Coasts GI, GW 1-3 [P1] Flashcards
What is swash and backwash?
Swash: brings mats. onto beach (dep) at an angle
Backwash: removes mats. from beach at right angle
Explain wave refraction.
Wave front curves in on protruding landform, conc. wave energy leads erosion.
Wave front curves out in bay, dispersing wave energy, deposition
Factors affecting wave energy (3)
- fetch
- wind speed
- wind duration
Incr incr
What are currents?
Large scale continuous water movement driven by prevailing winds.
What are longshore currents?
Currents that flow parallel to coasts; aid longshore drift
Value of coral reefs 7
- coastal prot , slows waves - prevent erosion, absorbs wave energy - prot infra
- food and jobs via fisheries
- major attraction for snorkelling
- supports bio diversity : breeding grounds
- construction mats : coral rubble
- pharmaceuticals : undiscovered drugs
- aquarium trade : impt aquatic species
What are human activities at coasts?
- pollution
- infrastructure (CA removed/eroded)
- sand removed: HA/ leans reclaimation
What is hydraulic action
- hydraulic action: waves strike against rock, trapping air; air compressed by waves: pressure in rocks; repeatedly compressed: rocks shatter
What is abrasion
As waves break sediments carried are hurled against coast; knock and scrape: weakens surface, breaks down coast
What is attrition
Rock particles carried by waves knock together, breaking into smaller pieces
What is solution
Sea water reacts with water soluble mats in coast, dissolving them
Explain longshore drift (4)
- Waves approach coast at angle of wind. carry mats up in same direction by swash
- Backwash returns at right angle, bringing some mats with it
- Process repeated when next wave breaks
- Mat. is moved along coast in zigzag manner parallel to coast
How are cliffs and shore platforms formed?
- Hydraulic action, abrasion erode a crack/ joint, gradually enlarging to form a notch
- Notch further deepened to form hollow space: cave
- Further erosion, cave roof collapse to form steep cliff
- Further erosion overhanging cliff formed, collapses, mats accumulated at foot of cliff
- Gently sloping pattern at base: shore platform
How are headlands and bays formed?
- Coast has rocks with diff resistance to erosion
- Less resistant erodes faster than more resistant: uneven coastline
- More resistant protrude: headlands
- Less resistant: curve inwards as eroded: bays
How are caves arches and stacks formed?
- Headlands: some rocks less resistant. Erosion via hydraulic action and abrasion. Waves attack lines of weakness and undercut it. Forms cave
- Cave dev. on both sides. Erosion joins them together: bridge (arch) formed
- Arch may collapse forming stack (pillar of rock)
How are spurs and tomobolos formed?
- By longshore drift: abrupt bend in coastline, continue to dep mats in same direction
- Accumulate and forms a ridge of sediment from where coast changes direction: spit
Hook/ curve may dev as conc wave refraction - Spit: one end mainland one end extend into ocean. May connect mainland with offshore island: tómbolo
Sea walls DexaL
D: walls along coast reflect waves: absorb wave energy
Ex: Isle of Wight, UK: reflect waves absorb wave energy
A/S: high degree of protection, prevents further erosion. Ensure max dissipation of wave energy.
L: costly to build and maintain, base may erode and collapse
Gabions DexaL
D: wire cages filled with crushed rocks. Along shore or behind beach, prevent/reduce coastal erosion: weaken wave energy
Ex: East Coast park when first reclaimed, removed after vandalised
A: absorb wave energy better than sea walls: gaps allow water to filter thru; successful against Hugh energy waves
L: very unsightly, expensive to maintain, damaged easily
Breakwaters
D: Structures parallel/ on end to coast. Break force of oncoming waves. Create zone of calm water: shelter harbour for boats
Ex: East Coast park: protect reclaimed shoreline. Act like headlands: area of clam water behind, sediment build up in J shape
A: zone of calm water, sheltered harbour for boats
L: Aesthetically unappealing, may cause flooding and erosion problems, costly, uneven protection
Groynes
D: Low walls at right angle, retain sediments from longshore drift. Reduce wave energy, dep mats on updraft side
Ex: Sandy hook New Jersey, USA. Groynes perpendicular to beach trap sand going north from longshore currents
A: absorb/ reduce wave energy, causes deposition, sustain and extend beach
L: unsightly, expensive to build and maintain, no mats dep of downdrift side
Tetrapods
D: four pronged concrete structures: dissipate wave energy. Stacked in interlocking position. Pre casted, can be replaced quickly.
Ex: Crescent city, north California, USA. Protect from coastal erosion, reduce tsunami impacts: 31 times bet 1933 and 2008
A: reduce erosion, reduce wave energy as water passes thru
L: aesthetically unappealing, expensive, dangerous to swimmers and boats
Beach nourishment
D: using sand from external source to replenish on depleted beach: wide sandy area to protect land
Ex: Cape May point New Jersey usa
A: wide beach: effective energy absorption
L: expensive and time consuming, may suffocate corals, may erode again
Planting vegetation and stabilising dunes
D: mangroves- dense root system; sand dunes: stabilised by planting grass: roots anchor preventing erosion
Ex: Trition place West Australia: vegetated sand dunes prevent erosion
A: stabilise coastlines
L: costly maintenance: paths for human traffic
Encouraging coral reef
D: help weaken wave energy, breeding ground for fish. Artificial: place lasting mats eg, concret onto sea floor to be colonised
Ex: Maldives in the Indian Ocean: coral growing program since 1996- steel rods 45 m long placed off coast, charged with electricity to speed up growth
A: reduces wave energy and wave height, natural barrier
L: 20-30 years for visible results, may not be significant
Limiting damaging activities
D: Banning/ limiting activities that interrupt fiction of natural systems
Ex: port Phillip Melbourne: sand dunes were trampled- fenced off dunes and built separate paths
A: restore coasts, allow function of natural systems, allow recovery
L: less attractive less tourism less income, may be costly
Protect coastal resources eg fish
D: prevents depletion and exploitation eg fish
Ex: Goat island marine reserve New Zealand: marked off zones prevent fishing
A: prevent extinction, marine reserves become tourist attractions
L: threatens fisherman’s livelihood
Restrict development
D: to deal with threat of natural hazards- retreat: relocation, avoidance, regulating development, defence- engineering measures m
Ex: USA: Federal emergency management agency steers development away
A: prevent damage to infrastructure, less cost to rebuild
L: people cannot use the resources that coastal enviros have
How do coastal areas support human activity
- fisheries and aquaculture
- housing and transport
- tourism and recreation
Support human activity : fisheries and aquaculture (dexaL)
Where fish are bred and raised to meet demand, farming of fish
Kung krabaen bay
- protected coastal woodland
- underdeveloped stretches of coastline
- mangroves protect area from storms
- mangrove forest : shrimps spend early stages of lives for prot
- areas cleared from these are good for shrimp as waterlogged
- shrimps sold for econ
- KKB royal dev Center offers training and research to support fishing and agricultural dev
- clearing of mangroves (deforestation)
- coastline more vulnerable to erosion from storms and pollution
- 2002, farmers in nearby villages gained about 92.3k baht per household per year
Support human activity: housing and transport (DexaL)
Building for ppl to live in, movement of ppl or goods from one place to another
Kukup Msia
- mangroves
- mudflats
- sheltered coast, Low energy waves
- tourism income
- floating fisheries : $$ / food
- sewage pollutes water
- overfishing impact local ecosystem
Supports human activity: tourism and recreation
Temp movement of ppl for leisure or recreation, activities done for enjoyment
Sentosa sg
- sheltered artificial beaches
- fine sand
- coastal dev
- boosts economy
- ONE(^o)15 marina, a hotel and marina (facilities)
- incr pollution from tourists
- sand for beach or land reclamation : suffocate corals
What is a coral reef?
Coral reefs dev at or slightly below sea level on the seabed
Made of thousands of tiny animals, coral polyps, which secrete rock like deposits of calcium carbonate to prot its soft body
As coral polyps die new ones continue living, CaCO3 skeletons accumulate as limestone
Enviro conditions for coral reef growth (5)
- avg salinity of 34-37 parts/thousand
- moderate amt of water movement - enough O2
- sea surface temp not lower than 17-18
- amt of sunlight : clear saline water 10-60m deep - enough sunlight : algae photosynthesis
- turbidity of water (murkiness) Low enough for sunlight
Global distribution of coral reef and mangrove ecosystems
- most around tropics
- most near coastline of sheltered coasts
What is a mangrove
Salt tolerant tropical or sub tropical plants, grow in conditions most plants cant
Adaptations of mangroves : roots 3
- Prop roots
Anchor trees firmly in soft muddy ground
Ensures will not be uprooted or swept away by waves - Aerial roots (up)
Take in O2 in day when not submerged - Kneed roots
Helps trap soil for plant growth
Adaptation of mangroves : seeds and leaves 2 each
Leaves salt secretors : excrete excess salt on underside
Leaves have drip tips : rainwater drains easily
Javelin shaped fruits : pierce soft mud to germinate immediately
Buoyant fruits
Allows to float away and germinate in other coastal areas
Conditions for mangrove growth
- Low energy waves (shelter coasts) - rooting and sediment deposition
- saline environment - adapted for high salt
- high turbidity murky water
- tropical/sub tropical climate
- muddy waterlogged soil (mudflats)
Value of mangrove ecosystem
- dense root system : prot from erosion / wave energy
- breeding ground and habitat for fish
- aquaculture
- fuel wood - prod fo charcoal
- cultural : pre colonial times, home to sea faring populations eg orang Seletar
- food for animals and humans eg fruits of some can be juiced
Pressures coral reef : fishing methods 2
Spear fishing
Belize/Bonaire the Netherlands
Selective depletion disrupts ecosystem food chain
Eg parrot fish eat algae that many inhibit coral growth
Dynamite blasting and use of cyanide to stun fish
Philippines / Indonesia
Coral reef habitat destroyed
Pressures coral reef : coastal dev 2
Reclamation and extension of land via clumping of sand and rock onto reef
Japan
Coral reefs suffocated by sediments
Expansion of coastal resorts and housing : incr waste
Pressures on coral reef ecosystems: climate change
Rapid changes in sea temps and levels faster than ability to adjust
Seychelles 30% reduction
Coral bleaching when higher sea temps - loss of algae, coral turns white
Pressures on coral reef ecosystems pollution
Excess fertilisers and chemicals from agricultural land
Oils and heavy metals from industrial wastes
Sewage from urban areas deposited into sea
Philippines , sewage: Sri Lanka
Water become murky, block sunlight, coral die
Pressures coral reef : recreational use of coast
Tourism activities eg building facilities, trampling and anchoring of boats
Sri Lanka
Waste into water stresses coral, boat anchors damage coral
Pressure on coral : over collection
Over collecting for personal use
Philippines
Weakens corals disrupts ecosystem more vulnerable
Pressure on coral : siltation
Sediments from areas being cleared of forest washed into water
India
Corals suffocate, water filled with sediments
Pressures mangroves : pollution
Urban and industrial activities - untreated wastes dumped into water
Peru
Pollution can overwhelm balance of mangrove ecosystem
Pressures mangroves: clearing for fuel and charcoal
Cleared for fuel and charcoal, esp in regions with Low income economies
Indonesia
Less fish breeding grounds, more vulnerable to erosion
Pressure on mangrove : rising sea levels
Rising sea levels and extreme storm activity due to acceleration of climate change
Gulf of Thailand
Mangroves have trouble colonising areas further inland despite RSL due to competition for space w human activities
Pressures on mangroves : coastal development / land reclamation
Reclaimed for housing industry recreation
Caribbean island
Mangroves largely disappear, coastal waters polluted from human activities
Pressures mangrove ecosystems : conversion to other land uses
Thousands of hectares of flat well watered mangroves are converted to shrimp fames and paddy fields
Vietnam/ Thailand
Mangroves cleared to make space , coasts become more vulnerable
How to make data more reliable
- Take more instances of measurement
- repeat at more sites
- repeat daily at same time
- repeating hourly
Etc
Field sketching steps 10
- Use clipboard to rest paper
- Draw a frame/border
- Use soft pencil and eraser
- Give a title that locates the sketch (place name, grid ref)
- Decide on sketch focus, ignore unnecessary details
- Write direction of view (compass, bearing, written descriptions)
- Divide paper into 3 : sky+horizon, mid ground, foreground
- Start by drawing furthest things
- Label main elements, write number next to each feature
- Numbers can refer to annotations of scene
Photography steps 5
- Decide on purpose: what it will show, how it will be used
- If being compared, ensure similar viewpoint and perspective
- Identify position: sheltered, easily accessible, unobstructed view
- Put main focus in middle
- Make notes in recording sheet: time, date, location, weather conditions, direction
Photography considerations to make 4
- poor weather conditions
- difficulty accessing suitable sites
- purpose: clear and linked to aims
- consider time of developing/ manipulating a photo
Using photographs and sketches editing and labels and comparison 3
- photo editing used to crop label annotate digital shots
- labels : previous features and landforms, geology, gradient, smooth/rough textures, structure: joints/faults, vegetation
- photos can be compared: before/after, diff times
Longshore drift measurement equipment and steps 5,10
E:
- float eg orange
- stopwatch
- measuring tape
- wind vane
- recording sheet
S:
1. Find safe spot with clear view of ocean
2. Wind vane for wind direction, rec
3. Choose dist eg 10m
4. Lay measuring tape close to water, mark start and end with poles
5. Go to slightly before start pt, roses orange into breakers just behind
6. Start timing when orange passes start
7. Stop timing when orange passes end, rec
8. Observe pattern of travelling path, rec
9. Repeat for avg results
10. Identify direction of sediment movement nothing relative location of poles
Beach profile/gradient equipment and steps 4,10
E:
- measuring tape
- clinometer
- 2 ranging poles
- rec sheet
S:
1. Identify line of transect (perpendicular)
2. Constant: 4pts, equal 2m int. Undulating: points of significant changes
3. Ranging pile at A and B straight, don’t sink in sand
4. Measuring tape across LOT
5. Position clinometer on pole A
6. 2 ppl same height hold clinometer at eye lvl, align w top of others head
7. Note angle where string crosses protractor scale, rec
8. Rec dist between A and B
9. Repeat 3-6 between B-C, C-D
10. using graph paper draw graph. Connect points w smooth line
How to identify the high water mark
The highest point the waves reach
- line of debris / diff sand colour wet and dry
- if multiple lines, line closest to sea
- if high tide, measure water edge
Imagine a beach gradient graph rn
. D
C/___
B/____
_A/__
Measuring exposed groyne height equipment and steps 3,4
- metre ruler
- camera
- rec sheet
- Identify and rec each side of groyne: updrift and Downdrift sides
- Use metre ruler to measure groyne top to sediment surface (both sides)
- Take digital pics to illustrate diff in sediment lvls
- Repeat for each groyne/ according to sampling method
Sediment analysis equipment and steps 9, 16
- containers to collect samples
- pen/marker
- weighing machine/ balance
- vernier calibers
- Set of sand sieves
- oven
- quadrant
- power’s scale of roundness chart
- rec sheet
- Identify line of transect
- Sampling method
- Conduct sampling at LOT
Fine
4. Collect 200g and label
5. Repeat collection at all points
6. Dry samples in oven
7. Weighing scale measure 100g
8. Pour thru sieve set
9. Weigh and retained in each
10. Calc % retained from 100g, rec
11. Repeat 7-10 at all points
Rough, coarse, and irritating
12. Place quadrant on pebble beach acc. sampling method
13. Pick 10-15 samples randomly within quadrant
14. Measure long axes w ver.cal
15. Determine angularity (refer to scale), rec
16. Repeat 12-15 at all points
Measuring cliff height equipment and steps
- tape measure
- clinometer
- calculator
- recording sheet
- At safe dist from cliff measure dist using tape measure (A)
- use clinometer towards to top of cliff to measure angle (B)
- calc height: (A x tanB) + height of observer
Measuring wave height equipment and steps 2,6
Crest-trough
- metre ruler
- rec sheet
- Go into water (not above knees) far enough to measure a wave
- Place metre ruler into water touching beach floor
- Measure height of crest and trough as wave passes
- When wave passes mark top and bottom of wave on ruler, measure height and rec
- Subtract trough from crest to get height
Measuring wave period equipment and steps 3,5
Time taken for 10 C&T to pass / 10
- metre ruler
- stopwatch
- rec sheet
- Go into water (not above knee) far enough to measure a wave
- Place meter ruler into water touching beach floor
- Use stopwatch, time duration for 10 successive C&T to pass , rec time and no of waves (10)
- Repeat twice
- Clac avg timing on sheet
Measuring wave frequency equipment and steps 3,7
No of waves pass in 5min / 5
- metre ruler
- stopwatch
- recording sheet
- Go into water (not above knee) far enough to measure a wave
- Place meter ruler into water touching beach floor
- Use stopwatch time 5 min
- Count wave no (C&T) in 5 min
- Record time and no. on sheet
- Repeat twice
- Calc avg timing on sheet
Destructive waves (wave analysis)
Height: >1m
Period: 5-6s
Length: <20m
Frequency: 10-14/min
Steepness: >0.025m
Constructive waves (wave analysis)
Height: <1m
Period: 8-10s
Length: up to 100m
Frequency: 6-8/min
Steepness: <0.025m
Calculating wave steepness
Wave height/wave length
Factors effecting longshore drift measurement 3
- tidal and wind conditions (speed)
- obstructions to floats eg rocks
- place slowly: less momentum
