Rivers: Hazards & Opportunities (Cambridge (CIE) IGCSE Geography): Flashcards
Exam code: 0460 & 0976
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Define bankfull discharge.
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Define bankfull discharge.
A river's bankfull discharge is when it is full to the top of its banks; beyond this point, water overspills onto the floodplain.
Define floodplain.
The flat area of land on either side of a river that is covered by water when the river floods.
What are the two main natural hazards of living near a river?
Flooding and erosion.
Describe the two main natural causes of river flooding.
Heavy, torrential rain, which produces high overland flow because water cannot infiltrate; and a prolonged period of steady rain, which saturates the ground and again produces high overland flow.
Besides heavy rainfall, give three other natural causes of river flooding.
Landslides, snow and ice melt, and storm surges that push water up the river channel.
Although the root cause of flooding is ______, the risk is increased by human activities such as urbanisation and deforestation.
Although the root cause of flooding is precipitation, the risk is increased by human activities such as urbanisation and deforestation.
How can human activity increase the risk of river flooding?
Through urbanisation, deforestation, building bridges and dams, human-induced climate change and agriculture.
True or False?
Flooding and river bank erosion are unrelated and rarely occur together.
False.
They often occur together, because both result from increased discharge and velocity.
How can flooding increase the spread of disease?
Floodwater can become a breeding ground for disease-carrying animals such as mosquitoes, and can be contaminated by bacteria that spread diseases such as cholera.
In 2019, what was the impact of riverbank erosion in northern Bangladesh?
It destroyed the homes of 8,000 people.
Why is the silt deposited by river flooding useful?
It is rich in minerals and nutrients, making it ideal for growing crops.
Water from a river can be used to ______ farmland to help crops grow.
Water from a river can be used to irrigate farmland to help crops grow.
True or False?
River bank erosion can lead to the displacement of populations.
True.
Erosion causes the loss of farmland, housing and transport routes, which can displace the people living there.
When does a river flood occur?
When a river cannot contain all the water it is transporting, so water flows out of the channel onto the floodplain.
Explain how urbanisation increases the magnitude and frequency of floods.
It creates impermeable surfaces such as roads; it adds gutters and sewers that increase drainage density; and riverside facilities reduce the channel's carrying capacity.
Why do smaller, circular drainage basins have a higher flood risk?
They respond more quickly to rainfall than larger or linear basins, so water reaches the channel faster.
Impermeable rocks and soil decrease infiltration and percolation, which increases ______.
Impermeable rocks and soil decrease infiltration and percolation, which increases overland flow.
Give three social impacts of river flooding.
Homes destroyed leading to homelessness; deaths and injuries; and lack of clean water leading to disease. (Also food shortages, loss of jobs, damaged transport, loss of energy supply.)
Give two economic impacts of river flooding.
Destruction of infrastructure such as roads that must be repaired; and increased insurance costs. (Also crop destruction, closure of businesses, reduced house prices.)
Define hard engineering.
Flood management that involves building structures or changing the river channel, e.g. dams, levées and straightened channels.
Define soft engineering.
Flood management that works with the natural processes of the river and surrounding environment; it is an example of mitigation, aiming to minimise damage rather than prevent flooding.
How do dams and reservoirs reduce flooding?
They enable the amount of discharge downstream to be controlled.
Contour ploughing involves ploughing fields ______ the slope rather than up and down, giving water more time to infiltrate.
Contour ploughing involves ploughing fields across the slope rather than up and down, giving water more time to infiltrate.
True or False?
Afforestation is a fast-acting, short-term flood management strategy.
False.
Afforestation is a long-term strategy because trees take time to grow; it increases interception and infiltration and reduces surface runoff.
For a flood strategy to be sustainable, what two aims must it meet?
It must both reduce flood risk and protect the environment; examples include afforestation, river restoration and wetland conservation.
In which mountain range do both the Ganges and Brahmaputra have their source?
The Himalayan Mountains.
In Bangladesh, the Ganges becomes the River ______, where it joins with the Brahmaputra River.
In Bangladesh, the Ganges becomes the River Padma, where it joins with the Brahmaputra River.
Give two natural causes of flooding in Bangladesh.
Low-lying land in the Ganges delta at or just above sea level; and the monsoon climate, bringing heavy, prolonged rains. (Also tropical cyclones and melting Himalayan snow and ice.)
How does deforestation in upland areas contribute to flooding in Bangladesh?
It leads to less interception and infiltration, which increases overland flow.
How has human-induced climate change increased flood risk in Bangladesh?
It has increased melting of Himalayan snow and ice (raising discharge) and may have raised the frequency and severity of tropical cyclones.
In the July 2019 flood in Bangladesh, roughly how much of the country was underwater?
About one-third of the country.
In the July 2019 flood, ______ was severely affected, displacing over 6,000 refugees.
In the July 2019 flood, Cox's Bazaar was severely affected, displacing over 6,000 refugees.
True or False?
All flooding of the Ganges/Brahmaputra is harmful and has no benefits.
False.
'Normal' floods are vital to provide fertile soil and irrigation; however, flooding is increasingly becoming more unpredictable and extensive.
Who funded Bangladesh's Flood Action Plan (FAP)?
The World Bank and several high-income countries (HICs).
Name three measures proposed in Bangladesh's Flood Action Plan (FAP).
Construction of levées/embankments; building 5000 flood shelters; and a more effective flood warning system. (Also flood monitoring, floodwater storage, dams and reducing deforestation.)
Give two reasons the Flood Action Plan (FAP) was not seen as a success.
Many parts (dams, floodwater storage) were never completed due to inadequate funding and corruption; and over 8 million people were forced to move for the construction. (Also downstream areas suffered more and maintenance was unaffordable.)
Newer suggestions such as better flood forecasting and well-stocked flood shelters are less damaging to the environment and ______ to maintain than hard engineering.
Newer suggestions such as better flood forecasting and well-stocked flood shelters are less damaging to the environment and cheaper/easier to maintain than hard engineering.
In the July 2019 flood in Bangladesh, roughly how many people were affected?
Approximately 5 million people were directly affected.
Why was outside funding needed for Bangladesh's Flood Action Plan (FAP)?
Bangladesh is a Low-Income Country (LIC) that lacks the money for large flood schemes.
Define river pollution.
River pollution occurs when harmful substances contaminate the water; human activity is the main source.
Give three ways agriculture causes river pollution.
Wastewater from silage and slurry; fertilisers, herbicides and pesticides dissolving in rainwater; and soil erosion. (Also traces of animal medicines.)
How does industry pollute rivers?
Through oil spillages; using water as a coolant and returning it warmer; and releasing toxic substances from industrial processes.
Domestic premises discharge polluted water into rivers through ______, washing water, and traces of medicines taken by humans.
Domestic premises discharge polluted water into rivers through untreated sewage, washing water, and traces of medicines taken by humans.
Define eutrophication.
Eutrophication is the enrichment of water by nutrients (nitrates and phosphates from fertilisers), causing excessive plant and algae growth and a fall in dissolved oxygen.
How does oil pollution from industry harm river wildlife?
Oil stays on the water surface and coats wildlife and plants, so they cannot eat, move or fly.
How does domestic sewage affect river water quality?
It increases nitrogen levels and introduces bacteria, is harmful to wildlife, and can cause chemical burns (from chlorine-treated water).
True or False?
Medicines in wastewater are easily removed by standard water treatment.
False.
Medicines are difficult to remove in water treatment, so they remain in the water and may contain ingredients harmful to humans or wildlife.
What are the three levels of river pollution management?
Changing human activity; regulating and reducing pollutants at the point of emission; and cleaning up pollutants and restoring the ecosystem after pollution.
Promoting the use of ______ fertilisers and eco-friendly detergents can reduce the release of pollutants into water bodies.
Promoting the use of organic fertilisers and eco-friendly detergents can reduce the release of pollutants into water bodies.
How can the release of pollution into rivers be reduced?
Through effective wastewater treatment (removing nitrates and phosphates) and enforcing strict industrial regulations with monitoring and reporting.
Name two strategies used to restore polluted river ecosystems.
Dredging (with absorbents such as activated carbon) to remove sediment and capture pollutants; and re-establishing native vegetation and aquatic species.
Where is the source of the Nairobi River?
Its source is the Ondiri swamp, to the west of Nairobi.
Much of the pollution in the Nairobi River comes from informal settlements such as Kibera and ______, which lack sewage and sanitation systems.
Much of the pollution in the Nairobi River comes from informal settlements such as Kibera and Mathare, which lack sewage and sanitation systems.
Roughly how much solid waste is produced in Nairobi each day?
About 2475 tonnes of waste per day.
How do industries such as tanneries pollute the Nairobi River?
They dispose of waste, including heavy metals and toxins, directly into the river; mining waste is also washed in by rain.
Which water-borne diseases result from sewage bacteria in the Nairobi River?
Typhoid, cholera and dysentery.
What health effects do heavy metals and toxins in the Nairobi River cause?
Increased rates of cancer, damage to human and animal nervous systems, and birth defects.
Fertilisers have increased eutrophication and the growth of ______, which grows rapidly, clogs waterways and reduces oxygen levels.
Fertilisers have increased eutrophication and the growth of water hyacinth, which grows rapidly, clogs waterways and reduces oxygen levels.
True or False?
The Nairobi River is only used for leisure and is not a drinking-water source.
False.
The Nairobi River is the only source of water for many people in Nairobi, used for cleaning, bathing, washing and watering; consuming it leads to health issues.
Give two reasons past efforts to clean the Nairobi River failed.
Lack of funding and lack of enforcement; there was also corruption in local and national government. (Also lack of education, data and effective waste management.)
What was the Nairobi Rivers Commission (launched February 2023) set up to do?
Employ over 12,000 people to clean the river and plant trees; introduce a plastic tax; and involve and educate local people about their waste's impact.
How does the National Environment Management Authority (NEMA) help manage Nairobi River pollution?
It requires industries to remove waste before discharging it, and uses monitoring and fines that have helped reduce toxic waste levels.
The Nairobi River Regeneration and Engineering Works Programme (March 2025) aims to build sewage pipes and ______ plants to prevent untreated wastewater entering the river.
The Nairobi River Regeneration and Engineering Works Programme (March 2025) aims to build sewage pipes and treatment plants to prevent untreated wastewater entering the river.
Which capital city does the Nairobi River flow through?
It flows through Nairobi, the capital of Kenya.
Where does much of Nairobi's solid waste end up?
Much of it is disposed of in the river.
Into which sea does the Mekong River drain, and through what feature?
The South China Sea, through the Mekong Delta.
On the Mekong, the wet season ______ (May to November) brings significant rainfall and river flows, leading to annual flooding.
On the Mekong, the wet season monsoon (May to November) brings significant rainfall and river flows, leading to annual flooding.
Give one human cause of flooding on the Mekong River, with a specific example.
Dam construction: in 2015, water was released from the Nuozhadu Dam due to dangerously high reservoir levels, causing flooding lower down the valley.
Give two positive impacts of flooding on the Mekong River.
Flooding deposits fertile silt, boosting agricultural productivity in the delta; and it supports the Mekong's diverse fish populations and fisheries. (Also replenishes water resources.)
What does the Mekong River Commission (MRC) do to manage flooding?
An inter-governmental organisation that has established monitoring stations at 138 points along the river to forecast flooding and provide early warnings.
True or False?
The Mekong Delta is rising, which reduces its flood risk.
False.
The Mekong Delta is sinking due to groundwater extraction and reduced sediment deposition, making it more vulnerable to flooding.
How long is the Ganges River?
The Ganges is 2,510 km long.
An estimated ______ million litres of sewage is discharged into the Ganges every day, much of it untreated.
An estimated 3,000 million litres of sewage is discharged into the Ganges every day, much of it untreated.
Which industrial cities along the Ganges contribute large amounts of waste, and what types?
Kanpur and Varanasi; waste includes tannery waste from leather production, chemical waste and heavy metals such as lead.
How do religious and cultural practices add to Ganges pollution?
Through mass bathing during festivals and the disposal of dead bodies and cremation remains in the river.
Which endangered species is threatened by reduced biodiversity in the polluted Ganges?
The Ganges river dolphin, affected by toxins and heavy metals.
What are the aims of the Namami Gange Programme (2014)?
Treat urban sewage via Sewage Treatment Plants (STPs), improve solid waste management, enforce industrial-waste regulations, promote afforestation and biodiversity, and educate local communities and religious leaders.
Ganges cleanup has been hindered by corruption, underfunding, and a lack of ______ of environmental regulations.
Ganges cleanup has been hindered by corruption, underfunding, and a lack of enforcement of environmental regulations.
Roughly how many people live in the Ganges River's drainage basin?
Approximately 400 million people live in its drainage basin.
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