Code of Federal Regulations Title 43. Public Lands:  Interior § 43.8351.0–6 Policy

(a) Hiking, horse riding, and motor trails shall be located, constructed, and maintained where they are found to be feasible and would improve recreation opportunity and quality. Established trails shall be marked or signed and made known to the public by other means.

(b) Certain rivers and sections of rivers that are flowing free of the influence of dams or other major man-made alterations and that possess outstanding scenic, recreational, geological, biological, cultural, or historical features shall be preserved as free flowing streams. The immediate river area shall be managed to protect the natural, cultural, or historical features that make the river or river segment outstanding.