flood and erosion defences on the river mersey. we will learn: the different flood and erosion...

Flood and erosion Flood and erosion defences on the defences on the

river Merseyriver Mersey

We will learn:We will learn:

• The different flood and erosion defences The different flood and erosion defences on the river Merseyon the river Mersey

• How these solutions workHow these solutions work

Tasks:Tasks:

• Make a list of the types of flood defences and Make a list of the types of flood defences and describe themdescribe them

• Visit survey sites along the Mersey and identify the Visit survey sites along the Mersey and identify the type of erosion or flood protection you see.type of erosion or flood protection you see.

Causes of flooding on the Causes of flooding on the MerseyMersey

• Large catchment area, (Peat on Gritstone)Large catchment area, (Peat on Gritstone)

• Catchment area is in the hills of the Peak Catchment area is in the hills of the Peak District. Prevailing winds are moisture District. Prevailing winds are moisture laiden. Rain can be persistent.laiden. Rain can be persistent.

• Steep sided valleys down to Stockport.Steep sided valleys down to Stockport.

• Large areas of hardsurfaces in Stockport Large areas of hardsurfaces in Stockport and South Manchester drain quickly into it.and South Manchester drain quickly into it.

Flood damageFlood damage

• On the map shade in areas next to the On the map shade in areas next to the river (and Tributaries) that are at risk of river (and Tributaries) that are at risk of flooding. These areas will be within one flooding. These areas will be within one contour line from the river.contour line from the river.

• Shade in a different colour, areas within Shade in a different colour, areas within this area where buildings are at risk of this area where buildings are at risk of flooding.flooding.

• Create a key on your map to explain these Create a key on your map to explain these shadings.shadings.

Hard EngineeringHard Engineering: Generally defined as : Generally defined as a controlled disruption of natural a controlled disruption of natural processes using man made structures.processes using man made structures.

Soft EngineeringSoft Engineering: Use of ecological : Use of ecological practices to reduce erosion and practices to reduce erosion and stabilise river banks while enhancing stabilise river banks while enhancing habitats and saving money.habitats and saving money.

River Flood defence and River Flood defence and erosion protection erosion protection definitionsdefinitions

DamsDams

Hard engineeringHard engineering

Hard engineeringHard engineering

Deepen the river/Dredging

Hard engineeringHard engineering

Embankments/LeveesLevees

Embankment / LeveeEmbankment / Levee

Hard engineeringHard engineering

Straighten ChannelsStraighten Channels

Hard engineeringHard engineering

• Bank Bank reinforcement reinforcement with Gabions with Gabions (steel baskets)(steel baskets)

Hard engineeringHard engineering

Banks reinforced with concrete

Hard engineeringHard engineering

Overflow ChannelsOverflow Channels

Soft engineeringSoft engineering

Plant trees / ForestsPlant trees / Forests

Soft engineeringSoft engineering

Allow FloodingAllow Flooding

Soft engineeringSoft engineering

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

• There can be resistance to There can be resistance to development restrictions in areas development restrictions in areas where there is a shortage of housing.where there is a shortage of housing.

Flood DefencesFlood Defences

Draw a spider diagram to show the different soft Draw a spider diagram to show the different soft and hard engineering solutions for protection the and hard engineering solutions for protection the land beside rivers from erosion and flooding.land beside rivers from erosion and flooding.

Write a short sentence to describe each one. Write a short sentence to describe each one.