AQA GCSE Geography · 3.1.3

Flooding and river management

50 revision questions with answers for 3.1.3 Flooding and river management in AQA GCSE Geography (spec 8035). Practise with flashcards, a topic quiz, a random quiz across the course, 5 crosswords, or read every question and answer below. Not official AQA material.

All 50 questions and answers

Question 1 · Spec 3.1.3.3
What is a river flood?
Answer:
When a river's discharge is too great for its channel, so water overtops the banks and spreads onto the floodplain.
Question 2 · Spec 3.1.3.3
How do heavy rain and run-off cause flooding?
Answer:
If rain falls faster than the ground can absorb it (infiltration), water runs over the surface into rivers quickly, sending discharge up and causing flooding.
Question 3 · Spec 3.1.3.3
How does precipitation affect flood risk?
Answer:
Intense, prolonged or repeated rainfall, or rain on already saturated or frozen ground, produces more run-off and so a higher flood risk.
Question 4 · Spec 3.1.3.3
How does geology affect flood risk?
Answer:
Impermeable rocks such as clay and granite cause rapid surface run-off and high flood risk. Permeable rocks such as chalk and limestone let water soak in, lowering the risk.
Question 5 · Spec 3.1.3.3
How does relief affect flood risk?
Answer:
Steep slopes send water quickly to the river, so flash floods are more likely. Flat floodplains flood easily when rivers burst their banks.
Question 6 · Spec 3.1.3.3
How does soil saturation affect flood risk?
Answer:
Soil that is already full of water, after earlier rain, cannot absorb more, so extra rainfall runs straight into the river.
Question 7 · Spec 3.1.3.3
How do human activities affect flood risk?
Answer:
Urbanisation, deforestation, farming methods and building on floodplains increase run-off or the number of people at risk.
Question 8 · Spec 3.1.3.3
How does urbanisation increase flood risk?
Answer:
Tarmac and concrete are impermeable, and drains carry water quickly to rivers, so there is more run-off and less lag time.
Question 9 · Spec 3.1.3.3
How does deforestation increase flood risk?
Answer:
Fewer trees means less interception and transpiration, and roots no longer hold soil, so more water reaches rivers faster along with more silt.
Question 10 · Spec 3.1.3.3
How can farming increase flood risk?
Answer:
Ploughing up and down slopes, compacted soil from heavy machinery and bare winter fields increase run-off.
Question 11 · Spec 3.1.3.3
Why does building on floodplains increase flood risk?
Answer:
Floodplains are the natural overflow area of a river. Buildings put more people and property at risk and reduce the land available to store floodwater.
Question 12 · Spec 3.1.3.3
How might climate change affect flooding?
Answer:
It may bring more intense rainfall and higher sea levels, increasing the frequency and severity of river and coastal flooding.
Question 13 · Spec 3.1.3.3
What is a hydrograph?
Answer:
A graph showing the discharge of a river over time, often alongside rainfall, used to show the relationship between precipitation and discharge.
Question 14 · Spec 3.1.3.3
Name the main features of a storm hydrograph.
Answer:
Rainfall bars, base flow, rising limb, peak discharge, falling limb and lag time.
Question 15 · Spec 3.1.3.3
What is peak discharge?
Answer:
The highest river discharge reached during a storm, shown by the top of the hydrograph curve. Flooding occurs if it exceeds channel capacity.
Question 16 · Spec 3.1.3.3
What is lag time?
Answer:
The time between the peak rainfall and the peak discharge. A short lag time means water reaches the river quickly.
Question 17 · Spec 3.1.3.3
What are the rising limb and the falling limb?
Answer:
The rising limb shows discharge increasing as run-off reaches the river. The falling limb shows discharge decreasing after the peak.
Question 18 · Spec 3.1.3.3
What is base flow?
Answer:
The normal level of a river fed by groundwater when there has been no recent rainfall.
Question 19 · Spec 3.1.3.3
What does a flashy hydrograph show?
Answer:
A steep rising limb, high peak and short lag time. It is typical of urban areas, steep slopes, impermeable rock and saturated ground, with a high flood risk.
Question 20 · Spec 3.1.3.3
What does a gentle hydrograph show?
Answer:
A shallow rising limb, low peak and long lag time. It is typical of permeable rocks, forested catchments and gentle slopes, with a lower flood risk.
Question 21 · Spec 3.1.3.3
How can you describe a hydrograph?
Answer:
State the peak discharge and when it occurs, the lag time, how steeply discharge rises and falls, and the base flow, using figures from the axes.
Question 22 · Spec 3.1.3.3
How does urbanisation change a hydrograph?
Answer:
It makes the rising limb steeper, the peak higher and the lag time shorter, because surfaces are impermeable and drains speed up run-off.
Question 23 · Spec 3.1.3.3
How does vegetation change a hydrograph?
Answer:
Trees intercept rain and take up water, so the lag time is longer, the peak lower and the rising limb gentler.
Question 24 · Spec 3.1.3.3
What are the two approaches to managing river flooding?
Answer:
Hard engineering (artificial structures) and soft engineering (working with natural processes to reduce or avoid flooding).
Question 25 · Spec 3.1.3.3
What is hard engineering for flooding?
Answer:
Building structures to control the river, such as dams and reservoirs, straightening, embankments and flood relief channels.
Question 26 · Spec 3.1.3.3
What are dams and reservoirs?
Answer:
A dam across a river stores water in a reservoir and releases it slowly, reducing flood peaks and providing water supply and hydroelectric power.
Question 27 · Spec 3.1.3.3
Give the costs and benefits of dams and reservoirs.
Answer:
Benefits: control flow, supply water and power, create recreation areas. Costs: very expensive, flood farmland and homes, trap sediment and disturb ecosystems.
Question 28 · Spec 3.1.3.3
What is channel straightening?
Answer:
Removing meanders to make the channel shorter and straighter so water flows faster and flood water is carried away from the area quickly.
Question 29 · Spec 3.1.3.3
Give the costs and benefits of straightening.
Answer:
Benefits: reduces flooding in the area and may speed up water. Costs: increases flood risk downstream, causes erosion and damages habitats.
Question 30 · Spec 3.1.3.3
What are embankments?
Answer:
Raised banks built along the river, usually from earth, which increase the capacity of the channel so water stays within it.
Question 31 · Spec 3.1.3.3
Give the costs and benefits of embankments.
Answer:
Benefits: relatively cheap and protect land behind them. Costs: can fail or be overtopped, look unnatural and increase flood risk downstream.
Question 32 · Spec 3.1.3.3
What are flood relief channels?
Answer:
Artificial channels that divert some of a river's water around a town or vulnerable area when the main channel is full, e.g. the Jubilee River.
Question 33 · Spec 3.1.3.3
Give the costs and benefits of flood relief channels.
Answer:
Benefits: very effective at protecting settlements. Costs: expensive, take up land and may disrupt habitats.
Question 34 · Spec 3.1.3.3
What are flood warnings and preparation?
Answer:
Agencies forecast floods and warn people via text, radio and sirens. Individuals prepare with flood plans, sandbags, flood boards and moving belongings upstairs.
Question 35 · Spec 3.1.3.3
Give the costs and benefits of flood warnings and preparation.
Answer:
Benefits: cheap, save lives and reduce damage. Costs: do not stop flooding, rely on accurate forecasts and people responding, and flash floods give little warning.
Question 36 · Spec 3.1.3.3
What is flood plain zoning?
Answer:
Planning rules that stop or limit building in high flood-risk areas. Floodplains are used for parks, farmland or playing fields.
Question 37 · Spec 3.1.3.3
Give the costs and benefits of flood plain zoning.
Answer:
Benefits: cheap and prevents damage. Costs: restricts development, so land may cost more elsewhere and existing buildings are not protected.
Question 38 · Spec 3.1.3.3
How does planting trees reduce flood risk?
Answer:
Trees intercept rainfall and take up water, and roots help soil absorb it. This slows run-off and lengthens lag time, especially in upland catchments.
Question 39 · Spec 3.1.3.3
Give the costs and benefits of planting trees.
Answer:
Benefits: cheap, sustainable and adds habitat and carbon storage. Costs: takes years to grow, uses land and is less effective in extreme floods.
Question 40 · Spec 3.1.3.3
What is river restoration?
Answer:
Returning a river to a more natural state by re-meandering, removing embankments, and reconnecting it with its floodplain so water can spread safely.
Question 41 · Spec 3.1.3.3
Give the costs and benefits of river restoration.
Answer:
Benefits: reduces flood peaks downstream, improves wildlife and looks natural. Costs: land is flooded, so needs agreement, and it may not protect towns on its own.
Question 42 · Spec 3.1.3.3
Compare hard and soft engineering for flood management.
Answer:
Hard engineering gives strong, direct protection but is expensive and can increase flooding elsewhere. Soft engineering is cheaper and more sustainable but may be less effective.
Question 43 · Spec 3.1.3.3
Boscastle floods: where and when?
Answer:
On 16 August 2004 a flash flood hit Boscastle, a small tourist village in north Cornwall on the Rivers Valency and Jordan, which meet in the village before reaching the harbour.
Question 44 · Spec 3.1.3.3
What were the causes of the Boscastle flood?
Answer:
About 180-200 mm of rain fell in a few hours on saturated ground. Steep slopes and impermeable rock brought rapid run-off into a narrow valley, and bridges blocked with debris.
Question 45 · Spec 3.1.3.3
What were the social impacts of the Boscastle flood?
Answer:
About 58 properties were flooded and roughly 150 vehicles swept away. Around 150 people were rescued, mainly by helicopter, but nobody died.
Question 46 · Spec 3.1.3.3
What were the economic and environmental impacts of the Boscastle flood?
Answer:
Businesses, shops and the tourist trade were badly hit and damage cost millions of pounds. Debris and pollution reached the harbour and river habitats were disturbed.
Question 47 · Spec 3.1.3.3
What flood management scheme was built at Boscastle?
Answer:
A scheme costing around £4.5 million, completed in 2008. The River Valency channel was widened and deepened, new bridges were built, the car park was raised, and flood walls and drains improved.
Question 48 · Spec 3.1.3.3
Why was the Boscastle scheme required?
Answer:
Boscastle had no modern defences and sits at the confluence of two fast-responding rivers, so a similar storm could cause damage again, endangering people and tourism.
Question 49 · Spec 3.1.3.3
Evaluate the Boscastle flood scheme.
Answer:
Social: homes and businesses are better protected. Economic: it supports tourism but cost millions. Environmental: channel work and tree management disturbed habitats, and a very large storm could still cause flooding.
Question 50 · Spec 3.1.3.3
Why can straightening a channel increase flooding downstream?
Answer:
Water moves faster through a straight, shorter channel, so a larger flood peak reaches downstream areas sooner and with less time to prepare.

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