Post on 03-Feb-2016
description
Risk classification of veldfires as a basis for
prioritising the establishment of FPAs
What does the Act require?
The Act requires a consistent basis for the setting of priorities for veldfire management interventions.
Setting priorities requires an assessment of the risk of veldfire in various localities.
Rationale (1)
Veldfire risk is the chance of a veldfire igniting, spreading and causing damage to one or more assets, measured in terms of likelihood and consequence.
The risk classification used is therefore based on:– the likelihood of the natural vegetation
burning– the consequence should a fire occur.
Rationale (2)
The risk classification so derived is then assigned to each municipality.
But first, the fire types occurring within each municipality have to be determined.
Determining the fire type (1)
Start at the biome level. Vegetation within the biomes come from
the work of Low and Rebelo (1996) (see next slide).
For example, vegetation types in the Fynbos Biome are:(West Coast Renosterveld, North-Western Mountain Renosterveld, Central Mountain Renosterveld, Grassy Fynbos, South & South-Eastern Coast Renosterveld, Escarpment Mountain Renosterveld, Laterite Fynbos, Sand Plain Fynbos, Limestone Fynbos and Mountain Fynbos)
Vegetation of South Africa, Lesotho and Swaziland:
Low and Rebelo (1996)Department of Environmental Affairs and Tourism,
Pretoria
Determining fire types (2) For all vegetation types a fire type
is assigned. A fire type is a set of vegetation
types having a similar frequency and nature of veldfire. (This is determined from available literature)
– e.g. Fynbos Fire Types: (Laterite Fynbos, Sand Plain Fynbos, Limestone Fynbos and Mountain Fynbos)
Veldfire risk is accessed for each fire type using standard risk assessment techniques
Likelihood of a veldfire occurring
(adapted from Standards Australia, 1999). Likelihood
rating:Likelihood: indicative frequency
Description
Almost certain 1 in 2 years Is expected to occur
Likely 1 in 5 years Will probably occur
Possible 1 in 10 years Might occur at some time
Unlikely 1 in 20 years Could occur at some time
Rare 1 in 100 years May only occur in exceptional circumstances
Level Social Economic Environmental Catastrophic Death. Negative impact for large
part of the community or region. Long-term outside resources needed for recovery.
Permanent loss of species or habitats.
Major Extensive injury and evacuation.
Serious financial loss. Outside assistance needed.
Temporary loss of species and habitat destruction needed several years to recover.
Moderate Medical treatment needed.
Localised damage to property. Short-term external assistance needed.
Serious impacts needing a few years to recover.
Minor First aid at scene. Slight damage to assets. No external help needed.
Environmental assets recover rapidly.
Insignificant No injuries. No damage to property. Minor temporary impact
Consequences in terms of social, economic and
environmental impacts
Likelihood Rating
Consequence Rating
Insignificant Minor Moderate Major Catastrophic Extreme (almost certain)
Moderate Moderate High Extreme Extreme
High (likely) Low Moderate High Extreme Extreme Moderate (possible) Low Moderate High High Extreme Low (unlikely) Low Low Moderate High High
Risk levels in terms of likelihood and consequences
Risk level Action needed Extreme Priority areas for risk reduction measures High Risk reduction measures by all relevant
agencies Moderate Routine precautions to be undertaken by
landowners Low No action required as veldfire is unlikely and
consequences are negligible
Actions to take depending on the level of risk
Risk assessment and assessed risk levels in each fire type in South Africa.
Fire type Likelihood of critical veldfire scenario
Consequence of critical veldfire scenario
Veldfire risk level
Forest Rare Moderate Low
Thicket Rare Moderate Low
Arid Woodland Possible Major High
Moist Woodland Likely Catastrophic Extreme
Sparse Arid Woodland Rare Minor Low
Succulent Karoo Rare Minor Low
Nama Karoo Unlikely Minor Low
Grassy Nama Karoo Possible Minor Medium
Coastal Grassland Likely Minor Medium
Sour Grassland Almost Certain Catastrophic Extreme
Sweet Grassland Likely Moderate High
Fynbos Possible Moderate High
Renosterveld Unlikely Moderate Medium
Risk classification method (at municipal level)
Assume a critical fire scenario for each fire type.
Judge consequences of the scenario.
Assess the likelihood of the scenario.
(Above from existing reports)
Classify risk accordingly.
Assign fire risk to each municipality
Determine extent of fire type within municipality (Overlay municipality boundaries with Low and Rebelo map which is based on untransformed vegetation)
>30% of area with highest fire risk determines fire type for that area
The risk level is determined by the dominant fire type
Risk level is downgraded if higher risk types are found in areas where they are not a hazard to assets (e.g. Fynbos in isolated mountains)
Qualitative explanation of risk classifications
Moist woodland and sour grassland both rated as extreme
Fynbos rated as high
Assessed veldfire risk levels in some of the municipalities of the Western Cape, in each fire danger region.
Fire danger regionMunicipality
codeName of
municipalityMajor town
Veldfire risk level
Critical fire type
Bokkeveld WC022 Witzenberg Ceres H Fynbos
WCDMA01 WCDMA01 (Cedarberg)
Citrusdal H Fynbos
Breede River WC025 Breede Valley Worcester M Fynbos (patchy)
WC026 Breede River/Winelands
Montagu M Renosterveld
Cape Agulhas to Mossel Bay
WC042 Langeberg Riversdale H Fynbos
WCDMA03 WCDMA03 (De Hoop Nature
Reserve)
Bredasdorp H Fynbos
Cape Hangklip to Cape Agulhas
WC031 Theewaterskloof Caledon M Renosterveld
WC032 Overstrand Hermanus H Fynbos
WC033 Cape Agulhas Bredasdorp M Renosterveld
WC034 Swellendam Swellendam M Renosterveld
SA Municipalities classified by veldfire risk
Conclusion:
This veldfire risk assessment provides a basis for prioritising FPAs, and assigning resources accordingly.
Those areas with the highest fire risk get the first FPAs.
An example at a finer scale
This approach can be used at finer scales e.g. Cape Peninsula National Park
However, a comprehensive spatial database of the hazards and the social, environmental and economic assets is needed
Veldfire likelihood map(Courtesy of the Cape Peninsula National Park)
Veldfire consequence map (Courtesy of the Cape Peninsula National Park)
Veldfire risk map (Courtesy of the Cape Peninsula National Park)