Forest Trail Handbook

SECTION IV.—LOCATION

15.—TRAIL LOCATION

Before definitely selecting the route for a project, a thorough reconnaissance survey should be made. This will enable the locator to secure the best possible topographical, geographical, and fire-control service location. Hazard maps and other fire-control data should be checked previous to making the final selection. Too much emphasis cannot be given to the importance of this phase of trail work.

During the reconnaissance survey, always definitely select and locate control points, and get their elevation and approximate intervening distances.

The instruments needed in trail reconnaissance, in addition to the ordinary tools of a woodsman, are an Abney level or hypsometer for laying out grades and measuring slopes, and in certain instances an aneroid barometer for ascertaining elevations.

With the approximate distance and elevation between two control points known, add two ciphers to the elevation figures and divide by the distance expressed in feet to ascertain the approximate uniform grade between them. Example:

In trail location, as far as practicable—

Avoid:

(a) Swamps and boggy land.

(b) Creek bottoms and arroyos subject to damaging floods.

(c) Slopes subject to snowslides.

(d) Locations subject to snowdrifts.

(e) Slides (see fig. 1).

(f) Unstable ground.

(g) Steep slopes.

(h) Bluffs and ledges.

(i) Frequent crossings of streams where fording is difficult and impracticable.

(j) Location requiring construction of bridges and culverts.

(k) Heavy clearing.

(l) Switchbacks where practicable. In instances where the use of switchbacks is good business, make the legs as long as the topography will permit.

Favor:

(a) Southern exposures.

(b) Ridges.

(c) Benches.

(d) Natural openings.

(e) Open timber.

(f) Light stands of brush.

Items (b) to (f), inclusive, should be favored even at the sacrifice of grade.

Do not lose sight of the desirability of having trails pass camping places, horse feed, water, and points which furnish a broad view of the surrounding country. These items are of special importance to recreation and fire-control trails.

FIGURE 1.—Principles to be observed in locating trails: A, 15 percent grade to escape rock and hard land by climbing onto bench; B, Rocky and hard; C, Bend in trail to escape large rocks; D, 30 percent minus grade for 200 feet; E, 15 percent plus grade for 350 feet to shorten trail across canyon with flat bed; F, Rocky flat to edge of steep slate sidehill; G, 18 percent slope of sidehill, no grading; H, 20 percent grade for 500 feet to escape bluff; I, Bluff of rock; J, 30 percent slope, no grading; K, Reverse 8 percent for 50 feet on each side; L, Rocks, tan bark oak, and heavy brush; M, Open point, switch backs on 15 percent to 18 percent grade to escape rock and tan bark oak sidehill; N, Water falls and rapids; O, Solid ground; P, Camp; Q, Meadow. (click on image for a PDF version)

Always bear in mind that trails are used by a class of travel that is but little affected by undulations and a steep pitch here and there, and that they are not associated with vehicles, the carrying capacity of which is limited by the steepest pitch. Remember, too, that trails are used by foot travelers and saddle or pack animals, traveling single file, and usually in a walk. Lay out trails accordingly, and never be influenced by the idea that later a trail may be converted into a road.