Management Strategies (DP IB Geography)
Revision Note
Pre-event Management Strategies - Volcanoes
There are signs warning of an eruption before most volcanic eruptions
Pre-event management of volcanoes includes monitoring these signs so that people can be evacuated and warned
Volcanologists (scientists who study volcanoes) monitor changes using GPS, tilt meters, satellites, seismometers and gas detection
Signs of an eruption include:
Magma rising, which can be detected by heat sensors and satellites
Changes in surface level as rising magma causes bulges
Increased emissions of sulphur dioxide and other gases
Increased seismic activity caused by magma movement detected by seismometers
Methods of monitoring volcanoes
Improved prediction of volcanic eruptions has led to a decrease in death tolls
Diversion channels
Lava flows can be managed by constructing diversion channels
These are used to direct the flow away from economically valuable areas or areas of population
Pre-event Management Strategies - Earthquakes
It is not possible to predict earthquakes:
An understanding of tectonic activity can help scientists identify areas most at risk
Over 90% of earthquakes occur on or near plate boundaries
Building design and construction can be used to reduce the impact
Earthquake resistant building design
Hazard mapping can also be used to predict areas at highest risk
Land use zoning can then ensure that valuable buildings are not built in these areas
Tsunami
For earthquake-induced tsunamis, scientists are unable to predict the earthquake itself
When the earthquake happens, this will be detected by the global network of seismometers, which will locate the epicentre of the earthquake
Ocean monitoring technology can then be used to detect a tsunami
Warnings can then be issued to coastal areas that may be affected
Tsunami warning system
Sea walls have also been built to reduce the impact of tsunami
After the 2011 Tokohu tsunami in Japan, the height of the sea wall was increased to over almost 15 meters in places
Pre-event Management Strategies - Mass Movement
The management of mass movement needs to control the factors that affect the risks, including:
Slope angle and stability
Drainage
Human activities
Erosion
Terracing or re-grading of slopes
Terracing or re-grading reduces the angle of the slope
Revegetation
Stabilises the slope material, increasing the amount of stress that the slope can withstand
Reduces slope saturation by take-up of water through the roots and increased interception
Decreases erosion, which affects the stability of the slope
Improving drainage
Water makes slopes more unstable
Improved drainage reduces saturation of the slope
This reduces the weight of the material and therefore the risk of mass movement
Stabilisation structures
Use of pinning:
Steel rods are drilled into the slope to support the weight of the slope
Bolts can also be used to transfer the weight from the surface to the interior of the slope
Pinning is often used in combination with netting, which contains any falling material
Shotcrete shoring is when a mixture of cement and aggregate is applied to the slope; this strengthens the slope and reduces erosion
Retaining walls and gabions, which hold the slope in place
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