Storm Damage

[Buzzsurgeon]

I have had more call outs in the last two months for storm related tree damage that the last 15 years put together.

 

Yew, copper beech, cherry, chestnut, willow, cedar, plum, poplar all limbs torn off or left hanging.

 

Cherry and robinia wind thrown

 

These are just the ones I can rember off the top of my head I am sure there are others.

 

Has anyone else had a run of call outs?

[Marcus B-T]

This is sort of the subject of a seminar I gave recently and which will be published in a paper.

 

It is like this. Failures as we all know are complex things. The complexity comes about becasue it is not enough that a tree is decayed at any point for it to fail. A fialure comes about due to a coincidence of factors and events. This is why we talk about likelihood of failure rather than probability of failure.

 

Suppose we have X number of trees in a population that are all equaly decayed such that a wind force of sufficinet strength would cause them to fail in a similar way. The first thing that must coinside for the failure to occur is that the wind forces must be present, i.e. no significant wind no failure. Next the wind must get to the tree, so if the tree is even partly sheltered then the tree may not be hit by sufficient wind load to cause the failure. If the wind is only just sufficient then only the most exposed examples will be at risk. Next the sufficient wind forces have to be captured so the smaller, more compact the tree the less likely it is to fail. Lastly the seasonal timing of the event is critical. A deciduous tree is less likely to fail when its leaves are gone, an evergreen tree in mixed woodland is more likely to fail when surrounding trees have lost their leaves. This is just the basics there are other factors and scenarios based on the type of failure.

 

What we have had this year is very lush canopies casued by the harder winter increasing available N because basically the grass and other things that usually lock up N stopped growing over the wihter period as they should do. This combined with storms at a time of year when we shouldn't have them, saturated soils, and storms from unusually directions such as the North North East. It is a regional thing though. Interestingly there has been a drop off in Horse Chestnut Failures where there is Leaf Minor present, no leaves left to capture the wind.