Sunday, February 16, 2014

Trail Guide: Construction in rocky soils

Rocky or coarse soils are common on hills and mountains in British Columbia. Many trail construction guidebooks say that these soils should be avoided. Avoiding these soils may be impossible in some areas.

Rocky soils make for difficult construction and poor results if the tread or walking surface of the trail has projecting rocks or any rock larger than 4 inches within the top 4 inches of the walking surface. Foot traffic tends to move the finer soil from around a big rock so that it projects above the surface and becomes a tripping hazard.

Rocks in coarse soil can be used to advantage. In northern Europe, many fields have dry-stone walls or fences built from the stones removed from the fields to enable cultivation. Rock found in coarse soils can be used to advantage during trail construction by using dry-stone construction techniques.

The basic tools needed are a rock bar, a sledgehammer (with safety goggles), a shovel, mattock and wheelbarrow. A mason's hammer and chisel make a handy addition.
The rock bar is essential for prying and moving large rocks. It is a good idea to paint the rock bar in some bright color because rusty steel tends to blend into the forest. The wheelbarrow is used for end- hauling or moving soil and rock up and down the trail. The garden wheelbarrow show above can be used for trail work, but there are folding wheelbarrows with a canvas receptacle that are more suitable.

The following sketch illustrates the general technique for making use of rocks to build a trail in coarse soil:

This type of construction is known as half bench construction, because the outside edge of the trail is built up above the ground surface using dry-stone wall methods.

Face rock 1 is embedded and fill rocks 1 are filled in behind. Fill any spaces between the face rock and the fill rock with small stones.

Dry-stone works through the friction of overlapping rocks. Face rocks 2 should overlap face rocks 1. Overlapping face rock 2 on fill rocks 1 will also help to tie the structure.

The technique is really a hand sorting exercise and removal of the larger rocks for constructing the wall and base should leave gravel and finer soil material for the tread or walking surface.

If the trail is being constructed on an uphill gradient rocks can be moved from in front to behind and the finer soil is left to pull over the sub-grade or base. Thin nitrile coated work gloves are helpful to reduce wear and tear on the hands.

Dry-stone relies on the contact and friction between rock. While it is important to get relatively good contact and fitting between the face rocks seeking perfection will slow the work considerably. The outside rock face is usually sloped slightly inward for greater stability. The face rock wall need not have smooth surface. A rough surface looks more natural and little projections, nooks and crannies in the surface encourage mosses and re-vegetation. Filling any spaces between the face rock and the fill rock with small stones increases the stability of the face rock.

Half bench construction using dry-stone offers several advantages. It disturbs less soil and area than full bench construction. The trail is elevated above the surface of the ground and this along with the rock sub-grade helps to drain the trail. Trail surfaces should be out-sloped to help water drain off the trail.  On climbing sections or gradients additional provision needs to be made for cross draining or directing water that tends to flow down the trail, off the trail to prevent erosion. The best method is grade reversals or little dips built into the trail. In half bench construction the height of the retaining wall can be reduced at the dip to enable water to flow off. The second method are water-bars. Water-bars are diagonal structures running across the trail surface at 45 degrees. There are several ways that these can be constructed. Temporary water-bars can be made with a diagonal hump of surface material. Foot traffic wears down this type rather rapidly and they need to be rebuilt before each wet season. Water-bars can also be constructed out of rock. Single line rock water-bars are a line of rocks embedded into the trail at 45 degrees to form a barrier to water flow. These also tend to fill up in front of the rock and can become ineffective if not maintained. Double rock water-bars are a double line of rocks placed in the surface at 45 degrees with a drainage trench of approximately one foot in between. These tend to be self cleaning and if they do get plugged they can be cleaned with the heel of a hiking boot. Gradient reversals or double rock water-bars are the most sustainable solutions.

How frequently should cross drainage be installed in trails? Some guides show tables requiring more frequent cross drains as gradient increases. Generally you need more frequent cross drains as gradient increases. Erosion becomes a serious issue or trails with a gradient of 15% or more. Steep trails with gradients of 20% or 30 % should have cross drains every 10 meters. Assess the terrain, soil and moisture conditions on the slope above the trail. If there is a long slope above the trail with thin rocky soils, you can expect considerable overland flow during snow-melt or rain storms. It the trail is built or sands or gravels with little clay binding material, it will be more susceptible to erosion. A spring may need its own cross drain. Think of a spectrum of one cross drain per 100 meters on very gentle gradients and favorable conditions increasing to one cross drain per 10 meters on steep gradients and likelihood of considerable overland water flow.

Half bench construction should not be attempted in fine soil materials. You need to have rock to build up the outside edge of the trail. End hauling materials in a wheel barrow is a feature of half bench construction. Some spots will lack sufficient large rocks, while others will have insufficient fine materials to make a 4 inch deep tread surface with no 4 inch+ rocks and stones. If stretches of fine soils are found along the route, revert to full bench construction. Rather than waste fine materials, end-haul them down hill for surfacing. While the sketch shows two lifts of dry stone in the retaining wall, it can go from one lift to many lifts if the trail is being built around a rock out crop. Trail construction in rocky soils requires ingenuity to come up with a good solution for the circumstances. There may be no fine materials on some sections, and the flat sides of rocks can be laid to provide a walking surface.

Monday, February 10, 2014

Locating a Forest Trail

 An amateur is someone that loves, likes or takes an interest in some thing or activity. Forest trails are often located and built by amateurs. Trail amateurs need to use professional methods if they get involved in the location of a forest trail.

A forest trail is a narrow road. Forest roads provide access to forest resources. The forest trail provides access to recreational resources. Most trails have some target or destination that may be a mountain top, lake or waterfall. Points of interest along the way add to the trail experience.

There is more to locating a trail than finding some way through the forest between point A and Point B. Professional forest engineers that locate forest roads and trails usually make their business to gain a comprehensive understanding of the entire landscape as the first step in locating a trail or trail system.

Existing information in the form of topographical maps, geology and vegetation maps, aerial photographs and satellite images is collected. Preliminary field reconnaissance adds reality to the available information and some control points on a trail route or system may be evident at an early stage. A narrow point on a river or stream may provide the only feasible bridge crossing and the trail will need to go there. Every landscape is different, but there are usually some major control decisions. Do you go below the cliff or start climbing at a reasonable gradient to get above the cliff? Control points are points that you need to go through owing to the physical restrictions of terrain and topography. Added to these are points of interest that help to identify the route corridor.

Locating the trail requires a little more than connecting the dots between the control points and points of interest. Thorough field reconnaissance should be undertaken at this stage. Forest engineering professionals usually walk the ground until they have a good three dimensional image of the local topography in their mind. This may be supplemented with surveyed lines with distance and slope measurements to establish elevations. Tag lines or flagged test lines at a certain gradient may be tried to determine if it is feasible to get between points in the landscape. Global Position System way points may also feature in the effort to gain a good three dimensional picture of the topography.

Thorough field reconnaissance should also identify:

  • Environmentally sensitive sites 
  • Wet sites with organic soil that pose problems for trail construction
  • Intermittent streams, springs, rocky slopes with thin soils that may give storm water flows capable of damaging a trail
  • Additional points of interest
The final location of the trail should try to provide the best solution in the circumstances. It is best to avoid sensitive sites and other problems and route the trail elsewhere. However, some landscapes are challenging and it may be necessary to locate a trail through some sensitive site or other problem area. A wet site may be unavoidable in the approach to the only feasible stream crossing. Some special treatment in the construction of the trail sections will be required. A site investigation involving a little digging during location might reveal that the wet site does not have deep organic soil so a built up trail surface or turnpike section will be required rather than a corduroy section where the trail surface floats on a bed of logs or perhaps styro-foam.

 In some ecosystems, environmentally sensitive or rare sites often occupy extremely wet or extremely dry sites. A route corridor for a trail might need to cross a bench or relatively flat area with rock bluffs below and above. There is a dry rocky site on part of the bench with little forest cover, but with a ground vegetation of rare wildflowers. Owing to the terrain and lack of forest cover it is also a viewpoint. The textbook solution is to try to avoid the sensitive site by leaving a fringe of trees between the trail and sensitive site. Trail users will find the sensitive site and viewpoint and beat a spur trail to the sensitive site and then trample the sensitive site in search of views. The alternative solution is to find the best viewpoints on the sensitive site and route the trail through these so users can take a photograph without leaving the trail. While the trail does remove a very small percentage of the sensitive site, the total impact will be much less than the wide area trampling induced by the textbook solution. The job of trail location is often one of comparing various factors of two or more alternative locations along the route corridor. Think it through, make notes of the various factors and develop a rationale for selecting the final location.

The knowledge of a forest landscape gained from existing information, maps and thorough field reconnaissance needs to be supplemented with engineering to arrive at a good final location. A road or trail needs to be engineered with some thought about the mechanical or physical abilities of the machine or animal that will use the road. Hiking trails are built for human beings. Humans can negotiate very steep or even vertical slopes and go almost anywhere. A trail can be located to embrace the "inner monkey" and take a challenging uphill and down dale route, but it will not be a trail that will provide a desirable hike and it will also have some physical sustainability problems.

A trail should provide for ease of walking or marching along. This can be done on gradients of up to approximately 15% gradient (15 up for 100 along). Steeper gradients require more of a climbing step. Trail gradients of greater than 15% are subject to greater water erosion, if special drainage precautions are not built and actively maintained. Moderate trail gradients of 15% or less provide for ease of hiking and fewer sustainability problems. Moderate gradients make for a well engineered trail. Do not try to estimate gradients. Use a clinometer (instrument for measuring gradient)!

Another human limitation needs to be considered. We trip and fall with ease. Walking surfaces on trail should be free of projecting rocks, roots and other tripping hazards. While this problem can be reduced with quality trail construction, coarse soils or soil with a lot of large rocks require more effort and special techniques in trail construction to arrive at a good safe walking surface. Steep trail sections requiring steps or other rock armoring increase the likelihood of falling. While coarse rocky soils and the need for steps cannot be completely avoided, the trail locator needs to think about these factors and may need to carry some digging tool to assess soil and construction conditions.

A trail location should provide the user with efficiency of effort. It should get the user to the destination without unnecessary wandering around in both the horizontal and vertical planes. In the horizontal plane it should head generally in the direction of the destination without unnecessary meandering that adds extra distance and possible confusion as to direction. Unnecessary meandering in the vertical plane will strain the user. Sometimes a downhill section in an uphill trail is unavoidable owing to topography. If your trail location that goes to the top of a mountain has many downhill sections on the way up and they are not absolutely necessary owing to terrain, then you probably need to relocate before you build.

Locating a trail is more than finding the way from A to B in the forest. You first have to find out about the forest and the landscape and develop a mental three dimensional image of the landscape, its points of interest and sensitive places. One or more possible route corridors through the landscape can be identified with this knowledge and reconnaissance effort. The routes can be compared and contrasted to identify the better route corridor. Once a route corridor is selected, the final location can be examined and perfected. The final location should be surveyed, measuring distances and marking distance stations on the ground, collecting trail gradient and side slope gradients, supplemented with notes on the drainage and construction of the trail.

Sunday, February 2, 2014

What should the University of Victoria do?

Dunsmuir Lodge, situated on Mount Newton on the Saanich Peninsula just north of Victoria, borders on John Dean Provincial Park and the Pauquachin First Nation Reserve. The 100 acre forest and lodge was gifted to the University of Victoria in 1985. The University operated the lodge as a conference and educational centre until 2009.
When the University ceased to operate the lodge in 2009 there was considerable public interest in the future of the property. In 2010, the University gave the Pauquachin First Nation an exclusive option to purchase the property until May 2011. The University of Victoria has not sold the property.
It is time to renew public debate on the Dunsmuir Lodge property. The land and lodge was a gift to a public institution. The University of Victoria needs the approval of the Minister of Advanced Education under section 50 of the BC University Act to sell the property. The property is already within the public domain.
It is perhaps a little ironic that the University of Victoria chose to name the property after the Dunsmuir family. While the Dunsmuir family are remembered for the construction of castles in Victoria, another part of the family legacy has bearing on the disposition of the lands on Mount Newton.
Enclosure, at term usually associated with European history, refers to the conveyance of land from the common or public interest into private ownership. Dunsmuir pulled off a spectacular feat of enclosure on Vancouver Island. He got the Canadian Government to pay him to construct the Esquimalt to Nanaimo Railway and as a bonus got the E&N Land Grant, involving a huge chunk of eastern Vancouver Island, from British Columbia. The land grant took up a sizeable portion of the Coastal Douglas Fir zone on Vancouver Island. Since most of the zone was privatized, there have been limited opportunities to establish Parks or Protected Areas.
The Dunsmuir Lodge lands on Mount Newton could make an important addition to parks or protected areas in the coastal Douglas Fir Zone. The adjacent John Dean Provincial Park is home to the only piece of coastal old growth on the Saanich Peninsula. The area of old growth lies on a north facing moist site where it has been protected from fires for hundreds of years. The Dunsmuir Lodge lands are also north facing and its forest is maturing and will regain old growth characteristics in a few decades.

If the Dunsmuir Lodge Lands were added to John Dean Provincial Park it would make an important addition to the protected areas in the coastal Douglas Fir zone.  The land will remain in natural condition for the enjoyment of the public and also the Pauquachin First Nation.  Mount Newton or Lauwelnew, meaning place of refuge, will be respected.