Hazard Mitigation

The first stage of hazard management is to identify the hazards. When a hazard is identified, models are used to establish the likely extent, intensity, and frequency of events to create a hazard map. The hazard map is used in combination with an assessment of the vulnerability of people or objects exposed to the hazard to determine the risk. Actions to change the established risk are to do nothing, to avoid the hazard, to mitigate through education, to monitor and forecast changes in the hazard, and to mitigate or eliminate the hazard through engineered solutions. The action depends on the risk, the physical parameters of the hazard and mitigation techniques, and the projected economic and social cost.

No Action

In some instances, a hazard exists but is such low intensity or low frequency that it is not mitigated. For example, unstable slopes may be identified in backcountry British Columbia. If the site is not valuable for recreation or industrial uses, no action will be taken.

Avoidance

Avoidance of a hazard involves preventing people or objects from being in a vulnerable situation, thus negating the risk. This may be done through restricting or controlling development in hazard zones. An example of this is the probable runout path of any further failures from the Barrier (site of 1855 Rubble Creek), which has been barred from any development or even overnight camping due to the high intensity risk with a probability of occurrence unlikely to occur within any given lifetime, but likely to occur within the lifespan of a community. If development has already taken place, governments may choose to buy-out and move people and buildings. This happened with the community of Frank, where only a fire hydrant remains at the original location.

In shorter timespans, avoidance may take place through shutting down access to a location when forecasting indicates a higher probability of an event. This is a common tactic in avalanche mitigation, temporarily shutting down access to backcountry recreation areas or roads.

Education

Educating the public on how to identify a hazard, how to avoid increasing the hazard, signs of impending disaster, and what to do in case of a disaster are vital to increasing community resiliency. This may be done formally through schools, such as at the University of British Columbia where the Natural Catastrophes undergraduate course has been taken by approximately 10% of the university population. It may also be done through outreach, public forums, advertising, and through local community service groups.

For landslides, mitigation involves teaching identification of the signs of potential failures, such as slope cracks or bulges, unusual seepage, and small rock or sediment falls. It also involves teaching what actions increase instability, like undercutting banks, loading the top of slopes, or disrupting water flow, which should be avoided.

Monitoring and Forecasting

Monitoring is used to create early warning systems, to detect changes over time and in relation to environmental conditions, and to increase scientific understanding of a phenomena. An example is equipment at the top of Turtle Mountain, which serves as a field laboratory and testing centre for new monitoring equipment, as a way to learn more about the structure of the mountain, and as an early warning system for Frank and the surrounding communities should another catastrophic rock avalanche occur. Monitoring of conditions is often used in partnership with forecasting, to create a state of heightened alert when certain conditions are met. This is commonly done with avalanches, where during peak season daily forecasts are made available to the public.

Engineered Solutions

When a risk is deemed unacceptably high, physically intervening in the hazard through engineered solutions may reduce the risk. For landslides, this includes improving drainage, reducing slope angle, unloading the top of the slope, building a berm across the toe, or manually stabilizing the slope through bolting, netting, spraying concrete, or scaling loose rock. Containment and diversion structures are used in the projected impact area. For landslides, catchment dams trap debris while allowing water to pass through (Lion’s Bay), while artificial channels redirect flow. With avalanches, sheds protect the road and berms redirect flow around roads.

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