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| Switchbacks (Photo credit: QuintanaRoo) |
Switchbacks and climbing turns are used to reverse the
direction of travel on hillsides and to gain elevation quickly. The difference
between the two is a climbing turn is a reversal in direction that maintains
the existing grade going through the turn without a constructed landing.
Climbing turns have a wider turn radius than switchbacks and are used on gentle
slopes, typically 15 percent grade or less. Ideally, 7-percent sideslopes are
best.
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| Trail switchback |
A switchback is also a reversal in direction, but they are
usually used on steeper terrain and have a relatively level constructed
landing. Switchback turns have tight corners because of the steeper grades.
A common problem with climbing turns is they are often built
on too steep of terrain. The advantages of climbing turns in appropriate
terrain is that a wider radius turn of 13 to 20 feet is relatively easy to construct.
Climbing turns are usually less expensive than switchbacks because much less
excavation is required and fill is not used.
Switchbacks are used in steep terrain with sidelsopes from
15 to 45 percent. Although switchbacks can be constructed on sideslopes of up
to 55 percent, retaining structures are needed on such steep slopes. The key to
successful switchback construction is adequate excavation, using appropriate
structures to hold the fill in place, and building psychologically sound
approaches.
Retaining structures keep dirt and rock in place. Retaining
walls are useful for keeping scree slopes from sliding down and obliterating
the tread, for keeping streams from eroding abutments, and for holding trail
tread in place on steep sideslopes. Two common retaining structures are the
rock retaining wall and the log crib wall.
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| Retaining wall on downslope of trail |
Steps are another trail element used to gain a lot of
elevation in a short distance. Steps are common on steep trails in New England
and much less common on western trails.
Next: Trail Science 106: The Trail Corridor
