Hazard Tree Safety

The C&O Canal National Historical Park welcomes millions of hikers, bikers, campers, horseback riders, and history enthusiasts each year. The park is also home to over 6.5 million trees. To ensure visitor safety, the National Park Service employs a comprehensive tree management strategy designed to protect people while preserving the towpath, structures, and a sustainable ecosystem.   

Keep Your Safety a Priority

Falling branches, limbs, and trees can cause hazardous conditions, and may pose risks to life and infrastructure, especially in developed areas. While in the park, please remain observant of your surroundings, particularly in campgrounds, picnic areas, and while on the towpath or other trails. Branches and trees may fall whether or not they are dead, and when there is no wind.

• Be Aware

Be aware of your surroundings. Trees, limbs, and branches can fall at any time.

• Be Attentive

Be attentive while hiking and biking, looking up and around regularly, especially during high winds.

• Be Cautious

Be cautious when selecting a place to park, camp, picnic, or rest. Look for dead, cracked, broken, or hanging branches, or under trees that are rotten at the base or have cracked bark peeling off the trunk.

What is a Hazard Tree?

A "hazard tree" is a tree, either alive or dead, that has a structural defect which makes it likely to fail (in part or entirety) and strike a person or property..

Each year, the park assesses trees for defects and trims or removes trees that pose direct risk to life or infrastructure from developed areas such as campgrounds, picnic areas, the towpath, and housing areas.

This routine maintenance of our trees helps us keep our visitors safe while promoting a healthy ecosystem and protecting the park’s natural and historic features.

Unfortunately, trees without apparent defects also fail, and tree hazards cannot always be immediately identified and abated or mitigated. Catastrophic tree failures can lead to serious injury or death and cause millions of dollars in property damage.

Tree Mortality

Tree mortality simply refers to the death of trees in a forest. Tree mortality is a natural process that often benefits a healthy forest ecosystem. Trees die due to naturally occurring events such as forest succession, storms, high water, floods, insect related mortality, and age-related weaknesses. Recently, many common tree species in the park are facing threats from invasive insects and diseases, including oak, beech, and ash trees. Dead trees, whether standing as a snag or on the forest floor as woody debris are essential habitat for certain woodland species.

However, these conditions can also create dangerous situations that may impact visitors and property. Many factors are taken into consideration when the arborists estimate the potential for tree failure and the damage that such failure could cause. The entire process of rating hazard trees is a thorough, systematic survey by knowledgeable inspectors.

Hazard Trees and Risk Management

The existence of dead and dying trees is part of the natural scene across the park. Given the nature of the park's mission, management objectives, and funding, it is not possible to completely eliminate the risks from falling trees or limbs. The purpose of hazardous tree management is to reduce the threat of falling trees in areas of the park where the highest number people and property are at greatest risk.

Tree Management Guidelines

The park follows National Park Service’s Management Policies for visitor safety. Further guidance for vegetation management within the National Park Service is contained within Director’s Order #77 “Natural Resource Management,” and Director’s Order #28 “Cultural Resources Management Guideline,” and their accompanying guidelines.

All work is undertaken by qualified people, and tree work follows accepted industry guidelines and standards, such as the International Society of Arboriculture and the Tree Care Industry Association for the assessment and removal of trees deemed a hazard to visitors.

Tree Inspections

Visitor safety in the park is our top priority. The main reason for removing hazard trees is to ensure visitor safety as they enjoy the park. When our arborists are assessing trees in the park, it is a root to leaf examination. Sometimes trees that appear healthy to the untrained eye can present a hazard.

Some of the factors they consider are:

• The location of the tree, and the likelihood of a tree failure striking a target.
• Whether the tree is live or dead.
• The amount of dead, broken, or free-hanging branches.
• Whether there is evidence of recent weakening of co-dominant stems or dead, forked, or multiple tops.
• If there are wounds, injuries, exposed or damaged roots, and associated decay or defect anywhere on the tree.
• The lean of a tree and factors that contributed to the lean.
• If there is evidence of lethal or weakening root, stem, or branch disease or insect infestation and, if so, to what extent.
• Any potential damage caused by human activities.

All these factors are taken into consideration when the arborists estimate the potential for tree failure and the damage that such failure could cause. The entire process of rating hazard trees is a thorough, systematic survey by knowledgeable inspectors. While some hazard trees can be treated without their removal, others must be removed in order to protect visitors from falling branches, limbs, and trees.

Marks of Trees (Paint, Ribbons, Tags, etc...)

There are many reasons a tree in the park might be marked or flagged. Paint marks often indicate that a professional arborist has rated a part or the full tree as a hazard during a thorough, systematic survey. This routine maintenance of our trees helps us keep our visitors safe while promoting a healthy ecosystem and protecting the park’s natural and historic features. Marking occurs in advance of treatment, so visitors may see marks on trees well in advance of any action.

Sometimes ribbons are put up by visitors without park approval for remembrance or geocaching; other times trees are illegally graffitied. Paint, ribbons, or other markings can be reported to the park to determine if they are park-approved.

Remember that not all tree markings indicate that a tree will be cut down or removed. Some markings are a sign that the tree needs to be pruned. Pruning may have occurred, and the mark might still be visible as the tree grows. The marks do not hurt the tree and will fade with time. While some hazard trees can be treated without their removal, others must be removed in order to protect visitors from falling branches, limbs, and trees. 

Environmental Impact

The park endeavors to preserve as many trees as possible in accordance with policy, conservation best practices, and sound principles of risk management. The park does not remove every tree with defects. Instead, the park focuses necessary removal efforts on areas with high visitation, such as the towpath or popular trails.

When trees are removed, the park works to protect the natural environment as best as possible. In certain areas, the park leaves dead trees on the forest floor to facilitate decomposition. Fallen trees provide habitat for animals and mulch for future understory plant growth.

In areas where the park conducts hazard tree removal, the park considers the need for replanting trees or other vegetation. When replanting is deemed appropriate, plantings consist of species that are native to the park or that are historically appropriate for the period or event commemorated.