Slope is also an important factor that limits the harvest area. WorkSafe BC’s OH&S regulations limit the use of rubber-tired skidders to a maximum ground-slope of 35% or less. For machines with tracks such as feller-bunchers, hoe-excavators, and crawling tractors – a ground-slope limit of 40% or less is set. Finally a hard limit of 50% or less, is set by WorkSafe BC for all other forestry equipment specially designed to work under steep-sloped conditions. On sites where the ground-slope exceeds 50%; cable-yarding, helicopter-logging and hand falling must be used to preserve the health and safety of working personnel (OH&S Regulations, 1998). Besides, steep slope should also be protected for carbon sequestration and risk management. With all these factors being considered, we decided to exclude all areas have a slope higher then 40%.

Map 6. Slope distribution

As can be seen from the map 6, 100% of our AOI has a slope under 40%. Therefore we set relatively flat land (0 to 10% slope) to be more preferred (given a weight 2), while areas with significant slope levels (10 to 40 %) to be less preferred (given a higher weight 1).