Lake Mountain risk assessments

April 17, 2015

Arboricultural management

Lake-Mountain-6Arboricultural consultancy can lead to assessing trees in varied and interesting environments from indigenous roadside reserves to streetscapes and parks and gardens and private properties, both urban and rural.  Many wonderful trees have been assessed that could tell many stories, some lived in times previous to our own and may still stand once some of us are gone.

One such arboricultural assessment that Tree Logic was lucky to be involved in was an assessment of trees around the Lake Mountain Alpine Resort in the Victorian Alps.

Lake Mountain is a 1,433 metre (4701 ft) high mountain with the resort situated in a saddle between Lake Mountain and Echo Flat that ironically does not have a lake.  Lake Mountain is named after George Lake, who was the Surveyor-General of the area, including the mountain.

Lake-Mountain-1During the 2009 bushfires, the resort and surrounding landscape suffered considerable damage and the after effects are still evident today.  The tree component of the landscape destroyed in 2009 was mostly regrowth from the Black Friday fires of 1939, that consisted of Snow Gums (Eucalyptus pauciflora) and Alpine Ash (Eucalyptus delegatensis).  The drive through Marysville and up the mountain showed some of the devastation that occurred on Black Saturday, dead trees formed stands across the mountain ridges at every turn and across the valleys.  This was the sight that welcomed us as we arrived at Lake Mountain Alpine Resort.

Lake-Mountain-2It has been over six years since Black Saturday fires and the charred landscape is regenerating (the amazing phenomena that is plant adaption to their environment and the influences of their environment) and the lives of these trees continue.  Like all living organisms, they are subject to decay and dead trees usually decay at faster rates than living trees.  This was the occurrence at the Lake Mountain Alpine Resort, the dead trees surrounding the resort were decaying and management could see that they presented a risk to the patrons who visit the resort.  The trees also presented a risk to infrastructure that is critical to the operation of the resort.

This is where Tree Logic became involved.  Resort management could see the risk the trees presented and needed assistance on how to assess and manage them.  The assessment looked at several areas that were of high importance to the resort, where visitors congregated for periods at a time and areas surrounding critical infrastructure.  The assessment consisted of determining tree species, size, structure and attributing each tree with a risk rating based on several criteria.  The risk rating was to provide a qualitative rating to each tree as a method of prioritising works.  Tree health was assessed on trees that had not been killed outright by the fires.  The management options included; tree removal, crown reduction, branch removal or habitat pruning.

The degradation of dead trees follow a predictable pattern, initially leaves and small branches are lost followed by branches of increasing size.  Bark detaches from the trunk and decay enters the trunk and roots.  Armed with this understanding and the criteria set out in our risk rating and arboricultural descriptors, the assessment commenced.  The assessment made recommendations for two-hundred and twenty seven (227) trees in total.  Most of the recommendations were for tree removal, followed by crown reduction, limb removal, habitat pruning followed by trees requiring multiple works.

Lake-Mountain-3Tree risk protocols say that dead trees and branches have a high likelihood of failure and present a high risk particularly in areas of concentrated use.  The wisest decision is often to remove the trees to mitigate the risk from areas of concentrated use and targets of high value.  The assessors were careful not to fragment the dead tree stands as this may increasingly expose the remaining trees to the prevailing conditions, including wind and snow.  Where trees were set further back from targets and it was likely that the outer crown was likely to fail, then pruning works were recommended as to minimise fragmentation and provide protection to the underlying regrowth.  It was with careful consideration that each tree was assessed and the recommendations reflected the appropriate management strategy for not just the tree, but to the tree as part of the landscape.

Lake-Mountain-5The role of fire in the landscape can have devastating effects that are still evident years later and trees can present more of a risk today than after the initial phase of a fire.  Where trees present a risk in areas occupied by people or critical infrastructure, they must be managed in a considered and methodical manner to ensure the safety of all those who visit and enjoy the Lake Mountain Alpine Resort in Victoria.

David Phillips

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