Saturday, September 15, 2012

Sustainable hiking trail surveys

Hiking trails in forests and Parks may have developed haphazardly over the years leaving a trail system that may not be sustainable.  Existing trails can be surveyed to determine their sustainability and the need for improvements, re-locations or completely new route corridors.

A survey of the existing trails requires necessary equipment as illustrated in the photo.

A surveyor's or cruiser's vest is a handy way of carrying the measuring chain, a compass and clinometer, a waterproof paper notebook, flagging tape and a GPS unit. GPS units with maps can do a good job of positioning the horizontal alignment of a trail as you traverse the trail. The gradient or vertical alignment of the trail is best recorded the old fashioned way. The trail is traversed measuring sections of the same grade. The distance, the gradient of the trail, the gradient of the side slope is recorded. Two people are required, a surveyor or recorder and the chain man who pulls the chain ahead to the next change in trail gradient. Additional data on rock and soil conditions, viewpoints, junctions and other points of interests are recorded and referenced to the GPS track.

Once the gradient and other measurements are recorded for each section, a judgement of the sustainability of each section can be noted. Some sections with gradients under 10% may be unsustainable owing to soil and moisture conditions such as a swamp or a bog. If you are on a side hill a pattern or a relationship between gradient and sustainability usually becomes evident. Provided that there are no soil or water problems, trail sections with gradients of 10% or less usually demonstrate little erosion from foot traffic. The hiker walks with a flowing motion on these gradients. On gradients above approximately 10% the hiker switches into a climbing step or a braking step if going downhill. Depending on the amount of clay or cohesive material on the trail tread some foot erosion becomes evident and is almost always present when the gradient gets to 20% unless the trail surface is solid rock. In addition to foot erosion, steep trails are more susceptible to erosion from water flow. Look for rocks larger than 4 inches or 10 centimeters wearing out of the trail surface to become tripping hazards.

Data from the survey notebook can be reviewed later. It may be possible to relocate a section that is unsustainable. However, if a trail has many sections that are unsustainable owing to excessive gradient, a whole new route corridor is indicated.

Trails may be unsustainable for reasons other than poor physical condition, erosion etc. A trail route that does not take hikers to points of interest in the landscape, or takes an indirect location to the final objective such as a mountain top encourages pioneering of shortcuts and more people disturbance especially if the area is protected. A trail that goes to the summit of a distant mountain should climb there with a minimum of avoidable downhill stretches on the way up. Poor route corridors encourage shortcuts and confusing networks that contribute to people getting lost and requiring search and rescue efforts.

A sustainable trail survey that takes notes and measurements provides a data narrative for each trail segment. It supports the larger picture task of assessing the suitability of the existing trail system in the landscape and planning necessary changes, de-activation, improvements and new routes.

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