On early Sunday morning I awoke to the sound of heavy rain beating
down on my bedroom skylight. Still half-asleep,
I remembered that it was “Hurricane Day” – the day when Hurricane Irene was
predicted to make landfall in New York.
For the first time in over 25 years, NY was going to experience a direct
hit, and everyone was scrambling around in hurricane-mode. The news and weather service had implored
everyone days earlier to make necessary preparations and abide by mandatory evacuations
– evacuations that affected 370,000 people in NYC and many more on Long Island. Our place was not in any of the flood-prone areas,
so thankfully we were able to stay. But
that didn’t mean we were immune from damage, so in the days prior, we too made
our preparations, getting everything off our back deck, making sure we had
flashlights and candles, and lowering the temperature of our fridge so that
food would be less likely to spoil in the event of a power outage.
Photo: Our Japanese Zelkova lost only dead limbs and some leaves during the storm, Commack
So with much hesitation, build-up, and excitement, I got out
of bed Sunday morning and cautiously peered out the rain-splattered window. Outside, I saw Irene - an impenetrable layer
of dark gray clouds from which rain poured down ferociously. Her winds swept the limbs of our mature White
Pines upwards in great gusts and made them look like they were dancing Christmas
trees. I looked out at our Japanese Zelkova
and watched its branches move about its trunk in strange oscillations. “Eh, not so bad out,” I thought to myself and
went back to sleep, glad that the cataclysmic, doomsday scenario that was
building inside my mind had not come true.
In the days after Irene, I learned bits and pieces of
information about the hurricane’s impact, and I also learned how cut-off from
the world I felt with no electricity for 52 hours! (Good thing we had those
candles!) But I cannot complain when half a fridge full of groceries was our biggest
loss. As I drove around Long Island, I
realized that many others were not so fortunate. In Garden City where my parents live,
breath-taking oaks that had stood the test of time, were lying in ruins across
streets, cars, and houses. In only a
five block area, I counted at least 10 mature oak trees down. My parents’ house was spared, but many of the
neighbors I grew-up with were not as lucky.
70 ft. tall trees that I had walked past in elementary school fell over
as easily as toothpicks, leaving a wake of destruction. The town arborists were working round the
clock to get the streets clear.
Photo: A mature, healthy Pin Oak crushes home and car, Garden City
I stared at a house a few homes down from my parents’ that
was crushed by what had been an enormous Pin Oak (Quercus palustris). The roof
was caved in and branches and leaves were now part of their living room décor. Somehow the tree had also managed to crush
their car. “Why did this tree fall?” I
wondered to myself. Trees that are
unhealthy and have root or trunk decay are pre-disposed to failure during
high-wind events. But this tree was
healthy and had no decay. Trees that
endure root severance from recent construction or sidewalk replacement are also
pre-disposed to failure. But this
sidewalk was maybe 15 years old and no construction had taken place. “It must be that the root system was uneven,”
I thought, since there were more roots in the lawn area than under the
concrete. But then I looked down the
block and saw another toppled Pin Oak that had had a vast area for its roots to
grow. Why did so many trees fall for
what seems like no good reason??
Photo: More oaks windthrown by Hurricane Irene, Garden City
According to the National Weather Service, 4 inches of rain
fell on Sunday in Central Park and the highest wind gust speed recorded at
LaGuardia airport was 67 mph. Typically lasting
for about 20 to 40 seconds, wind gusts create a complex sway motion in the branches
of a tree as the limbs move out of step with one another. This movement helps prevent the tree from
developing a dangerously large, pendulum-like sway. But if the branch movement does not use up or
dissipate enough energy, the energy can be transferred to the main trunk which if
a sufficient force can topple the tree (James, K. 2003. Journal of
Arboriculture 29(3)). Saturated soils
and high winds from Irene were simply too much for some of our trees to endure.
Photo: Trees that have structural defects like this root girdled Red Oak (Quercus rubra) are pre-disposed to failure during high wind events, Garden City
Researchers have found that some tree species are more
adapted to withstand hurricane-force winds than others. After studying urban trees that survived
devastating hurricanes in Florida, it was found that certain qualities made
some trees more wind-resistant. Losing
leaves during the hurricane meant higher survival; native trees showed better
survival than non-natives in some studies; tree species with a higher wood
density had a higher survival rate; and surprisingly, decurrent trees with a
spreading branch habit had significantly higher survival compared with
excurrent trees with an upright, single straight trunk habit (Duryea et al.
2007. Arboriculture and Urban Forestry 33(2)).
This type of excurrent branch habit combined with saturated soils and
high winds may have led to the Pin Oaks’ downfall.
Although the climate and soils are obviously very different
in Florida, a list of Wind-Resistant Trees compiled by Florida researchers may
prove to be useful here. When
re-planting your fallen trees, consider planting trees with the highest or
medium-high wind resistance and avoid planting trees with medium-low or lowest
wind resistance. (From Urban Forest Hurricane Recovery Program series, Chapter
5 – Wind and Trees: Lessons Learned from Hurricanes, by Duryea and Kampf). For more information, visit The University of
Florida’s Trees and Hurricanes webpage at: http://hort.ifas.ufl.edu/treesandhurricanes/index.shtml
Tree Species with the
Highest or Medium-High Wind Resistance (NOTE: tree species that only grow in the
north were not included in the study)
Acer palmatum,
Japanese maple
Betula nigra, river birch
Carpinus caroliniana, ironwood
Carya glabra, pignut hickory
Carya tomentosa, mockemut hickory
Cercis canadensis, red bud
Chionanthus virginicus, fringe tree
Cornus florida, dogwood
Diospyros virginiana, common persimmon
Ilex glabra, inkberry
Ilex opaca, American holly
Lagerstroemia indica, crape myrtle
Liquidambar styraciflua, sweetgum
Magnolia grandiflora, southern magnolia
Magnolia virginiana, sweetbay magnolia
Magnolia x soulangiana, saucer magnolia
Nyssa sylvatica, black tupelo
Ostrya virginiana, American hophombeam
Quercus shumardii, Shumard oak
Quercus stellata, post oak
Taxodium distichum, baldcypress
Tree Species with the
Lowest or Medium-Low Wind Resistance
Acer negundo,
boxelder
Acer rubrum,
red maple
Acer saccharinum, silver mapple
Celtis laevigata, sugarberry
Celtis occidentalis, hackberry
Fraxinus pennsylvanica, green ash
Morus rubra,
red mulberry
Platanus occidentalis, sycamore
Prunus serotina, black cherry
Quercus alba, white oak
Quercus phellos, willow oak
Salix x sepulcralis, weeping willow
Ulmus americana, American elm
