Windthrow

We had expected a strong wind, and we had no idea what to expect. NOAA forecasts indicated a front with steep pressure gradients. We had bought the house among the tall trees only a few months before. The wind had always been muted among the Douglas-fir and Western Red Cedar, passing distantly through the crowns of trees several hundred feet tall and several hundred years old. We had never experienced a windstorm among the trees. Until that night.

That night the wind raged among the trees, demented. Branches broke with the sound of small arms fire; entire trees fell to the ground with the sound of artillery. That night the sky was at war with the earth.

In the morning the ground was concealed beneath layers of sheared Olympic_Blowdown_3evergreen branches. Both roads leading to the highway were blocked by downed trees, some tightly entangled as if for support but overtaken by the same fate. Houses had been stove like wooden hulls dashed upon the rocks. Enormous trees littered the ground, sticks scattered in a children’s game. Until that morning I hadn’t realized the vulnerability of trees.

Trees don’t always die singly. Sometimes entire forests die in a single tempest. In January 1921 a windstorm swept the Olympic Peninsula and felled billions of board feet of timber, the equivalent of 20% of the annual US consumption by one estimate; enough lumber to build 600,000 wood frame homes. There was an eye witness.

We left the machines and started to run down the road toward a space in the forest where the timber was lighter. Just after leaving the car, I chanced to look up and saw a limb sailing through the air toward us; I caught Mrs. Hill by the hand and we ran; and instant later the limb, which was about 12 inches in diameter, crashed where had stood. In three or four minutes we had climbed over two immense tree trunks and reached the place in which I thought was our only chance to escape serious injury or possibly death. The southeast wind roared through the forest, the falling trees crashed to the ground in every direction from where we stood. Many were broken off where their diameter was as much as 4 feet. A giant spruce fell across the roadway burying itself through the planks within 10 feet of where we stood. Three tops broke off and sailed through the air, some of the trees fell with a crash, others toppled over slowly as their roots were torn from the earth.

Huge stands of hemlock were “literally torn from the ground and tossed into impenetrable tangles.” An entire herd of 200 Roosevelt elk were killed by falling timber. The storm was afterwards known as the Olympic Blowdown of 1921.

It’s called windthow by scientists who study the destructive effect of wind upon trees but blowdown is still the common Olympic_Blowdown_2name in the Pacific NW. Windthrow can result from any number of reasons: weakness induced by disease; reduced holding power of saturated soil; shallow root structure; the impact of falling trees; or the overwhelming strength of the wind. During the Olympic Blowdown the winds were measured in excess of 100 miles per hour – hurricane strength.

Now when I hear the wind moving through the canopy of tall trees, when I see the trees bend and sway in the wind, I think of them differently. Once I thought them impervious. Now I know they’re vulnerable, individually and en masse. Now I know that living among them is both a cause for wonder and concern.

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