Rivers Flashcards
(67 cards)
1
Q
What are the 4 processes of erosion?
A
- abrasion
- hydraulic action
- attrition
- solution
2
Q
What are the 2 processes of transportation?
A
- saltation
- traction
3
Q
What is abrasion?
A
-small boulders scratch and scrape their way down the bank, wearing the bank and bed
4
Q
What is hydraulic action?
A
- water is forced into cracks by the fast flowing river
- repeated causes weakened rocks, banks
5
Q
What is attrition?
A
-stones transported down the river collide with each other and the banks and causes the stones to be small and round
6
Q
What is solution?
A
-dissolving of rocks e.g chalk and limestone
7
Q
What is saltation?
A
-small pebbles and stones bounce along the river bed
8
Q
What is traction?
A
-large boulders and rocks are rolled along the river bed=bedload
9
Q
Describe the upper course of a river
A
- wet and boggy valley
- narrow and shallow river
- steep v-shaped valley
- more vertical some lateral
- waterfalls
- small streams
10
Q
Describe the middle course of the River Tees
A
- there are gorges as the waterfall moves upstream
- river meanders-changing shape
- the town Yarm=in a meander (18km from sea)
- less rainfall
- 95%of land is farmland
- river is at it’s most powerful + broadens out
11
Q
Describe the lower course of a river
A
- flat and floodplain
- no power for erosion
- small bedload and fine silt
- large cities and factories built on the marshy land
12
Q
Describe the middle course of a river.
A
- large sized bedload, smoother rocks
- lateral erosion=wide river
- area of warmer temps and less rain
- towns built
- arable and pastoral farming
13
Q
Describe the upper course of the river Tees.
A
- the source starts where Cumbria borders county Durham and is a big soggy mass
- cuts a v-shaped valley and carries lots of sediment
- at 5km, the angular rocks are mainly smooth
- high force waterfall, made of rhinestone
- the flow rate = 20km per second
14
Q
Describe the lower course of the river Tees.
A
- carries a small amount of material
- next to a factory, used for ships to off load goods
- 15 degrees at the end
- man made
- Stockton on Tees= the main town
15
Q
How do waterfalls occur?
A
-when a band of hard rock overlies softer rock
16
Q
What does splash back cause?
A
- hydraulic action which weakens the rock behind the fall of water.
- the undercutting leads to an overhang
17
Q
What develops at the bottom of the waterfall?
A
-An indentation which turns into a plunge pool
18
Q
What happens when the overhang breaks off?
A
-rocks swirl in the plunge pool creating abrasion
19
Q
What is created as the undercutting continues?
A
- the waterfall retreats upstream creating a gorge
- the gorge retreats and grows longer
20
Q
What is an interlocking spur?
A
-projections of high land entering the valley from alternate sides
21
Q
How are interlocking spurs made?
A
- the winding path of the river is due to obstacles being in the way
- the river takes the easiest route over the land resulting in projections of high land
22
Q
Why do rivers meander and how are meanders created?
A
- due to obstacles in the way
- fastest flowing on outside bend which cause lateral erosion making the river wider
- outer bends are eroded by abrasion and hydraulic action
23
Q
What is the fastest flowing part of a river called and why is it the fastest?
A
- the thalweg
- there is less friction because it is the deepest part
24
Q
How are ox-bow lakes created?
A
- the meanders become very narrow and at times of high discharge, the river takes the shortest route and does not meander
- the deposition of alluvium seals off the meander forming a straight river channel
- The cut off meander is called an ox-bow lake
25
What is the name for a dried up meander?
-meander scar
26
How are levees made?
- at times of high discharge, the river will overflow it's banks
- the increase in friction =drop in river's velocity, resulting in the river's load being deposited (coarsest and sediment deposited first)
- as this process repeats, the deposition builds up creating natural levees
27
How are floodplains created?
- the deposition at the slip-off slopes provides sediment to build up on the valley floor
- the river carries large amounts of suspended load and when it floods, it is deposited onto the flood plain as alluvium
- this process builds up the flood plain
28
List some human factors that affect flood risk. (7)
- new infrastructure increases impermeable surfaces
- more houses are being built on flood plains
- when new houses are built, roads must also which increases impermeable surfaces
- deforestation reduces interception and the roots no longer take water from the soil
- felling results in the soil getting saturated, run-off occurs and river discharge increases
- farming, loss of hedges =less interception
- ploughing fields= more channels for the water to run down ending up in river
29
List some physical factors that affect flood risk.
- heavy rain and sudden bursts=surface runoff, discharge increases and flash floods occur
- snow melt=release of stored water results in surface runoff
- steep slopes=surface runoff occurs before rain v=can infiltrate soils
30
What is the difference between deforestation and felling?
- felling=cutting down a few trees
| - deforestation=large scale removal of trees
31
What is the rising limb on a hydrograph?
- period of rising river discharge following periods of rainfall
- the upward line of the hill
32
What is (basin)lag time on a hydrograph?
- time difference between the peak of the rainstorm and the peak flow of the river
- arrow line from the bar graph to the top of the hill
33
What is the recession limb on a hydrograph?
- period of time when discharge is falling after reaching peak
- the downwards part of the hill
34
What is the through flow on a hydrograph?
- the horizontal flow of water within the soil layer
| - dot line in between hill
35
What is storm flow on a hydrograph?
-the water that arrives in the river during surface run off
36
What is the baseflow on a hydrograph?
-normal discharge of the river
37
Where is Morpeth?
- situated in a loop of the river Wansbeck
- Northeast UK
- 15 miles from Newcastle upon Tyne
- 12 miles from North sea
38
When was the Morpeth flood?
-6th and 7th of September, 2008
39
What were the causes of the Morpeth flood?
- prolonged rainfall, 235% that could be expected for a month
- river Wansbeck=narrow and steep sided=lots of surface run off
- soil already saturated because of wet summer
- increased urbanisation since 1960
- trash screens at the culverts of tributary were blocked
40
What was the peak water level in Morpeth?
-3.99m
41
What were the social impacts of the Morpeth flood?
- 400 residents evacuated due to mud in houses
- 913 residential properties affected
- shelter provided in King Edward high school
- 198 properties in middle greens area did not receive a flood warning
42
What were the economic impacts of the Morpeth flood?
- 89 commercial properties affected, stock destroyed
- overall damage =£40 million
- Morpeth flood disaster raised over £20,000
43
What is the flow rate of the river Tees?
-20km per second
44
What temp is the river Tees towards the end?
-15 degrees
45
When does angular material turn smooth in the river Tees?
-5km
46
What % of rainfall happened before the Morpeth flood?
-235% of the rainfall expected for a month
47
How many properties in middle greens area did not receive a flood warning?
-198
48
How many residential properties were affected in Morpeth?
-913
49
How many residents evacuated due to mud in their home?
-400
50
How many commercial properties were affected?
-89
51
How much money was the overall damage of the flood?
-£40 million
52
How much did the Morpeth flood disaster fund raise?
-£20,000
53
What are the pros and cons of building dams and reservoirs?
- expensive, ecosystems disrupted, can cause landslides
| - highly effective, creates jobs, reduces green house gases
54
What is suspension?
-fine, light material e.g alluvium is held up and carried within the river flow=suspended load
55
What is a flood relief channel?
-artificially made channel that is designed as a backup channel for floods
56
What is a pro and con of flood relief channels?
- habitats destroyed
| - reduces flooding
57
How do planting tees help reduce the impacts of flooding?
-more interception
58
Pros and cons of planting trees?
- creates new habitats and cheap
| - loss of potential grazing land
59
Pros and cons of flood warnings and preparation?
- only effective if people listen
| - cheap, people can evacuate and take valuables with them
60
How much did insurance costs increase to after the Morpeth flood?
-£900 per year to £2,500 per year
61
How much water was Morpeth high street under at the peak of the flood?
-60cm of water
62
What were the responses to the Morpeth flood?
- By 2010, £2.25 million was spent on essential work and repairs
- replaced waterproof seals on flood walls
- repaired damaged culverts + removed debris and silt
- environment agency created a new evacuation route
- in August 2015, a multi million pound flood defence, including a dam and storage area on the Mitford estate
- a new flood defence wall-1.8 m tall and 3 flood gates constructed in High Stanners
63
How much money was spent on repairs by 2010?
-£2.25 milliom
64
When and where was the multi million pound flood defence built?
- August 2015
| - Mitford estate
65
How tall was the new flood defence wall in Morpeth?
-1.8m
66
What area was the new flood defence wall in Morpeth?
-High Stanners
67
How does using alternative energy production and planting trees reduce the rate of global warming?
- trees take in CO2
- renewable energy does not produce greenhouse gases
- increasing CO2 in atmosphere increases the greenhouse effect, causing the planet to become warmer
