Windstorms are natural disturbance agents in forests playing a role in
natural forest regeneration. In Finland, the most severe individual
windstorms have commonly damaged 2–4 million m3 of timber. In addition
to financial losses caused to forest owners, windthrown trees have in many
cases seriously disrupted the functionality of the national power grid.
Communicating windstorm risks in duty forecasting is difficult. In this
study, we aimed at developing windstorm impact estimates for forest damage in
Finland to help the forecaster to improve communication of the risks of
windstorms. We have compared the volume of forest damage caused by the most
intense windstorms in Finland during the recent decade to the observed
maximum inland wind gust speeds associated with the same windstorms. It was
found out that the volume of forest damage follows approximately a power
relation as a function of wind gust speed with a power of ∼10. This is
a tentative estimate because of a short time series and small number of
inspected windstorms. Moreover, also wind direction, location of the affected
area and soil properties among other factors have an impact to the amount of
damage as illustrated in our inspection. Despite the shortness of the time
series, we believe that our results demonstrating the steep increase in the
impacts of windstorms with an increasing windstorm intensity are valuable.
However, more detailed investigations with longer time series are needed in
order to more specifically communicate the windstorm risks and their impacts
in boreal forests.</p
