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