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.

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