Slides in this set
Flood Prediction and Warning
· In the UK rivers are constantly monitored by
the Environment Agency. Methods of collecting data:
· Records of flood events are used to help
predict future ones. 1. Weather radar shows
· Anyone concerned can ring Floodline and likely and actual rainfall in
receive automatic telephone warnings. weather systems
approaching the UK.
· The Environment Agencies mapping
system is based on the National Flood Risk 2. Automatic rain gauges
Assessment (NaFRA), which uses a measure the amount of rain
method called Risk Assessment for that has fallen in each
Strategic Planning (RASP).
· This calculates the risk of flooding by taking
into account location, flood defences.etc. 3. River gauges record the
and a location is put into one category: discharge along a river.
· Low: chance of flood each year <1 in 200
· Moderate: 1in75 1in 200 Flood prediction software is
· Significant: >1 in 75 then used to model likely
Advantages / Disadvantages
By predicting floods: Problems with flood prediction:
· Authorities can prepare defences · How effective the preparations are
and emergency services before a depends on local authorities and
flood occurs, therefore reducing support of voluntary and official
damage to homes, farmland and agencies.
businesses. · Prediction and warnings don't help
· It can help to chose what type of to reduce the chance of the river
flood defences should be used in bursting its banks, therefore have
an area. to be used with other management
· Intangible losses including; loss of strategies or defences.
life and injury, and the damage
caused to human health and long-
term well-being, can be prevented.
· Technology is always improving
and becoming more accurate.
· Less damage means costs and
disruption of daily lives are greatly
· Residents can take precautions to
protect their property or can be
· Channelisation is an attempt to alter the natural flow of the watercourse. This
can help to prevent flooding as the channel capacity has been increased and
this can help prevent the riverbank from eroding. This can help reduce the risk of
a river breaking its channel during high flow.
·One way channelisation occurs is through resectioning involving widening a
making a channel deeper to improve hydraulic efficiency. This increases the
capacity the river can hold so lowers the chance of flooding.
· Realignment involves taking out the meanders so the increased gradient
moves the water away more quickly due to it being straighter. Making a channel
straighter and deeper also help drain surrounding wetlands and provide more
manageable rivers and the land can be used for development.
· Revetments are used to help strengthen the bank while wind dykes or training
walls at the sides of the channel focus the main current of the river concentrated
to the centre
·In developed areas, rivers can be covered in concrete culverts that restrict the
movement of the river and help remove runoff from impermeable surfaces…read more
Problems and Disadvantages
· All of the measures are costly
· High maintenance costs only have short term advantages. If not
maintained, the river may revert back to the way it use to be.
· Long term effects can mean more downcutting in the upstream river
sections and increased disposition in the lower course of the river. These
factors may lead to catastrophic flooding in the future
· Stopping a river flow through its natural meander path can also lead to an
increased flood risk
· The whole basin has to be looked at to reduce the risk of flooding as only
managing small sections of a river can upset the river further up or down
its course due to the existing equilibrium is disrupted
· Channelisation can upset the eco systems and reduce habitat diversity as
changes in the river change the environment creatures are used to
· Can be seen as being an eye-sore as it may not look natural…read more