegetation, like salt marshes and mangrove forest, reduces flood risk Vegetation stabilises existing sediment and traps new sediment, raising the height of the land above sea level Vegetation absorbs wave energy, reducing wave impact and erosion, and reduces the distance waves travel onshore before the energy is exhausted An 100 m belt of mangrove forest is estimated to reduce wave height by 40% A 1 km belt of mangrove forest reduces the height of a storm surge by 0.5 m An estimated 50% world's mangrove forest removed since 1950 - 1/4 of the loss for the creation of shrimp farms, and lots removed for tourist beaches Bangladesh contains the 180 km Sundarbans, the largest mangrove forest in the world. However, 71% is experiencing some vegetation removal. Some parts are eroding at 200 m p.a

Answer 74

Global Sea Level Rise Global sea level rise increases the risk of flooding in low lying coastlines (duh) Mean global sea level rose by 20 cm in the 1900. 50% of the Netherland and large areas of the East Anglian Fens are now below sea level, but protected by coastal defences IPCC predicts a further 18-59 cm rise in sea level by 2100 Bangladesh - a 40 cm sea level rise would permanently submerge 11% of Bangladesh, creating 7-10 million environmental refugees Maldives - 50 cm sea level rise would permanently flood 77% of the Maldive Islands' land area.

Answer 75

Storm surge events can cause severe coastal flooding with dramatic short term impacts (depressions, tropical cyclones) Depressions are areas of low air pressure generating surface winds that spiral into the centre of low pressure in an anti-clockwise direction. They occur in mid-latitutes, like the UK. Storms are depression, areas of low surface pressure that generate strong winds (UK 90 kph, tropical regions 65 kph) They occur in areas just north and south of the equator. Tropical cyclones are areas of very low surface air pressure (deeper depressions) generating very strong winds (118 kph +) They're classified on the Saffir Simpson scale into 5 categories, where the fifth has winds of over 250 km. High air pressure depresses the ocean surface, lowering local sea level. Low air pressure allows the ocean surface to dome upwards, raising local sea level. A 1 millibar reduction in air pressure leads to a 1 cm rise in sea level. A storm surge is a temporary rise in local sea level produced when a depression, storm or tropical cyclone, reaches the coast. The rise in sea level during the storm surge is accentuated: At high tide, particularly spring tide Shape of coastline funnels into increasingly narrow space Sea bed shallows towards coast Storm surges can produce severe coastal flooding on low-lying coastlines. Force of onshore current of storm surge water can cause rapid coastal erosion. Impact of storm surge increased by large destructive waves whipped up by strong storm winds on top of the already higher sea level - rapid coastal erosion.

Answer 76

Short term impacts: Deaths and injuries to people immediately through drowning or collapsing buildings Subsequent deaths from hypothermia (homes destroyed), water borne diseases (sewer systems and freshwater pipe destroyed), natural causes (transport routes to medical care cut) Destruction of infrastructure - roads, railways, ports, and airports flooded or destroyed Damaged water pipes, electricity transmission lines and sewage systems - no power or water. Homes destoyed - older houses worse standards, cheap in poor areas - homes on marginal low lying land (slums and shanty towns) most vulnerable - reconstruction may take several years, richer (insurance) likely to be rehoused first Businesses destroyed - factories, offices - loss of power, interruption of raw material delivery, workers killed/injured/can't get there - agricultural land contaminated - crop harvest lost

Answer 77

Category 4 cyclone, air pressure 944 mb, 240 kmph and 6 m storm surges Impact worsened by: funnel shape of the Bay of Bengal focussing water on Bangladesh at the bay apex. Out flowing discharge from the Ganges and Brahmaputra rivers combine with coastal flooding. Intense rainfall from cyclone increases flooding. Coastline from unconsolidated delta sediment - easily eroded. Deforestation of mangrove swamps. 60% of Bangladesh low lying, less than 3 m above sea level 15,000 people killed and 55,000 injured. 1.6 million homes destroyed. 8,000 km of roads, 700 km of electricity transmission lines and 900 fresh water tube wells destoyed Crops destroyed on 600,000 ha of agricultural land Total damage estimated at $1.7 billion However, the impacts of deaths were much lower than in the 1970 Bhola Cyclone where 300,000 were killed. ($90 million economic loss) Improved warnings, embankments and cyclone shelter network saves many lives.

Answer 78

80+ mph winds Storm coincided with spring tide In the North Sea the coastline narrows into a funnel shape for a storm approaching from the north - storm surge funnelled - sea shallows towards coast - severe coastal flooding. Average 3 m storm surge in East Anglia, but 6 m at Blakeney in North Norfolk 2 people killed. 18,000 evacuated. Coastal defences breached in Yorkshire and Kent and 1,400 homes flooded. At Hemsby in Norfolk sand dunes were eroded, seven houses and a lifeboat station destroyed East coast rail services suspended for one day Total economic loss estimated at $100 million Impacts much lower than the 1953 storm surge when 307 people were killed, 65,000 ha of farmland flooded and there were an economic loss equivalent to $1.2 billion today This was prevented by: improved flood defences in 2013, including the Thames Barrier (raised during the storm), which protected 800,000 homes according to Environment Agency estimates Improved forecasting and efficient evacuation also saved lives and mitigated in areas where flooding or erosion still occurred. United Kingdom, Storm Xavier, December 2013

Answer 79

High Confidence Sea level will rise by 18-59 cm by 2100 however the pace and extent of sea level within the predicted range is uncertain due to population growth, economic development, natural positive and negative feedback, political commitment to restrict GHG emissions. it is also affected by adaption: building sea walls, e.g. on the North Norfolk coast, 3 m sea wall on Malé. new artificial island, Hulhamalé created by the reclamation of sediment from the sea bed between 1997-2002, which is 4 m above sea level and cost $32 million to construct. building earth embankments, like the bunds in Bangladesh storm surge barriers across river mouths - Thames Barrier, Eastern Scheldt Barrier in the Netherlands (part of the 2.5 billion euro project begun after the 1953 storm surge) restoration of mangrove forest - protection belts, e.g. Sri Lanka replanting after the 2004 Indian Ocean tsunami killed 6,000 people in one coastal village where mangroves were cleared, but only 2 deaths in an adjacent village protected by a mangrove forest mitigation - efforts to reduce magnitude of event. Reducing GHG emissions to limit level of global warming would mitigate sea level rise and cyclone intensity. Delta flooding The are area of the world's major deltas at risk from coastal flooding is likely to increase by 50% Medium Confidence Wind and waves Some evidence of increase wind speeds and large waves Coastal erosion Erosion will generally increase because of the combined effects of changes to weather systems and sea level Low Confidence - evidence weak and uncertainty high Tropical cyclones The frequency is likely to remain unchanged, but there could be more larger storms Predicted to increase in strength by 2-11% by 2100. Associated rainfall will increase by 20%. Cyclone intensity would increase due to warmer ocean surface temperature and warmed atmosphere holding more moisture. Number of tropical cyclones not predicted to increase - combination of factors form them, and a warm ocean temperature is only one of them. In the North Atlantic, the number of tropical storms becoming hurricanes has risen from 6 in the 1900s to 8 per year from 2000-2016 However, this is only low confidence - no observed increase in maximum intensity in the Pacific and Indian Oceans over the last 20 years of monitoring. The number and intensity of tropical cyclones is highly variable each year and decade - no statistically significant long term trend. Storm surges These are linked to depressions that are likely to become more common More intense tropical cyclones will exhibit even lower surface air pressure producing larger temporary sea level rises as storm surges and increasing the risk of coastal flooding Depressions Polar front jet streams will accelerate, possibly increasing the number and intensity of depressions and storm surges in mid-latitudes The magnitude and timing of all these changes is uncertain.

Answer 80

Economic Loss of (or damage to) property in the form of homes, businesses and farmland, so relatively easy to quantify. The losses tend to be very localised and costs depend on the land's use and location. In 2015, the EA valued English agricultural land at £21,000 per ha, and industrial/business land at £500,000 per ha. Residential land can vary from £500,000 (North Yorkshire, cold climate, boulder clay) to £2.1 million per ha (Dorset, warm climate, Jurassic coast). Re-rerouting a two lane road can cost between £150,000 and £250,000 per 100 m. The collapse of the section of coast supporting the South Devon Main Line Railway in February 2014 cost £35 million to repair, and businesses in the South West lost £60 million. Other consequences: Economic losses to businesses if areas become unattractive and depopulated. A whole village could be at risk (part social) Falling property values, and an inability to sell property Unexpected recession can cause localised loss: In 1993 140 mm of rain in 2 months led to the collapse of the £2 million Holbeck Hall Hotel in Scarborough, in a slump of 1 million tonnes of boulder clay. Loss of a major asset, and the costs of buying a new home An inability to insure against the loss (because its a certainty, not a risk)* *There is little help available for those who lose their homes to the sea. There is no national compensation scheme. The UK has the 'Coastal Change Pathfinder' projects, 15 two-year projects funded in 2010 by DEFRA which: Gave the East Riding of Yorkshire £1.2 million, and funded relocation and demolition for 43 homes. Cover the cost of property demolition and site restoration Provide up to £1000 in relocation expenses (removal vans, storage...) Provide up to £200 in hardship expenses Have 'rollback' policies, giving people fast tracked planning approval to build a new home somewhere else The Environment Agency estimates 800 properties will be lost by 2035 Overall, though, the economic losses are small because: Erosion happens slowly; a small number of properties are affected over decades. Property at risk looses its value to buyers long before it is at risk from erosion Areas of high-density population, such as towns and villages, tend to be protected by coastal defences. (which means the actual economic loss is much lower)

Answer 81

Social Relocation Cost (can be quantified) Break up of community, loss of friends and activities like a football team or classes Also stressful! Loss of livelihoods (which can be quantified) Source of income (can be quantified) Financial problems and job searching leads to stress (and divorces, etc...) There are also losses in amenity value and economic losses to businesses if areas become unattractive and depopulated. For example, abandoned buildings, damaged roads, rerouted footpaths, loss of access to beach. (Amenity value is the value in cultural, human well-being and economic terms of an attractive environment people enjoy using.) Unattractive environment - cliff collapse, failing sea defences and blocked roads/paths

Answer 82

Consequences in Developed Countries Australia (future flooding) The IPCC estimates a sea level rise of 28-98 cm sea level rise by 2100, with the most likely rise being 55 cm A 1 m rise would flood: 116,000 homes causing property damage of US $72 billion; $87 billion worth of commercial property threatened $67 billion road and rail infrastructure. 5 power stations, 258 emergency service stations, 75 hospitals and 44 water and sewage plants. Social costs would include the break up of communities, loss of livelihood, e.g. fishing, tourism, and amenity loss (?) Coral reefs forming the Great Barrier Reef will die if they are unable to grow fast enough to keep up with sea level rise, leading to a loss in tourism income. North Sea Flood, UK, 2013 (Part of the winter storms) Storm surges reached heights of more than 5 m (e.g. in Hull) On the 5 December 2013 a large storm surge hit the east coast of the UK causing widespread flooding along the coast. Low pressure, high winds and high tidal pressures combined Social 2 deaths in the UK Hundreds of people were evacuated from Rhyl, in Denbighshire Loss of amenity value - nature reserve damaged in Skegness Loss of livelihood - businesses affected in Lowestoft, Suffolk as the harbour area, railway station and southern section of the town centre were flooded Economic The EA reported 1,400 homes flooded in England and Wales Damage of about £1 billion over the course of the winter All rail services cancelled in Scotland 40,000 homes in Scotland and Northern England lost power

Answer 83

Consequences in Developing Countries Philippines (Emerging country, effects of flooding) IPCC estimates a rise of 60 cm - 1 m by 2100 in the Philippines Economic A 1 m rise would cause $6.5 billion of property damage San Fernando in the north of Luzon predicted to lose 123,000 m^2 beach with $95,000 p.a. tourism revenue Fishing industry losses estimated at $168,000 p.a. Much of the threatened area is poor shanty towns, e.g. Cavite City and Las Piñas in Manila, with low property value Social A 1 m rise would affect 2.3 million people, and 62% of Manila in the south of Luzon Island Loss of livelihood - fishing, tourism Loss of amenity value - San Fernando beach Social cost high as alternative employment is difficult to find in the formal sector Philippines 2013, Typoon Haiyan One of the most powerful tropical storms ever with a 4-5 m surge Economic Damages of about US $2 billion, centred on the city of Tacloban In Tacloban 90% of structures destroyed or damaged Social At least 6,300 deaths 30,000 injured 1.9 million homeless 6 million displaced - 20,000 fled to Manila

Answer 84

Environmental refugees are those forced to leave their homes because of natural processes, including sudden ones such as landslides or gradual ones such as erosion or rising sea levels. It's not a term used by the UN High Commission for Refugees. It includes refugees and internally displaced people. IPCC predicts that climate change will produce a sea level rise of 26-82 cm by 2100, which would create environmental refugees by: Flooding Salt water encroachment (into groundwater, for drinking, irrigation and industry) Coral bleaching (which acts as a sea defence) The places most at risk from the sea level rise predicted by 2100 are the Maldives, Tuvalu, the Seychelles and Barbados. Tuvalu's highest point is 4.5 metres above sea level, and most land is only 1-2 m above New Zealand grants residency to 75 Tuvalu citizens each year under the Pacific Access Category Ballot as rising sea levels decrease its land area. In 2014 New Zealand courts granted the Alesana family permanent residence on their basis as 'climate change refugees' 80% of people in the Seychelles live and work at the coast Coral reefs, which act as a natural coastal defence against erosion, are being destroyed by global warming-induced coral bleaching Water supply is limited and at risk from salt-water incursion as sea level rises and groundwater is over-used They have small and narrow economies based on tourism and fishing, which is easily disrupted. They have high population densities and very limited space, so no opportunity for relocation. Developing or emerging countries lack the funds to finance coastal defences to protect huge lengths of coastline. Maldives have an average height of 1.5 m above sea level, but the population of 400,000 is too large to be easily accommodated elsewhere. Its government is negotiating with India, Sri Lanka and Australia to buy land. The worst-case scenario for Tuvalu and parts of the Maldives is that some, or all islands will have to be abandoned, creating environmental refugees. Hurricane Katrina, USA, 2005 Created 1 million environmental refugees when a 7 m storm surge flooded New Orleans Most were internally displaced within the USA but 30% did not return to New Orleans Typhoon Haiyan, 2013 This and other possibly climate change driven storm events since 2008 have produced 6.8 million internally displaced environmental refugees

Answer 85

This is the traditional management process for erosion/flooding, encasing the coastline in concrete, stone and steel. The aim is to directly stop physical processes altogether (such as erosion or mass movement) or alter them to protect the coast (such as encouraging deposition to build larger beaches) Advantages It's obvious to at-risk people that something is being done to protect them, its reassuring A 'one-off' solution that could protect a coastline for decades Disadvantages Costs are usually very high, and there are still ongoing maintenance costs Even very carefully designed engineering solutions are prone to failure Coastlines are made visually unattractive and the needs of a coastal ecosystem are usually overlooked Defences built in one place frequently have adverse consequences further along the coast

Answer 86

Vertical stone or timber 'fences' built perpendicular to the coast and spaced along the beach. Their purpose is to prevent longshore movement of sediment and encourage deposition, building a wider, higher beach. Impact on physical processes: Deposition and beach accretion Prevention of longshore drift, sediment starvation and increased erosion downdrift Cost £150-250 per metre

Answer 87

Concrete with steel reinforcement and deep-piled foundations; can have a stepped and/or 'bullnose' profile, to dissipate wave energy A physical barrier against erosion. They often also act as flood barriers Modern sea walls are designed to dissipate, not reflect, wave energy Destruction of the natural cliff face and foreshore environment If reflective, it can reduce beach volume £3000-10,000

Answer 88

Stone, timber or interlocking concrete sloping structures which are permeable Purpose: To absorb wave energy and reduce swash distance by encouraging infiltration Reduce erosion on dune faces and mud banks Reduced wave power Can encourage deposition and may become vegetated

Answer 89

Large igneous or metamorphic rock boulders weighing several tonnes (offshore rip-rap) Forces waves to break offshore, rather than at the coast, reducing wave energy and erosive force \ Deposition encouraged between breakwater and beach Can interfere with longshore drift

Answer 90

This attempts to work with natural physical systems and processes to reduce the coastal erosion and flood threat. Usually less obvious and intrusive at the coast May be cheaper in the long term Not suitable for all coasts

Answer 91

Beach Nourishment Artificial replenishment of beach sediment to: replace sediment lost by erosion, to enlarge the beach so that it dissipates wave energy and reduces erosion and increases the amenity value of the beach. £20 million per km of beach Ongoing costs are high Sediment must not be sources from elsewhere in the sediment cell

Answer 92

Cliff Regrading and Drainage Cliff slope angles reduced to increase stability Re-vegetated to reduce surface erosion. In-cliff drainage reduces pore-water pressure and mass movement risk. Costs of £1 million per 100 m Can be disruptive during construction

Answer 93

Dune stabilisation Fences are used to reduce wind speeds across the dunes, dunes are then replanted with marram and lyme grass to stabilise the surface This reduces erosion by wind and water. Fencing costs £400-2000 per 100 m and replanting £1000 per 100 m (1400-3000) Can be very cost effective in the long term.

Answer 94

Coastal communities around the world face the dynamic nature of the coast's everyday environment. They increasingly face threat from: rising global sea levels, but there is uncertainty about the scale and timing of the rise increased frequency of storms and the possibility of increased erosion and flooding To cope with these threats, communities need to adapt and employ sustainable coastal management. to ensure the well-being of people and the coastal environment. (Sustainable coastal management means managing the wider coastal zone in terms of people and their environment livelihood, social and cultural well-being, safety from coastal hazards, as well as minimising environmental impacts. Sustainable coastal management: Managing natural resources (fish, farmland, water supply) to ensure long-term productivity Managing flood and erosion risk where possible, or relocating to safe areas Creating alternative livelihoods before existing ones are lost to the sea Adapting to sea level rise by relocating, alternative building methods and water supplies Educating communities to understand why change is needed and how to adapt. Monitoring coastal change and adapting to unexpected trends Adopting sustainable coastal management may lead to conflict because: coastal natural resources may have to be used to less in order to protect them - so some people lose income relocation may be needed where engineering solutions are too costly or not technically feasible some erosion and/or flooding will always occur, as engineering schemes cannot protect against all threats. future trends, such as sea level rise, may change, creating uncertainty and the need to change plan.

Answer 95

ICZM is coastal management planning over the long term, involving all stakeholders, working with natural processes and using 'adaptive management', i.e. changing plans as threats change. ICZM is a holistic approach used to manage coasts. It dates from the Rio Earth Summit in 1992 and has a number of key characteristics: The entire coastal zone is managed, not just the narrow zone where breaking waves cause erosion and flooding. This includes all ecosystems, resources and human activity in the zone. It recognises the importance of the coastal zone to people's livelihoods as, globally, very large numbers of people live and work at the coast - but their activities tend to degrade the coastal environment. It recognises that management of the coast must be sustainable, meaning that economic development has to take place to improve the quality of life of people but that this means to be environmentally appropriate at equitable. ICZM works with the concept of littoral cells, or sediment cells. These contain sediment sources, transport paths (flows) and sinks. Each littoral cell is isolated from adjacent cells, and can be managed as a holistic unit. The coastline can be divided up into littoral cells and each cell managed as an integrated unit. In England and Wales there are 11 sediment cells. Each cell is managed either as a whole unit or a sub-unit. In both cases a plan called a Shoreline Management Plan (SMP) is used. The SMP area is further divided into sub-cells. SMPs extend across council boundaries, so many councils must work together on an agreed SMP to manage an extended stretch of coastline.

Answer 96

In the UK, coastal management is overseen by DEFRA (Environment, Food and Rural Affairs). Since DEFRA introduced Shoreline Management Plans in 1995 there have been only four policies available for coastal management, which differ greatly in their costs and consequences. 1) No active intervention No investment in defending against flooding or erosion, whether or not coastal defences have existed previously. The coast is allowed to erode landward and/or flood. 2) Strategic (managed) realignment Allow the coastline to move naturally (in most cases to recede) but managing the process to direct it in certain areas. 3) Hold the line Build of maintain coastal defences so that the position of the shoreline remains the same over time. 4) Advance the line Build new coastal defences on the seaward side of the existing coastline. Usually this involves land reclamation. Making decisions about which policy to apply to a particular location is complex. It depends upon: the economic value of the assets that could be protected, e.g. land the technical feasibility of engineering solutions: it may not be possible to 'hold the line' for mobile depositional features such as spits, or very unstable cliffs. the cultural and ecological value of land: it may be desirable to protect historic sites and areas of unusual diversity pressure from communities: vocal local political campaigning to get an area protected the social value of communities that have existed for centuries. SMPs plan for the future using three time periods called 'epochs'. These are: Up to 2025 2025-55 2055+ A hold the line policy applied to an area up to 2025 may become a managed realignment policy after 2025. This is because by 2025 sea level rise is likely to have made 'hold the line' a much more expensive policy to apply.

Answer 97

Cost-Benefit Analysis Cost-benefit analysis (CBA) is used to help decide if defending a coastline from erosion and/or flooding is economically justifiable. An example is Happisburgh in North Norfolk: The policy adapted in this area is 'no active intervention' This is because to defend the village would have an impact on the wider coastal management plan. Happisburgh would end up as a promontory, blocking longshore drift and causing further erosion downdrift. Longer term, the plan is managed realignment, although this would still involve property being lost to the sea by erosion. Costs of erosion: £160,000 could be available to Manor Caravan Park to assist in relocating to a new site Affected residents could get up to £2000 each (a total costs of £40-70,000) in relocation expenses plus the cost to the council of finding plots of land on which to build new houses. Grade 1 listed St Mary's Church and Grade 2 listed Manor House would be lost. Social costs as the village is slowly degraded, including health effects and loss of jobs. Benefits of erosion: By 2105, between 20 and 35 houses would be 'saved' from erosion, with a combined value of £4 million - 7 million 45 hectares of farmland would be saved, with a value of £945,000 The Manor Caravan Park would be saved, which employs local people. The cost of building coastal defences at Happisburgh is around £6 million, very close to the value of property that could be saved, and much higher than the compensation cost payable to local residents. Coastal managers argue that Happisburgh must be seen in the wider context of the whole SMP, further justifying the decision not to defend the village.

Answer 98

Environmental Impact Assessment (EIA) Coastal management usually requires an EIA to be carried out. This is quite separate from any CBA, although might inform the final CBA. EIA is a process that aims to identify: the short-term impacts of construction on the coastal environment the long-term impacts of building new sea defences or changing a policy from hold the line to no active intervention or managed realignment EIA is wide-ranging and includes assessments of: impacts on water movement (hydrology) and sediment flow, which can affect marine ecosystems because of changes in sediment load impacts on water quality, which can affect sensitive marine species possible changes to flora and fauna, including marine plants, fish, shellfish and marine mammals wider environmental impacts such as air quality and noise pollution, mainly during construction

Answer 99

Coastal management decisions directly affect people's lives. These effects can be positive or negative, producing perceived: winners: people who gain from a decision, either economically (their property is safe), environmentally (habitats are conserved) or socially (communities can remain in place) losers: people who are likely to lose property, their business or job, be forced to move, or see the coastline be 'concreted over' and see this as an environmental negative. In some ways this is inevitable because: coastal managers produce plans for entire SMP areas, so some areas are protected whilst others are not local councils and governments (DEFRA) have limited resources, meaning not all places can be protected There are examples where all stakeholders agree on a course of action. The Blackwater Estuary in Essex is an area of tidal salt marsh and low-lying farmland. Prone to flooding and coastal erosion, the farmland was traditionally protected by flood embankments and revetments Over the last 30 years it has become clear that building higher and more coastal defences in places such as Blackwater is not sustainable. The solution adopted was radical. In 2000 Essex Wildlife Trust purchased Abbotts Hall Farm on Blackwater Estuary, which was threatened by erosion and flooding. A 4000 ha managed realignment scheme was implemented by creating five breaches in the sea wall in 2002. This allowed new salt marshes to form inland. The scheme has a number of benefits: The Abbotts Hall Farm owners received the market price for their threatened farm The very high costs of a 'hold the line' policy were avoided, by flood risk was reduced Water quality in the estuary improved because of expansion of reed beds that filter and clean the water. New paths and walkways were created for leisure activities Additional income streams from ecotourism and wildlife watching were created. Important bird (dunlin, redshank, geese) and fish (bass and herring) nurseries were enhanced. The Blackwater Estuary shows that environmentalists, landowners, coastal managers and local people and businesses can all be kept happy, even when radical plans are adopted. Coastal Management in the Developing World In many parts of the developing world, such as the Maldives, parts of Vietnam, and the West African coast, erosion is rapid, often because of a combination of: upstream dams reducing sediment supply to the coast and disrupting local sediment cells rapid unplanned coastal development, urbanisation and the development of tourist resorts with piecemeal defences and no overall plan widespread destruction of mangrove forests for fuelwood and shrimp-ponds, exposing soft sediment to rapid erosion. In many cases the main 'losers' are the poorest people. Farmers and residents usually lack a formal land-title so cannot claim compensation (even if it were available). Coastlines become more vulnerable to sea level rise, the impact of tropical cyclone storms and even tsunami. When these disasters strike it is the poorest that lose everything. In many cases it is individual property owners that take responsibility for coastal defences in the absence of local council or government plans.

Answer 100

- weak or unstable lithology - long wave fetch and or destructive waves - cliffs which are vulnerable to mass movement - strong longshore drift

Answer 101

the dredging of the Hall sands in Devon has led to the exposure of the village of hallsands when the beach disappeared as there was no sediment feeding the beach. the village became far more threatened nothing remains.