roadWelcome to the third post in our Planning Your Road Network series. In our first post, Stand Tending 101: Planning Your Road Network, we outlined some basic steps to help determine what your road needs are and how to plan your road network.

The second post, Planning Your Road Network (PartII)—How Much Can You Do?, highlighted some of the decisions you need to make about hiring contractors and deciding what equipment to use.

Once you’ve thought through all those steps it’s time to think about construction.

Road construction begins with clearing of the right-of-way. All saleable wood from right-of-way clearing should be recovered, and tops, branches and stumps should either be buried beneath fill on the low side of the right-of-way, scattered into the forests, or piled and burned.

Construction should be timed for efficient working conditions—avoid trouble periods such as spring runoff and winter freeze. On poorly drained soils, road construction should be carried out during the dry season.

Geotextiles—woven or spun fabrics made from various organic and synthetic fibres—are often used to reduce the horizontal or vertical movement of road material. They are used on unstable road cuts or fill slopes to prevent erosion. Geotextiles are also laid down over rock ballast, puncheon or bridge decking to prevent fine silts from moving to the soil surface or into watercourses.

There may be instances where you do not want to disturb the root systems or disturb the flow of groundwater with ditches and removal of the overburden. When you place a road on soft, wet ground without removing the organic soil it is termed overlanding.

It is possible to use puncheon or corduroy (non-merchantable wood) placed tightly together, and covered with ballast. In addition, or alternatively, use a layer of geotextile as a separator to prevent the intermixing of mud that can work its way up to the running surface by the hydraulic pumping action of the traffic on the road.

Road width requirements will vary according to:

  • frequency of use
  • size of vehicles using the road
  • type of products moved

In general, a road with a finished surface of 4–6 metres is suitable for most forms of small-scale woodland transport. The right-of-way should extend approximately 1 to 
2 metres beyond the cut and fill to allow the safe travel of large vehicles.

The roadway itself should be higher than the surrounding ground to ensure that it does not become a drainage ditch. Woodland roads of 5 metre widths should have an average ditch depth of at least 0.5 metre and ditch width of 1 metre.

road constructionThese dimensions may vary widely, depending upon the construction material. Extra ditch width is recommended in silt and clay conditions, while shallower ditches are acceptable in rock.

On sidehills, cut bank slopes should not be steeper than 1:1 (1 metre of horizontal distance per metre of vertical rise); and fill bank slopes not steeper than 1.5:1 (1.5 metres of horizontal distance per 1 metres of vertical rise). For steep side slopes with potential for slumping, consider cutting the road profile deeper into the slope and moving the surplus material to fill or spoil areas.

Do not support your road on downslope stumps, trees or cull logs. Cut and fill banks can be seeded, planted or terraced for soil stability. If you believe there is a chance of slumping or sliding above or below your road, consider placing “willow wattle.” These are bundles of willow (Salix spp.) or cottonwood (Populus spp.) which are fixed across the slope with stakes of the same species.

Both these species have the ability to root readily, so as soil and debris accumulates behind the bundles, the stakes and the bundled material will grow into the hillside providing stability and erosion control.

As always, thanks to A Non-forester’s Guide to Small-scale forestry in British Columbia for the information excerpted above.

Please stay tuned for our next post where we dare to ask: What’s the secret to a good roadbed? If you can’t wait, you can find the complete resource online here.