Preparing Your Urban Forest for Storms

ARTICLE | Feb 13, 2017

Tips on How to Minimize Damage

Figure 1. A Certified Arborist Demonstrates Performing a Level 2 Inspection.

From my experience working with local governments, storm preparation is usually a huge concern among all residents and all departments. Urban forestry can be a concern, too.

When a storm event occurs, tree debris is often one of the first things a community must focus on. Trees can fail and when they do, they impact roadways, utility lines, street lights, intersections, personal property, and people.

Before power can be restored and primary responders can do their jobs, trees will need to be pruned, removed, and cleaned up. While it is impossible to be completely prepared for a storm incident, it is possible to be ready to react and minimize negative impacts from tree damage.

Your community's urban forest is made up of both public and private trees, and they are an important part of the community's infrastructure. Urban forests provide a host of environmental functions and services—from avoiding stormwater runoff, reducing energy consumption, increasing property values, absorbing CO2, and improving the quality of life in a community.

Unlike other components of a community's infrastructure, trees and urban forests continue to appreciate in value as they age and get larger, therefore increasing environmental functions and services.

Within a community, there are these two types of trees: assets and liabilities. Assets are trees planted in the right place for the right reason that do not pose an unacceptable level of risk to the community. Liabilities are trees posing an unacceptable level of risk to the community that do not provide an environmental function.

Dealing with a storm involves three distinct phases. The initial phase is all about preparation before the storm. The second phase is what you are doing during the actual storm, and the third phase is cleanup following the storm event.

The Calm Before the Storm

At the most basic level, an urban forest that is prepared for a storm event will be more resilient. This will save time and money, as well as provide a service to residents who do not have to live with the disruption and destruction from tree damage.


Tree risk assessments. Trees cannot be made to be 100 percent safe all of the time. However, they can be made safer by conducting tree risk assessments, which should be a component of every community's urban forest management plan.

Three levels of tree risk assessment can and should be performed throughout a community.

Level 1 inspection is a simple drive-by or walk-by "windshield" survey done annually. Level 2 is a 360-degree inspection taken from the ground level without the use of specialized equipment (see Figure 1).

Level 3 inspection is also 360 degrees but involves such specialized equipment as an aerial lift, drone, or Resistograph.

There are other types of tree risk assessment protocols but the most common one is the newest best management practice (BMP) developed by the International Society of Arboriculture (ISA). This methodology evaluates the "condition of concern" of a whole tree, branch, or trunk. The ISA BMP methodology evaluates:


• Likelihood of failure.

• Likelihood of impacting a target.

• Consequences of the failure.

By conducting a regularly scheduled tree risk assessment, work can be prioritized and trees identified as posing the most risk. Trees with the highest risk rating should be prioritized for such maintenance as removal, pruning, or cabling and bracing.

See the Elgin case study to find out how proactive risk mitigation can save you time and money.

Response and Recovery Plans

As noted earlier, one of the first issues that needs to be addressed when responding to a storm is clearing the streets and power lines from downed trees. Communication is key to ensuring that priority services are restored as soon as possible.

Most communities probably have some type of emergency response plan or system in place, but few incorporate an urban-forest-specific response plan.

The primary challenge from an urban forestry perspective with these types of plans is that once the initial cleanup is completed, there usually remains a large amount of debris and work that needs attention.

Roads and power lines are cleared, but homeowners and the community still need to clear out all the other debris. A good recovery plan incorporates opening priority streets and managing remaining debris. This can include setting up debris collection areas, renting specialized equipment like tub grinders, and bringing in contractors or using staff from other departments to help with cleanup.

One tool that can be useful for predicting how much debris a storm may produce is i-Tree Storm. This is free software created by the USDA Forest Service and can be found at

i-Tree Storm uses 2 percent of random street segments to inventory trees more than six inches in diameter and within 50 feet of either side of the right-of-way. By using the software, a community can better predict how much debris will need to be cleaned up.

Response and Cleanup

The cleanup after a storm event can take anywhere from a couple of days to several weeks, depending on the severity of the storm and the condition of the urban forest. One of the first steps that a community should take once a storm has passed is to conduct a Level 1 Rapid Assessment.

A qualified certified arborist can conduct this windshield "inventory" to properly identify immediate high-risk trees. This assessment should be done on all public streets and properties affected by the storm.

The Texas Forest Service has developed a free Level 1 Tree Risk Assessment mobile app that can be found at an app store and at Google Play. Additional information can be found at

If the storm is too large for your community to adequately respond, there is a high likelihood that the Federal Emergency Management Agency (FEMA) will be deployed. The U.S. Forest Service, in partnership with several state agencies, has also developed the Urban Forest Strike Team. UFST crews can be deployed immediately following a storm to assist communities in need that don't have staff with urban forest management expertise to reduce unnecessary loss of urban tree canopy.

UFST was created because trees are often removed that could have recovered and hazardous trees that should have been removed were retained. The team can help avoid these types of mistakes.

Elgin, Illinois, Case Study

In 2007, Elgin, Illinois, experienced two separate 70 mph wind events in a 24-hour period. These events generated more than 130 telephone calls and took three city tree crews and two contractor crews a total of seven days to respond to the calls.

In 2009, Elgin conducted a street and park tree inventory of its 60,000 trees and prioritized maintenance activities. Using American Recovery and Reinvestment Act monies, the city systematically implemented a risk reduction plan to remove 800 of the highest liability trees.

In 2010, the city was struck with an identical storm as the one in 2007, but this time, only 32 calls were received and two city crews handled all the calls in less than 24 hours. The city received 100 fewer calls and saved 765 man hours because of its proactive maintenance program.

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