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geog > rivers and coasts > Flashcards

rivers and coasts Flashcards

1
Q

what is mechanical weathering

A

the breakdown of rocks WITHOUT changings its chemical composition

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2
Q

what is freeze-thaw weathering

A

type of mechanical weathering
Freeze-thaw weathering occurs when rocks are porous (contain holes) or permeable (allow water to pass through). When temperatures drop, the water freezes and expands causing the crack to widen. The ice melts and water makes its way deeper into the cracks. The process repeats itself until the rock splits entirely.

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3
Q

what is chemical weathering

A

the breakdown of rock by changing its chemical composition

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4
Q

what is carbonation weathering

A

type of weathering that happens in warm and wet conditions. As rain goes through the air and into the ground, it grabs carbon dioxide, creating carbonic acid. This weak acid reacts with the calcium carbonate in stones when it seeps into the cracks.

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5
Q

what is mass movement

A

the shifting of rocks and loose material down a slope, slump or rockfall. It happens when the force of gravity acting on the slope is greater than the force supporting it.

It is more likely to happen when the material is full of water - water acts like a lubricant making the material heavier

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6
Q

what are slides

A

material shifts in a STRAIGHT LINE along a side plane

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7
Q

what are slumps

A

material ROTATES along a curved slip plane

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8
Q

what is rockfall

A

material BREAKS UP often along a bedding plane and falls down a slope

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9
Q

what are constructive waves

A 
waves that deposit material 
low frequency 
low and long (small gradient) 
powerful swash 
weaker backwash
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10
Q

what are destructive waves

A 
waves that erode the coast
high frequency 
high and steep 
powerful backwash
weaker swash
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11
Q

3 ways that waves wear away coasts

A

hydraulic power
abrasion
attrition

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12
Q

what is hydraulic power

A

waves crash against rock and compress the air in the cracks. This puts pressure on the rock. repeated compression widens the cracks and causes bits of rock to break off

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13
Q

what is abrasion

A

eroded particles in the water scrape and rub against rock removing small pieces

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14
Q

what is attrition

A

erodes particles in the water collide, break off into small pieces and become more rounded

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15
Q

describe longshore drift

A
  • material is transported along the coast by longshore drift
  • waves follow the direction of prevailing wind
  • they usually hit the coast at an oblique angle
  • the swash carries material up the beach (same direction as waves)
  • the backwash carries material down the beach
  • over time material zigzags along the coast
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16
Q

what are the four processes of transportation

A

traction
suspension
saltation
solution

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17
Q

what is traction

A

large particles like boulders are pushed along the sea bed by the force of the water

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18
Q

what is suspension

A

small particles like silt and clay are carried along the water

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19
Q

what is saltation

A

small pebbles and stones are bounced along the river bed.

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20
Q

what is solution

A

soluble materials dissolve in the water and are carried along

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21
Q

what is deposition

A

the dropping of material
- deposition occurs when water carrying sediment loses energy and slows down
- coasts build up when the amount of deposition in greater than the amount of erosion
deposition occurs more when there is a lot of erosion somewhere else or when lots of material is transported into another area

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22
Q

what is a concordant coastline

A

Alternating bands of hard and soft rock PARALLEL to the coast. Concordant coastlines tend to have fewer bays and headlands.

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23
Q

what is a discordant coastline

A

Alternating bands of hard and soft rock at RIGHT ANGLES to the coast. Headlands and bays from where there is alternating bands of resistant and less resistant rock. less resistant rock erodes fasters forming a bay with a gentle slope. Because the more resistant rock erodes slowly it juts out forming a headland

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24
Q

what are wave-cut platforms

A

waves erode cliffs to form wave-cut platforms

  1. erosion
  2. unstable rock, wave-cut notch
  3. collapsed material
  4. material is cleared
  5. cliff retreats and wave-cut platform forms
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25
Q

explain how beaches are formed

A

beaches are formed by deposition

  • they are found on coasts between the high and low water marks
  • formed by constructive waves
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26
Q

shingle beaches

A

created by high energy waves
steep
narrow
sand particles have been washed away but larger shingles left behind

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27
Q

sand beaches

A

created by low energy waves
flat
wide
sand particles are small so the weak backwash can move them back down the beach creating a long gentle slope

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28
Q

deposited sediment also forms…..

A

spits, bars and sand dunes, tombolos

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29
Q

what are spits

A
  • spits form at sharp coastlines
  • longshore drift transports sand and shingles past the bend and deposit them in the sea
  • string winds and waves curve the end of the spit
    the area behind the spit is sheltered from waves - plants can grow
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30
Q

what are bars

A

a bar is formed when a spit joins 2 headlands

a lagoon is formed behind the bar

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31
Q

what are sand dunes

A

formed when sand is deposited by longshore drift is up the beach by wind
obstacles cause the wind speed to decrease forming dunes
high winds come from the see from prevailing wind (south west )
marron grass stabilises dunes and holds them together

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32
Q

describe the costal landforms at Durdle door

A

arch formed by a concordant coastline

wave action opened up a crack in the side of the headland which developed into an arch

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33
Q

describe the coastal landforms at Chesil beach

A

a tombolo formed by longshore drift. it joins the Isle of Portland to the mainland. Behind Chesil beach is a shallow lagoon called The Fleet Lagoon

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34
Q

what is a tombolo

A

A tombolo is a sediment deposit at the coast formed by wave refraction and diffraction at the edges of an obstacle (natural or artificial) originally detached from the mainland.

a bar of sand or shingle joining an island to the mainland.

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35
Q

describe the upper course

A

steep gradient, has v-shaped valleys, steep sides, narrow, shallow channel, slow, vertical erosion

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36
Q

describe the middle course

A

medium gradient, gently sloping valley sides, wider, deeper channel faster, lateral erosion

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37
Q

describe the lower course

A

gentle gradient, very wide, almost flat valley, very wide and deep channel, lateral erosion

38
Q

long profile of a river

A

shows how the gradient changes

the path of the river flows downwards

39
Q

cross-profile of a river

A

show you what a cross-section of the river looks like

40
Q

what is vertical erosion

A

deepens the river valley and channel making it V-shaped
most common in upper course
downwards erosion

41
Q

what is lateral erosion

A

this widens the river valley an channel during the formation of meanders
dominant in middle and lower course

42
Q

what are the four processes of erosion

A

hydraulic action - the force of the river water colliding with rocks breaks rock particles away from the river channel
abrasion - eroded rocks picked up by the river scape and rub against the channel
attrition - eroded rocks picked up into each by the river crash and breaks into smaller fragments. Their edges are rounded off
solution - river water dissolves some types of rocks

43
Q

4 forms of transportation

A

traction - large particles like boulders are pushed along the river bed by the force of water
suspension - small particles like clay are carried along by the water
saltation - pebble-sized particles are bounced along the river bed by the force of water
solution - soluble material dissolve in the water and carried along

44
Q

deposition in a river

A

deposition is when a river drops material it’s transporting
its occurs when the a river loses velocity and energy
the volume of the water falls
the water is shallower
less energy = slower
at the mouth
(common at meanders)

45
Q

waterfalls….

A
  1. waterfalls forms where a river flows over an area of hard rock followed by area of softer rock (hard rock on top of the softer rock)
  2. The softer rock is eroded more than the hard rock creating a ‘step’ in the river
  3. As water flowed over the step it erodes more and more of the softer rock
  4. A steep drop is eventually created which is called a waterfall
  5. Hard rock is undercut by erosion and collapses
  6. The collapsed rock swirl around the water at the foot of the water creating plunge pool
  7. Overtime more undercutting causes more collapses. The waterfall retreats leaving behind a steep- sides gorge
    - hydraulic action, abrasion
46
Q

interlocking spurs

A
  1. In the upper course of a river most of the erosion is vertically downwards. This creates steep-sided, V-shaped valleys
  2. The river lacks power to erode laterally so they have to wind around the hillsides
  3. The hillsides that interlock with each other as the river winds around them are called interlocking spurs
47
Q

headlands and bays

A

Headlands and bays from where there is alternating bands of resistant and less resistant rock. less resistant rock erodes fasters forming a bay with a gentle slope. Because the more resistant rock erodes slowly it juts out forming a headland

48
Q

hard rock examples

A

limestone, chalk

49
Q

soft rock examples

A

sandstone, clay

50
Q

formation of meanders

A

meanders are formed by erosion and deposition.
They are large bends in a river in the middle and lower course (where the channel are shallow and deep sections, faster)
More erosion takes place on the outside of the bend forming river cliffs.
the current in slower on the inside of the bend because the river is shallower so eroded material is deposited on the inside of the bend, forming slip-off slopes

51
Q

formation of ox bow lakes

A

meanders get larger overtime and eventually turn into oxbow lakes

  1. Erosion causes the outside bends to get closer until there’s only a small bit of land left between the bends (neck)
  2. The river breaks through this land, usually during a flood
  3. The river flows along the shortest course
  4. deposition eventually cuts of the meander
  5. this forms an ox bow lake
52
Q

floodplains

A

flat areas of land that floods
on either side of a river
when a river floods, the water slows down, loses energy and deposits the material that it’s transporting. this builds up the flood plain. Deposition on the slip-off slopes of meanders also builds them up. Meanders widen as they migrate across floodplains laterally.

53
Q

what are levees

A

levees are natural embankments (raised banks) along the edges of a river channel
Overtime deposited material from erosion builds up creating levees along the edges of the channel

54
Q

what are estuaries

A

tidal areas where the river meets the sea

- found at the mouth of the river

55
Q

what are contour lines on a map

A

tells you the direction a river flows

  • orange lines
  • height is marked with numbers
  • steepness is determined by how close the lines are (steeper = closer together)
56
Q

upper course evidence on a map

A

waterfalls marked on map
cliff are marked with black blotchy lines
close contour lines show evidence of upper-course waterfall
river crosses lots of contour lines in a short distance (steep)

57
Q

lower course evidence on a map

A

land is low
no contours lines - flat land
river doesn’t cross contour lines = gently slopping

58
Q

river Clyde

A 
flows through Scotland 
160km long 
source is in the Southern Uplands 
Mouth is in west coast of Scotland
meanders, estuary, interlocking spurs, 4 waterfalls, gorge, floodplain
59
Q

hydrographs

A

A hydrograph is a graph showing the rate of flow versus time past a specific point in a river, channel, or conduit carrying flow. RESPONSE OF A RIVER AFTER FLOODING

60
Q

peak discharge - hydrographs

A

the highest discharge in the period of time you’re looking at

61
Q

lag time - hydrographs

A

the delay between peak rainfall and peak discharge

62
Q

rising limb - hydrograph

A

the increase in river discharge as rainwater flows into the river

63
Q

falling limb - hydrogen

A

the decrease in river discharge as the river returns to its normal level

64
Q

physical and human factors that affect flood risk/ causes of floods

A 
PHYSCIAL 
heavy rainfall 
geology (rock type) 
prolonged rainfall
relief (change in land height) 
density of drainage basin 
steep slopes
glacial and snow melt 
HUMAN
impermeable rock surfaces (urbanisation)
deforestation 
human management 
global warning (melt) 
land use 
dams and dams breaking
65
Q

two strategies to reduce the risk of flooding

A

hard engineering - man-mad structures built to control the flow of rivers and reduce flooding

soft engineering - schemes set up using knowledge of a river and its processes to reduce the effects of flooding

66
Q

hard engineering in rivers

A 
dams and reservoirs 
embankments - flood walls
levees 
dredging 
re-routing rivers / channel straightening
67
Q

soft engineering in rivers

A 
tree planting
floodplain zoning 
sandbags 
flood water pumping 
river restoration 
flood warnings
68
Q

flood management in oxford

A
  • divert water away from densely populated areas
  • increase water storage in the floodplain
  • plant 20,000 trees
  • reusing excavated material to build new flood walls and embankments to protects areas that remain at risk
69
Q

SEE issues with Oxford management scheme

A

Social:

  • construction will disturb residents
  • improve public footpaths
  • more confidence

Economic:

  • 120 million
  • 1000 homes and business protected

Environmental:

  • lots more trees
  • new habitats
70
Q

managing floods in Banbury

A

Banbury is a market town on the River Cherwell in Oxfordshire, England

  • Raising the A361 road in the flood storage are and adding improvements to the drainage beneath the road to prevent flooding
  • New earth embankments and flood walls to protect property and businesses
  • A new pumping station to transfer excess rainwater into the river below the town
  • The creation of a new Biodiversity Action Plan habitat with ponds, trees and hedgerows to absorb and store excess water
71
Q

why is management in Banbury needed

A

There were two major floods which occurred in 1998 and 2007. In 1998, the flood led to closing the town’s railway station, shutting local roads and caused £12.5 million of damage. More than 150 homes and businesses were affected. The social effect of the flood was that travel was stopped. The economic effect was that many homes and businesses were destroyed. The environmental effect was water entering the
reservoir.

The flood in 2007 extended over to much of Central England and Western England. Many homes and businesses were affected by the flood.

72
Q

social impacts of Banbury

A

The raised A361 rout into Banbury will be open during a flood, to avoid disrupting people’s lives

Quality of life for local people is improved with new footpaths and green areas.

Reduced levels of anxiety and depression through fear of flooding.

73
Q

environmental impacts of Banbury

A

Around 100000 tonnes of earth were required to build the embankment. This was extracted from nearby, creating a small reservoir.

A new biodiversity action plan habitats have been created with ponds, trees, and hedgerows.

Part of the floodplain will be deliberately allowed to flood if river levels are high.

74
Q

economic impacts of Banbury

A

The cost of the scheme was about £18.5 million.

Donors included an environmental agency and Cherwell district council.

By protecting 441 houses and 73 commercial properties, the benefits are estimated to be over £100 million

75
Q

hard engineering coastal defences

A

man-made structures built to control the flow of the sea and reduce flooding and erosion

  • sea wall
  • gabions
  • rock armour
  • groynes
76
Q

soft engineering coastal defences

A

schemes set up using knowledge of the sea and its processes to reduce the effects of flooding and erosion

  • beach nourishment and reprofiling
  • dune regeneration
77
Q

coastal management in lyme regis

A

powerful waves from the south west erode the sea cliffs causing them to collapse. Many properties were damaged.

phase 1 - 1990-1995 new sea wall constructed. 1.4 million project to stabilise rocks , rock armour, promenades

phase 2 - 2005-2007 beaches replenished, rock armour repaired, drainage system improved

phase 3 - was meant to prevent land slides (never happened)

phase 4 - 390 m sea walls and rock armour protecting roads and the town

78
Q

positive and negative effects of lyme regis

A

positive

  • trade increased
  • rock armour absorbs energy
  • people feel more correct
  • more money with tourism

negative

  • more tourists (more traffic)
  • important fossils being exposed
  • expensive
79
Q

flashy hydrograph

A

To say that a hydrograph is flashy means that the graph depicts sharp vertical jumps and equally steep vertical declines. Short lag time

80
Q

subdued hydrograph

A

hydrographs with gently inclined limbs, a low peak discharge and a long lag time.

81
Q

river tees

A

The River Tees is located in the north of England. The source of the River Tees is located in the Pennines and it flows east to its mouth where the river joins the North Sea.
The upper course has hard impermeable rocks. Here, vertical erosion has formed a V-shaped valley.
High Force, the UK’s largest waterfall at 21 metres high, is located in the upper course. An area of hard rock, called Whin Sill (or Whinstone), is located above a layer of soft rocks (sandstone and shale) and together they create this impressive waterfall.
middle course
As the River Tees starts to erode sideways (lateral erosion), it forms meanders. These can be identified in the middle course near Barnard Castle.
Lower course
Near Yarm, the meanders in the lower course are much larger, and oxbow lakes have formed. In this area there are also levees which have formed when the river has flooded.
The River Tees has a very large estuary with mudflats and sandbanks which supports wildlife in the area. Sites such as Seal Sands are protected areas.

82
Q

what is fetch

A

distance the wave travels before reaching the coastline

83
Q

what causes mass movement

A

weathering

84
Q

what is biological weathering

A

the action of plants or animals breaking rock apart

85
Q

flashy hydrograph drainage basin

A 
steep slope 
impermeable rock 
thin soil 
thin grass
urbanisation 
used for industry, dam built 
high density
86
Q

subdued hydrograph drainage basin

A 
gentle slope
permeable rock 
deep soil 
forest 
rural area
limited use of river
lower density
87
Q

delta

A

wetlands that form as rivers empty their water and sediment into another body of water

88
Q

Happisburgh

A

Hold the line – this is when coastal defences are built or maintained to protect a coastline against the impacts of sea level rise and coastal erosion/flooding. Often a mixture of hard and soft engineering strategies is used. This is often expensive but popular with local residents.
Retreating the line (managed realignment) – this is when people move out of the dangerous, most vulnerable areas and there is no defence against the elements. The coastline is often eroded inland creating salt marshes. This is less expensive but not always popular with local residents.

89
Q

reasons for management in Happisburgh

A

Rock type – the cliffs are made from less resistant boulder clay (made from sands and clays) which slumps when wet.
Naturally narrow beaches – these beaches give less protection to the coast as they don’t reduce the power of the waves.
Man-made structures – groynes have been installed to stop longshore drift and build up the beaches in certain places. This narrows unprotected beaches elsewhere even further, as new sand does not come down to replace sand eroded by waves.
Powerful waves – waves at Happisburgh travel long distances over the North Sea (so have a long fetch) which means they will increase in energy.

90
Q

why was management in lyme regis needed?

A
  • south coast tourist destination
  • population about 4000 growing in 16000 in summer
    powerful waves from the south west erode the sea cliffs causing them to collapse. Many properties were damaged.

geog (4 decks)

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