P1C Rivers and Coasts (Physical Landscapes UK) Flashcards
1
Q
Describe river erosion processes (4)
A
- hydraulic action- erosive force exerted by water
- attrition - sediment particles knock against each other and break into smaller/more-rounded pieces
- abrasion - river bedload grinds against the bed+sides
- solution - minerals dissolved into water
2
Q
Describe river transportation processes (4)
A
- traction - larger boulders/stones roll along river bed
- saltation - stones bounce along river bed
- suspension - smaller clay/silt/sand particles are carried without contact with river bed
- solution - dissolved minerals carried in water
3
Q
Define deposition
A
when a river loses its energy or volume, resulting in materials being transported to settle
4
Q
Define the two types of river channel erosion
A
- lateral - widens river channel
- vertical - deepens river channel
5
Q
describe the long profile of a river in the upper course
A
- (erosion) mostly vertical erosion by hydraulic action+ abrasion
- (transport) mostly traction - large boulders moved
- (deposit) - largest boulders deposited
- steep gradient at the source
6
Q
describe the long profile of a river in the lower course
A
- (erosion) very little erosion - only lateral erosion on outside of river bends
- (transport) mostly suspension - lots of small particles
- (deposit) deposition mainly occurs here
- flat gradient, reduces quickly in height as slope reduces
7
Q
Describe the cross profile of a river in the upper course
A
- (channel) narrow and shallow
- (valley) clear v-shaped valley
8
Q
Describe the cross profile of a river in the lower course
A
- (channel) wider and deeper
- (valley) widened, flood plains at sides of river
9
Q
describe how a waterfall forms a gorge
A
- river flows over hard rock
- hydraulic action+ abrasion undercuts soft rock underneath
- hard rock cap layer/overhang collapses into plunge pool
- hydraulic action+ abrasion+ attrition cause particles to become smaller and are washed downstream by traction+ saltation+ suspension
- as the waterfall retreats up river it leaves behind a steep vertical-sided gorge
10
Q
describe gorges
A
- very steep valley sides
- river channel takes up most of valley floor
- turbulent, fast-flowing water
- boulders in river bed
11
Q
describe interlocking spurs
A
- steep sides
- winding river
- narrow valley floor
- upper course
12
Q
describe how meanders form + properties
A
- river flows faster on outside of bend due to centrifugal force - results in erosion (hydraulic action/abrasion/attrition) on outer bank + undercuts to create a river cliff
- deposition occurs in slow-moving water on inside of bend - slip-off slope of sand+shingle forms
13
Q
describe how oxbow lakes form
A
- caused by continuous erosion of outer bank of a meander
- river eventually cuts through narrow neck
- deposition isolates a portion of the river as an oxbow lake
- over time may infill with sediment to form a scar
14
Q
describe difference between formation of levees and flood plains
A
- during a flood the heaviest/most coarse sediment is deposited at sides close to river as more difficult to transport - forms levees
- finest sediment is carried further+ deposited to form a flat flood plain
15
Q
describe formation of levees
A
- form in lower course- rivers have more water (tributaries+wider channel)- more likely to exceed capacity+ flood
- sediment carried by floodwaters onto floodplain- increased friction reduces velocity so sediment is deposited
- largest+heaviest sediment deposited closest to river channel
- over time builds up to create raised banks which are levees (steeper on river side)
16
Q
describe tidal estuaries
A
- formed by the sea level rising+ filling an existing river valley
- river carries sediment downstream+ deposits it at lower course of the river as it stops flowing when it reaches the sea
- mud flats form at bottom of estuary bed - visible at low tide
- sand bars form due to the deposition
17
Q
describe the use of dams and reservoirs
A
regulate the water flow and hold back the water in a reservoir
18
Q
describe the use of channel straightening
A
a meandering section of a river is engineered to be wider and straighter, shortens distance water travels and speeds water away from vulnerable areas (cities)
19
Q
describe the use of embankments
A
raising the banks of either side of the river channel (sometimes covered in grass/flowering plants)
20
Q
describe the use of flood relief channels
A
an extra channel bypasses and adds capacity to the main river, controlled by a weir/flood gate
21
Q
describe benefits and costs of dams/reservoirs
A
/ boosts tourism, highly effective, provides hydroelectric power, source of drinking water, new habitats
X flooding valley above dam displaces people, expensive, interferes with migration of fish, can destroy habitats, have to be dredged
22
Q
describe benefits and costs of channel straightening
A
/ moves water away more quickly/ improves efficiency, makes boat navigation easier, home owners no longer worry about flooding so invest in properties
X habitats destroyed, can cause flooding lower downstream, expensive, may use unattractive concrete linings
23
Q
describe benefits and costs of embankments
A
/ cheaper than other hard engineering, provides habitats, used for walking paths, increases river’s carrying capacity
X if breached water lies on surrounding land, needs continual maintenance, access to river is difficult for fishing/boating
24
Q
describe benefits and costs of flood relief channels
A
/ moves water away more quickly, home owners no longer worry about flooding so invest in properties, new habitats created
X habitats changed/destroyed, can cause flooding lower downstream, expensive, take a long time to build
25
describe causes of flooding (4)
* prolonged/heavy rainfall - soil becomes saturated leading to runoff
* geology - impermeable rocks cause surface runoff, increases river discharge
* land relief - steep-sided valleys cause water to flow quickly into rivers causing greater discharge
* land use - impermeable building materials (tarmac/concrete) prevent infiltration+ cause surface runoff
26
describe the uses and pros/cons of flood plain zoning (soft engineering for floods)
process of stopping land near river from being built on
/ low cost, preserves green spaces, reduces amount of impermeable surfaces
X housing shortage (fewer places to build)
27
describe the uses and pros/cons of flood warnings (soft engineering for floods)
warnings give people time to move possessions+ evacuate
/ very cheap, people+properties can be saved
X only effective if people respond
28
describe ways to prepare houses for floods (7)
* raise properties off ground
* tiled floors
* flood guards at doors
* waterproof coatings
* raised power sockets
* wall-mounted tvs
* no fitted carpets
29
describe the uses and pros/cons of planting trees (soft engineering for floods)
increases interception+evaporation+ transpiration+filtration, reduces run-off
/ more carbon dioxide absorbed, adds variety to landscape
X loss of grazing land
30
describe the uses and pros/cons of river restoration
a river that has previously been hard engineered is restored to a natural channel
/ new wetland habitats, slows down water flow and keeps it in the area for longer - reduces flooding, aesthetically pleasing
X loss of extra farm land
31
describe the location of a UK town at risk of flooding and its causes of flooding (3P/3H) (case study)
Boscastle, north coast of Cornwall, 2004
* torrential rain/storm - 200mm rain fell in 24hrs - ground is saturated so increases runoff (P)
* trees were cut down - increases runoff (H)
* small drainage basin - water reaches town quicker (reduced lag time) (P)
* steep v-shaped valley sides - fast water velocity (P)
* settlements built downstream on narrow flood plain - impermeable materials eg. concrete reduce lag time (H)
* car park built from impermeable tarmac - increases runoff (H)
32
describe the impacts of flooding at Boscastle (case study)
* houses+bridges destroyed
* businesses destroyed eg. visitor centre, tourism devastated
* people worried+ evacuated
* 116 cars washed into sea
* economic damage - fall in house prices, £300m lost
33
describe the responses to the flood at Boscastle (case study)
* channel was widened+ deepened+ straightened
* bridges made wider+ higher to allow more water through
* raised car park+ built with a permeable material - cars less likely to be swept away/ reduces runoff
* dead trees+ trees close to river removed - prevents them from being swept away+ causing blockages
* **land use zoning** - prevent construction on river bank so residential buildings protected
-> planning+protection but unable to predict
34
describe what causes waves (3)
* wind speed
* wind duration
* the fetch - size of area/distance wind is blowing over
35
describe constructive waves
* created in calm weather, less powerful
* deposit material on the beach
* swash is stronger than backwash
* low wave height
* forms a gently sloping, sandy beach
36
describe destructive waves
* created in stormy weather
* erode the beach+cliff
* backwash is stronger than swash
* big+strong waves with high frequency
* forms a steep, pebble beach
* offshore bar forms as material eroded is deposited at bottom of sea bed
37
describe types of weathering (3)
* chemical/carbonation - rainwater dissolves calcium carbonate rocks (limestone/chalk);
the iron in rocks oxidises/rusts
* mechanical - due to extreme temps (freeze-thaw, heating+cooling);
when sea spray gets into cracks in rock then evaporates to form crystals that push the crack apart
* biological - plant roots grow into rock cracks and push them apart
38
describe types of cliff erosion (7)
* freeze-thaw erodes the top of the cliff
* biological - plant roots grow in rock cracks+expand
* corrosion from crystalised salt in rock cracks
* hydraulic action when water gets into cracks
* solution - rock eroded by acidic seawater
* attrition - rocks smash into one another
* abrasion - rocks grind against cliff
39
describe how headlands+ bays form
* discordant coastline - alternating layers of hard rock (chalk/limestone) +soft rock (sand/clay) perpendicular to coast
* waves erode soft rock more quickly by abrasion+attrition so these parts retreat inland forimg bays
-> beaches form in bays due to longshore drift+deposition where waves are less strong
* headlands of hard rock jut out into the sea (cliffs)
40
describe the formation of wave-cut platforms
* sea waves erode base of a cliff/headland (abrasion/hydraulic/corrosion) forming a wave-cut notch
* cliff becomes unstable+collapses, cliff retreats
* backwash carries away material, leaving a wave-cut platform
41
define hard and soft engineering
hard - large scale construction, expensive, tries to prevent flooding by absorbing shock of waves+ creating barrier
soft - more natural/ environmentally friendly, reduces impact of flooding with less intervention
42
describe the formation of spits and bars
* sediment is carried by longshore drift
* when there is a change in the shape of the coastline, deposition occurs and a long thin ridge of material forms a spit
* a hooked end forms if there is a change in wind direction
* waves cannot get past spits so silts are deposited in the sheltered salt marshes/ mud flats behind
* a bar forms when the spit connects with land
43
describe the formation of a sea stack/ stump
* a crack in the cliff is continually eroded by hydraulic action+ abrasion until a cave forms
* more rock is eroded at the base to form an arch, and chemical+ freeze-thaw weathering occurs at the rock above
* the rock above is weakened and collapses leaving an isolated pillar of rock and forming a stack
* the stack is eroded to form a shorter stump
44
describe the formation of sand dunes
* obstacles (driftwood) are dropped on beach
* onshore wind blows sand onto beach which is trapped by obstacles
* plants (marram grass) grow+ stabilise dune with roots, so more sand is trapped
45
describe the use and cost of sea walls
£5000 per m, curved face to deflect waves back to sea, made from concrete/stone, build-up of beach material at base of sea wall (toe protection)
46
describe the use and cost of groynes
£1000 per m, fence-like structure constructed at right angles to coast, traps material transported by longshore drift
47
describe the use and cost of rock armour
£1500 per m, large boulders placed in front of a cliff or sea wall, protects coastlines, absorbs shock of waves
48
describe the use and cost of gabions
£110 per m, a cage filled with rocks/concrete, protects coastlines
49
describe benefits and costs of sea walls
/ protects base of cliff from erosion, can prevent coastal flooding
X expensive, unattractive, makes access to beach difficult
50
describe benefits and costs of groynes
/ prevents movement of beach material by longshore drift, allows the build-up of a beach, more natural-looking beach for tourists+ residents
X unattractive, makes access to beach difficult, may cause issues further along the coast
51
describe benefits and costs of rock armour
/ absorbs energy of the waves, can be local rock so more natural-looking
X unattractive, makes access to beach difficult, requires maintenance
52
describe benefits and costs of gabions
/ absorbs energy of the waves, can be local rock so more natural-looking, relatively cheap
X unattractive, makes access to beach difficult, expensive to rebuild
53
describe pros+cons of beach nourishment
sediment is replaced from other sources/ sediment from downdrift is moved updrift by lorries+dredgers
/ wider beach attracts tourists, looks natural
X requires maintenance
54
describe pros+cons of beach reprofiling
transfer of material from lower to upper beach to make sides steeper
/ residential areas behind beach are protected, looks relatively natural
X steep+high beach can be uninviting/restricts access
55
describe pros+cons of dune regeneration
restoring sand dunes using vegetation or fences to stabilise dunes+ provide a barrier to collect sand
/ protects residential areas behind beach, cheap as local plants are replanted
X requires maintenance, beach is inaccessible during plant growth, fertilisers used
56
describe the process of mass movement
* rain/flood saturates permeable rock on surface making it heavier
* waves or river erodes base of the slope by hydraulic action+abrasion
* the weight of the permeable rock weakens the impermeable rock underneath so it collapses
* debris at base of cliff/slope is transported away by waves/river
57
describe types of coastline (2)
* concordant - alternating hard+soft rock layers parallel to coast - forms a smooth coast
* discordant - alternating hard+soft rock layers - form headlands+bays due to erosion - jagged coast
58
describe key terms used in a flood hydrograph (6)
* peak rainfall - the hour of greatest rainfall during a storm (shown on bar chart)
* peak discharge - the time of maximum discharge in river (shown at top of line graph curve)
* rising limb - period of rising river discharge following rainfall
* falling limb - period of falling river discharge
* lag time - time between peak rainfall and peak discharge
* normal flow - base flow of the river (shown at bottom of graph)
59
describe the location of a UK town and issues (case study)
Medmerry, coast of south England
* previous shingle bank was vulnerable- frequently breached
-> £5m in damages in 2008
* bank was costly+ required maintenance/reprofiling
60
describe a coastal realignment scheme used (case study) (2)
Medmerry, coast of south England
* used managed retreat - a breach was made in the shingle bank to allow land behind to be flooded
* clay embankment built around intertidal area to contain floodwaters
61
describe pros+cons of the coastal realignment scheme used at Medmerry (case study)
/ protects properties+water treatment plant+ mobile home park, created salt marshes good for wildlife habitats+ cattle farming, nature reserve for intertidal habitats, cheaper than hard engineered sea defences
X agricultural land lost, landowners require compensation, disturbs existing species' habitats
