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Hazard Tree Management for Camps
The saving of human life will take precedence over all other management as the Park Service strives to protect human life and provide for injury free visits.
— National Park Service
Camps with standing trees have a special responsibility - the management of those trees in the interest of the visitors, guests, and staff. Trees are an integral part of any camp, but like any other living thing, they require maintenance. As the number of visits around and under them increases, the chance of an accident increases. Attitudes of camp directors about tree maintenance are separated into two groups, those who have had an accident, or near miss, and those who have not.
A camp's staff that has never experienced a hazard tree accident usually makes statements such as - "That tree has been there for many years and it hasn't failed yet." "Hazard trees are an acceptable risk." "The board doesn't want anything done to the trees." "We don't want to change the looks of the camp." Or, "We don't have time."
Camp staff that have had a hazard tree event usually makes statements such as - "Go through camp and take care of every defective tree, we don't want any more accidents!" "One more accident, and parents won't send their kids here." And "We can plant other trees!"
Camps usually have well thought out safety plans for wet floors, insects, vehicles, water, sunburn, food, equipment, etc., but, regarding trees, there is usually a sense that not much can be done, that chances of hazard tree accidents are remote enough to be an acceptable risk, or the love of trees outweighs the hazards.
Trees fail and branches fall on a regular basis across trails and use areas. Maintenance staff ordinarily clean up the litter, and it's back to life as usual. When failed trees damage cabins and other structures, maintenance staff clean up and repair buildings . . . and life in camp goes on, with possibly some discussion about what could have happened if someone was there at the time.
This attitude was acceptable when not much information was available about what makes a tree fail or what factors precondition a tree to fail. The science has always existed, but some outdoor recreation organizations have not had access to the information about tree defects. The forest products industry, government agencies, and research organizations have information readily available for the general public and outdoor recreation enthusiasts. Responsible camp managers now have the tools necessary to identify and rectify hazardous tree situations in their camps. The results should be safer camps.
Most hazard tree accidents occur during storms. Storms do serve an important task. They "mop-up" hazards created by previous storms, but they also create new hazards. They remove weak trees and/or branches during a predictable time - the storm event. They also create additional hazards as well as weakened situations that may or may not wait for the next storm. Depending on the severity of the wound or break, a slight breeze may be all that is necessary to cause failure. Some of these failures occur during perfectly calm weather. Branches over a trail that are broken and being suspended by other branches - called "widow-makers" by woods-workers - are the most common of these. Trees leaning, with decay in their root systems, are a definite risk for unpredictable failure. In cases where there is decay, failure is on a definite schedule based on the weight of the hazard, the speed of the decay, and, of course, weather.
A tree's failure is seldom caused by one factor. Because there are so many factors affecting a tree's stability, there is always a level of uncertainty as to if, how, or when it will fail. There is certainty, however, that defective trees have a higher potential for failure than normal trees. Uncertainty is presented by the following variables:
- Weather - wind, snow, ice, and rain at different levels and combinations.
- A tree's characteristics - species, age, height, crown, sail, health, arrangement, and degree of lean.
- Pathogens - tree infections (Sometimes pathogens are hidden within the tree, or they may be very visible. Pathogens accelerate a tree's hazard potential.)
- Soils - the soil's structural makeup and the amount of moisture it is holding (e.g., rainwater lubricates soil, reducing its capacity to anchor a tree's roots).
There is often uncertainty about how or when a tree will fail, but we should not use this as an excuse to avoid treating the situation. If we know that an unsafe tree exists, it is irresponsible to leave its failure to chance.
A rating system is a good tool for managing hazard trees. It can alert us to potential problems and give us an idea as to the level of weakness or strength of a tree based upon its structure. A rating system is not infallible, but it can help predict a tree's potential for failure. Tree failure usually involves a combination of factors that do not necessarily present themselves in a predictable succession of events.
Besides alerting us, rating systems are good for recording data on trees with defects and for plotting the progression of such defects, but, more considerations are necessary for an effective management program. Good hazard tree management is to conduct a comprehensive analysis of the trees and their environment.
A Practical Program
A practical hazard tree management program recognizes three basic categories, or levels, of trees.
- Level One - trees that offer a clear and present threat; they can fail on their own.
- Level Two - trees that are defective, but those defects are not significant enough to present an imminent threat.
- Level Three - trees that are normal in health and structure.
All level one trees should be abated. All level two trees should be managed. A level two tree's defects should be analyzed, its potential targets should be determined, and choices should be weighed. Level three trees should be protected and managed in such a way as to keep them healthy and free from defects. The principle behind a hazard tree program is to first identify and remove those hazards that offer a clear, immediate threat, and then to create a management plan for the other trees.
Hazard Tree Management Plan
A good hazard tree management plan should be established by a professional or the most qualified people the organization has available. In some cases, a professional can train the staff, who then can write and manage the plan. The plan should start with goals and objectives, then field evaluations, and succeeding treatments, if necessary. The plan should be written with good records of activities and dates. Follow-up evaluations should be done on a routine basis, at least annually, as well as after all storms. A map of the facility is a necessary tool. It can specifically identify and record problem areas. Any tree within striking distance of a use area should be analyzed. The Hazard Tree Handbook, can be used as a guide (see the Resources at the end of this article).
Evaluations in areas with few trees can be done with a single survey. Evaluations in areas with a large amount of trees should be done in two phases. The first phase is to identify level-one hazards only. After those hazards are identified and treated, then a second survey is conducted to identify the level-two hazards. These trees will require the most considerations.
Decisions have to be made as to whether to remove, modify, monitor, or avoid. Specific evaluations should be made as to why the tree is less than normal, what the potential damage is, and what action is taken to prevent this potential failure or damage from occurring. Consider the following when conducting evaluations: dead trees; uncharacteristically leaning trees; dead branches; disease and/or damage to the roots, bole, and crown; mushroom-like growth anywhere on a tree; cavities and holes; thinning foliage; cracks and splits; oversized limbs; and dead or broken branches on the ground.
After level-one hazards are removed, proper evaluations, considerations, decisions, and planning for the remaining trees can begin. The level three, or normal, healthy trees should be evaluated for whatever outside factors can affect them (e.g., fire, disease, other trees, and damage from people and their various activities). Protective measures to preserve these trees should be considered.
The age of the tree is a very important factor. As an example: During the 1920s and 1930s most of western Washington State was logged for its timber. About a third of this logged area naturally regenerated to Red Alder. The lifespan of Red Alder is sixty to eighty years. Today in the year 2002, there are many camps functioning among these over mature, dying, and dead trees, and accidents are happening. Some camp staff prudently treat the situation, and some feel that no action is necessary.
It is important to know the age of the trees in your camp and the expected lifespan of these species. As trees approach maturity, branches start to die and fall, the root systems begin to fail, disease has had a chance to wreak havoc and earlier defects are now poised for failure.
Adjacent trees can present information about any tree under consideration. Some diseases spread from tree to tree. Insects attacking certain trees can move to other trees. Activities, such as roads, trail, and campsite construction and maintenance, can damage trees - particularly the roots and lower bole. It is almost a sure thing that one pathogen or the other will infect any exposed wound, resulting in a progressively weaker tree.