coastal systems and landscapes Flashcards
What is a coastline?
a part of land near the sea that is an open system, as it interacts with its surroundings
What is a closed system?
one that doesnt interact with its surroundings
What is a dynamic equilibrium?
when inputs and outputs of a system are balanced
What are the inputs of a coastline?
-energy from waves, wind, tides, currents
-sediment
-geology
-sea level change
What are the ouputs of a coastline?
-dissipation of wave energy
-accumulatioon of sediment above tidal limit
-sediment removed beyond coastline
What is fetch?
the distance a wave has travelled
What are the different zones of a coastline?
-backshore
-foreshore
-nearshore
-inshore
-offshore
What is the backshore zone?
the area above the high tide mark, affected by wave action only during major storm events. Where sand dunes are located
What is the foreshore zone?
the area between the high tide and the low tide mark
What is the nearshore zone?
the area of shallow water beyond the low tide mark, where a wave breaks
What is the inshore zone?
area between LWM and point where waves cease to have influence on land beneath them
What is the offshore zone?
area beyond the point where waves don’t have impact on land beneath them
What are the characteristics of a constructive wave?
-long wave length
-little wave height
-strong swash
-weak backwash
-found on low energy coastline
What are the characterisitics of a destructive wave?
-short wave length
-wave height over 1m
-weak swash
-strong backwash
-found on high energy coastline
What is wave refraction?
the distortion of wave fronts as they approach an intended shoreline
What are tides?
changes in water levels of the sea/ocean due to the gravitational pull of the moon
Explain spring tides
when the sun and moon are both align in a straight line with the earth, highest tidal range
Explain neap tides
when the moon and sun are positied at 90 degrees from the earth, lowest tidal range
What is a sediment cell?
a stretch of coastlin usually bordered by 2 prominent headlands where movement of sediment is more or less contained
What are the inputs of a sediment cell?
-cliff erosion
-onshore currents
-river transport
-wind blown sediment from land
-subaerial processes (weathering/mass movement)
-marine organisms
What are the outputs of a sediment cell?
-sand dunes (backshore)
-beaches (foreshore)
-bars (nearshore)
-barrier islands (offshore)
What are the components/flows/transfers in a sediment cell?
-longhsore drift
-swash/backwash
-tidal currents
-sea/ocean currents
-wind
What is the coastal sediment budget?
balance between sediment added and removed in a sediment cell
What is weathering?
the breakdown/disintegration of rock from its orgignal place or close to ground surface
What is freeze-thaw weathering?
-water enters cracks in rock
-it freezes and expands widenin gthe crack
-ice melts and water goes deeper in crack
-process repeats until rock splits
What is salt crystallisation?
when sea water evaporates causing salt crystals to grow, exterting pressure on the rock causing cracks to widen. Slat also erodes ferrous rock.
What is wetting and drying?
When rocks such as clay expand when they are wet and contract when dried
What is carbonation?
rainwater absorbing CO2 from air to create carbonic acid which when reacting with calcium carbinate can easily dissolve it
What is solution? (weathering)
when rock minerals such as salt are dissolved
What are examples of mechanical weathering?
-freeze thaw
- salt crystallisation
-wetting and drying
What are examples of biological weathering?
root activity
seaweed acids
rock boring
birds
What are examples of chemical weathering?
carbonation
oxidation
solution
How does root activity weather rock?
roots grow into cracks and exert pressure, splitting rock
How can birds weather rock?
dig burrows in cliffs - weakening the rocks
What is hydraulic action?
when a breaking wave traps air as it hits a cliff face and pushes it into cracks in a cliff face. When water draws back, an explosive effect is caused due to the change in pressure (also known as cavitation)
What is wave quarrying?
the force of water impacting rocks (also known as wave pounding)
What is abrasion/corrasion?
Material hurled at a cliff face
or
sediment being drawn back and forth on platform (bottom) grinding it away
What is attrition?
rocks which carry out abrasion are worn into smaller pieces by bashing against each other - sandpaper effect
What is solution? (erosion)
the dissolving of calcium based rocks
What is coastal erosion affected by?
wave steepness
fetch of wave
sea depth
human activity
What is longshore drift?
occurs when waves approach a shore at an angle. Sediment is pushedup the beach via swash and pulled back into the ocean by backwash
sediment in backwash is picked up by oncoming wave
ovetime sediment moves in zig zag motion
What factors influence mass movement?
level of cohesion in sediment
height of slope
slope angle
temperature
level of saturation
What are landslides?
occur when sofer rock cliffs or ones with deposited material slip as a result of ‘failure’
What are rock falls?
occur from cliffs undercut by sea or on slopes affected by mechanical weathering
What are mudflows?
when heavy rain causes large amounts of fine material to flow downhill
What is slumping/rotational slip?
where softer material overlies more resistant materials . Sections of cliff face rotate and ‘slump’
What is soil creep?
very slow and continous movement of individual soil particles downslope
What are the inputs/ outputs of a coastline?
wave energy, wind currents and tides
What are the stores/ components of a coastal system?
barrier beaches, offhsore bars, spits
What is an example of negative feedback at a coast?
groynes
What is an example of positive feedback at a coast?
Headlands and Bays
Wave cut platform
What are the sources of energy in coastal environments?
winds
waves - constructive and destructive
currents and tides
What are the different processes of transportation at a coast ?
Traction – larger material rolls along the sea floor
Saltation – beach material bounces along the sea floor
Suspension – beach material is suspended within the water and moved by the waves
Solution - beach material is dissolved in the sea water and moved by the waves
longshore drift - sediment moving in zig zag movement
How do headlands and bays form? Give a named example
headlands and bays form on a discordant coastline, where there are bands of hard and soft rock. Soft rock (like limestone and clay) is eroded more quickly, which leads to the formation of a bay. Due to wave refraction, bays are eroded more easily and headlands stick out in the ocean which are made of hard rock (like chalk )
Describe the formation of wave cut platforms
The waves attack the base of a headland and erode it more quickly
A wave cut notch is formed
The cliff collapses due to being unstable leaving a wave cut platform which is only visible at low tide.
The cliff face retreats
Describe the formation of stacks and stumps
Cracks are widened in the headland through the erosional processes of hydraulic action and abrasion
Waves continue to grind away at the crack, it opens up to form a cave
Cave becomes larger and breaks through the headland to form an arch
Roof of the arch becomes too heavy and collapses into the sea. This leaves a stack (an isolated column of rock)
The stack is undercut at the base until it collapses to form a stump
What are the 2 types of beaches ?
Drift aligned - waves come at and angle so longshore drift takes place
Swash aligned - waves are paralle4l to coastline to little horizontal movement
How are spits formed?
Drift aligned beach where longshore drift occurs
Waves approach the shore at an angle due to the prevailing wind, swash carries sediment onshore
Backwash then removes sediment out to sea in a straight line due to gravity
Overtime, this transport sediment along the coast in a zig zag
There is a change in shape in the headland which causes this to continue and deposit out to sea.
Larger sediment is deposited first and begins to accumulate forming a “spit” out to sea
The point closest to the headland is the proximal point, the distal point is the furthest away
Eventually, spits will curve and “hook” due to the tides, waves and currents
This shelters the water behind it leading to a salt marsh
A compound spit is different, as it has several “mini spits” which form off of the main spit.
What are the 2 types of spits?
Simple - simple spit that cane be hooked
Compound -has several “mini spits” which form off of the main spit.
How are tombolo’s formed?
Drift aligned beach where longshore drift occurs
Waves approach the shore at an angle due to the prevailing wind, swash carries sediment onshore
Backwash then removes sediment out to sea in a straight line due to gravity
Overtime, this transport sediment along the coast in a zig zag
There is a change in shape in the headland which causes this to continue and deposit out to sea.
Larger sediment is deposited first and begins to accumulate forming a “spit” out to sea
The spit will continue out to sea until it connects to an island
How are bar’s formed?
Drift aligned beach where longshore drift occurs
Waves approach the shore at an angle due to the prevailing wind, swash carries sediment onshore
Backwash then removes sediment out to sea in a straight line due to gravity
Overtime, this transport sediment along the coast in a zig zag.
There is a change in shape in the headland which causes this to continue and deposit out to sea.
Larger sediment is deposited first and begins to accumulate forming a “spit” out to sea.
This forms in coves and headlands and bays, eventually the deposited material re- joins the headlands
This forms a lagoon behind it
What are barrier islands?
Long, thin, sandy stretch of land, oriented parallel to the mainland coast that protects the coast from the full force of powerful storm waves
Between the barrier island and the mainland is a calm, protectedwaterbody such as a lagoon or bay
How are sand dunes formed?
- wind blows sediment onshore
-sediment deposits behind an obstacle - embryo dunes are the youngest, smallest dunes
- the first plants that start to from are called pioneer plants e.g maram grass - roots bind sand together making its stable
-foredunes then form and then yellow dunes
-dune slacks are low-lying areas within dune systems that are seasonally flooded and where nutrient levels are low - grey dunes follow up
-mature dunes are the ones at biodiversity climax
Estuarine mudflat/saltmarsh environments and associated landscapes; factors and processes in their development.
Eustatic, isostatic and tectonic sea level change: major changes in sea level in the last 10,000 years
What are ridges and runnels?
ridges and troughs running parallel to coast near LWM
they are formed by deposition during backwash
broken by drainage channels
What are ripples?
small elomgated ridges froming on the beach
waves and currents flow across loose sand which forms ripples along whole length of beach
What are cusps?
semi circular shaped ‘depressions’ with coarser material around edge and finer material in centre
formed by a collection of waves reaching the same point and backswash scouring out finer material
What are berms?
small ridges that form near HTM
deposited by swash of constructive waves
What is a storm beach?
a ridge found near the back of the beach composed of larger sediment picked up during a storm
What is thermal expansion?
when water takes up more space when it gets more warmer
What is isostatic change?
rising or falling of a land mass relative to the sea resulting from the release of the weight of the ice after the last ice age
What is eustatic change?
Variations in the sea level resulting from changes in the amount of liquid water entering oceans e.g melting ice caps
What is an emergent coast?
coastlines created where there has been a relative fall in sea level
What is an submergent coast?
coastlines created where there has been a rise in relative sea level
What is tectonic change?
sea-floor spreading stretches the basin making the sea level fall
What are examples of a sumergent landforms?
rias
fjords
dalmation coasts
What are rias?
drowned river valleys
river valleys flood only showing high land
e.g. Kingsbridge estuary in South Devon
What are fjords?
drowned glacial valleys
U shaped valleys left by glaciers are submerged
e.g. Western Norway
What are Dalmation coasts?
areas of the world where valleys
(especially glacial valleys) lie parallel to each other. Appear to be a
series of islands that run parallel to the coastline
What are examples of emergent landforms?
raised beaches
relict cliffs
What are raised beaches?
when land has risen in comparison to sea levels - level of land is now higher than it used to be
What are relict cliffs?
Wherever land has risen from the sea in the past and cliffs can often be seen that are no longer reached by the sea
gentle vegetated slopes are seen
e.g. north-west of Scotland
What is an emergent coast?
a coastline exhibiting features associated with falling sea levels
e.g. raised beaches and relict cliffs
What is a submergent coast?
a coastline exhibiting features associated with rising sea levels
e.g. Rias and Fjords
What are fjords and a named example?
a drowned glacial valley e.g. western Norway
What are Dalmatian coasts and a named example?
coasts that form where especially glacial valleys lie parallel to each other and then are flooded, only tops are seen e.g. Dalmatian Coast -Croatia
What is a cost benefit analysis?
when costs are forecast and compared to expected benefits
What is hard engineering?
physical changes to a coastline to a coastal systems to control natural processes
What is soft engineering?
natural systems are used to defend against natural processes
What is a sea wall?
Pros and Cons
a recurved structure that deflects waves back to sea
-provide a physical barrier and raise height of beach
-need drain outlets, easily eroded if cracks are present
What is rock armour?
Pros and Cons
large boulders placed in front of a cliff to absorb wave energy
-angular to expand surface area
-not secured in place, can be moved by waves
What are gabions?
Pros and Cons
smaller boulders contained in steel wire mesh cages
-absorb wave energy
-can be eroded by waves
What are reventments?
Pros and Cons
concrete/wooden structures placed across a beach
-take full force of energy
-wooden is easily eroded
What is cliff fixing?
Pros and Cons
driving metal bars into cliff face
-stabilises cliff and absorbs wave energy
-expensive
What are offshore reefs?
Pros and Cons
offshore reefs
-force waves to break offshore
-difficult to install
What are barrages?
Pros and Cons
large structures that prevent flooding on major estuaries
-act as a dam across an estuary
-unappealing to tourists, alters habitat
What are beach nourishment?
Pros and Cons
replaces material lost through longshore drift
-low environmental impact
-ongoing maintenance cost
What is dune regeneration?
Pros and Cons
replanting vulnerable areas with marram grass
-provide natural protection from the sea
-no guarantee that the sand dunes will stay in place. They may be damaged by storms or by people walking over them.
What is managed retreat?
Pros and Cons
abandoning current line of sea defences and exposing land to sea
-act as a defence against rising sea level
-infrastructure and properties lost
What is land use management?
Pros and Cons
encouraging landowners to give up land for grazing
-decreases infrastructure lost
-cannot remedy damage done
What are the pros and cons of doing nothing?
-owners lose land
-let nature take its course
What are the 4 DEFRA strategies?
-hold the line (MAINTAIN CURRENT POSITION OF COASTLINE)
-advance the line (EXTEND COASTLINE OUT TO SEA)
-managed retreat (ALLW RETREAT IN MANAGED WAY)
-do nothing
What is integrated coastal zone management?
establishing sustainable levels of economic and social activity
What is background information on Odisha?
-South-east coast, bordering Bay of Bengal
Straight coastline, 480km long
6 deltas ‘Hexadeltaic’ region or ‘Gift of the Six Rivers’
1435km² mangrove forest
Chilika Lake - salty lagoon renown for bird life Less salty in monsoon
season
Coastline of deposition, significant sediment store.
Rivers important transfer of sediment to the system.
What are opportunities in Odisha?
Flat land for settlement.
Variety of marine and coastal flora/fauna including mangroves, sea grasses, salt marshes, sand dunes, estuaries and lagoons. Large stocks of fish, mammals, turtles
Potential for offshore wind, tidal and wave energy
35% of coastline has significant minerals and heavy metal deposits e.g. clay and limestone
Opportunities for offshore oil and natural gas and mining
Many people employed in fishing and aquaculture such as shrimps
Cultural and archaeological sites along the coast attract tourists as well as beaches and wildlife sanctuaries. Chilika Lake Bird Sanctuary has over 150 species.
What are risks in Odisha?
Rates of erosion increased in recent decades through natural processes and human intervention
Increasing concern about vulnerability to storm surges and tsunamis as well as longer term threats from rising sea levels
Risk of storm surges from tropical cyclones (climate change)
Attempt to halt erosion with hard engineering removes important input of sediment that is needed to form beaches, dunes and barrier beaches
50 years ago Odisha had average 5.1km of mangroves, today 1.2km
What are the erosion/deposition rates in Odisha?
Findings from 2011 Assessment of Shoreline Change:
- 46.8% accretion, 36.8% eroding, 14.4% stable.
- Most accretion is in the north near deltas
- Most erosion in the south. Here hard-engineering structures protect ports
- Kendrapara, Bhadrak and Baleshwar have 50% higher accretion elsewhere due to mangroves
Shoreline change most significant at river mouths
What were the 2 cyclone events in Odisha?
October 2013 Cyclone Phailin struck near Gopalpur. Wind speeds of 200mph – power lines torn down, trees uprooted, 1 million evacuated, 44 died, 500,000 agricultural crops destroyed, economic loss of US $700,000. Ecosystem surrounding Lake Chilika may take years to recover
What management has took place in Odisha?
ICZM - Integrated coastal zone management
Establish sustainable economic and social activity
Involve stakeholders e.g. Odisha State Disaster Management Authority and Wildlife Wing of Forest and Environmental Department and Greenpeace India
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