How trees withstand a storm

Sep 12, 2011
Mark Rudnicki, associate professor of forest ecology. (Jessica Tommaselli/UConn Photo)

As Hurricane Katia slowly approaches the East Coast, many people are still cleaning up from Hurricane Irene, whose high winds last week caused trees to fall, leaving millions without power.

“If you want to understand how trees fall over, you have to understand their mechanical properties and the loads they experience,” says UConn associate professor of forest ecology Mark Rudnicki. While many trees fell during Irene, the vast majority didn’t “because trees have a lot of ways to stay up,” he says. Rudnicki’s research includes studying some of the mechanisms by which trees stay up.

Inside of a forest, the main way trees withstand heavy wind loads is by colliding with nearby trees, explains Rudnicki. Trees also streamline – adapt their shape to the wind flow and effectively have a smaller sail – reducing the wind force that is applied and thus decreasing their risk of falling.

Another, more permanent strategy to streamline is to shed branches in the wind. “After Irene, I noticed stiffer trees such as oaks lost branches, but did not see many completely fail,” Rudnicki says.

With Katia looming near Bermuda, the main threat of more power outages is still trees, he notes. With so many trees towering over power lines in Connecticut, even with homeowner permission it would be very expensive to remove them, he says.

“I think homeowners are reluctant to allow professionals to remove or even trim their trees because we love our trees – just the way they are,” Rudnicki says. However, when a falling tree is very likely to hit a power line, its risk rating goes way up. If we focus on the fact that extreme winds are relatively infrequent, then we probably perceive the risk as too low.

It is fortunate that Irene had become a tropical storm by landfall, adds Rudnicki. The 1938 hurricane hit Connecticut as a category 3, and retained hurricane force winds all the way to Quebec. A repeat of that would cause unprecedented tree-related power outages and would take much longer to clean up, he says.

Even though arborists and urban foresters have a rigorous approach to assessing hazardous tree defects that can be used to reduce risk, it is very difficult to predict the failure of an individual tree. with no hazardous defects still fail, says Rudnicki, and we need to make progress in this area.

Explore further: Giant anteaters kill two hunters in Brazil

add to favorites email to friend print save as pdf

Related Stories

The Dynamics of Forest Canopy Motion

Jan 29, 2010

(PhysOrg.com) -- While it’s well known that wind causes trees to sway, it’s less widely recognized that the movement of the trees in turn affects the wind. Mark Rudnicki, an assistant professor in the ...

Judge rules for Floridians who lost trees

Dec 11, 2007

A Palm Beach, Fla., circuit court judge has ruled in favor of homeowners who lost citrus trees when the state tried to halt the spread of canker disease.

Recommended for you

Giant anteaters kill two hunters in Brazil

Jul 26, 2014

Giant anteaters in Brazil have killed two hunters in separate incidents, raising concerns about the animals' loss of habitat and the growing risk of dangerous encounters with people, researchers said.

Study indicates large raptors in Africa used for bushmeat

Jul 24, 2014

Bushmeat, the use of native animal species for food or commercial food sale, has been heavily documented to be a significant factor in the decline of many species of primates and other mammals. However, a new study indicates ...

Noise pollution impacts fish species differently

Jul 24, 2014

Acoustic disturbance has different effects on different species of fish, according to a new study from the Universities of Bristol and Exeter which tested fish anti-predator behaviour.

User comments : 0