River Landscapes Flashcards
(71 cards)
1
Q
what is the long profile of a river
A
the long profile takes the form of a concave curve. the steepest gradient is in the uplands near the source of the river. further downstream, the gradient is reduced
2
Q
how does the cross profile change throughout the river
A
The channel becomes wider and deeper with the distance downstream
3
Q
why does the upper course of the valley be narrow and steep sided
A
due to vertical erosion by the river combined with weathering and mass movement of the valley slopes
4
Q
why does the middle course of the valley be wider
A
due to lateral erosion from meandering rivers
5
Q
why does the lower course be wide and flat
A
sediment dumped by the river as it slows down and loses its energy
6
Q
what is a fluvial process
A
river process
7
Q
what are the three types of fluvial process
A
- erosion
- transportation
- deposition
8
Q
what is hydraulic action
A
the power of flowing water to erode the river’s bed and banks
9
Q
what is solution (the type of erosion)
A
dissolving of solubles in water such as limestone and chalk
10
Q
what is traction (type of transportation)
A
large particles rolled along the river bed by the force of the water
11
Q
what is saltation (type of transportation)
A
a bouncing or hopping motion by pebbles too heavy to be suspended
12
Q
what is suspension (type of transportation)
A
particles suspended in the water
13
Q
what is solution (type of transportation)
A
particles/chemicals dissolved in the water
14
Q
what landforms result from river erosion
A
- interlocking spurs
- waterfalls
- gorges
15
Q
where are interlocking spurs commonly found
A
in the upper course of the river
16
Q
why do interlocking spurs occur
A
there is mostly vertical erosion rather than lateral in the upper course which means that the river is forced to flow around the jutting out pieces of land rather than cutting into them
17
Q
what two erosion processes erode the plunge pool
A
- hydraulic action
- abrasion
18
Q
Characteristics and formation of landforms resulting from erosion – interlocking spurs, waterfalls and gorges.
A
. - use rivers booklet
19
Q
how are waterfalls created
A
- when water flows over hard rock then soft rock, the soft rock erodes faster through hydraulic action and abrasion to form a step
- the step is eroded further and deeper to form a plunge pool, as well as starting to undercut the rock
- the undercut leaves very little support for the hard rock so it cracks and falls into the plunge pool
- the fallen rock is used in abrasion which further erodes the plunge pool
the process repeats and the waterfall recedes upstream
20
Q
what is a gorge
A
a steep sided valley where the river once was
21
Q
how are meanders formed and why are slip off slopes formed
A
- most water is directed towards the outside of the bend which means it flows faster so had more energy - eroding fast
- the inside bend there fore has less water which means it is shallower, slower and has less energy so it deposits its material
- this builds up over time to form the slip off slope
22
Q
where are meanders commonly found in a river course
A
middle and lower course
23
Q
what are riffles and pools
A
the shallow and deep areas of a meander respectively
24
Q
how are oxbow lakes formed
A
- the neck of the meander narrows due to erosion on opposite sides
- the neck is finally broken through and the water then adopts the shorter route
- deposition occurs at the edges and cuts off the old meander until it is completely separate
25
what are three landforms that result from deposition
- leveés
- flood plains
- estuaries
26
how do leveés form
when rivers flood:
- as the water overtops the river banks, there is a sudden localised drop in velocity of the water that had previously been flowing very fast along the river
- this causes sediment in suspension to be deposited at the river bank
- heavier sediment is deposited first and this traps the finer sediment
- with each successive flood the deposited material raises the river banks
27
what are flood plains and how do they form
- extensive, flat areas land mostly covered by grass
during a flood:
- water containing large quantities of alluvium (river silt) pours out over the flat valley floor
- the water slowly soaks away leaving behind the deposited sediment
- repeated flooding forms a thick alluvial deposit which is fertile and often used for farming
28
how are estuaries formed
- incoming tides force seawater and sediment up the river channel, mixing with river water flowing in the opposite direction
- where the fresh and salt water meet, velocity falls rapidly resulting in significant deposition
- over time these muddy sediments break the water surface to form extensive mudflats
- vegetation colonises the mudflats to form saltmarshes
29
characteristics of a waterfall
- a step in the long profile of a valley which fast flowing water falls off
- considerable drop
- deep plunge pool eroded by hydraulic action and abrasion
30
what is an estuary
where the freshwater of a river meets the sea (saltwater)
31
example of a waterfall along the River Tees
high force
32
where is the source of the River Tees
at Cross Fell in the Pennines
33
where along the river Tees can a meander be found
the town of Yarm is enclosed by a meander on 3 sides
34
list all the major landforms of erosion and deposition along the River Tees
it has all the landforms that we study:::
- source
- v-shaped valleys and interlocking spurs
- waterfall
- floodplains and meanders
- leveés
- estuary
35
what physical factors affect the flood risk of an area
- heavy or prolonged precipitation
- impermeable rock
- steep slopes (water travels fast down slopes and also collects in one area instead of being spread out)
36
what human factors affect the flood risk of a river
- deforestation (not being used as well as not being caught by their umbrellas)
- urbanisation (concrete)
- farming (bare soils transfer water quickly, ploughing creates runnels for water to rapidly flow through)
37
what is a hydrograph
a graph to show how much water gets into a river after a rain storm
38
what are four hard engineering strategies for flood management
- dams and reservoirs
- channel straightening
- embankments
- flood relief channels
39
benefits of building a dam/reservoir - flood management
- hydroelectric power
- recreation
- wetland habitats
- source of drinking water
40
costs of building a dam/reservoir - flood management
- high costs
- loss of farmland and homes and habitats(flooded area)
- can affect migrating fish
41
how does channel straightening help to prevent floods
cutting of meanders to create a more efficient channel better suited to the rapid transfer of water
42
costs of channel straightening - flood management
- increases flood risk downstream in meandering sections
- can be expensive and high maintenance
- aquatic life affected by change in velocity of the water
43
benefits of channel straightening - flood management
- effective
- insurance premiums may be reduced for home owners
- navigation improved
44
how do embankments help to prevent flooding
increase the amount of water the river can hold by building up the sides of the river
45
costs of embankments - flood management
- can be expensive
- look artificial and unattractive
- more serious flooding if the embankment fails
46
benefits of embankments - flood management
- river channel has an increased capacity for carrying water
- create walkways
- new river bank habitats can be created
47
costs of flood relief channels - flood management
- expensive
- regular maintenance is required
- habitats may be disturbed
48
benefits of flood relief channels - flood management
- be very effective in reducing risk in high value areas
- new recreational opportunities
- new aquatic habitats
- insurance premiums reduced
49
examples of soft engineering strategies for reducing flood risk
- flood warnings
- floodplain zoning
- planting trees
- river restoration
50
costs of flood warnings - flood management
- need for monitoring equipment, scientific expertise
- people might not respond and react appropriately
51
benefits of flood warnings - flood management
- sustainable
- safety at a lower cost
52
what is floodplain zoning - flood management
local planning to restrict land uses in high-risk areas
53
costs of floodplain management - flood management
- restricts economic development
- hard to implement when urban developments have already taken place there
- land could be used to alleviate housing shortages
54
benefits of floodplain management
- low cost
- protects and conserves wildlife habitats
- reduces additional impermeable surface coverage
55
how does planting trees help reduce flooding
increases the interception and also absorb it to use themselves
56
disadvantages of planting trees - flood management
- can reduce habitat diversity
- loss of potential farmland
- can lead to increased acidity in soils
57
benefits of planting trees - flood management
- creates habitats
- natural method
- helps to absorb carbon
- relatively inexpensive
58
what does river restoration involve - flood management
creating meanders to slow down water flow. this increases risk of flooding in that area but decreases the risk downstream
59
costs of river restoration (putting a meander into the river) - flood management
- can be expensive to construct and maintain
- change in land use
- creates more flooding in that area which can inconvenience people trying to use the land
60
benefits of river restoration - flood management
- recreates a natural, attractive environment
- effective
- restores wetland areas, increasing biodiversity
61
location of York
in the north of england at the confluence of the River Ouse and river Foss
62
why was a flood management scheme required in York
- York regularly floods: serious flooding has occurred in six of the last 60 years
- the floods in 2000 were the worst on record
63
facts about the flood in York in 2000
- over 500 properties flooded
- 19,000 hectares of farmland affected
- ouse rose 5.5 meters above its normal level
64
what management strategies were put in place for flooding in York
- the Foss Barrier
- Embankments at Leeman Road
- Floodplain zoning: Clifton Ings
- Flood relief channels around acomb
- Flood gates on Marygate
65
what did the Foss barrier do
built to prevent water from the River Ouse backing up the River Foss
66
what do the embankments at Leeman road do
increase the capacity of the river channel
67
what has happened at Clifton Ings to prevent flooding
floodplain zoning
it has been left as an open, undeveloped floodplain that can store millions of meters of water
68
what do the flood relief channels around Acomb do
divert water directly into the Ouse downstream of York
69
what were the social issues with the flood management schemes in York
- reduced risk of flooding
- transport disruption during times of flood reduced
- cycleway made wider and resurfaced
70
what were the environmental issues with the flood management schemes in York
- some habitat destruction needed
- however two ponds were created which have created new wetland habitats
71
what were the economic issues with the flood management schemes in York
Foss Barrier upgrade cost more than double what was estimated
- total cost estimated £83 million
however
- increased potection for homes and businesses
- lower insurance premiums
