How can hazards be managed to reduce their impacts? Flashcards
What are the stages in reducing impacts from earth hazards?
- Prediction
- Risk assessment
- Prior prevention
- Planning
- Preparation
- Warnings
- During prevention
- Response
- Recovery
- Redevelopment
What are ways of managing mass movement hazards?
- Drainage
- Reduce slope angles
- Retaining walls
- Rock bolts
- Reforestation
- Hazard mapping
How does drainage work in managing mass movement hazards?
Reduce the water content on slopes by installing drainage systems e.g. concrete interceptor drains at the top of the slope. Water adds to the mass of material on a slope and pore water pressure weakens the material, making it incoherent and less stable
How do retaining walls work in managing mass movement hazards?
Build walls (or gabions) at the base of a slope to provide support and reduce undercutting (by erosion and weathering) and the risk of slope failure
How does reforestation work in managing mass movement hazards?
Trees reduce the amount of soil moisture in slope materials and tree roots resist downslope forces
How does hazard mapping work in managing mass movement hazards?
Using aerial photographs and fieldwork identify slopes that are at risk of failure and map the hazards. Situations which might lead to mass movements include steep slopes, bedding planes inclined downslope, hummocky topography and slope scars indicating precious slope failures etc.
What ways are there of mitigating volcanic hazards?
- Monitoring
- Diversion of lava flows
- Hazard mapping
- Warning and evacuation
What are tilt metres?
Tilt meters are highly sensitive instruments used to measure ground tilt (rotation) near faults and volcanoes caused by fault slip and volcanic uplift.
What are seismometers?
used to pick up the vibrations in the Earth’s crust. An increase in vibrations may indicate a possible earthquake.
How is monitoring used to manage volcanic hazards?
Increases in seismic activity often precede an eruption. Earthquakes and tremors develop as magma forces its way to the surface and fractures brittle rocks inside volcanoes. The resulting seismic waves are recorded by networks of seismometers on the volcanoes surface.
Gravity is also measured. As magma fills the reservoir within the volcano, gravity increases.
Gases emitted by fumaroles are sampled. Increasing levels of sulphur dioxide (SO2) and hydrogen chloride (HCI) emitted by the magma are a sign of an impending eruption. So too is ground deformation (or inflation) which results from magma accumulating below the surface. This can be measured by GPS to within an accuracy of 1cm.
How is diversion of lava flows used to manage volcanic hazards?
Small lava flows on the flanks of Mount Etna in Sicily have been successfully diverted away from centres of population. At Heimaey, in Iceland, the fishing harbour was saved from destruction by lava through spraying with sea water
How is hazard mapping used to manage volcanic hazards?
The paths followed by ancient lahars can be mapped from sediments to show areas which historically have been at most risk
How is warning and evacuation used to manage volcanic hazards?
Lahar detection warning systems have been installed at the vicinity of Mount Rainier in Washington state. Detection triggers an automatic alert and emergency managers initiate evacuation.
How is warning and evacuation used to manage volcanic hazards?
Lahar detection warning systems have been installed at the vicinity of Mount Rainier in Washington state. Detection triggers an automatic alert and emergency managers initiate evacuation.
What does managing earth hazards effectively depend on?
- The nature of the hazard – its severity, scale, frequency, any build-up signs etc.
- The level of preparation and awareness of risks
- The nature of the area – its structure, geology, relief, climate etc.
- The level of development – research, technology, available communications, warnings etc.
- The nature of the population – density, education, mobility, level of perception, etc.
- Political organisation – coordination, priority, existence of emergency plans etc.
