On a steep slope the number that governs is side slope, not grade. A machine can climb far more than it can safely traverse, and machines go over sideways, not backwards. Everything else follows from that: the work is planned across the fall line, production drops to roughly half of the equivalent flat site and sometimes a third, and the machine selection shifts toward low-ground-pressure tracked carriers or remote-controlled units where an operator on board is not acceptable. Wet soil is the condition behind most slope incidents, so the window is dry and firm, not frozen. Ice removes traction exactly where it is needed. Removing vegetation from a bank can reduce its stability instead of improving it, so the erosion plan is part of the clearing plan. Nothing in a photograph, a contour map or a slope percentage makes a slope safe to work; only an on-site assessment does.
The short answer
A slope that looks workable in a photo may not be safe or productive in person; every steep site needs field assessment.
| Measurement | Why it decides the job |
|---|---|
| Fall-line grade | Sets whether a conventional machine can climb it at all |
| Side slope | The number that governs stability: machines tip sideways |
| What lies below the work | A house, road or stream downhill changes method, not just caution |
| Soil and ledge | Traction and whether the head can reach grade |
| Wetness and seeps | The most common condition behind slope incidents |
| Escape route and turnaround | One way in and out is worked very differently |
| Overhead hazards | A hung limb over a slope is a separate job first |
Test access and slope in the field
Measure both fall-line grade and side slope. Show what lies above and below the work, loose rock, ledge, stumps, wet seams, overhead hazards, turnaround, and escape paths. A machine that can climb a slope may not be able to work or exit it safely.
The sequence, in order
- Photograph the slope from the side, from across the valley if possible.
- Measure side slope as well as fall-line grade.
- Identify everything downhill of the work zone.
- Check for seeps and soft seams after rain, not in a dry week.
- Confirm a turnaround and an escape route exist.
- Plan stabilisation for the first heavy rain after the work.
What goes wrong
- Photographing a slope from the top, which flattens it completely.
- Treating fall-line grade as the whole answer.
- Working wet.
- Assuming clearing a bank makes it more stable.
Vermont's logging water-quality rules and steep-slope clearing
Steep clearing that also removes timber can fall under state forestry rules. The Department of Forests, Parks and Recreation explains that the Acceptable Management Practices for Maintaining Water Quality on Logging Jobs were adopted as rules under Vermont's water quality statutes in 1987 and revised effective August 11, 2018. They govern the parts of a steep job that move water: skid trails, water bars and stream crossings.
Some towns have folded the same practices into their own bylaws. Killington, for example, requires development to comply with them as a minimum. The practical step for a steep site is to ask the county forester whether the job counts as logging, and to write the grade limits, the drainage spacing and the stream-crossing method into the scope before the machine leaves the trailer.