1. _____________

9. ___________

8. ___________

7. _______________

The Hydrological (water) Cycle

4. __________

2.__________

1

Surface run-off Evaporate

Infiltration Transpiration

Through-flow Condense

Groundwater flow Precipitation

Groundwater store Interception

6. _______________In-put

Out-put

FlowStore

1. Precipitation

9. Transpiration

8. Evaporation

7. Groundwater Flow

4. Infiltration

2.Interception

2

Surface run-off Evaporate

Infiltration Transpiration

Through-flow Condense

Groundwater flow Precipitation

Groundwater store Interception

6. Ground water store

The Hydrological Cyclehttp://www.bbc.co.uk/education/clips/zcp4d2p

Rap: https://www.youtube.com/watch?v=i3NeMVBcXXU&app=desktop

In-put

Out-put

FlowStore

1. Precipitation

9. Transpiration

8. Evaporation

7. Groundwater Flow

4. Infiltration

2.Interception

3

In-put

Out-put

FlowStore

6. Ground water store

The Hydrological Cycle

Title: What causes flooding and how can

we prevent it?

Objectives:

Identify the human and physical causes of

flooding

Categorise and describe methods of hard

and soft engineering

Explain the advantages and disadvantages

of these methods

Title: What causes river flooding and

how can we prevent it?

Amount of precipitation?

Previous weather?

Dry or Saturated ground?

Steep or gentle slopes?

Impermeable or permeable rock?

Forest or Open Land?

Urban or Rural land use?

Size of Drainage Basin?

Do now: 1. Write each factor in your book.

2. Write a sentence next to the statement to say whether this will increase or decrease flooding.

What conditions will slow the time it takes for the

water to reach the channel?

Amount of precipitation?

Previous weather

Dry or Saturated ground?

Steep or gentle slopes?

Impermeable or permeable rock?

Forest or Open Land?

Urban or Rural land use?

Size of Drainage Basin?

Stick this into your books and around it make notes on how each affects discharge.

Key Word: Lag Time – the amount of time it takes water to reach a river after a period of precipitation

Title: What causes flooding and how can we prevent it? Lesson

Objectives:

Categorise

and describe

methods of

hard and soft

engineering

Explain the

advantages

and

disadvantages

of these

methods

Identify the

reasons for

flood defences

Factor How might this affect the amount of water in a

river? Complete the sentences:Amount of

precipitation

The heavier the rain is……

Relief (how steep

the land is)

If the land is steep then……..

Type of

rock/surface

(impermeable =

NO WATER CAN

PASS , permeable

= WATER CAN

PASS THROUGH)

If the surface is IMPERMEABLE then……………..

If it is PERMEABLE then………….

Amount of

vegetation (trees)

If there is more vegetation then…………

If the vegetation is deforested then……

Title: What causes flooding and how can we prevent it? Lesson

Objectives:

Categorise

and describe

methods of

hard and soft

engineering

Explain the

advantages

and

disadvantages

of these

methods

Identify the

reasons for

flood defences Factor How might this affect the amount of water in a river?

Amount of

precipitation

The heavier the rain is the more water there is to flow into the

river causing there to be a higher discharge.

Relief (how

steep the land

is)

If the land is steep then the precipitation might flow more quickly

into the river leading to a higher discharge.

Type of

rock/surface (impermeable =

NO WATER CAN

PASS , permeable

= WATER CAN

PASS THROUGH)

If the surface is IMPERMEABLE then the water cannot infiltrate

and so will flow more quickly into the river leading to a higher

discharge.

If it is PERMEABLE then more rain will infiltrate and go through

the ground taking longer to reach the river leading to a lower

discharge.

Amount of

vegetation

If there is more vegetation then there are more plants to

intercept the precipitation which means there will be a lower

discharge in the river.

If the vegetation is deforested then there will be less to

intercept the precipitation leading to more surface run off and a

higher discharge in the river

Title: What causes flooding and how can we prevent it? Lesson

Objectives:

Categorise

and describe

methods of

hard and soft

engineering

Explain the

advantages

and

disadvantages

of these

methods

Identify the

reasons for

flood defences

A hydrograph shows the

amount of water

entering the river over a

number of days.

URBAN HYDROGRAPH RURAL HYDROGRAPH

Characteristics

Reasons for

this

Is the…..

Lag time short or long?

Peak discharge high or

low?

Rising limb steep or gentle?

Consider…..

Ground surface type

Vegetation

Previous weather

Relief of land

URBAN HYDROGRAPH RURAL HYDROGRAPH

Characteristics Short lag time

High Peak Discharge

Steep Rising Limb

Long lag time

Low Peak Discharge

Gentle Rising Limb

Reasons for

thisImpermeable Surface (e.g.

concrete) causing more surface

run-off so water reaches river

quicker

Deforestation so no trees to

intercept so water reaches river

quicker

Open farm land so water can

infiltrate into the ground and

takes longer to reach river

May be gentle sloping so less

surface run-off, meaning less

water reaches the river

Less deforestation so more trees

to intercept the rain so less

reaches the river

Title: What causes flooding and how can we prevent it? Lesson

Objectives:

Identify the

reasons for

flood defences

Explain the

advantages

and

disadvantages

of these

methods

Categorise

and describe

methods of

hard and soft

engineering

Complete your table to

describe the different

methods of hard and soft

engineering

Type of engineering Description Costs Benefits Rank

Dam & Reservoir

Dams are often built along the course of a river in order to control the amount of discharge. Water is held back by the dam and released in a controlled way. This controls flooding.

River engineering or Straightening

The river channel may be widened or deepened allowing it to carry more water. A river channel may be straightened so that water can travel faster along the course. The channel course of the river can also be altered, diverting floodwaters away from settlements.

Afforestation

Trees are planted near to the river. This means greater interception of rainwater and lower river discharge.

Flood plain zoning

The river is allowed to flood naturally in places, to prevent flooding in other areas - for example, near settlements.

Flood warning and preparation

Local authorities and the national government introduce policies to control urban development close to or on the floodplain. This reduces the chance of flooding and the risk of damage to property.

Do nothing Do not put anything in place and allow the flood plain to flood and for individuals to deal with the damage.

Type of engineering Description Costs Benefits Rank

Dam & Reservoir

Dams are often built along the course of a river in order to control the amount of discharge. Water is held back by the dam and released in a controlled way. This controls flooding.

Dams are very expensive to build. Land behind the dam is lost to the reservoir. This could be farm land or people’s houses. The dam stops the fertile load of the river reaching downstream so can reduce soil fertility downstream.

Reservoirs are a store of water which reduces the risk of flooding. The reservoir water can be used as drinking water. The dam could be used for HEP.

River engineering or Straightening

The river channel may be widened or deepened allowing it to carry more water. A river channel may be straightened so that water can travel faster along the course. The channel course of the river can also be altered, diverting floodwaters away from settlements.

River engineering is also expensive but not as expensive as a dam. It can harm the river as plants etc. may be lost. Flooding may occur downstream as the flood water is carried there faster. There is more erosion downstream as the water moves there quicker.

Water moves out of the area quickly so there is less risk of flooding. It is useful in urban areas, especially if a river wall is also built.

Afforestation

Trees are planted near to the river. This means greater interception of rainwater and lower river discharge.

The trees will take up land that could be used for something else e.g. farmland.

It is very environmentally friendly.

Flood plain zoning

The river is allowed to flood naturally in places, to prevent flooding in other areas - for example, near settlements.

If you can’t build on the flood plain it may mean that there aren’t any suitable building sites for an urban area. This does not help areas which have already been built on flood plains

Risk of flooding is reduced as you are not on the floodplain. This will also reduce loss of life and cost of flooding.

Flood warning and preparation

Local authorities and the national government introduce policies to control urban development close to or on the floodplain. This reduces the chance of flooding and the risk of damage to property.

Warnings don’t stop a flood from happening so there will still be effects. People may not have access to warnings Living in a place where there are lots of warnings might make it hard to get house insurance. Too many false warnings might mean people start to ignore them.

The impact of flooding is reduced as people can move possessions, put sandbags down and evacuate.

Do nothing Do not put anything in place and allow the flood plain to flood and for individuals to deal with the damage.

There is not reduced risk of flooding. A flood is likely to cause lots of damage and maybe increased loss of life.

No money is spent. The river remains natural.

Which is most effective and why?