Flood Management Strategies

Question 1

How do we chose which places to protect?

Answer 1

Isn’t enough money to protect everywhere, use a cost benefit analysis

Large settlements and import any industrial sites are more likely to be protected than small settlements or farmland

Question 2

What are the two forms of flood management?

Answer 2

Hard engineering and soft engineering

Question 3

Define hard engineering

Answer 3

Defences are man made structures that reduce flooding

Question 4

What are the disadvantages of hard engineering?

Answer 4

They’re expensive to build and maintain, need technical skill, poorer countries can’t afford these flood defences

Floods happen less often but can be more hazardous if they do happen, e.g. if dam breaks then a huge amount of water is released

Natural processes are disrupted, e.g. crops don’t get fertile silt from river sediment during low-level flooding

Can be ugly

Question 5

What are four hard engineering flood management strategies?

Answer 5

Dams
Channel straightening
Levees
Diversion spillways

Question 6

Explain a dam

Answer 6

Dams are huge walls built across rivers, reservoir is formed behind the dam melody water is caught by the dam, prevents flooding downstream, Water is released as steady flow through out the year

Question 7

Benefits of a dam

Answer 7

Turbines can be built into the dams, generate electricity

Steady water release allows irrigation of land below the dam through out the year

People can use the reservoir for recreational activities

Question 8

What are the disadvantages of a dam?

Answer 8

Very expensive

Land is flooded when a reservoir is created, often destroys farmland and forces people to move elsewhere

Affect wildlife e.g. can prevent salmon migration upstream

They trap sediment normally carried in rivers, can cause dam to fail, increased erosion downstream as there’s less protective sediment being deposited

Question 9

Explain channel straightening

Answer 9

Where meanders are removed by building artificial cut-throughs, makes the water flow faster, reduces flooding because water drains downstream more quickly and doesn’t build up to a point where the river channel can’t contain it anymore.

Question 10

Benefits of channel straightening

Answer 10

Takes less time to navigate the river because it has been made shorter

Question 11

Disadvantages of channel straightening

Answer 11

Flooding may happen downstream instead as flood water carried there faster

More erosion occurs downstream because the river flows faster

Alternating river channels disturbs wildlife habits

Question 12

Explain levees

Answer 12

Are embankments built along rivers, river can hold more water without overflowing and so it floods less often

Question 13

Advantage of a levee

Answer 13

They allow the flood plain to be built upon

Question 14

Disadvantages of levees

Answer 14

They’re quite expensive

There’s a risk of severe flooding if the levees are breached

Question 15

Explain diversion spillways

Answer 15

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.

Question 16

Advantages of diversion spillways

Answer 16

Prevent flooding because river discharge is reduced

Spillways often have gates that can be opened, so release of water can be controlled

Question 17

Disadvantages of diversion spillways

Answer 17

An increase in discharge when the diverted water joins another river could cause flooding below that point

If spillways are overwhelmed, water will flood areas not used to flooding, could cause even bigger problems

Question 18

What is the aim of flood management?

Answer 18

To protect homes, businesses and the environment from flooding

Question 19

Define soft engineering

Answer 19

Defences use knowledge of the whole river basin and its processes to try to work with nature

Question 20

What are the advantages of soft engineering strategies?

Answer 20

They’re cheaper to maintain than hard engineering strategies

Flooding is more predictable, reducing the risk of an unexpected disaster

Can improve opportunities for recreation, such as fishing

Think they’re more attractive than hard engineering schemes

Question 21

What are the four soft engineering schemes?

Answer 21

Land use management
Wetland and river bank conservation
River restoration
Alteration of urban surfaces

Question 22

Explain land use management

Answer 22

Planning restrictions prevent buildings or roads being constructed in the flood plain.

Use of the flood plain is restricted to things like playing fields, allotments or parks. More water can infiltrate so there’s less surface runoff which reduces discharge.

Question 23

What are the benefits of land use management?

Answer 23

There are no new buildings or roads on the floodplain to be damaged, impact of any flooding is reduced

Provides recreational opportunities e.g. football fields

Question 24

What are the disadvantages of land use management?

Answer 24

Restricts development, a big problem when there’s a shortage of housing

Can’t be used in areas that are already urbanised

Question 25

Explain wetland and river bank conservation

Answer 25

Wetlands store flood water and also slow it down, reduces flooding downstream.

Conserving or re-establishing wet,ands gives natural protection from flooding. Planting trees and shrubs along the river bank increases interception and lag time, reduces discharge.

Question 26

What are the benefits of wetlands and river bank conservation?

Answer 26

Vegetation protects the surface soil from erosion

The vegetation provides habitats for wildlife

Question 27

What are the disadvantages of wetland and river bank conservation?

Answer 27

Less land is available for farming

Question 28

Explain river restoration

Answer 28

Involves making the river more natural e.g. by removing man-made levees.

Flood plain can then flood naturally, as water spreads out over the flood plain the rivers discharge is reduced

Question 29

What are the benefits of river restoration?

Answer 29

Little maintenance is needed, rivers left in its natural state

The river provides a better habitat for wildlife

Question 30

What are the disadvantages of river restoration?

Answer 30

Local flood risk increases, esp if nothing is done to prevent major flooding

Question 31

Explain alteration of urban surfaces

Answer 31

Building porous pavements or soakaways increases infiktration, reduces rapid surface runoff to the river channel. Reduces lag time, reduces discharge.

Question 32

What are the benefits of alteration of urban surfaces?

Answer 32

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

Question 33

What are the disadvantages of alteration of urban surfaces?

Answer 33

It’s expensive

Question 34

What is the most sustainable food management strategy? Why?

Answer 34

Soft engineering LOWER ECONOMIC COST AND ENVIRONMENTAL IMPACT

HE is often more expensive and disrupts natural processes, SE tends to be cheaper and require less time and money to maintain than HE.

SE is designed to integrate with the natural environment and it creates areas like wetlands, important habitats for wildlife.