In this lesson, participants will:
- know how aerial photographs, forest cover and topographic maps can
be used within a GIS environment to produce landscape-level maps of
This lesson contains 10 pages. It introduces the methods and results
of a GIS-based process for building empirical models and hazard maps
of windthrow risk. The major steps and information sources used are
summarized below. As well, read the linked reference
articles for additional background information.
There are three basic approaches to windthrow risk assessment: observational,
mechanical and empirical. The diagnostic framework used in the FS 712
Field Cards and introduced in Lesson 2 of this course extends the observational
approach by adding calibration and feedback steps. This makes it semi-empirical
Using the capabilities of GIS for assembling large datasets, empirical
models of windthrow risk can be built using stand-level information
contained in forest cover maps and topographic maps.
Once models are built, they can be entered into the GIS for production
of landscape-level maps. The following screens describe the process
and results of a study on northern Vancouver Island. Read the paper
by Mitchell, Hailemariam and Kulis
for background on this study.
The purpose of presenting this method in this course is to make participants
aware of the potential of using GIS to build empirical models and maps,
and to set the stage for a development planning exercise. Most forest
companies are now using GIS for drafting, but few are using them for
analysis. Even without building empirical models, maps of windthrow
patterns are very useful for observational evaluation of windthrow risk,
and can contribute to improved planning by identifying orientation and
recurrence of damaging winds, and locations subject to recurring damage.