Advantages and Disadvantages of Hard Engineering Techniques
,Hard,
engineering technique
Embankments
Advantages
Description
These are raised banks
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along the river.
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Channelisation
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.
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Can be used as a path
{or pedestrians beside
the river.
Concrete embankments
are effective at stopping
bank erosion.
Earth embankments
provide habitat for
plants and animals,
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Disadv-antages.',,,;.
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Th€ banks are often not
built high enough.
Concrete embankments
are ugly and spoil the
view.
Altering the river
channel may lead to a
greater risk of flooding
downstream, as the
water is carried there
Effectively protects
immediate area because
water is moved away
quickty.
,,. Long lasting.
faster.
Unnatural and visually
intrusive.
Ftood relief channels
The channel course of the
river can also be altered,
diverting floodwaters
away from settlements.
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They require a large
Makes the people who
live close to the main
river safer as the flood
amount of land which
might be difficult to
purchase particularly if
it is productive
water is diverted into
the relief channel.
,':. Can be used for water
farmland.
Extremely expensive.
sports.
Dams are o{ten 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.
.
Waier is usually stored
Building a dam can be
in a reservoir behind
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the dam. This water can : *
then be used to
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generate hydroelectric
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power or for recreation
,
very expensive.
purposes.
downstream.
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Sediment is often
trapped behind the wall
of the dam, leading to
erosion further
: ,', Settlements and
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agricultural land may be
lost when the river vaiiey
is flooded to forrn a
reservoir.
Flood walls
A vertical barrier usually
made from prefabricated
concrete.
Can be used in areas
where space is limited.
Easily and quickly
erected in
pre-constructed
n
They have to be
assembled very well so
that water doesn't get
through joints.
sections.
Storage areas
A large depression close to
the river that will fill with
water if the river overflows
and therefore protecting
the surrounding land.
Natural looking.
Does not damage the
environment.
Need a large area of
land that is not being
used.
Only come into use
when the river has
flooded.
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Advantages and Disadvantages of Soft Engineering Techniques
Soft engineering technique
Floodplain zoning
Advantages
Description
Local authorities and the
national government
introduce policies to
control urban
development close to or
on the floodplain.
Disadvantages
A very cheap way of
reducing the risk of
There can be resistance
damage to property.
It is sustainable because
it reduces the impact of
flooding and building
damage is limited.
AIso because the
developments in areas
where there is a
shortage of housing.
Enforcing planning
regulations and controls
may be harder in LlCs.
to restricting
{loodpiain has not been
built on, surface runoff
is less likely to cause
flooding.
Washlands
The river is allowed to
flood naturally in
wasteland areas, to
prevent flooding in other
areas, for example, near
settlements.
Very cost effective as
nothing is built.
Provides potential
wetland sites for birds
and plants.
The deposited silt may
Large areas of land are
taken over and cannot
be built on.
Productive land can be
turned into marshland.
enrich the soil,
subsequently turning
the area into
agricultural land.
Warning systems
A network of sirens which
A very cheap system.
give people early warning
Electronic
of possible flooding.
communication is a very
effective way of
The Environment agency
uses TV, radio. email, fax,
teK and phone messages
to keep people informed.
informing people.
Because the people
have warning of floods
The sirens could be
vandalised, so they are
tested annually.
There might not be
enough time for
residents to prepare.
they can move valuable
belongings to a safer
place.
Afforestation
Trees are planted in the
This is a relatively low
It
catchment area of the
river to intercept the
rainfall and slow down the
cost option.
It improves the quality
of the environment.
are planted which can
make the soil acidic.
Dense tree plantations
flow of water to the
Soil erosion is avoided
as trees prevent rapid
run off after heavy
spoil the natural look of
the landscape.
It increases fire risks
river.
is
often conifers that
rainfall.
because of leisure
Very sustainable.
activities in the forest.