1. Hard and soft engineering techniques
Learning Objectives:
To compare the advantages and disadvantages of river defence techniques
To consolidate our knowledge of river landscapes, river processes and river flooding

2. Flood Engineering Techniques
Hard engineering is a method of river flood management which involves major construction work
Soft engineering is a method of river flood management which works or attempts to work with natural river processes. It does not tend to involve major construction work e.g. Floodplain zoning

3. HARD ENGINEERING
These are structures built by engineers, with the help of geographers and hydrologists.
They are expensive and often not an option in LICs.
They often have a negative impact on the environment and can even cause more flooding further down the river’s course.
Use a full page and write the following headings along the top of the page:
Method Description Comment
Write notes on each technique as we go through the following slides.

4. Flood banks
These are raised
1) Can be used as a path
1) The banks are
banks along the river, so it can hold more water.
for pedestrians beside
often not built
the river.
high enough
2) Concrete embankments
2) Concrete
are effective at stopping
embankments
bank erosion.
are ugly and
3) Earth embankments
spoil the view.
provide habitat for
plants and animals.

6. Channelisation
(straightening and deepening of the river)
The river channel may
1) Effectively protects
1) Altering the
be widened and
immediate area because
river channel may
deepened allowing it
water is moved away
lead to greater
to carry more water. A
quickly.
risk of flooding
river channel may be
2) Long lasting
downstream, as
straightened so that
the water is
water can travel faster
carried there
along the course
faster.
2) Unnatural and
visually intrusive.

7. Los Angeles channelisation

8. Flood relief
The channel course
1) Makes the people who
1) They require a
channels
of the river can be
live close to the main
large amount of
altered, diverting
river safer as the flood
land which might
floodwaters away
water is diverted into
be difficult to
from settlements.
the relief channel.
purchase
2) Can be used for water
particularly if it is
sports.
productive farmland.
2) Extremely
expensive.

9. Construction of a flood relief channel

10. Dams and reservoirs
Dams are often built
1) Water is usually stored
1) Building a dam is
along the course of a
in a reservoir behind the
very expensive.
river in order to control
dam. This water can then
2) Sediment is often
the amount of discharge.
be used to generate
trapped behind the
Water is held back by the
hydroelectric power or
wall of the dam,
dam and is released in a
for recreation purposes.
leading to erosion
controlled way.
further downstream.
3) Settlements and
agricultural land may
be lost when the river
valley is flooded to
form a reservoir.

12. The Three Gorges Dam in China
Use the resource sheet to complete a fact file on this example of a hard engineering scheme. Write your fact file around the map of China.
Include:
Its main features,
Why it was built?
The impact : social, economic, environmental.
Extension work – How to get the A/A*
Use the booklet to add more detail to your case study:
1. The history of flood events on the Yangtze (table 2),
2. Why can the 3 gorges be described as a multi-purpose scheme?
3. What does displacement mean and how have people been re-settled?
4. What have the impacts on the Yangtze ecosystems been like?
5. Add the detail from figure 1 to your map.
6. What hazards has the dam created?
Do you think it should have been built? Do the benefits outweigh the costs?

13. Flood walls
A vertical barrier usually
made from prefabricated
concrete.
1) Can be used in areas
where space is limited.
2) Easily and quickly erected
in pre-constructed sections.
1) They have to be
assembled very well
so that water doesn't
get through joints.

14. Flood wall on the River Moskva, in Moscow

15. Storage areas
A large depression close
to the river that will fill
with water if the river
overflows and therefore
protecting the surrounding
land.
1) Natural looking
2) Does the damage the
environment.
1) Need a large area
of land that is not
being used.
2) Only come into
use when the river
has flooded.

16. Barriers, such as the Thames Barrier.
The barrier is raised when a high tide or flood is forecast.

17. SOFT ENGINEERING
These do not involve expensive structures, but instead uses the natural features of the drainage basin to control flooding.
It involves planning the land use in the drainage basin.
Forecasting and warning systems are also important

18. Floodplain
zoning
Local authorities and the
national government
introduce policies to
control urban development
close to or on the flood
plain.
1) A very cheap way of
reducing the risk of damage
to property.
2) It is sustainable because
it reduces the impact of
flooding and building
damage is limited.
3) Also because the flood-
plain has not been built on,
surface runoff is less likely
to cause flooding.
1) There can be
resistance to
restricting developments
in areas where there is a
shortage of housing.
2) Enforcing planning
regulations and controls
may be harder in LICs.

19. Washlands
The river is allowed to flood
naturally into wasteland
areas, to prevent flooding
in other areas, for example,
near settlements.
1) Very cost effective as
nothing is built.
2) Provides potential
wetland sites for birds and
plants.
3) The deposited silt may
enrich the soil, turning
the area into agricultural
land.
1) Large areas of land are
taken over and cannot be
built on.
2) Productive land can be
turned into marshland.

20. Warning
systems
A network of sirens which
give people early warning
of possible flooding. The
Environment Agency uses
TV, radio, , fax, text
and phone messages to
keep people informed.
1) A very cheap system.
2) Electronic communication
is a very effective way of
informing people.
3) Because the people have
warning of floods they can
move valuable belongings
to safer places.
1) The sirens could be
vandalized, so they are
tested annually.
2) There might not be
enough time for residents
to prepare.

21. Afforestation or
Flood abatement
Trees are planted in the
1) This is a relatively low
1) It is often conifers that
catchment area of the river
cost option.
are planted which can
to intercept the rainfall and
2) It improves the qulaity of
make the soil acidic.
slow down the flow of water
the environment.
2) Dense tree plantations
to the river.
3) Soil erosion is avoided as
spoil the natural look of
trees prevent rapid runoff
the landscape.
after heavy rainfall.
3) It increases fire risks
4) Very sustainable.
because of leaisure
activities in the forest.

22. How can we manage the Cumbria Floods?
Use the map to help you suggest and explain which management techniques you would put in place. Hard or soft engineering? Where? Why?

23. Flood proofing
This is where buildings are either designed or altered to make them less at risk of flooding.
Do you recognise
this place?

24. ACTIVITY:
1. Use the photo of Skipton, you have been given, to annotate with evidence of flood management. Try to identify evidence of the different types of hard and soft engineering. 2. Draw 2 spider diagrams, one for soft and one for hard engineering schemes and include their advantages and disadvantages. The Environment Agency manage floods in England and Wales.

25. Your task: You work for the Cumbrian Flood Action Group.
You have a brief to report to the Environment Agency and the Cumbrian County Council your views on the flood.
Go back to the previous page where you have already:
1. Stuck the OS map of the area in to the centre of a double page,
2. Around the edge of the map included details on why it happened, it’s impacts (social, economic and environmental) and the responses to the event.( Put these in neat boxes with headings)
NOW:
3. On the same map label your ideas on which hard and soft engineering techniques should be used to protect Cockermouth against a future flood event of this magnitude.
Outline the benefits and problems of each around your base map.
You must also state your reasons for the choices you made (weighing up the balance between social, economic and environmental benefits). Be prepared to present this to the rest of the class!
Resources available to you:
You have been given a resources pack to help you produce your report, as well as a base map of the area to detail your ideas for your flood alleviation plan.
Use your notes on methods of flood protection looked at in lessons.

26. What decisions have the Environment Agency made?
Open the sealed envelope to find out!
Cumbrian Floods of 2009 What are the proposals for flood alleviation? Flood defence works begin! Innovative developments in Cockermouth.

27. Plenary: Name and describe each method of flood management.
Relief channels
Washlands
Floodwalls d.
Flood warnings g. e. f.
Channelisation
Afforestation
Floodplain zoning

28. HARD SOFT Engineering Engineering
Floodwalls
Flood warnings
Channelisation
Floodplain zoning
Flood relief channels
Washlands
Afforestation
Flood relief channels
Floodplain zoning
Afforestation
Channelisation
Washlands
Flood warnings
Floodwalls