Post wildfire natural hazard risk analysis
After severe wildfires, an area can be more vulnerable to increased precipitation in which extra moisture is not absorbed fully in the soil. This may lead to increased water runoff that overwhelms natural and man-made drainage features. Landslides, debris flows, and floods can result, threatening public safety and damaging infrastructure.
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The post-wildfire natural hazards risk analysis (PWFNHRA) process allows for the province to study burned areas and determine if a risk is present. This process begins with a screening exercise, wherein wildfires greater than 50 Ha in size undergo a desktop review to determine the potential for these risks as well as the steepness of the terrain. This process starts as soon as fires are listed as ‘under control’ by BC Wildfire Service. Fires with identified risks with terrain steep enough to generate possible hazards are then selected for a reconnaissance-scale review.
The reconnaissance review typically consists of:
- A helicopter overflight
- On-the-ground verification of burn-severity and soil characteristics
- Verification of suspected values at risk such as homes and provincial or community infrastructure
First Nations and non-First Nations communities undergo the same process in B.C.
The goal is to complete the overflight and field work as soon as smoke clears and fire suppression fighting activities, while perhaps still ongoing, are in mop-up stage. A report is usually completed within 2 weeks, and provided to impacted communities and partners through the Ministry of Emergency Management and Climate Readiness (EMCR). If moderate or high risk is indicated, a detailed PWFNHRA may be required.
For a detailed PWFNHRA, community experts are given the opportunity to provide input and local knowledge to the study. The procurement process for the study starts as soon as the reconnaissance report is complete, with a goal of delivering a completed detailed report prior to onset of winter if possible. Once completed, these reports are also distributed to affected communities and partners through EMCR. Where relevant, high-level recommendations for risk mitigation options are included for specific elements at risk.
Mitigation options may require additional assessment to:
- Estimate hazard magnitudes more precisely
- Identify the most cost-effective solution
- Produce detailed designs
These detailed options assessments would be the responsibility of the owner of the at-risk value, as would be costs to implement mitigative options. Affected individuals are to work with their local government to determine options for funding mitigative works; whereas First Nations communities would work with EMCR and Indigenous Services Canada to determine options for funding mitigation efforts. All other local governments would work with EMCR as a first step to identify funding options.