Flood Management Strategies

Question 1

What is the aim of flood management?

Answer 1

To protect homes, businesses and the environment from flooding as flooding can have severe social, economic and environmental impacts.

Question 2

What is the cost benefit analysis?

Answer 2

The process used to decide which places need to be protected and how they are going to be protected as there isn’t enough obey to protect everywhere. Large settlements and important industrial sites e.g. power points are more likely to be protected than small settlements or farmland.

Question 3

What is hard engineering?

Answer 3

Manmade structures that reduce flooding.

Question 4

What are the disadvantages of hard engineering?

Answer 4

1. Expensive to both build and maintain, and they need technical skill, meaning poorer countries can’t afford these flood defences.
2. Floods happen less often, but can be more hazardous if they do happen.
3. Natural processes are disrupted e.g. crops don’t get fertile silt from river sediment during low-level flooding.
4. They are anaesthetically pleasing.

Question 5

Explain a dam.

Answer 5

Dams are huge walls that are built across rivers. A reservoir is formed behind the dam. Flood water is caught behind the same, which prevents flooding downstream. The water is released as steady flow throughout the year.

Question 6

What are the benefits of dams?

Answer 6

1. Turbines are built into the dams, so generate electricity.
2. Steady water release allows irrigation of land below the dam throughout the year.
3. The reservoir can be used for recreational activities e.g. sailing.

Question 7

What are the disadvantages of dams?

Answer 7

1. Expensive.
2. Land is flooded when a resevoir is created. This often destroys farmland and forces people to move elsewhere.
3. Wildlife can be affected e.g. they can prevent salmon migrating upstream to breeding ground.
4. They trap sediment normally carried in rivers, this can cause the dam to fail. OR it can increase erosion downstream, as there’s less protective sediment being deposited.

Question 8

What is channel straightening?

Answer 8

Meanders are removed by building artificial cut troughs. This makes the water flow faster, reducing flooding as water drains downstream quicker, so it doesn’t build up to a point where the channel can’t contain it anymore.

Question 9

What are the benefits of channel straightening?

Answer 9

The river takes less time to navigate as it has been made shorter.

Question 10

What are the disadvantages of channel straightening?

Answer 10

1. Flooding may happen downstream, as the water is being carried there faster.
2. More erosion occurs downstream because the river is flowing faster.
3. Altering river channels disturbs habitats.

Question 11

What are levees?

Answer 11

Embankments built along rivers. The river can hold more water without overflowing so it floods less often.

Question 12

What are the extra benefits of levees?

Answer 12

They allow the flood plain to be built upon.

Question 13

What are the disadvantages of levees?

Answer 13

1. Expensive

2. Risk of severe flooding if the levees are breached.

Question 14

What are diversion spillways?

Answer 14

Channels that take water elsewhere if the water level in the river is too high. Water is normally diverted around an important area or to another river. They prevent flooding as river discharge is reduced. The spillways often have gates that can be opened, so the release of water can be controlled.

Question 15

What are the disadvantages of diversion spillways?

Answer 15

1. An increase in discharge when the diverted river joins another river could cause flooding below that point.
2. If the spillways are overwhelmed, water will flood areas not used to flooding, possibly causing bigger problems.

Question 16

What are soft engineering defences?

Answer 16

They work with, not against, the river basin as they use the knowledge to work with nature.

Question 17

What are the general advantages soft engineering?

Answer 17

1. They’re cheaper to maintain than hard engineering defences, which important for poorer countries.
2. Flooding is more preciatbld, reducing the risk of an unexpected disaster.
3. They can improve opportunities for recreation such as fishing.
4. More attractive than hard engineering defences.

Question 18

What is land use management?

Answer 18

Planning restrictions prevent buildings or roads being constructed on the flood plain. Use of the flood plain is restricted to things such as football pitches, allotments or parks more. More water can infiltrate so there’s less surface run off, which reduces discharge and flooding.

Question 19

What are the extra benefits of land use management?

Answer 19

1. There are no new buildings or roads on the flood plain to be damaged, so the impact of any flooding is reduced.
2. It provides recreational opportunities e.g. football fields.

Question 20

What are the disadvantages of land use management?

Answer 20

1. It restricts development, which is a problem especially in areas where there is a housing shortage.
2. It can’t be used in areas that are already urbanised.

Question 21

What is wetland and river bank conservation?

Answer 21

Wetlands store floodwater and also slow it down. This reduces flooding downstream. So conserving or re-establishing wetlands gives natural protection from flooding. Planting trees and shrubs along the river bank increases interception and lag time, and reduces discharge. This also decreases flooding.

Question 22

What are the extra benefits of wetland and river bank conservation?

Answer 22

1. Vegetation protects the surface soil from erosion.

2. The vegetation provides a better habitat for wildlife.

Question 23

What are the disadvantages of wetland and river bank conservation.

Answer 23

Less land is available for farming.

Question 24

What is river restoration?

Answer 24

This involves making the river more natural e.g. by removing man-made levees, meaning the flood plain can flood naturally. As the water spreads out over the flood plain the rivers discharge is reduced, which reduces flooding downstream.

Question 25

What are the extra benefits of river restoration?

Answer 25

1. Little maintenance is needed as the river is left in its natural state.
2. The river provides a better habitat for wildlife.

Question 26

What are the disadvanatges of river restoration?

Answer 26

Local flood risk can increase, especially if nothing is done to prevent major flooding.

Question 27

What is alteration of urban surfaces?

Answer 27

Building porous pavements or soak ways increases infiltration, which reduces rapid surface run off to the river channel. This increases lag time, which reduces discharge and flooding.

Question 28

What are the extra benefits of alteration of urban surfaces?

Answer 28

Any pollutants in the water are filtered out by the soil before the water reaches the channel.

Question 29

What are the disadvantages of alteration of urban surfaces?

Answer 29

its expensive.

Question 30

How can the impact of flooding be reduced?

Answer 30

Weather forecasts and flood warnings.

Question 31

What are weather forecast and flood warnings? How do they work?

Answer 31

The Envrionment Agency monitors weather forecasts, rainfall and river discharge. They warn people about possible floods through TV, radio, newspapers and the internet. This means people can evacuate before the flood happens, saving lives. people can also move possessions and use sandbags to help reduce damage if flooding occurs.

Question 32

What are the disadvantages of weather forecasts and flood warnings?

Answer 32

1. Some people might not be able to access the communication network.
2. Flash floods may happen to fast for warnings,
3. People may ignore warnings if they were inaccurate in the past.

Question 33

Explain why soft engineering is more sustainable than hard engineering.

Answer 33

Hard engineering if often expensive and disrupts natural processes, where soft engineering tends to be cheaper and requires much less money and time to maintain. Soft engineering is designed to integrate with the natural environment and it creates areas like wetlands, which are important habitats for wildlife. Soft engineerings a more sustainable management strategy than hard engineering as it has a lower economic cost and environmental impact.