Forest Investment Account

Abstract of FIA Project 6065003

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Windthrow Hazard Mapping using GIS, Weyerhaeuser Stillwater Timberlands

Author(s): Mitchell, Steve
Subject: British Columbia, Forestry, Silviculture/Forest Management Systems, Technology/GIS/Modeling/Remote Sensing
Series: Forest Investment Account (FIA) - Land Base Investment Program - Innovative


Damaging winds impact seriously on the intent and implementation of integrated resource planning. In BC, the coastal region is most affected and there has been a history of wind damage in Weyerhaeuser's operations on Vancouver Island and the adjacent mainland. Windthrow occurrence along cutblock boundaries was mapped using aerial photographs. Using ArcView Geographic Information System (GIS), buffers 25m deep were created adjacent to cutblocks harvested between 1990 and 2001 for 5 sample mapsheets. Each of these buffers was divided into 25*25m segments. A total of 14,000 forested segments were obtained and used to study the relationship between cutblock edge windthrow and other stand level variables within the Stillwater operating area (TFL 39 Blocks 1 and 5, Powell River). Ten percent of segments had at least 40% of segment area damaged and 20% loss of canopy. Cedar dominated stands suffered the least windthrow compared to those dominated by other species. Segments with high topographic exposure, windward facing boundaries, boundary projections, taller stands, and stands with higher site index were more likely to be wind damaged. Regression models were fit using stand, site, ecosystem, wind and management variables to predict probability of damage. The best-fit models had a predictive accuracy of 72%. One of these models was selected to produce windthrow hazard maps for Blocks 1 and 5 of the operating area.

For further information, please contact Steve Mitchell, University of British Columbia (

Updated September 08, 2005 

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