Flood and erosion
defences on the river
Mersey
We will learn:
• The different flood and erosion defences on the
•
river Mersey
How these solutions work
Tasks:
• Make a list of the types of flood defences and
•
describe them
Visit survey sites along the Mersey and identify
the type of erosion or flood protection you see.
Causes of flooding on the Mersey
• Large catchment area, (Peat on Gritstone)
• Catchment area is in the hills of the Peak
District. Prevailing winds are moisture
laiden. Rain can be persistent.
• Steep sided valleys down to Stockport.
• Large areas of hardsurfaces in Stockport
and South Manchester drain quickly into it.
Flood damage
• On the map shade in areas next to the
river (and Tributaries) that are at risk of
flooding. These areas will be within one
contour line from the river.
• Shade in a different colour, areas within
this area where buildings are at risk of
flooding.
• Create a key on your map to explain these
shadings.
River Flood defence and erosion
protection definitions
Hard Engineering: Generally defined as a
controlled disruption of natural processes
using man made structures.
Soft Engineering: Use of ecological practices
to reduce erosion and stabilise river banks
while enhancing habitats and saving
money.
Hard engineering
Dams
Hard engineering
Deepen the river/Dredging
Hard engineering
Embankments/Levees
Embankment / Levee
Hard engineering
Straighten Channels
Hard engineering
• Bank
reinforcement
with Gabions
(steel baskets)
Hard engineering
Banks reinforced with concrete
Hard engineering
Overflow Channels
Soft engineering
Plant trees / Forests
Soft engineering
Allow Flooding
Soft engineering
• Planning: Local authorities 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.
• There can be resistance to development
restrictions in areas where there is a
shortage of housing.
Flood Defences
Draw a spider diagram to show the different soft and hard
engineering solutions for protection the land beside rivers
from erosion and flooding.
Write a short sentence to describe each one.