Rivers Flashcards
(167 cards)
1
Q
What cycle is a drainage basin in?
A
Part of the hydrological cycle in which water is recycled between the sea, atmosphere and the land
2
Q
What is the drainage basin?
A
Te area drained by a river and its tributaries
3
Q
What is the boundary of the drainage basin called?
A
The watershed
4
Q
What is the watershed normally?
A
A higher ridge of land which separates one drainage basin from another
5
Q
What does the water in a river flow in?
A
A channel
6
Q
What is the place where a river begins called?
A
The source
7
Q
What is the place where a river ends called?
A
The mouth
8
Q
What is a confluence In a river?
A
The point where 2 rivers meet
9
Q
What is a tributary?
A
A smaller branch of a main river
10
Q
Which 3 main things do rivers do?
A
Erode the land, transport rock and dissolved sediment, deposit natural material.
11
Q
What do rivers need to transport and erode material?
A
Energy
12
Q
What is a lot of a rivers energy used to do?
A
Over come friction with the bed and banks
13
Q
What will a river do if it has too much energy?
A
Erode the land
14
Q
What will a river do if it does not have enough energy?
A
Deposit material
15
Q
What does a river use to erode its banks and bed?
A
The material that it transports
16
Q
What happens as the velocity of the river increases?
A
the load it can carry increases and as does the rate which it can erode
17
Q
Where is erosion on a river most effective?
A
In the upper course as due to weathering and erosion the river has lots of sediment which it uses to erode
18
Q
What is the rate of erosion in a river effected by?
A
Load- the amount of material the river carries, velocity, gradient, geology- rock type, ph, human impact.
19
Q
How does the amount of a load a river carries cause a change in the amount of erosion ?
A
Heavier and sharper the load = the greater the potential for erosion
20
Q
How does velocity effect the rate of erosion in a river?
A
Greater velocity = more erosion
21
Q
How does the gradient of the land effect the rate of a rivers erosion?
A
Greater gradient = greater amount of erosion
22
Q
How does the geology effect the rate at which a river erodes?
A
Soft rocks are more easily eroded
23
Q
How does the ph or the river effect the rate at which it erodes?
A
Solution increases where the water is more acidic
24
Q
How does human impact effect the rate at which a river erodes?
A
Deforestation, dams and bridges interfere with the natural flow and frequently end up increasing erosion rates
25
What are the 4 types of erosion?
Hydraulic action, attrition, abrasion, solution.
26
How does hydraulic action erosion occur?
The sheer force of the water hitting the beds erodes them overtime
27
How does abrasion erosion occur?
The load the river is carrying repeatedly hits the bank
28
How does attrition erosion occur?
Rocks bang against each other
29
How does solution erosion occur?
When the river flows on certain rocks e.g chalk or limestone, the rock dissolves
30
What are the 4 types of transportation ?
Saltation, suspension, solution and traction
31
How does the traction method of transportation occur?
Method used for moving the largest material as the boulders are too heavy to loose contact with the river bed so materials are rolled along
32
How does the transport method of saltation occur?
Small stones and graves of sand are bounced along the bed
33
How does the transportation method of suspension occur?
Very fine materials are carried in the water - that move as the river flows
34
How does the transportation method of solution occur?
The dissolved load - only occurs in certain rock types and is invisible
35
What is deposition?
When a river drops or leaves behind the load lt has been carrying
36
When does deposition occur?
Where there is a fall in the velocity (speed) of the river, when there is a drop in the amount I water(volume). This can be when a river enters a lake or the sea or when there is a change in the gradient
37
What are some features of the upper course of a river?
Steepest slope, vertical erosion(downwards), deposition of large materials, predominantly erosion
38
What are some features of the middle course?
Decreasing gradient, transportation
39
What are some features of a lower course of a river?
Lateral erosion(sideways), deposition of small materials, flatter slope, lost of deposition
40
How does the shape of the river valley change downstream?
V-U
41
What are some features of a v shaped valley?
Rocky bed, most erosion, narrow stream, slowest flowing, large load, vertical erosion
42
What are the features of the valley in the middle course of a river?
Fairly wide river, lateral erosion(valley widening), less rocky, erosion and deposition, load size reduced.
43
What are some features of the valley in the lower course?
Wide river, smooth bed, alluvium deposition, deposition, river appears to flow slowly but usually has the fastest flow, small load
44
What is weathering?
When the valley sides are worn away and the stream removes the debris
45
What are interlocking spurs?
When the river goes around the hills, called spurs they look as if they lock together
46
How is a waterfall formed?
Hard rock overlies soft rock- overhang is created as the different rocks erode at different rates- overhang collapses into the plunge pool as it can't support its weight- waterfall retreats upstream creating a gorge- the cycle repeats again
47
What is a meander?
A bend in the river
48
What creates a small river cliff?
On the outside bend of a river the water is flowing quickly this causes erosion by hydraulic action creating a small river cliff
49
How is a slip off slope created?
On the inside bend of a river the water is flowing slowly, this causes deposition which creates a slip off slope
50
How is an ox-bow lake formed?
A meander forms, the neck of the meander gets narrower over time due to erosion on the outer bend, due to continued erosion and often during a flood the water travels straight across the quickest route, the river deposits rocks and soil at the edges cutting off the meander creating an ox-bow lake. This eventually dries up leaving a scar.
51
What is a levee?
A raised bank either side of the channel in the Lowe course, formed by the river flowing
52
How is a levee formed?
During a flood banks are overtopped and larger material is deposited near the channel as speed and energy is lost, layers of material form from successive floods causing the levees to increase in height
53
What is a flood plain?
A wide, flat area of land either side of the river in its lower course
54
What is precipitation ?
Any form of moisture which reaches the ground e.g rain snow or frost
55
What is interception ?
When water is prevented from reaching the surface by Trees or grass
56
What is surface storage?
Water held on the surface e.g puddles
57
What is infiltration ?
Water sinking into the soil/rock from the ground surface
58
What is soil moisture?
Water held in the soil
59
What is percolation?
Water seeping deeper below the surface
60
What is ground water?
Water stored in the rock
61
What is transpiration?
Water lost through pores in vegetation
62
What is evaporation?
Water lost from ground / vegetation surface
63
What is surface run off?
Water flowing on top of te ground
64
What is throughflow?
Water flowing through the soil layer parallel to the surface
65
What is groundwater flow?
Water flowing through the rock layer parallel to the surface
66
What is 'water table'?
Soil where no more water can be absorbed
67
What occurs when a surface is permeable?
Lets water in- water soaks down through soil, throughflow and ground flow to reach the river
68
What occurs when a surface is impermeable?
Lets no water in therefore water reaches the river by surface run off
69
What is river discharge?
The amount of water passing a measuring point In a river channel at any given time recorded in cubic metres per second
70
What is a rivers regime?
The pattern of a rivers discharge throughout the year
71
Why does river discharge fluctuate?
Weather, relief(height and slope of the land), rock type, human land use
72
How does the weather cause river discharge to fluctuate?
Rain = high river levels, temperature = affects loss of water high temperature means more evaporation
73
How does the relief of land effect river discharge?
Effects the rate at which water runs off the surface and into rivers. Gentle slopes allow time for infiltration to occur. Steep slopes encourage fast run off as the water spills rapidly downwards due to gravity.
74
How does rock type effect river discharge?
Rock type is important is determining how much water infiltrates and how much stays on the surface. River discharge is higher when surfaces are impermeable as the water is forced to the river via surface fun off however permeable surfaces allow infiltration and this takes much longer for water to reach the river.
75
How does human land use effect river discharge?
Deforestation = Terese can't intercept and use water and urbanisation means there are less permeable surfaces.
76
What are flood/storm hydrography used to show?
The discharge of a river after a storm
77
What is lag time ?
The difference between peak rainfall and peak discharge on a storm/flood hydrograph
78
What is the approach segment on a flood hydrograph?
Shows the discharge of the river before it rains
79
What is the rising limb on a flood hydrograph?
Result of a rapid increase in rainwater reaching the river
80
What is the falling limb on a flood hydrograph?
When some rain water is still reaching the river but in decreasing amounts
81
What is a flood?
A normal river occurrence in the lower course of a river when the water in a river overtops its banks
82
What are the main causes of a river flooding?
Heavy or prolonged rainfall, snow melting
83
What happens to water when it lands on a steep slope?
The water has no chance to infiltrate into the ground so quickly flows to the river via surface run off
84
What happens to water when it lands on a permeable surface such as grass or soil?
In infiltrates into the ground and takes longer to reach the river as it travels to the river via throughflow or ground flow
85
What happens to water when it lands on an impermeable surface such as concrete or tarmac?
It can't infiltrate info the soil so it flows over the ground to the river as surface run off
86
What happens to water when it falls quickly or heavily?
There is more chance of flooding as the water doesn't have time to infiltrate into the soil so it flows to the river as surface run off
87
What happens when Terese are cut down?
More chance of flooding as there is less interception and Trees would also absorb some water up through soil so not as much water would reach the river
88
What was special about the year 2000?
The wettest year for a century in the U.K. And one of the 4 wettest years in history since records began in 1766
89
Why does flooding occur in autumn?
Dry surfaces due to high temperatures in the summer means water is unable to infiltrate so flows to rivers as surface fun off
90
Why does flooding occur in spring?
Snow melts and ground could still be frozen resulting in more surface run off
91
When was the boscastle flood?
Monday 16th August 2004
92
Where is boscastle?
Cornwall
93
What caused the boscastle flood?
Heavy rain hit the area causing 6cm (2 inches) of rain to fall in 2 hours- caused the ground to become saturated water surface run off. Steep valley sides. 2 rivers joining = more water in the first place
94
What were some short term effects of the boscastle flood?
50 cars washed away into the harbour, many buildings totally ruined by floodwater, 6 buildings + 1 bridge collapsed, 10ft water wall of water swept through the village, uprooted Trees piled 30ft high against buildings, the main road through the village washed away, bridge blocked by Terese and cars washed downstream, windows ripped out of shops and houses.
95
What were some long term effects of the boscastle flood?
Clean up bill was estimated the following day to be millions, the village was almost totally reliant on tourism so since it was destroyed less tourists would come until it had been redone.
96
What are some immediate responses to the boscastle flood?
Fireman cut their way through roofs to allow trapped people to escape, RAF and coastguard deployed 7 helicopters to rescue people, more than 120 people air lifted to safety, 17 fire appliances and 95 firefighters rescued more than 50 people, up to 1000 residents and holiday makers put into emergency accommodation, coast guards watched the harbour to ensure no one was washed away.
97
What were some long term responses of the boscastle flood?
Man made culverts were made wider to allow more water to flow easily to the river, government promised extra support and funding to clean up the area, the clean up bill estimated to run up to millions the next day.
98
Which river runs through boscastle?
River valency
99
When was the Bangladesh flood?
2004
100
Where was the Bangladesh flood?
Dhaka
101
What physical reasons caused the Bangladesh flood?
Heavy monsoon rains from may -September, 80% of the country is a floodplain, flat low lying land - 75% of land is only 10m above sea level, all 3 rivers have their peak flow at the same time, rivers are blocked and their channels are shallow because of deposited silt
102
What are some human causes of the Bangladesh flood?
Deforestation in Nepal and the himilayas increases surface sun off and deposition flowing downstream, urbanisation of the floodplain due to increasing population has increased frequency and magnitude of floods, building dams in India has increased the problem of sediment in Bangladesh, poorly maintained embankments (leeves) leak and collapse in peak times of discharge
103
What were some short term effects of the Bangladesh flood?
Electricity supply's disturbed, over 60% of the land flooded, 1040 people killed, 7 million homes destroyed, airport flooded, shortage of drinking water and food.
104
What were some long term effects of the boscastle flood ?
23.5 million made homeless, diseases such as cholera, bronchitis add dioreah spread, 100,000 people suffered from diahoreah, food shortage due to destroyed crops, farmers lost money and unable to plant next crop, flood cost the country 1 billion.
105
What were some immediate responses to the Bangladesh flood?
Water purification tablets distributed, medicines, clothing and blankets given out, food aid was given, people rescued by boat and helicopters.
106
What are some long term responses to the Bangladesh flood?
Emergency flood warning systems and plan rescue services created, government gave free seeds to farmers, reduce deforestation in areas in the upper course, flood embankments built along the river, locals began to rebuild their homes, flood protection shelters built, upstream dams built to hold back water when there is too much.
107
Why do MEDC's cope better with floods than LEDC's?
MEDC's have: better technology e.g helicopters , services and management e.g 999, more money to help those in need and money for repairs, flood warnings issued, flood management systems to reduce effects, better built buildings, + in LEDC's many live on the floodplain
108
What are the 4 main flood management strategies (soft engineering)?
Flood warnings, preparation, flood plan zoning, 'do nothing'.
109
What is the flood management system of flood warnings?
The environment agency warns people about possible flooding through TV, newspaper, radio and the internet
110
What are some advantages of flood warnings?
Impact reduced as warnings give time to move possessions upstairs and put sandbags in position or evacuate
111
What are some disadvantages of flood warnings?
Don't stop the flood from happening, might be hard to get insurance in a place which gets many flood warnings, people might not hear the warnings.
112
Why is the flood management strategy of preparation?
Buildings are modified to reduce the amount of damage a flood can cause, people make plans for what they would do in a flood e.g keep torches, important documents and blankets close.
113
What are some advantages of the flood management method preparation?
Impact of flooding is reduced as buildings are less damaged and people know what to do, people are less likely to worry when they are prepared.
114
What are some disadvantages of the flood management method preparation?
Doesn't guarantee safety, could give people a false sense of security, expensive to modify homes and businesses
115
What is the flood management method of flood plan zoning?
Restrictions prevent buildings being built on parts of a flood plain which is likely to flood
116
What are some advantages of the flood management strategy flood plan zoning?
Risk of flooding reduced as less impermeable surfaces created, impact of flooding reduced when there is nothing there to be flooded.
117
What are some disadvantages of the flood management strategy flood plan zoning?
Expansion of urban areas is limited, is no help in areas which have already been built on
118
Where is the flood management strategy of 'do nothing' used?
Where there is nothing to protect
119
What does the flood management strategy of 'do nothing' involve?
No money spent on new or existing methods as flooding is thought to be a natural process and people should accept the risks of living in an area likely to flood
120
What are some benefits of the flood management strategy 'do nothing' ?
The river erodes material is deposited on the flood plain making farmland more fertile, cheap and sustainable
121
What are some disadvantages of the flood management strategy 'do nothing' ?
The risks and effects are not reduced so the flooding will probably cause a lot of damage
122
What are the dimensions of the 3 gorges dam?
181m high and 2.3km wide.
123
When was the 3 gorges dam built?
1994 - 2006
124
Where is the 3 gorges dam?
Yichang on the river Yangtze
125
How much did the 3 gorges dam cost?
25.5 billion
126
What was the area flooded in order to make the 3 gorges dam?
632km squared
127
What is hard engineering ?
The use of technology in order to try and control rivers
128
What is soft engineering?
Trying to work within the constraints of the natural river system
129
What is a multi - purpose project?
A large scale venture with more than 1 aim e.g flood control, water supply, navigation
130
How does river straightening reduce flood risk?
Water can flow quicker down the river causing the water to clear quicker, less blockages since the water isn't looping around and around.
131
What are some factors of hard engineering ?
Expensive, works against nature, man made structures to control the flow of the river, immediate results, not sustainable
132
What are some features of soft engineering?
Works with nature, much cheaper, sustainable, uses knowledge of a river and it's process to reduce the effect of flooding
133
What is sustainable river management?
Not destroying resources if the environment for future generations.
134
What are the 4 main methods of hard engineering flood management?
Dams as reservoirs, channel straightening, building flood walls, dredging.
135
What is the hard engineering strategy of dams and reservoirs?
Huge walls built across rivers in the upper course and a reservoir is behind them
136
What are benefits of building dams and reservoirs?
Stops flooding, source of HEP, created tourism, creates jobs for construction
137
What are some disadvantages of building dams and reservoirs?
Expensive, area drowned to create them, destroys natural environment, stops sediment reaching areas further down the river
138
What are some advantages of channel straightening ?
Reduces risk of flooding
139
What are some disadvantages of Chanel straightening?
Moves risk of flooding further down the river, expensive, destroys area, constant maintenance and the river naturally wants to meander
140
What is the flood management strategy of building flood walls?
Walls along the side of a river to increase the level of a river before it floods
141
What are some advantages of building flood walls?
Reduce risk of flooding, protect properties and businesses
142
What are some disadvantages of building flood walls?
If they fail flooding is worse, expensive, unattractive, destroy the natural environment.
143
What is the flood management strategy of dredging?
Removing material from the river so the river can hold more water
144
What is an advantage of dredging?
Reduces the risk of flooding.
145
What are some disadvantages of dredging?
Expensive, destroying habitats, needs constant maintenance.
146
How many people were relocated due to the valley they lived in being flooded in the making of the 3 gorges dam?
1.3 million people
147
Why is reduced flow of sediment due to the 3 gorges dam a bad thing?
Will harm agriculture downstream as farmers rely on silt to make the soil fertile
148
What was lost due to the 3 gorges dam?
Sacred temples, 200 settlements
149
What are some social advantages of the 3 gorges dam being built ?
New settlements built with better sanitation and housing, provide water for the valley towns and allow transfer of water to areas of shortage, tourist cruise ships able to sail the river at all times, 100 million people living downstream and 250000 hectares of farmland down stream protected from flooding
150
What are some environmental disadvantages of the 3 gorges dam neon built?
Changing the flow of the Yangtze could lead to the extinction of the surgeon and river dolphin, will trap silt causing the reservoir to silt up and this will cause increased erosion below the dam, lots of good quality lost due to deliberate flooding of the valley, located on a major earthquake fault it holds so much water it could cause an earthquake.
151
What is a concern about the 3 gorges dam?
It could break causing colossal flooding
152
How will tourism be effected as a result of building the 3 gorges dam?
Scenic quality of the 3 gorges is lost
153
Where is there surplus amounts of water in the U.K.?
Areas which receive a lot of rain but are sparsely populated e.g north west England, Scotland and wales
154
Where is there water deficit in the U.K.?
South east England and east England where less rain is received however they are densely populated
155
Why is water demand in the U.K. Increasing?
Individuals use more e.g baths, showers, dishwashers, washing machines etc. Increasing population.
156
How is water demand met sustainably?
Water meters, houses designed with better water efficiency, rainwater can be collected, bath water can be used to flush toilets, more people are taking showers instead of baths, water leaks quickly fixed by water companies.
157
What is water stress?
Amount of water available does not meet the demand
158
How can water be transferred?
By pipeline but this is costly or by river - this is easier and cheaper.
159
How is Kielder reservoir unusual?
Benefits of it far outweighed the negatives
160
How is kielder reservoir the largest in the U.K.?
By capacity as it holds 200 billion litres
161
What are the dimensions of kielder reservoir ?
27.5 mile shoreline, 10km long, area of 10km squared
162
Where does kielder reservoir serve?
Tyneside, wearside, teeside
163
Why was the kielder reservoir built?
Planned in the 1960's to meet growing demand for water, high rainfall, few people would need to be displaced, relatively few habitats lost, out migration of the young would be reduced.
164
What are some environmental factors of the kielder reservoir?
Northumbrian water monitor the area to maintain good quality water, an eco village nearby is powered by waste chips from the forestry process, conservation hatchery for salmon breeds, the forestry commission ensure the woodland is extracted sustainably whilst environments are protected, water levels remain high, habitats protected
165
How many people visit kielder reservoir each year?
1/4 of a million
166
What are some economic factors if building the kielder reservoir?
Caravan sites, youth hostels and hotels accommodate people bringing money to the area, jobs made available due to construction and maintenance of the dam, visitor centre as local shops benefit from tourism, forestry around the reservoir generates cash.
167
What are some social factors of the kielder reservoir ?
Schools and youth groups use the area for recreation, skyspace hilltop observatory and sculpture trail created, mountain biking downhill trials and horse riding paths created, the Calvert trust provides activities for the disabled, and orienteering course and water sports, bird watching facilities opened in 2008.
