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Tree Hazard Assessment
Tree Hazard Assessment
We want to limit the likelihood of any person being injured by tree fall. A Tree Hazard Assessment should be done before establishing camp, for an activity (like abseiling), or a place where a group spends time (like at lunch).
Some tree characteristics to observe and consider as indicators of potential hazardous trees are:
- Co-dominant or multiple trunks: Bark which has built up between the trunks forces the trunks apart. This can cause trunk failure at the joint.
- Included bark: This is bark which is compressed and trapped between trunks or branches as the tree grows. The bark which has been ‘included’ in the tree as it grows generates a weak point in the trunk or limb.
- Excessive end weight and unbalanced, asymmetrical crowns: Some branches are very long and very heavy. Fruit production, rain and snow can accelerate limb failure in this type of branch.
- Cracks and splits: Indicate weaknesses and damage in the structure of the tree.
- Wounds: Tree wounds often conceal larger faults in the tree and are entry points for disease and parasites which can greatly weaken the tree.
- Decay and cavities (eg fire hollows): Indicate weaknesses and damage in the structure of the tree. The level of damage is often much more extensive than initially observed.
- Fungus and other pathogens: Fungus often indicates the tree is being destroyed from the inside out. Other tree pathogens include insect infestations (eg termites), other plant species (eg vines or parasitic plants like mistletoe), and microorganisms (bacteria and other disease)
- Hangers: Hangers are a limb which has been broken and is still dangerously suspended in the tree.
- Deadwood: Dead limbs can be discarded by a tree at any time.
- Soil disturbance and Root depth: For example, erosion, machinery disturbance and burrowing animals can dramatically weaken a tree. Raised pads around a tree base indicate imminent failure. Some trees evidently have very shallow root depth.
- Trees with excessive lean: Stay out of the target area of leaning trees. This includes trees leaning over waterways.
- Failure History: trees that have experienced failures in the past are likely to again.
- History of camping area: A popular camping area may have had tree fall debris collected for firewood. A debris clean area can be deceptive when evaluating tree hazards.
- Species: for example, Angophora and certain eucalyptus species
- Dead trees: for example, the sunken forest on Lake Yarrunga
- Other human impacts: like partially felled trees, wire fencing or ropes strangling a tree, etc.
(Scroll down for example images)
Co-dominant or multiple trunks
Co-dominant or multiple trunks
- Bark which has built up between the trunks forces the trunks apart. This can cause trunk failure at the joint.
Included bark
Included bark
- This is bark which is compressed and trapped between trunks or branches as the tree grows. The bark which has been ‘included’ in the tree as it grows generates a weak point in the trunk or limb.
Excessive end weight and unbalanced, asymmetrical crowns
Excessive end weight and unbalanced, asymmetrical crowns
- Some branches are very long and very heavy. Fruit production, rain and snow can accelerate limb failure in this type of branch.
Cracks and splits
- Indicate weaknesses and damage in the structure of the tree.
Wounds
- Tree wounds often conceal larger faults in the tree and are entry points for disease and parasites which can greatly weaken the tree.
Decay and cavities
- Indicate weaknesses and damage in the structure of the tree. The level of damage is often much more extensive than initially observed.
Fungus and other pathogens:
- Fungus often indicates the tree is being destroyed from the inside out. Other tree pathogens include insect infestations (eg termites), other plant species (eg vines or parasitic plants like mistletoe), and microorganisms (bacteria and other disease)
Hangers
- Hangers are a limb which has been broken and is still dangerously suspended in the tree.
Deadwood
Deadwood
- Dead limbs can be discarded by a tree at any time.
Soil disturbance and heaving
- For example, erosion (including bank erocision), machinery disturbance and burrowing animals can dramatically weaken a tree. Heaving is the lifting of one side of a root plate – the ground is raised (and often loose) on one side of the tree. These raised pads around a tree base often indicate imminent failure.
Trees with excessive lean
- Leaning trees may be well rooted, but should still be avoided. This includes trees leaning over waterways.
History of camping area
- A popular camping area may have had tree fall debris collected for firewood. A debris clean area can be deceptive when evaluating tree hazards. May or may not have warning signs!
Species
- for example, Angophora and certain eucalyptus species
Dead and dying trees
Dead and dying trees
- for example, the sunken forest on Lake Yarrunga, NSW
Other human impacts:
Other human impacts:
- like partially felled trees, wire fencing or ropes strangling a tree, etc.
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