WINDARC - Classification of wind damage risk
The authors present results of a long-term research of a wind damage risk based on historical facts and mathematical models. The classification of a wind damage risk represents a final phase in the determination of wind damage risk localities. The damage risk is divided into a permanent damage risk and a temporary damage risk. Defining permanent risk areas is based on the existence of factors that cannot be influenced by man (the character of the soil, terrain and all climatic factors. Permanent Exposure Classification (PERMEX) is created by integrating Terrain Exposure Classification (TEREX), which evaluates the terrain exposure to wind, and Partial Model of Damage Risk Based on the Soil.
The final WINDARC classification results from combination of the PERMEX classification and Combining Partial Model of Damage Risk Based on the Forest Stand. Each section of stands within the examined area is ranked by the rate of wind damage risk into a corresponding class of WINDARC classification. Stands ranking into wind damage risk classes 1-4 are considered relatively stable and the wind damage risk is rather low in them. The danger of calamities rises with the damage risk classes 5-6. Stands classified into the 5th class of wind damage risk are threatened sporadically. Mostly there occur only single fallen tree or a group of windfalls caused by local anomalies (like local soil disposition or rot), area wind damages are rare. The risk exposure is up to 30 %. The wind damage risk further grows in the class 6. The cutting interventions should be pursued respecting the risk exposure about 50 %. In such classified stands wind damages occur over larger areas (about 0.5 ha). The damage risk classes 7-9 represent a significant danger of wind damages, which grows naturally with the class 9. In the class 7, the risk of calamities ranges between 60-70 %. In classes 8-9 of wind damage risk the hazard of wind damage damage ranges between 80-100 %. Then the occurrence of a calamity in stands classified like this depends just from the probability of a climatic situation causing the wind damage. The scope of the wind damage depends from the intensity and character of the airflow. The protection of stands in these risk classes is very questionable and often consists above all in a passive approach meaning the man's intervention should not worsen the wind damage risk. The research results were presented at IUFRO international conference Wind and Other Abiotic Risks to Forests on August 10 -14, 1998. There also were presented the results of the STORMS project pursued in selected EU countries since 1994. The aim of all involved researchers is to establish a long-term forestry strategy of forest management that would ensure as good timber quality as possible along with a maximum decrease of wind- and snowbreak risk. The participating countries strive to create their own national programmes respecting their local conditions and specificity. The results presented by the authors allow their practical application in forestry management.
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