Additional red flag criteria
There are an enormous range of possible tree forms , environments , defects and hazards , and it is not possible to create hard-and-fast rules for what is a severe hazard . Common sense and experience will always be the most effective guides . For rescue teams without access to hands-on experience with tree hazard assessment , evaluating the impacts of compromised tree structure may be challenging .
The following table presents a list of additional ‘ red flag criteria ’ that should be considered when assessing a hazard .
Arborist activity
Recent changes
Instability
Severity of defect
Common sense
The climb plan and works plan of the arborists on site may help to evaluate the tree hazard . If the top of the tree is dead , for example , and the injured climber has chosen to set their climbing line below the dead part , it may be a sign that they have investigated the dead section and identified decay or damage .
If possible , other crew members on site should be consulted to gain any useful information about the condition of the tree and the suitability of potential anchor points .
Any defect or hazard which appears to have occurred recently , or to have recently altered the condition of the tree , should usually be considered with more caution than hazards which have been present in the tree for some time .
Examples of recent changes could be movement of the tree in the soil , a new crack or split , or evidence of recent failure .
Recent changes may also include recent mechanical damage , or other forms of damage such as bushfire .
Where there is evidence that the tree is putting on new wood in response to a defect , the defect has probably been there for some time and may be of less concern to most rescue plans .
An unstable tree or tree part is one in which unnatural movement can be detected , or where the defect can rapidly increase .
For example , where a tree ’ s roots can be felt to be moving in the ground , where soil heave is evident , or where a crack has potential to suddenly extend during natural wind movement , this would be described as unstable .
Some defects ( such as insect damage ) are not usually a high priority concern without other contributing factors . Where the damage or defect is severe however , these may be cause for reporting a high priority hazard .
An example of this would be severe borer or termite damage . An active and extensive borer attack may cause structural failure within weeks even without the loads applied during rescue .
As stated above , the most useful guide to assessing the hazard posed by tree defects will always be common sense and experience .
If you are familiar with the tree species , and there are a lot of trees growing with similar defects , and not many examples of recent failures , it probably isn ’ t too severe a concern .
If there are no other trees with similar defects , or if you have found a defect that is significantly more extensive or severe than what you can see elsewhere , it may require consideration in your rescue plan .
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