Modelling The Risk Of Windthrow For BetterForestry Decisions

Abstract

A rationale for providing decision support in complex situations by the use of computer models is outlined and exemplified with the hazard windthrow in forestry. A presentation of a system of models for formal assessment of the risk of windthrow is included. The risk of windthrow depends on the stability of the trees, and the frequency of occurrence and magnitudes of strong winds (exposure). Our approach to model the risk of windthrow is centred on these aspects and includes i/ a modified version of the Finnish model HWIND used to calculate the stability of the forest stands, ii/ a model for parameterising aerodynamical properties of the landscape surrounding each individual forest stand, and iii/ the Danish exposure model WA^P for simulating the distributed wind climate over the terrain in terms of probability distributions for wind speeds in different wind directions. For the system of models, predicted windthrow compares well with recorded landscape level distribution of windthrow. The system of models will be used to provide more reliable estimates of the risk (probability) of windthrow than can be made without the models. These estimates will be used for evaluating silvicultural treatments and forestry planning activities in relation to the risk of windthrow under present and future climatic conditions. In this way the uncertainty in the decision situation may be reduced and the possibility for reducing the risk (probability) of windthrow in forestry can be explored. Risk Analysis II, C.A. Brebbia (Editor) © 2000 WIT Press, www.witpress.com, ISBN 1-85312-830-9