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15 mark essays plans for CIE paper 1 physical geography
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15 mark essay plans for paper 1 physical geography, CIE a level (12 essay plans)
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RIVERS:1.With the aid of examples, examine the extent to which hard/soft engineering prevent river
flooding
Hard engineering can prevent river floods
E.g Dams
o Dams are built along the course of a river in order to control discharge by holding
water back and releasing it in a controlled way. This can help to regulate the
discharge in a river, meaning if there has been heavy rainfall, the dams can hold
back water to prevent rivers exceeding bank-full conditions and flooding à e.g Swan
dam in Egypt has reduced flooding by 30%.
E.g raising levees/ embankments
o By raising the banks of the channel, the capacity of the river is increased, meaning
that discharge volumes which may previously have caused a flood will no longer.
o But, such effectiveness in preventing flooding is reliant on the banks being raised
high enough
However, some strategies prevent flooding at the expense of increasing the risk elsewhere
E.g diversion spillways
o The use of forecasts and warnings merely allow people to prepare for the event of a
flood and make no attempt at trying to stop the event from happening.
o The use of diversion spillways to move the river channel away from areas of high-
value land prevent such areas from flooding à on the Mississippi through New
Orleans canals à prevents flooding in areas of higher land value, but may increase
the risk of flooding occurring downstream, therefore not completely preventing it.
E.g channel straightening
o Makes the river straighter in order to allow water to flow through a specific area
more quickly.
o This can be effective at preventing the build-up of flood waters in and around urban
areas with valuable land, for example, but may then increase the risk of flooding
downstream due to the water reaching these areas more quickly
However, some hard engineering strategies are less useful in the prevention of river floods
as they focus more on the reduction of their impacts
E.g retention basins
o Areas in which floodwater can be diverted and stored at times of risk à River Rhine
near Strasbourg, used to store floodwater do decrease flood risk downstream
o This strategy is not effective in preventing river flooding as it is only useful once the
rivers capacity has been exceeded, therefore it is merely reducing the impacts, not
preventing the flood
Overall, hard engineering strategies can prevent river flooding to some extent, in the case of
dams and the raising of levees. However, often with the prevention of flooding in one area,
hard engineering strategies simply increase the risk in other areas, therefore cannot be said
to be completely effective in preventing all river flooding due to focussing on areas where
there is a greater risk. Despite some strategies of hard engineering only reducing the impacts
of the flooding rather than preventing it, hard engineering strategies provide the best
method in reducing and preventing river flooding in comparison to forecasting and warning
, Soft engineering strategies can prevent river flooding
E.g afforestation
o By planting trees in the catchment area, they intercept water and take water out of
the soil, reducing the amount of rainfall that ends up in the river channel. This can
help to slow down flow of water into the river as well as reducing the volume which
ends up there, thereby preventing flooding.
However, many soft engineering strategies focus on restabilising natural areas to
accommodate floodwaters, therefore do not prevent the risk of flooding
E.g river restoration
o River restoration reintroduces meanders to rivers and restores physical process.
Reversing channel straightening by making a river more sinuous can reduce flood
peaks, water velocities and attenuate flow by slowing and storing flood water.
o However, by reinstating these natural processes and in turn increasing river
retention, it merely allows the river to flow as it had prior to the defences put in to
stop such events, therefore it does not necessarily prevent flooding, but re-
establishes surrounding floodplains to allow the river to do so and continue its
natural course and reduce possible negative impacts of previous hard engineering
strategies
E.g wetland conservation
o This protects the natural floodplain of the river, enabling flood waters to dissipate
here without disrupting or affecting people
o It can aid local biodiversity and protect disappearing wildlife
o However, such natural defence may not always be reliable, and it is not preventing
flooding, but similarly to river restoration reinforcing the natural area to allow the
waters to go somewhere at times of high discharge
In conclusion, although some soft engineering strategies can help reduce river discharge,
such methods are much more effective in reducing the impacts of the flooding through the
reestablishment of natural defences to river flooding. In the prevention of flooding as a
whole, hard engineering strategies target these more effectively in the short term
prevention of floods.
2.With reference to a recent river event, explain the causes of the flood and evaluate attempts to
reduce its impacts
Colombo flood, May 2016
o Causes:
Tropical storm Roanu bought 350 mm of rainfall over 3 days, 1 months
worth
Augmented monsoon season à heatwaves caused temperature in the Indian
subcontinent to reach 40 degrees, creating a deeper low pressure and
resulting in an augmented monsoon season, where 4-6x more rainfall fell
than in the same period of time in 2013
Landscape of the Kelani Ganga and surroundings à steep valley sides
accelerated surface run off and through flow to the channel, and there was
no floodplain to allow the floodwater to dissipate à very low-lying area
means the water table is very close to the surface
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