Geography Flooding

Flooding

How do trees reduce flooding?

Trees intercept the rain.

Evapotranspiration reduces the amount of water that reaches the river.

Water is taken through the roots and so less enters the river .

What is a flood?

A flood occurs whenever a river overflows its banks
(exceeds its ‘bankfull discharge’).

However, a flood becomes a problem when the water rises to a level where it threatens property and/or life.

Why do rivers flood?

Rivers usually flood due to a range of physical factors.

These physical factors can be divided into climatic factors

and drainage basin characteristics. Human intervention

can also make flooding worse.

Dams

Dams can be multi-purpose:

They hold back the spring meltwater and so stop the floods.

They release this water in the dry summer to irrigate the intensive fruit and vegetable growing areas. The water is also used for cooling in nuclear power plants.

In addition, the dams produce hydroelectric power (HEP).

Hard Management Methods - Dams

1.These trap and store water and let it out in a controlled way.

2.They can generate electricity.

3.They are a massive change to the ecosystem.

4.They trap sediment that would normally go downstream.

5.They’re very expensive.

6.They’re very effective.

Hard Management Methods - Embankments

1.They are raised banks along the river.

2.They effectively make the river deeper so it can hold more water.

3.They’re expensive.

4.They don’t look natural.

5.They protect the land around them.

Hard Management Methods - Flood Walls

1.Built around settlements and important factories or roads.

2.They’re quite expensive.

3.Don’t look natural.

4.They’re pretty effective.

Hard Management Methods -

Straightening and deepening the river.

1.Also called channelising the river.

2.Makes the water move faster so it doesn’t build up and is less likely to flood.

3.This changes the ecosystem totally.

4.Spoils the natural look of the area.

5.The water builds up further down the river where it isn’t channelised.

Hard Management Methods - Storage Areas

1.Water can be pumped out of the river and stored in temporary lakes.

2.Then it’s pumped back when the river has gone down a bit.

3.Effective but you need a large spare bit of land that isn’t used so you can flood it.

Soft Engineering - Washlands

1.These are parts of the floodplain that are allowed to flood.

2.They can’t be built on.

3.They’re usually used for sport pitches or natural reserves.

Soft Engineering - Land-use Zoning

1.Here the land has different building controls depending on how far away the river is.

2.Land next to the river isn’t allowed to be used for building.

3.The next land zone can be but only for low-risk housing.

4.The last zone is for high-risk buildings like hospitals, old people’s homes, dangerous factories, etc.

Soft Engineering - Afforestation

1.This is re-planting trees in the catchment.

Soft Engineering - Warning Systems

1.Warnings are issued by the Environment Agency so that people can put sandbags by their homes, take furniture upstairs or even evacuate the area.

	Flooding
	How do trees reduce flooding?
	Trees intercept the rain. Evapotranspiration reduces the amount of water that reaches the river. Water is taken through the roots and so less enters the river .

	What is a flood?
	A flood occurs whenever a river overflows its banks (exceeds its ‘bankfull discharge’). However, a flood becomes a problem when the water rises to a level where it threatens property and/or life.

	Why do rivers flood?
	Rivers usually flood due to a range of physical factors. These physical factors can be divided into climatic factors and drainage basin characteristics. Human intervention can also make flooding worse.

	Dams
	Dams can be multi-purpose: They hold back the spring meltwater and so stop the floods. They release this water in the dry summer to irrigate the intensive fruit and vegetable growing areas. The water is also used for cooling in nuclear power plants. In addition, the dams produce hydroelectric power (HEP).

	Hard Management Methods - Dams
	1.These trap and store water and let it out in a controlled way. 2.They can generate electricity. 3.They are a massive change to the ecosystem. 4.They trap sediment that would normally go downstream. 5.They’re very expensive. 6.They’re very effective.

	Hard Management Methods - Embankments
	1.They are raised banks along the river. 2.They effectively make the river deeper so it can hold more water. 3.They’re expensive. 4.They don’t look natural. 5.They protect the land around them.

	Hard Management Methods - Flood Walls
	1.Built around settlements and important factories or roads. 2.They’re quite expensive. 3.Don’t look natural. 4.They’re pretty effective.

	Hard Management Methods - Straightening and deepening the river.
	1.Also called channelising the river. 2.Makes the water move faster so it doesn’t build up and is less likely to flood. 3.This changes the ecosystem totally. 4.Spoils the natural look of the area. 5.The water builds up further down the river where it isn’t channelised.

	Hard Management Methods - Storage Areas
	1.Water can be pumped out of the river and stored in temporary lakes. 2.Then it’s pumped back when the river has gone down a bit. 3.Effective but you need a large spare bit of land that isn’t used so you can flood it.

	Soft Engineering - Washlands
	1.These are parts of the floodplain that are allowed to flood. 2.They can’t be built on. 3.They’re usually used for sport pitches or natural reserves.

	Soft Engineering - Land-use Zoning
	1.Here the land has different building controls depending on how far away the river is. 2.Land next to the river isn’t allowed to be used for building. 3.The next land zone can be but only for low-risk housing. 4.The last zone is for high-risk buildings like hospitals, old people’s homes, dangerous factories, etc.

	Soft Engineering - Afforestation
	1.This is re-planting trees in the catchment.

	Soft Engineering - Warning Systems
	1.Warnings are issued by the Environment Agency so that people can put sandbags by their homes, take furniture upstairs or even evacuate the area.