Landscape Systems

• Why are coastal landscapes viewed as a system?

  Coast is constantly changing (dynamic) - driven by wave energy.Each component of coastal system - inputs, processes, stores and outputs
• Examples of inputs,outputs and stores

  • Inputs - Wave, wind, tidal energy, currents, sediment, geology, seal level change
  • Outputs - Dissipation of wave energy, accumulation of sediment above tidal limit, sediment removed beyond local sediment cells
  • Stores - Erosional landforms e.g cliffs, stacks, stumps and depositional landforms e.g spits and beaches
• Example of negative feedback in coastal landscape


  • Beach is in dynamic equilibrium
  • Sediment eroded from beach during storm (destructive waves)
  • Sediment deposited offshore (offshore bar)
  • Waves forced to break out at sea. Energy is dissipated and reduces erosion of beach.
  • After storm passes, constructive waves return and redistribute sediment back

  Repeats
• Example of positive feedback


  • Vegetation on sand dune is trampled by tourists
  • Sand becomes exposed
  • Sand is eroded by wind
  • Vegetation struggles to regrow and hold dunes together 

  Repeat from 2nd bullet point!
• Sources of coastal sediment

  • Terrestrial - erosion from cliffs can input direct sediment including fluvial deposition, mass movement, weathering, marine erosion, aeolian deposition and longshore drift
  • Offshore - inlcuding marine deposition and aeolian processes
  • Human - beach nourishment
• Where does energy come from in coastal landscapes?

  • Potential - material on slopes
  • Kinetic - wind and waves
  • Thermal - heat from sun
• Sediment cells


  Stretches of the coastline where the movement of sediment, sand and shingle is largely self-contained. Can be considered a closed system but easy for fine sediments to find their way through headlines and into neighbouring cells.
• Sediment budgets


  • More sediment enters than leaves - positive sediment budget and coastline extends
  • More sediment leaves than enters - negative sediment budget and coastline retreats
• How do waves and winds shape coastlines?

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  • Frictional drag of winds moving across the surface of the ocean. This creates turbulence.
  • Onshore winds are particularly effective at driving waves towards the coast
  • If winds blows at angle, the resultant waves will also approach obliquely and generate longshore drift
  • Wind is a moving force and is able to carry out erosion (transportation and deposition)
• How waves break


  • As waves approach shallow water, their depth is less than half their wave length.
  • Friction with the seabed increase. 
  • The base of the wave begins to slow down and the circular oscillation of the wave becomes more elliptical (oval)
  • Wave length decreases as water sets more shallow, but the height of the wave increases until the upper part spills or plunges over, it breaks.
• How do tides shape coastal landscape?

  • Tides are the periodic rise and fall of the sea surface and produced by the gravitational pull of the Moon and to a lesser extend, the Sun.
  • The moon pulls the water towards it creating a high tide and there is a conmpensatory bulge on the opposite side of the Earth.
  • Tidal range can a significant factor in the development of coastal landscapes. In enclosed seas, tidal ranges are low and so wave action is restricted to a narrow area of land

   
• How does the geology (lithology) shape coastal landscape?

  • Lithology is the physical and chemical composition of rocks.
  • Bonds between particles that make up the rock are quite weak. Basalt is made up of dense interlocking crystals, are highly resistant and are more likely to form prominent coastal features (cliffs and headlands)
• How does the geology (structure) shape coastal landscape?

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  • Structure concerns properties of individual rock type such as jointing, bedding and faulting. Includes permeability of rocks.
  • In porous rocks (chalk), the tiny air spaces separate the mineral particles. These pores can absorb water (primary permeability)
  • Carboniferous limstone is permeable as water seeps into limestone because of its many joints (secondary permeability)
• How does the currents shape coastal landscape?

  • Rip currents are caused by tidal motion or by waves breaking at right angles to the shore
  • Cellular circulation is generated by deffering wave heights parallel to the shore. Water form the top of breaking waves with a large height travels further up the shore and then returns through the adjacent area where the lower height waves have been broken.
  • Once rip currents form, they modify the shore profile by creating cusps which help perpetuate the rip current.
• Equation for water balance

  Precipitation = Evapotranspiration + streamflow ± storageP = E + Q 
• Cloud formations


  • Driving force behind cloud formation and precipitation is the global atmosphere circulation model.
  • Heat generated is transferred from the poles by ocean currents and winds
• Precipitation

  Convectional Rainfall:

  • Sun heats up the ground
  • Warmer air rises, cools and condenses at the dew point
  • Eventually, the water will accumulate and fall due to gravity

  Relief Rainfall:

  • Moist and warm air form the sea rises up the mountain.
  • Air cools, condenses so clouds and rain is formed
  • Air drops down over high ground, losing temperature and increasing amount of waste it can hold.

  Frontal Rainfall:

  • Warm air forced to rise over cold air
  • Air cools and condenses as it rises, forming clouds and rain.
  • Ferrel and Polar cell meeting.
• Troposphere


  • Lowest point of the Earths atmosphere and is where all weather takes place. Contains approx 75% of atmospheres mass and 99% of water vapour and aerosis.
  • It gets colder by approx 6.5 degrees per km.
• Formation of Bays and Headlands

  1. Headland form on discordant coastlines
  2. The headland faces erosion due to wave refraction.
  3. Faults/joints of weakness are exaggerated by wave erosion of hydraulic action and abrasion.
  4. Caves form as the faults widen between high and low tide marks.
  5. Cave extends through the headland forming an arch.
  6. Wave attack continues to widen the base of the arch, weakening the support
  7. Arch may collapse, resulting in a stack, such as Old Harry in Dorset.
  8. Further erosion at the base may cause additional collapse creating a stump, which may only be seen at low tide.
• Formation of Shore Platforms

  1. Destructive waves undercut the cliff between the high and low tide marks, forming a wave cut notch.
  2. The shape of the cliff behind will be steeper, and the wave cut notch more prominent.
  3. The wave cut notch weakens the support for the rock strata above, leading to collapse.
  4. Wave action removes the debris, ensuring wave action continues to attack the base of the cliff.
  5. As the cliff retreat continues, a gently seaward sloping shore platform is created at the base of the cliff. E.g Flamborough Head on the Holderness Coastline.
• Formation of Cliffs from Shore Platforms


  1. The platform is rarely smooth due to abrasion
  2. Eventually the platform becomes so wide that the friction from the platform slows the waves and they break on the platform itself, ceasing the undercutting.
  3. If the tidal range is less than 4m then a small cliff will form at the low tide and high time marks.
  4. If the tidal range is greater than 4m the erosion will be more spread out so the shape will be more uniform.
• Formation of caves, arches, stacks and stumps

  1. Due to wave refraction, energy is concentrated on the sides of headlands.
  2. Erosional processes = small cave may develop on one side, or even both sides, of the headland.
  3. Wave attack is concentrated between high and low tide levels
  4. Continued erosion = an arch is formed.
  5. Continued erosion widens the arch and weakens its support.
  6. Aided by weathering processes, the arch may collapse, leaving an isolated stack separated from the headland. 
  7. Further erosion at the base of the stack = collapse leaving a stump. This may only be visible at low tide.
• Formation of geos and blowholes

  1. Geos are narrow, steep sided inlets formed by weakness in the rock (e.g joints/faults) that have eroded more rapidly than the surrounding rock.
  2. Begin as tunnel-like caves, in which hydraulic action = forcing air and water into the joints, widening them.
  3. When total roof collapse occurs, the geo is formed.
  4. E.g Huntsman’s Leap, Pembrokeshire
  5. If a geo begins to form, but there is not full roof collapse, then a blowhole may occur, where partial collapse occurs along a vertical shaft within the rock e.g Trevane, Cornwall
• Formation of beaches


  1. Accumulation of material between lowest tides and highest storm waves.
  2. High energy, destructive waves will remove sediment offshore, creating a flatter beach profile, whilst low energy, constructive waves will create steeper profiles.
  3. At the mean high tide mark, ridges form due to deposition at the top of the swash
  4. If swash and backwash have a similar strength and a collection of waves reach the same point then cusps will form
  5. Cusps have been known to occur on Chesil Beach in the UK.
• Formation of spits


  1. Spits are long, narrow beaches that are attached to the land at one end, and extend out across a change in the direction of the coastline.
  2. They are formed by longshore drift in one, dominant direction.
  3. The end of the spit is recurved due to wave refraction around the coastline
  4. The sheltered area behind the spit will have reduced wave energy so deposition will continue to occur = salt marsh
  5. If a spit forms across a river estuary, the river current will prevent the spit from reaching the land on the other side. E.g Spurn Head, Holderness
• Formation of Offshore Bars


  An onshore bar is a stretch of beach that extends across an indentation in the coastline, such as a cove or bay, until it joins onto the land at the other end. It can be anywhere from a few meters to over 1km in length.
• Formation of Tombolo


  A tombolo is a beach that connects the mainland to an offshore island. It often develops first as aspit, as longshore drift (usually in one dominant direction) transports and then deposits materialwhere the coastline changes direction and wave energy is lost.
• Location of Rhone Delta


  The River Rhone flows into the Mediterranean Sea just to the west of Marseilles in southern France. The delta lies between the two major distributaries of the River Rhone; the Grande Rhone and the Petit Rhone, which diverge 4 km north of Arles.
• Landforms in Rhone Delta

  Longshore drift has moved sand to create lagoons trapped behind the onshore bars and spits. 

  The delta is very gently sloping. 

   

  Dunes form when the winds blow from the sea, and dry sand is moved up the beach by saltation. The sand becomes trapped by obstacles on the berm or the point- of the highest spring tides.

   

  The high levels of sediment accumulation from river deposition have created a gently sloping coastal landscape. Waves break early on the shore and their energy is dissipated by the beach and delta sediment. 
• How Rhone Delta has changed over time

  The Rhone delta has formed over the last 7000 years since the sea level rise at the end of the last ice age finished. The current shoreline began to take shape at the beginning of the eighteenth century when a flood moved the course of one of the channels of the Rhone to its present-day position. 

   

  This led to material at the mouth of the abandoned channel being moved to form the Beauduc Spit. in the nineteenth century the mouth of the Grand Rhone changed position due to human management reducing it from three channels to one.
• Physical factors that influence Rhone Delta

  Tidal range - Tidal range of 30cm reduces the amount of land exposed to coastal erosion and which creates very few currents to carry material away.

   

  Deposition -  In 1900 was 50 tonnes per minute. The high deposition rate is due to flocculation of the particles in the high salinity Mediterranean sea.

   

  Sediment - The river collects a large amount of sediment from the young sedimentary rocks in the Alps.
• Location of Holderness

  Located in Yorkshire from Flamborough to Spurn Head.

   

  Clay, silt and mud geology and high energy environment make it one of the most rapidly eroding coastlines in England.

   

  Prevailing wind from the South West.

   

  Length of fetch is 1500 km across the North Sea
• Landforms in Holderness

  The Holderness Cliffs - the cliffs are made from boulder clay formed from material left by ice sheets. They are retreating at an average rate of 2 metres per year - due to rainwater eroding the clay and rip currents excavating the cliff. 

   

  Spurn Point = 6 km long. It is made of sand and shingle. Sediments brought here by longshore drift are deposited. A salt marsh has developed behind the spit.

   

  Hornsea, Mappleton and Withernsea beaches were formed by the deposition of sand and shingle, which has been eroded from the coast to the north.
• How has Holderness changed over time

  The Holderness cliffs - Boulder clay cliffs are formed from material left by ice sheets. They are retreating at an average rate of 2 metres per year

   

  Flamborough Head - Wave quarrying can result from the sheer weight of the waves striking the cliffs or from air being trapped in faults and acting pneumatically as waves break.

   

  Spurn Head - Spit = growing at around 10 cm each year winter storms periodically threaten to cut through the narrow neck and detach it from the mainland.
• Physical factors affecting Holderness coastline

  Weather – Winter storms produce stronger waves and higher sea levels. Rain they bring intensifies land-based processes. The saturated clay = increased runoff leading to slumping

   

  Geology - The two main types of rock found along the coast are chalk and boulder clay. The more resistant chalk has survived large-scale erosion and this has created the classic features of Flamborough Head.
• Eustatic and Isostatic

  Changes in the volume of water in the global ocean store are known as eustatic changes. These changes are influenced by variations in mean global temperatures, affecting both the amount of water in the ocean store and its density.

   

  It should be appreciated that sea level change is relative as it is also affected by changes in land level. These changes, known as isostatic, are not considered here
• How do coastal landforms change over time as temperatures decrease?

  A decrease in global temperature leads to more precipitation being in the form of snow. Eventually this snow turns to ice and so water is stored on the land in solid. The result is a reduction in the volume of water in the ocean store and a worldwide fall in sea level. Raised beaches are areas of former shore platforms that are left at a higher level than the present sea level. They are often found a distance inland from the present coastline.

   
• How do coastal landforms change over time as temperatures increase?

  Submergent Landforms - Those that are formed when sea levels rises, flooding formerly exposed land areas. Rias are submerged river valleys, formed as sea level rises. Fjords are submerged glacial valleys.

   

   
• Need for management in Sandbanks, Dorset


  • The beach is a major tourist attraction. Blue Flag award for water quality, and being gently sloping it is safe for family swimming.
  • It provides protection and shelter from waves for Poole Harbour = popular and safe place for water sports
  • Climate change= £18m of damage to residential properties will occur in the next twenty years.
  • It has a large number of high value commercial properties built on it - Sandbanks Hotel and Haven Hotel
  • Residential properties are in high demand (£10m)
• Management Strategies in Sandbanks

  Rock Groynes - This not only restricts sediment from entering the harbour entrance, thereby keeping access free for shipping, but also absorbs wave energy, and reduces rates of erosion. It is estimated that without this action, erosion rates would be about 1.6 m per year.

   

  Beach Recharge - Sand dredged from offshore is sprayed onto the beach, a process known as ‘rainbowing’. This currently costs about £20/m3, however, there is an alternative that costs £3/m3. Over 3.5 million m3 of sediment have been added to Poole Bay beaches.