• how and why it takes place in drainage basin

• aspects that cannot be changed: rock type

• aspects that can be changed: amount of forest

• Hydrographs: to advise the authorities on flood management

• Hydrographs: shows how a river responds to a period of rainfall over a short period of time.

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To manage flooding​

• Opportunities vs hazard

• Risk: damage and loss of life

• Government priorities: to protect people and environment from flood

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​Living on a flood plain

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​To stop the flood from happening

Flood prevention

​to have procedures to protect people and property in place

​​Flood protection

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​​Flood Management

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​​Hard engineering techniques​

​​Soft engineering techniques

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​​Ways to do flood prevention

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​​Dams

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​​Barriers and flood walls

​​embankment or levees

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Flood prevention: hard engineering​

​​Dredging and straigthening channels

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​​Canals and waterways

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​​Involves building artificial structures which try to control rivers, tend to be more expensive. Each hard engineering strategy has its advantages and disadvantages​

The dam traps water, which builds up behind it, forming a reservoir. Water can be released in a controlled way.

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​Advantages

• to produce electricity by passing the water through a turbine within the dam.

• Reservoirs can attract tourists.​

Dams and Reservoirs

The dam traps water, which builds up behind it, forming a reservoir. Water can be released in a controlled way.

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Dams and Reservoirs

​Disadvantages

• Very expensive.

• Dams trap sediment which means the reservoir can hold less water.

• Habitats are flooded often leading to rotting vegetation. This releases methane which is a greenhouse gas.

• Settlements are lost leading to the displacement of people. In developing countries locals are not always consulted and have little say in where they are relocated.​

​​Advantages

• More water can be held in the channel.

• It can be used to reduce flood risk in built-up areas.

Disadvantages

• Dredging needs to be done frequently.

• Speeding up the river increases flood risk downstream.

River straigthening and Dredging

​​Straightening the river speeds up the water so high volumes of water can pass through an area quickly. Dredging makes the river deeper so it can hold more water.

​​Raising the banks of a river means that it can hold more water.

Embankment​

.Advantages

• Cheap with a one-off cost

• Allows for flood water to be contained within the river.

Disadvantages

• Looks unnatural.

• Water speeds up and can increase flood risk downstream.

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Advantages

• Removes excess water from the river channel to reduce flooding.

Disadvantages

• Expensive to build.

• If water levels continue to rise, the relief channel may also flood.

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Flood relief channel​

The floodwater flows into the relief channel and is taken either to an area where it can be absorbed, or re-enters the river further down its course.

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Flood prevention:
soft engineering​

​​It does not involve building artificial structures, but takes a more sustainable and natural approach to managing the potential for river flooding. Each approach has its advantages and disadvantages.

​​a system of sirens and warnings and evacuation procedures

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​​temporary, moveable metal barriers that can be put up quickly

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a store of sand and sandbags for emergency use​

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Flood prevention: soft engineering

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Advantages

• More expensive buildings and land uses are further away from the river, so have a reduced flood risk.

• Less damage is caused, leading to fewer insurance claims.

Disadvantages

• Not always possible to change existing land uses.

• Planners have to decide what type of flood to plan for.

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Floodplain zoning

Allowing only certain land uses on the floodplain reduces the risk of flooding to houses and important buildings.

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Case Study:

The Elbe River

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NO NEED TO DO THIS

​Study Source B on pg. 90

• Observe carefully all information that you can get from Source B: the colors, numbers, name of places, location, etc. (5 mins)

• Answer the following questions

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