Rivers Flashcards
1
Q
What is a drainage basin?
A
An area within which water, supplied by precipitation, is transferred to an ocean, lake or larger stream
2
Q
What is a watershed?
A
The imaginary lines that separate adjacent drainage basins
3
Q
Is a drainage basin and open or closed system and why?
A
An open system. This is because it connects to a larger water body (ocean/ lake)
4
Q
Define ‘River Discharge’
A
The volume of water passing a given point over a set time
5
Q
What is the formula for river discharge?
A
River discharge = cross-sectional area x mean velocity of water
6
Q
What is the unit for river discharge?
A
cubic meters per second (cumecs)
7
Q
What are the factors affecting river velocity? (4)
A
-> Gravity - the gradient of the river
-> Frictional resistance with the bed + bank - this opposed downstream flow
-> volume of water - i.e. from precipitation
-> channel shape
8
Q
What are the different flows of water?
A
-> Laminar flow
-> Turbulent flow
9
Q
Define ‘Hydraulic radius’
A
The efficiency of a stream’s shape
10
Q
What is the formula for hydraulic radius?
A
Hydraulic radius = cross-sectional area/ wetted perimeter
11
Q
What is the wetted perimeter?
A
The water touching the river’s edge
12
Q
Choose the correct word.
The higher the hydraulic radius ratio, the more/less efficient the stream is, and the smaller/larger the frictional loss
A
- more
- smaller
13
Q
What is the ideal river shape?
A
A semi-circular river shape
14
Q
Where is water stored?
A
-> Aquifer
-> Cryosphere
15
Q
What is an aquifer?
A
A body of rock and/or sediment that holds groundwater
16
Q
What is groundwater?
A
Groundwater is the word used to describe precipitation that has infiltrated the soil beyond the surface and collected in empty spaces underground.
17
Q
Describe the movement of water into an aquifer
A
It moves slowly downwards from the soil into the bedrock. When water slowly drips into porous materials, it is called percolation
18
Q
What is a ‘water table’ ?
A
The upper layer of the saturation zone
19
Q
What is a cryosphere?
A
Freshwater held in a snow and ice environment
20
Q
What is the Bradshaw model?
A
A model depicting how the characteristics of the upper course of a river vary to the lower course
21
Q
What are the best conditions for laminar flow?
A
-> shallow channels
-> low velocity
-> smooth, straight channels
22
Q
What are the best conditions for turbulent flow?
A
-> high velocities
-> complex channel shapes (i.e. meanders)
-> Cavitation - pockets of air that explode under high-pressure
23
Q
Which area in the river is fastest? why?
A
The middle of the river. It is affected by no friction due to the river bed, banks or air
24
Q
What is vertical erosion? where is it usually found? and what does it create?
A
Downwards erosion
usually found in the upper course
creates v-shaped valleys
25
What is lateral erosion? where is it usually found? and what does it create?
Sideways erosion
usually found in the middle to lower course
creates wide and flat U-shaped valleys
26
What are the factors affecting the rate of erosion? (6)
load
pH
velocity and discharge
gradient
geology
human impact
27
What are the types of erosion?
- Hydraulic action
- Attrition
- Abrasion
- Solution
28
Briefly describe Hydraulic action, Attrition, Abrasion and Solution
Hydraulic action -
the force of the water wearing away at the river bed and banks
Attrition -
when two rocks collide with force. They break down and become smoother and rounder
Abrasion -
Rocks are dragged along the bed, creating a sandpaper effect that wears down the rock making them smoother and rounder
Solution -
River water is slightly acidic due to CO2 absorption.
29
What are the types of transportation?
traction
saltation
suspension
solution
30
Briefly describe the 4 types of transportation?
traction-
large boulders pushed along the river bed
saltation-
smaller particles are bounced along the river bed. They hit other particles, passing on the energy to continue bouncing
suspension-
when lightweight material is held by the river. Does not touch the river bed or banks
solution-
any material carried by being dissolved in the water
31
What is deposition?
When the river velocity falls, its energy falls to. This causes it to put down its load
32
What is the ‘capacity’ of a river?
How much the river can carry
33
What is the ‘competence’ of a river?
The largest particle the river can carry
34
How is a waterfall formed?
1. The soft rock under the hard rock breaks away due to hydraulic action
2. This creates a soft rock undercut
3. Due to the missing soft rock, the hard rock's weight is no longer supported, and the overhang collapses. This accumulates in the river below
4. The velocity enhances erosion in the waterfall, creating a plunge pool (this is done through hydraulic action)
5. The sediment, collected from the collapsed overhang, erodes through abrasion and attrition
6. The waterfall retreats upstream, leaving behind a gorge
35
How is a meander formed?
1. As the river erodes laterally it forms large bends
2. The velocity increases on the outside of these bends, eroding the river bank
3. As most of the river’s energy and velocity is on the outer bend, the inner bend loses energy and deposits material, e.g. sand and shingle
4. The outer bend erodes and this creates a river cliff
5. This erosion and deposition moves the bend in a certain sideways direction, creating a meander
36
How is an oxbow lake formed?
1. As a meander erodes laterally, the neck gets closer and closer, until it breaks
2. The river has now found a quicker way to flow, leaving a horseshoe-shaped lake, disconnected from the river, called an oxbow lake
37
How is a levee formed?
1. When a river floods, the sediment carried by the river is suspended in the water
2. During this flood, a river will lose its energy, and will deposit sediment onto the floodplain
3. It deposits the larger particles first because they are the most heaviest. The smaller particles are deposited further away from the river’s edge
4. After the flood, the levee is left
5. Now the river has a larger capacity to hold more water. This means when there is a higher volume of precipitation, the floodplains are at a smaller risk of flooding
38
How is a delta formed?
1. A delta is formed in the lower course of a river when the river reaches the sea
2. The river slows down and loses energy
3. It has to deposit some of the rocks and sediments that it has carried downstream. The deposition begins with large, impermeable rocks and finishes with silt and sand further downstream.
4. These depositions create smaller tributaries or channels for the river to flow through.
39
What are the 4 types of deltas?
1. Hybrid delta
2. wave-dominated delta
3. Tide-dominated delta
4. river-dominated delta
40
What is infiltration capacity?
How much water can be absorbed by the soil
41
What is a storm hydrograph?
It shows how a river channel responds to key processes of the hydrological cycle
river discharge is plotted against time
42
Urban vs rural hydrographs
URBAN: impermeable
RURAL: permeable
43
Physical factors affecting flood risk
Geology
Vegetation
Prolonged rainfall
Heavy rainfall
44
What is the lag time?
The time interval between peak precipitation and peak discharge/flow
45
What is lag time influenced by? (3)
(BIG)
- basin shape
- steepness (gradient)
- impermeability of rocks
46
What is a flood?
When the volume of water exceeds the rivers capacity and overflows onto a floodplain
47
What is a river regime?
The seasonal variation in the flow of the river
48
What is urban hydrology?
Urbanisation changing a drainage basin hydrology (i.e. sewers and drains)
49
Human factors affecting flood risk? (3)
- urbanisation
- deforestation
- man made structures - levees and embankments
50
What are the benefits of hydrographs?
- it can predict flood events based on precipitation and basin geology
51
What are the disadvantages of hydrographs? (2)
- The data does not stretch far back (only 50 years)
- It does not take historical events and basin surveys into account
51
What is climate modelling?
A climate model is a numerical representation of the climate system providing geological locations and elevations
52
PROS of climate modelling?
- It predicts advanced weather warnings, predicting tropical storms, therefore it helps save lives
53
CONS of climate modelling?
- inability to predict a flash flood
- the landscape is constantly changing due to human impact
54
What is the main attempt at flood prediction?
- weather forecasting
55
An increase in magnitude = ?
= decrease in frequency
56
What two flooding case studies do I need to know?
Indus system - Pakistan
Queensland, Australia
57
What is the development of Pakistan?
population
life expectancy
HDI
184.8 million
66 years
0.49
58
What is the development of Australia?
population
life expectancy
HDI
22.4 million
88 years
0.937
59
What is the relief of the Indus system, in Pakistan? and its affects
Mountainous - high river velocity - dangerous to transport along the river
60
What is the relief of Queensland, in Australia? where are most of the rivers usually found + what course are they?
Hardly any mountainous regions - lower course of the river in the South-east
61
What is the cause of the main flood event in the Indus system?
dammed water in India was allowed to flow downstream in Pakistan in 2010
62
What were the effects of the indus system flooding
- 2010 -> 2.5 million acres of cropland destroyed, 1300 people died, 2,500 homes destroyed
63
In which course of the river would a dam be built?
upper course
64
How could we mitigate against floods? (name 4)
- building less important infrastructure on floodplains
- Channel modification (for example, making it straighter and deeper)
- Preparing and educating people in flood-prone areas
- Building flood defences, i.e. dams, embankments, flood relief channels
65
What is hard engineering?
Man-made structures to control the natural behaviour of a river
66
What is soft engineering?
A natural approach to control river behaviour that minimises environmental impact
67
What is mitigation?
An effort to reduce the loss of life and prevent property damage i.e. by floods
68
How does afforestation mitigate floods? (3)
- Increase in interception (so water reaches a river at a slower rate)
- Absorbs rainwater through its roots
- Decrease in erosion (because of increased interception, there is less power for erosion to take place)
69
ADV and D.ADV of dams (name 4 positives and 3 negatives)
+ Hydroelectric power
+ improve irrigation for agriculture
+ tourism
+ store excess water to prevent floods
- expensive
- displacement of people during its construction
- Life cycles of habitats living in the water (like fish) get affected due to the construction of dams. Their life cycles are adapted to natural river habitat and flow regimes. By altering the flow, the physical surroundings are altered.
70
Name 3 examples of channel modification
- straightening the river
- raising the banks
- creating new channels
71
Give one example of channel modification, its use and one positive and one negative
Artificial levee - raising the banks of the river so it has a larger capacity
+ When water levels rise, there is a smaller risk of the water damaging the artificial banks, therefore reducing the risk of flooding
- All the river's power is flowing through a smaller space. Water levels are higher and water flows faster.
72
What is water stress?
Occurs when the demand for water exceeds the available amount during a certain period or when poor quality restricts its use.
73
What are some indications of water stress?
- per capita water supply is <1700 cm^3
- the area is subject to frequent water shortages
74
What are the problems with water stress?
problems related to food production, economic development and inadequate sanitation. It may also harm global supply chains
75
Finish the sentences:
1) When the world population is 3x, the water usage is ______
2) 1/2 global _______ disappeared
3) 20% freshwater species are now __________
4) many aquifers are _________
5) water tables are rising/falling
1) 6x
2) wetlands
3) extinct/endangered
4) depleted
5) falling
76
What is water usually used for?
domestic use, industry and agriculture
77
What is water quality?
the condition of the water with respect to its suitability for a particular purpose like drinking or swimming
78
What are some water-related diseases, and how many people does WHO estimate is going to die from them?
- typhoid
- hepatitis
- malaria
- cholera
4 million deaths a year
79
How might water quality be affected?
- sewage
- fertilisers/farming pesticides
- acids from industrial processes
80
Factors affecting access to safe drinking water (4)
- water availability
- water infrastructure
- cost of water
- quality of water
81
What is ‘nexus’?
The interrelationship, interdependence, and relations between water, food and energy
82
What is eutrophication? the steps
1) Nitrogen and phosphorus from agricultural fertilisers are washed off into lakes and ponds
2) This causes algal overgrowth
3) The algae accumulates at the top of the pond and stops sunlight from reaching the pond. The plants die an oxygen in the water is depleted
4) In these conditions, decomposers, like bacteria, thrive and make the lake more anoxic, as they decompose the dead plants
5) Without oxygen, fish and other organisms die
83
How is eutrophication an example of positive feedback?
As algae grow, there are good conditions for decomposers. The lake becomes more anoxic making good conditions for decomposers, making it more anoxic, and so on…
84
What is a case study for eutrophication?
China’s Li River
85
What are the three main problems related to high nitrogen concentrations in water from agricultural lands?
- Nitrogen compounds can cause undesirable effects in aquatic ecosystems - especially excessive algal growth
- Loss of fertiliser is an economic loss to the farmer -> impact of agricultural output
- High nitrate concentrations in drinking water may affect human health
86
What is salinisation?
When increased irrigation frequently leads to an increase in salt levels. This is because salt is left in the soil when the plants take up the water. Increased irrigation and precipitation add to this affect
87
How does salinisation occur?
- When shallow-rooted plants are planted, less water is taken in and the water table rises
- The salt rises (in the water) & kills the plants
- Without the plants, the soil cracks and erodes away
this occurs due to flooding of the land by seawater or brackish groundwater through the soil from below.
88
What is the case study for salinisation?
The Murray Darling Basin
89
What stakeholders are involved in salinisation?
- farmers
- consumers
- local people
90
What are the effects of salinisation?
- Financial loss of crops
- loss of land to soil
- increases deforestation to regain land
- construction (buildings) will have a shorter life
91
Where are droughts mostly located?
- Along the equator (e.g. western Sahara)
92
What is the relationship between population and droughts?
Increase in population = Increase in droughts (due to an increase in resource use)
93
What is the intertropical convergence zone (ITCZ)?
Occurs in an area, where the northern and southern hemispheres meet (along the equator). This is where warm air rises and cool air sinks
94
What is the process of the ITCZ?
1. warm air rises (lots of moisture). This has low-pressure
2. As it rises up, it cools and forms clouds. It holds a lot of moisture and lots of rainfalls (this will happen in rainforest regions)
3. The cold clouds move along and the cold air sinks. This has high pressure. In these regions many deserts are found because there is no moisture in the clouds, and therefore a lack of rain.
95
What is an el Niño?
It affects ocean temperatures, affecting how much it rains on land. It is usually associated with droughts
96
What is la Niña usually associated with?
flooding
97
What is the case study about scarcity and drought?
The horn of Africa (HoA) (2011)
98
Where and when did the HoA happen? and what happened
Between 2011-2012 a severe drought affected East Africa and caused a severe food crisis across Somalia, Ethiopia, Kenya
99
What was the worst affected country of the HoA?
Ethiopia
100
Why did the HoA happen?
A strong La Niña, over the Pacific, had interrupted seasonal rains in the HoA. This meant that the rains failed in this area, and people suffered due to extreme drought
101
What were the economic effects of prices due to the HoA event? (3)
- cereal prices rose to record levels
- prices for livestock decreased
- reduced purchasing power
102
What are the social effects of the HoA event? (6)
- Rebel activity from the Al-Shabaab
- 260,000 deaths
- Increased infant mortality and overall mortality
- 920,000 people fled from Somalia, Ethiopia and Kenya
- 440,000 people in 3 refugee camps, when the capacity was only 90,000
- 30% of children suffering from malnutrition
103
What are the environmental impacts of the HoA event? (2)
- Increased deforestation to house refugee camps for refugees
- increased drought cuased soil erosion and desertification
104
What are the political impacts of the HoA events? (1)
- The Ethiopian government has requested for aid for drought-related events every year since 1984
105
What is an aquifer? Give a characteristic of it
It is a body of rock/sediment that holds groundwater. It has good permeability
106
What are the 2 types of aquifers?
- confined
- unconfined
107
what is the water table affected by? (2)
- The rock type (permeability)
- the level of precipitation
108
What is an artesian well?
A well that brings ground water to the surface without pumping
109
How much does the Great Artesian Basin (GAB) in Australia Cover?
It covers a 1/4 of the eastern side of Australia
110
Why does the GAB attract population?
Because it has an access to an abundance of food and water
111
Positive impacts of the GAB? (4)
- Tourism
- Jobs
- Mining
- Agriculture
112
Name 3 growing human pressures
1. Increase population
2. Agriculture
3. Tourism
113
What case study are we doing for rivers in Africa?
River Nile
114
Describe the location of the River Nile. What countries does it flow through?
Flows through the North-Eastern/ Eastern Africa
Countries:
- Egypt
- Sudan
- Uganda
- Ethiopia
- South Sudan
115
Describe the population distribution along the River Nile
Densely populated near the mouth of the river in Egypt and around the source of the river
116
What is hydropolitics?
Rise of internationally shared water resources as a source of conflict
117
Types of human pressures that affect rivers, aquifers and lakes (3)
1. pressure for agriculture
2. overuse of aquifers for increasing demand - overpopulation
3. pollution of lakes and rivers
118
What is integrated drainage basin management (IDBM)?
The process of coordinating conservation management and development of water, land and other related resources across sectors within a given river basin, to maximise the economic and social benefits derived from water resources equitably while preserving and where necessary restoring freshwater ecosystems
119
What needs must IDBM relate to? (5)
- agricultural
- industrial
- recreational
- energy
- ecosystem
120
What is the case study that we will study for the IDBM?
The Mississippi River
121
what is the importance of the Mississippi River?
- It holds 92% of the country's farm exports
- $54 billion in agricultural products
- 1/2 goods and services consumed by US people produced with water from the Mississippi River.
122
What are the threats towards the Mississippi River? (3)
- Mississippi floods threatening people and economic activity
- an increase in the global demand for crops has resulted in an increase in the pressure of water resources
- much of the water infrastructure is ageing and needs replacing
123
What are the seven key elements to a successful IDBM initiative?
1. Vision
2. Integration
3. Scale
4. Timing
5. Participation
6. Capacity
7. Knowledge
124
Explain the seven key elements of a successful IDBM initiative
| Vampires In Space Time People Catching Kangaroos
Vision: a long-term vision for the basin, agreed upon by all stakeholders
Integration: collective decisions across all sectoral interests (e.g. fisheries, urban development, agriculture)
Scale: decision-making at the river basin scale
Timing: working within a strategic framework
Participation: active participation by all relevant stakeholder
Capacity: adequate investment from government and private sector
Knowledge: foundation of knowledge of the river basin and he forces that influence them
125
What is a wetland?
Areas of land whose soil is saturated with moisture either permanently or seasonally. They maybe covered partially/completely by shallow pools of water
126
What 3 type of wetlands are there? What do wetlands include?
They include:
- swaps
- marshes
- bogs
- water maybe salt water or fresh water or mixture of the two this is called brackish
127
Where are most the wetlands found?
How much of the land is wetland?
Has this differed from 100 years ago and by how much?
They are found in northern Canada/northern American region 6% of the land is wetland and 100 years ago this was double the amount
128
Name eight factors as to why wetlands are beneficial?
-Flood control
-groundwater recharge
-transport network
-tourism and leisure
-flora and fauna
-fisheries
-water purification
-storage of organic matter
129
Out of the eight factors as to why wetlands are beneficial which three factors have I chosen to remember for exams, and explain them
-> Flood control - can purposefully flood flood planes to limit damage elsewhere
-> Tourism and leisure-for example birdwatching rest and relaxation fishing and lake trips bring an income for local people
-> fisheries - brings in income, jobs (economic opportunities) and food source from local fisheries of a small scale
130
Name four factors that cause loss and degradation of wetlands
- Increase demand for agricultural land
- population growth = increased water usage
- alien species invasion
- introduction of an infrastructure project
131
Out of the six factors that cause loss and degradation of wetlands what are the most important three, and explain them.
- Population growth- an increase in water demand, food and land so wetlands are drained of the water or the source of water.
- urbanisation- population growth puts pressure on housing demand. With urban areas growing more, more wetland areas are being drained or inhabited, this can also cause pollution, disturbance of wildlife…
- increase demand for agricultural land- population growth increases food demand, so more wetlands are being artificially drained for agricultural land
132
What is an AGWI report card
The AGWI (American Great Watershed Initiative) measures the improvement of six sectors in relation to water resources, quality and availability for the Mississippi river -> it promotes healthy ecosystems and reduces flood risk
133
What is rainwater harvesting
A method to reduce water wastage by capturing rainwater before it evaporates/drains
134
What are the six community responses of water
1. water saving
2. customer pricing
3. new technologies
4. zoning
5. water purifications
6. rainwater harvesting
135
what are the inputs, outputs, flows and storages of a drainage basin
inputs:
precipitation
outputs:
Evaporation
transpiration
evapotranspiration
water flowing to sea
flows:
throughflow
overland/surface flow
groundwater flow
percolation
infiltration
storages:
river
groundwater aquifers
trees/vegetation
136
what is the hjulstrom curve
A diagram that shows the relationship between the velocity of the river and the size of its particles in order to be deposited, eroded and transported
137
Briefly describe what the Hjulstrom curves looks like
The Hjulstrom curve has the particle size in millimetres of the load on the X axis, velocity in metres per second on the Y axis and the graph is split into five sections signifying clay, silt, sand, gravel, pebbles and boulders. There are two curves: the entrainment velocity and the fall velocity. The entrainment velocity starts at a high velocity before falling at sand and silt and increasing again at gravel, pebbles and boulders. The fall velocity has a steady increase starting at 0.01 mm and increases until it is almost touching the entrainment velocity curve.
138
What is entrainment velocity
This is the velocity required to pick up the rivers load
139
What is fall velocity
The velocity required to drop or deposit the rivers load
140
Why is there a high entrainment velocity for clay even though clay is the smallest load
Although it is the smallest load clay tends to stick together therefore is harder to pick them up and a higher entrainment velocity is needed to do so
141
Why is the fall velocity higher in pebbles and boulders rather than clay, silt and sand
Larger boulders and pebbles require a higher velocity to pick them up, therefore anything lower than this velocity (the fall velocity) will cause them to be dropped. Whereas smaller particles of loads require very low velocities to pick them up and transport them therefore lower fall velocities are needed to drop them.
142
What does the area under the full velocity signify
For each piece of load, the area under the fall velocity is the velocity at which the load can no longer be carried and he dropped by the river
143
What are the three zones on the Hjulstrom curve and where are they located
- Transportation zone
- erosion zone
- Deposition zone
The erosion zone is located above the entrainment velocity, the transportation zone is located between the entrainment velocity and the fall velocity and the deposition zone is located underneath the fall velocity
144
what is the case study for dams?
The great Ethiopian renaissance dam (GERD) 2011
145
Where is the GERD located
The dam is located along the Blue Nile downstream of the Tana Lake in Ethiopia
146
state 3 facts about the GERD
- it stands 170 m tall
- it is Africa's largest hydroelectric plant
- it began generating electricity in February 2022
147
Name four advantages of the GERD
-The GERD will be used to generate 6000 megawatts of hydroelectric power
- increased water for irrigation improving the soil quality for crops and reducing the frequency and magnitude of droughts
- Ethiopia could double their electricity production which is useful for the 60 million people in Ethiopia who currently do not have access to electricity
- the Ethiopian government estimates that the GERD could account for 2% of the countries annual GDP
148
Name four disadvantages of the GERD
- Egypt uses the Nile as its main water supply, for 97% of its water needs. Numerous countries downstream of the dam will have a reduction in the amount of water available in the Nile (Egypt will lose one-third of its water supply)
- the dam may alter natural flow which could affect ecosystems and biodiversity downstream
- There have been geopolitical conflicts between the countries there is a lack of comprehensive agreements about the operation of the dam for all countries
- the construction of the dam has resulted in the displacement of communities
149
what is the case study for wetlands
the Kissimmee River, USA
150
what are the causes of wetland degradation of the Kissimmee river
- replacing wetland with cropland
- climate has caused more C02 to be taken in by wetlands - increasing the acidification levels - decreases conditions for aquatic life - decreasing biodiversity
151
what convention was utilised to protect the wetlands
The Ramsar Convention, 1971
152
what is the Ramsar convention - how many countries dos it include - what is its aim
An international treaty to conserve wetlands was signed by 172 countries that designatied the importance of wetlands on its natural reserve
153
What was done in order to conserve the Kissimmee River
- they had increased the water levels in order to sustain more life - there was an increase in wild fowl returning to the area
- they had pumped more oxygen so that it could be dissolved in order to retain aquatic life
154
What are the disadvantages when they aim to conserve the Kissimmee River
- it cost $410 million
- because of increasing climate change there was an increasing reparation within the wetland
155
What plants have they swapped to in the Murray Darling basin that had led to increased salinisation
They had swapped from native Australian plants to irrigated plants which meant that more water seep into the soil and there was an increase in the water table. An increase in the water table meant that more salt would reach the plants roots and we damage them which causes a loss of crops affecting financial and social aspects
156
What was the causes of the flooding in Queensland Australia
The river Burnett had topped its banks causing large areas of the state to flood, when tropical storm Tasha and abnormal rainfall from La Niña collided
157
What is the main effects of the flooding in Queensland Australia
- 35 people died
- 5900 people were evacuated from 3600 homes
158
What had they done to mitigate against flooding in Queensland Australia
They built the Wivenhoe dam which stopped to Brisbane flooding
159
What is an example of local communities aiming to improve water management
The ice stupas in Nepal
160
What are Ice stupas in Nepal and what kind of project was this
A conical ice shaped heap that stores winter water so that there is enough water in the summer when the ice melts - bottom up project
161
what are the 4 hard engineering schemes
- dams and reservoirs
- straightening and dredging the river
- embankments
- flood relief channels
162
what is 2 adv and 2 disadv of straightening and dredging the river + what is dredging/ straightening the river?
Straightening the river speeds up the water so high volumes of water can pass through an area quickly. Dredging makes the river deeper so it can hold more water.
Advantages
More water can be held in the channel.
It can be used to reduce flood risk in built-up areas.
Disadvantages
Dredging needs to be done frequently.
Speeding up the river increases flood risk downstream.
163
what are the 2 adv and 2 disadv of embankments? + what is an embankment?
Raising the banks of a river means that it can hold more water.
Advantages
Cheap with a one-off cost
Allows for flood water to be contained within the river.
Disadvantages
Looks unnatural.
Water speeds up and can increase flood risk downstream.
164
what is one adv and two disadv of flood relief channels? + what is a flood relief channel?
The floodwater flows into the relief channel and is taken either to an area where it can be absorbed, or re-enters the river further down its course.
Advantages
Removes excess water from the river channel to reduce flooding.
Disadvantages
Expensive to build.
If water levels continue to rise, the relief channel may also flood.
165
what are the 2 soft engineering techniques?
floodplain zoning
flood warnings and preparation
166
what are 2 adv and 3 disadv of flood warning and preparation? what is it?
The environmental agency monitors rivers and issues warnings via newspapers, TV, radio and the internet when they are likely to flood so people can prepare.
Advantages
People have time to protect their properties, eg with sandbags.
Many possessions can be saved, resulting in fewer insurance claims.
Disadvantages
Some people may not be able to access the warnings.
Flash floods may happen too quickly for a warning to be effective.
They do not stop land from flooding - they just warn people that a flood is likely.
167
what are 2 adv and 1 disadv of floodplain zoning? and what is this?
Allowing only certain land uses on the floodplain reduces the risk of flooding to houses and important buildings.
Advantages
More expensive buildings and land uses are further away from the river, so have a reduced flood risk.
Less damage is caused, leading to fewer insurance claims.
Disadvantages
Not always possible to change existing land uses.
168
how did eutrophication occur in the China Li river
- people used it as an informal dumping ground where farmers would throw dead pigs and cows
- mining in the mountains and factories with dump chemical waste into the river and the Chinese government did nothing. Therefore I'll be started to bloom turning the river green
169
What are the effects of eutrophication for China
- the water quality of drinking water was affected which caused 80% of outbreaks of disease diseases such as cholera, birth defect and cancer
- The algae caused a decrease in sunlight and oxygen which can lead to death of an ecosystem
- Tourism makes up 20% of the cities economic output in 2015 and the green colour of the river affected tourism
170
What stakeholders are affected by the Li river case study
- the Chinese government that did not do anything to stop the eutrophication
- miners and construction workers who are dumping waste into the river
- locals who are affected by the poor quality drinking water
- environmentalists are too afraid to speak up about the problem due to a fear of the government
171
What are some solutions to eutrophication
- planting buffer zones (says in plants like reads that absorbed nutrients really well and prevents them from running off into adjacent water bodies)
- avoid the use of year-round fertilisers, for example during rainy seasons as fertilisers are more likely to be washed off into water bodies
172
What caused the increase in salinity in the Murray Darling basin
- the clearance of native plants which can survive the salty environment
- increased irrigation which adds water to salty ground water aquifer
- the low rainfall and high temperature in the basin would lead to high rates of evaporation that leaves salt on the soil
173
How does salinity affect the Murray darling basin
- the high salt levels in the soil and the water can lead to plants dying
- the water is made undrinkable so animals and humans cannot use it
- it can cause damage to machinery and pipes by corrosion
174
What is being done in the Murray Darling basin
- using more efficient ways of irrigating (drip-flow irrigation - useful in hot climates like Australia) and returning more water to the environment
- creating salt exclusion zones that direct salt away from plants to minimise salt in water when plants intake them
- The Murray Darling Basin Ministry council adopted the basin salinity management strategy to tackle the salinity (2030)
