Rivers (unknown only)

Question 1

What is a hydrograph, and what are the different features on it?

Answer 1

A hydrograph shows how the discharge in a river changes in relation to rainfall.

• Peak rainfall - highest point of rainfall
• Rising limb - as discharge increases
• Peak discharge - highest point of discharge
• Lag time - time between peak rainfall and peak discharge
• Falling limb - as discharge decreases (this is slower than the rising limb)

Question 2

What are the factors affecting flood risk?

Answer 2

• Heavy rainfall
• Geology (rock type)
• Prolonged rainfall
• Relief (changes in land height)
• Land use (cities have many impermeable surfaces, increasing runoff; trees intercept rainfall on leaves, which evaporates, and also take up water in roots).

Question 3

What hard engineering methods deal with flood risk?

Answer 3

Dams and reservoirs:
- Reservoirs store water
- Can generate hydroelectric power
- Expensive
- Reservoir may flood existing settlements
- Material deposited in reservoir - less fertile land downstream

Channel straightening:
- Meanders are removed
- Water leaves the area quickly, minimising flood risk
- May flood areas downstream
- Increased erosion

Embankments:
- Raised walls along river banks
- The river can hold more water; less frequent flooding
- Expensive
- Severe flooding if water rises above embankments

Flood relief channels:
- Divert water if levels get too high
- Increased discharge where the rivers join back up again: potential for flooding

Question 4

What soft engineering methods deal with flood risk?

Answer 4

Flood warnings and preparation:
- Gives time to evacuate and protect possessions; reduced impacts
- Preparation doesn’t guarantee safety

Flood plain zoning:
- Prevent building on parts that are likely to be flooded
- Fewer impermeable surfaces
- Limits expansion of an urban area

Planting trees:
- Increased interception
- Reduces soil erosion
- Less land available

River restoration:
- Removing man-made levees for natural flooding
- Better habitats for wildlife
- Local flood risk can increase

Question 5

Where is the River Tees?

Answer 5

The River Tees is in the north-east of England, and its source is in the Pennine Hills.

Question 6

What features are in the upper course of the River Tees?

Answer 6

• Steep-sided V-shaped valley (vertical erosion)
• Large, rough load
• Bogs, marshland
• Interlocking spurs
• Cow Green Reservoir
• High Force Waterfall (hard windstone over soft limestone)

Question 7

What features are in the middle course of the River Tees?

Answer 7

• Wider, curving U-shaped valley (lateral and vertical erosion)
• Meanders
• Oxbow lakes

Question 8

what features are in the lower course of the River Tees?

Answer 8

• Very wide, flat valley (lateral erosion)
• Larger meanders
• Human industry, ports and settlements in Yarm, where two meanders were artificially cut off to straighten the channel to allow boats to sail inland quicker.
• Flood plains
• Levees

Question 9

Why were flood defences needed in Oxford?

Answer 9

• Oxford is at the confluence of the River Thames and the River Cherwell.
• In July 2007, there was intense flooding, causing over 250 homes to be evacuated, and later flooding occurred in 2014 too.

Question 10

What was the flood management scheme in Oxford?

Answer 10

• Excavating a flood relief channel outside the city centre.
• Using excavated material to build new flood walls and embankments.
• Planting 20,000 trees and shrubs around the excavated area
• Increasing water storage in the floodplain, and increasing capacity of bypass channel.

Question 11

What were the social impacts of the scheme?

Answer 11

• Compulsory Purchase Orders were sent to land owners whose land was needed to widen the flood plain.
• Construction disrupted residents’ lives, such as through noise pollution and large vehicles.
• The scheme improved public footpaths, providing more opportunities for recreation.
• Residents felt more confident their homes were flooded.

Question 12

What were the economic impacts of the scheme?

Answer 12

• Cost over £120 million in total, not all funding secured.
• Over 1000 homes and businesses better protected, so less risk of expensive damage and rising insurance costs.

Question 13

What were the environmental impacts of the Oxford flooding scheme?

Answer 13

• Over 2000 trees and 2 hectares of rare grassland were removed, although they were replanted.
• The scheme created over 20 hectares of new riverside habitats, improving biodiversity.