Additional Trail Elements Cont.
Wire baskets (often called gabions) are another retaining structure. Gabions are wire baskets filled with rock (figure 78). The baskets are wired together in tiers and can be effective where no suitable source of well-shaped rock is available. Gabions look more artificial (in the eyes of traditionalists at any rate) and may not last as long as a rock wall, depending on the type of wire used and the climate.
Steps are used to gain a lot of elevation in a short distance. Steps are common on steep hiking trails in New England and elsewhere and less common (but not unheard of) on western trails used by horses and mules. Wooden steps of all configurations are common in coastal Alaska (figure 79).
Sometimes steps are used on an existing trail to fix a problem caused by poor trail location or design. Often, the result is out of character with the desired experience and esthetics of the trail. Before you construct steps, make sure they are consistent with the expectations of those the trail is designed to serve.
Your goal is to design the height (rise) and depth (run) of the steps to match the challenge desired. Steps are harder to negotiate as the rise increases. The difficulty also increases as the steps are closer together.
Yet as the trail becomes steeper, the step must either be higher or the distance between steps must be shorter. Steps can be built into a trail that traverses the slope. This allows the traveler to gain elevation rapidly, without the scary steepness of a stairway.
The components of a step are: the rise, the run, a landing on easier grades, and often retainer logs (figure 80). The rise is the height of the face of each step. The run is the distance from the edge of one step to the base of the next step's face. The landing is the extension of the run above the step. In structures where the landing is composed of tamped fill material, logs are used to retain the fill.
Drawings of three types of steps; Overlapping rock stairway, individual steps-rock, and individual steps-logs. The drawing includes the text:
Hikers, especially backpackers, generally don't like steps and will walk alongside them if there is any opportunity. The steps need to be comfortable to climb or they won't be used. This means keeping the rise a reasonable 150 to 200 millimeters (6 to 8 inches) and the run long enough to hold a hiker's entire foot, 254 to 305 millimeters (10 to 12 inches, figure 81). It's helpful to corral the sides of steps with rocks to encourage users to stay on the steps.
The most important area of the step is usually the tread. This is where most users step as they climb. The top of the step (and landing) should be stable and provide secure footing. The edge of the step should be solid and durable. The face or riser of each step should not slope back too far. This is particularly important as the rise of the step increases.
If the stairway climbs straight up the hill, each step should be slightly crowned to drain water to the edges or be sloped slightly to one side. When the trail traverses a slope, each step and landing should be outsloped slightly. Water should not be allowed to descend very far down a set of steps or to collect on the landing. A grade reversal or drain dip is a good idea where the trail approaches the top of the steps.
Build stairways from the bottom up, at a break in the grade. Bury the first rock; it will act as an anchor. The most common mistake is to start part way up a grade. If you do so, the trail will wash out below the stairs. The bottom step should be constructed on a solid, excavated footing. If it is constructed on top of exposed rock, it should be well pinned to the footing. Each successive step is placed atop the previous step (figure 82). Wood steps are usually pinned to each other and to the footing. Dry masonry rock steps usually rely on the contact with the step below and with the footing to provide stability (figure 83).
Steps with landings are a bit harder to secure because the steps do not overlap. Each step can be placed in an excavated footing and the material below the rise removed to form the landing of the next lower step. Usually, this is the most stable arrangement. Or the step can be secured on the surface and fill can be used to form a landing behind it. When the landing consists of tamped fill, the material used to provide the rise does double duty as a retaining structure. These steps must be seated well to prevent them from being dislodged by traffic. For stock use, landings should be long enough, about 2 meters (6 ½ feet), to hold all four of the animal's feet (figure 84).
In all steps, the key is to use the largest material possible and to seat it as deeply as possible. Rocks should be massive and rectangular. On steps that traverse a slope, it helps to seat the upper end of the step in footings excavated into the slope.
Pavers can be used to armor switchback turns and steeper slopes, especially on trails designed for motorized traffic (figure 85). Some styles of pavers allow vegetation to penetrate them; others have voids that can be filled with soil, gravel, or other suitable material. In highly erodible soils, pavers combined with geotextiles are an option.