Making the most of Quantified Tree Risk Assessment
Although the QTRA method was originally designed to risk-assess individual trees, through continued use and development, it has become clear that the greatest benefits are realised when the system is applied at a strategic level. With considerable savings to be made not only in budgets but also in terms of tree, landscape and ecological benefits, can you afford to overlook this simplified tree assessment process?
The strategic approach can be applied wherever there is risk from the failure of trees. For anyone managing a large tree stock and the associated duty of care, the scale of the task can lead to reactive management and inconsistent decision making, whereas a simple overview of tree risk will enable the balanced and proportionate allocation of resources. In view of the often limited funds available for tree management and the need to provide ‘best value,’ QTRA can be an invaluable management tool.
By evaluating the relationship between trees and land use, the strategic target assessment broadly quantifies the value of those things that could be affected by tree failure. This exercise can be carried out at a local scale, such as within a park or residential area, or on a large scale, such as across a road network or a council’s entire administrative area. Assignment of probabilistic target values to land-uses or road classifications can provide a good starting point where resources are limited. Strategic assessments provide a baseline evaluation that can be refined as resources allow or if detail is required.
There are a range of tree assessment techniques that can be applied within the QTRA framework to provide highly effective tools for tree risk management. In the vast majority of situations, individual tree inspections will provide little more useful information than can be obtained from a less intensive drive-by or walkover survey. Is it really necessary to allocate substantial budgets to individual tree inspections if the objective is the reasonable management of what is generally already a very low risk?
“I like trees but….” is a sound bite often quoted by tree managers when discussing unreasonable pressures on trees. Perhaps we should ask ourselves whether or not we are applying similar principles to tree risk management; “I like trees but.....just in case”. Constantly putting tree safety under the microscope and seeking ever increasing detail leads to risk-aversion and perversely degrades social, ecological and landscape benefits whilst expending increasing budgets on risk control. Using the strategic assessment techniques, QTRA can help to provide a reasonable framework for tree risk management, resulting in more proportionate resource allocation, and less of an impact on our tree populations.
