Special Structures

• Climbing Turns
• Switchbacks
• Crib Walls and Other Retaining Structures
• Steps
• Maintaining Special Structures

This section covers some of the more complex trail structures. Switchbacks, crib walls, and similar structures are common in trail construction. They are often relatively expensive and difficult to design and construct correctly. Inadequate maintenance greatly shortens their useful lives. However, a well-designed, well-built trail structure can last for decades and be quite unobtrusive.

Special structures are more frequently used on low-challenge trails where easy, wide, and smooth grades are the management goal. The cost of building relatively easy trail into progressively more difficult terrain quickly becomes prohibitive (remember how many fortunes and lives were poured into constructing railroads). Keep in mind the Minimum Tool philosophy and build only as many structures as you absolutely need to reach your goal.

Switchbacks and climbing turns are used to reverse the direction of travel on hillsides and to gain elevation in a limited distance. What is the difference between the two? A climbing turn is a reversal in direction that maintains the existing grade going through the turn without a constructed landing. A switchback is also a reversal in direction, but has a relatively level constructed landing (Figure 57). Switchbacks usually involve special treatment of the approaches, barriers, and drainages. They are used on steeper terrain, usually steeper than 15 to 20 percent. Both of these turns take skill to locate and are relatively expensive to construct and maintain. Choosing when to use each one is not always easy.

Figure 57—Climbing turns can be built on gentler
slopes, usually not more than 15 to 20 percent.
Switchbacks are needed on steeper sites.

Trail designers should make every effort to minimize the use of these turns. Planning carefully to avoid impassable or very difficult terrain reduces the need for switchbacks and climbing turns.

User psychology (human or animal) is more important to the success of these structures than any other trail structure. The turns must be easier, more obvious, and more convenient than the alternatives. They work best when terrain or vegetation screens the view of travelers coming down the upper approach toward the turn. Avoid building sets of these turns on open hillsides unless the terrain is very steep. It's usually best not to build turns, or the connecting legs of a series of turns, on or across a ridge. The local critters have traveled directly up and down these ridges since the last ice age. They are not going to understand why you are building low hurdles in their path�and they will not be forced onto your trail and turns.

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