Coastal systems and landscapes Flashcards
coastal systems
coasts are open systems because they receive inputs from outside the system but they are considered closed systems as sediment cells
sediment cells
often bordered by headlands they are sections which sediment movement is almost contained and they are in dynamic equilibrium
sediment sources
rivers, cliff erosion, wind, glaciers, offshore bars and sinks, longshore drift
sediment budgets
Coastal management tool used to analyse the inputs and outputs of a coastal system
littoral zone
land between cliffs or dunes and offshore area past the influence of waves
wave formation
wind moves across the water creating ripples and waves, shallower seabed means waves become more horizontal, as the height increases velocity and wavelength decrease
factors affecting wave energy
strength of the wind, duration of the wind, size of fetch
constructive waves
formed in open ocean, long wavelength, 6-9 per minute, strong swash weak backwash, occur on gently sloped beaches
destructive waves
localised by stronger winds closer to the coast, short wavelength, 11-16 per minute, weak swash strong backwash
tides
difference in high and low tide is called the tidal range, tend to be larger in channels and estuaries
currents
underwater tides are caused by a buildup of water at the top of a beach and pose threats to the beaches and lives
high energy coastlines
more powerful waves, large fetch, typically have rocky headlands and landforms and more destructive waves
low energy coastlines
sheltered areas where fetch is lower so waves cant build in size, typically sandy beaches and more constructive waves
wave refraction
when waves hit a headland they turn and lose energy so the areas around are hit with weaker waves
erosion
removal of sediment from a coastline
abrasion
sediment is moved along the coastline forcing it to be worn down over time
attrition
Erosional process where rocks and pebbles hit against each other causing them to become more rounded
hydraulic action
air is forced into cracks in rocks as waves hit them, high pressure makes them widen eventually forcing them to break the rock
solution
acidic seawater can cause alkaline rocks to be eroded such as limestone
wave quarrying
breaking waves hit cliff faces exerting lots of pressure on them forcing them to break which also weakens them leaving them more vulnerable
factors affecting erosion
waves- destructive or constructive, beaches-they can absorb wave energy for cliffs behind, subaerial process- weathering and mass movement, rock type,
rock types
sedimentary rocks are cemented sedimented particles so are weaker, igneous are interlocking crystals so more stubborn, metamorphic crystals organised in the same direction so resistant
traction
transportation process where large heavy sediment rolls along the seabed forced by currents
saltation
transportation where smaller sediment bounces along the seabed pushed by currents but too heavy to be carried by water
suspension
transportation where where smaller sediment is carried by the water
solution
transportation where sediment is dissolved in the water and then carried
longshore drift
waves hit the beach at angles of the prevailing wind pushing sediment on the beach in that direction
deposition
sediment becomes too heavy waves too carry so is dropped, explaining why beaches are either sandy or rocky
mechanical weathering
freeze thaw- water enters cracks in rocks then expands breaking rock, salt crystallisation- water evaporates leaving salt which exerts pressure on rocks forcing cracks to widen, wetting and drying- some rocks expand when wet like clay and this repeated process weakens the rock
chemical weathering
carbonation- rainwater absorbs CO2 creating a weak carbonic acid which can then lead to dissolving the rocks, oxidation- minerals become exposed to oxygen they expand causing rock to crumble, solution- rock minerals are dissolved
biological weathering
plant roots- roots of plants grow in cracks exerting pressure, birds- some birds build burrows, rock boring- clams secrete chemicals that dissolve rocks, seaweed acids- sulphuric acid can dissolve rocks minerals, decaying vegetation- water flowing through it becomes acidic
mass movement methods
soil creep, mudflows, rockfall, landslide, slump, runoff
caves, arches, stacks and stumps
hydraulic action and abrasion cause small caves, overlying rock then collapses, caves widen because of erosion and subaerial processes opening up causing an arch, arch then falls under its own weight leaving a stack
cliff profile
steep cliffs- rock is strong and resistant, gentle cliffs- areas with weaker rocks, rate of retreat- likely to be higher if its unconsolidated material
wave cut notch and platform
when waves erode rock its concentrated at high tide mark usually though hydraulic action and corrasion create a wave cut notch, it becomes deeper then after a while fall in on its own weight leaving just the bottom part of the rock called a wave cut platform
beaches
depositional landform, swash aligned waves arrive perpendicular so little longshore drift, drift aligned waves arrive at an angle so more longshore drift
spits
longshore drift causes beaches to extent out to sea due to a change in the shape of the coastline, can’t extend all the way across an estuary become of the currents from the river
bars
when a spit join’s 2 headlands trapping water behind it
tombolo
when a bar connects a mainland to an offshore island and is caused by wave refraction off the coastal island reducing velocity
offshore bars
offshore region where sand is deposited because waves don’t have enough energy to carry the sediment to shore so drop it
dune plant succession
pioneer plans grow first for example marram grass, when they die they release nutrients which then means more vegetation can grow, embryo dunes and pioneer plants change conditions from harsh and salty to one where other plants can survive
salt marsh succession
- algal grows on mud which their roots bind together, 2.pioneer stage stabilise mud, 3.establishment stage grass grows creating a carpet of vegetation, 4. stabilisation plants grow and salt rarely gets beneath the surface, 5.climax vegetation rush, sedge and red fescue grass grows because the salt marsh is only submerged for a year
sand dunes
occur when prevailing winds blow sand to the back of beaches, embryo dunes, yellow dunes where vegetation may develop, grey dunes sand becomes soil, dune slack, water is trapped helping plants, heath and woodland, sandy soils develop so much more plantlike can prosper
mudflats and salt marshes
deposition occurs in river estuaries because flow of water from the river and sea meets and almost stops dropping sediment, can also occur behind a spit as they are sheltered
sea level change
isostatic- when land rises or falls relative to the sea and is localised, eustatic- affects the whole planet and could be down to thermal expansion or changes in glacial processes
emergent landforms meaning
land has been raised in relation to coastline such as arches, stacks and stumps
submergent landforms meaning
landforms occur when sea level rise or coastline sinks
submergent landforms examples
rias- rising sea levels flood inlets and valleys, fjords- rising sea levels flood deep glacial valleys, Dalmatian coasts- valleys running parallel to coast become flooded leaving a series of long islands
storm surges
a result of low pressure caused by large weather events such as tropical storms, raising sea levels and causing a flood threat
hard engineering examples
offshore breakwater-forces waves to break before shore, groynes- wood that traps sediment from LSD, sea walls-concrete that absorb and reflect wave energy, rock armour- large rocks which allow water through but reduce wave energy, revetments-wooden or concrete ramps which absorb wave energy
soft engineering examples
beach nourishment- sediment is taken from external sources to build up a beach, cliff regrading- reduces angle of beach so is less likely to collapse, dune stabilisation- marram grass planted so roots bind sand together, marsh creation-managed flooding allowing low-lying areas to flood
Cost benefit analysis
carried out before coastal management where costs and benefits are assessed and benefits have to outweigh costs
Integrated coastal zone management
large sections of coastline are managed with one management technique, it also talks about the human aspect of these projects
shoreline management plans
an SMP recognises all the activities that happen within a sediment cell human and natural
holderness technical information
over 50km from spurn head to flamborough, winter storms across the North Sea produce higher and stronger waves and the rain they bring intensifies sub-aerial processes
holderness stats
29 villages have been lost to sea since roman times, 2m erosion per year fastest in Europe, sometimes being 7-10 in one year because of storms
