Harrogate Borough Council
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Risk Management
What systems are used to measure tree risk?
| In any tree risk management system, there has to be a clear definition between HAZARD AND RISK, taking into consideration the proposed target area, its frequency of use and the probability attached to whole or part tree failure. |  |
Harrogate Borough Council is a licensed user of the Quantified Tree Risk Assessment (QTRA) system, which applies established and accepted risk management principles to tree safety management. Firstly, the targets (people and property) upon which trees could fail are assessed and quantified, thus enabling tree managers to determine whether or not and to what degree of rigour a survey or inspection of the trees is required. Where necessary, the tree or branch is then considered in terms of both impact potential (size) and probability of failure. Values derived from the assessment of these three components (target, impact potential and probability of failure) are combined to calculate the probability of significant harm occurring.
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QTRA moves the management of tree safety away from labeling trees as either 'safe' or 'unsafe', thereby requiring definitive statements of tree safety from either tree surveyors or tree managers. It quantifies the risk of significant harm from tree failure in a way that enables tree managers to balance safety with tree value and operate to a predetermined limit of reasonable or acceptable risk. |
For further information on this system, please visit: www.qtra.co.uk.