Section 3 of the Wild and Scenic Rivers Act calls for the establishment of boundaries within a river corridor to define the area to be protected. The act allows for river corridor boundaries that average no more than 320 acres of land per river mile, measured from the ordinary high water mark on both sides of the river. Boundaries, however, do not limit the protection of Outstandingly Remarkable Values, which must be protected regardless of whether they are inside or outside the corridor boundaries.

The Merced Wild and Scenic River boundaries are illustrated in figure 1. With the exception of the El Portal Administrative Site, the boundary is defined as one-quarter mile from ordinary high water (as defined by the U.S. Army Corps of Engineers in 33 CFR Section 328.3; see Glossary, Appendix C) for the length of the Merced River within Yosemite National Park. In El Portal, the boundary is defined by the 100-year floodplain or the extent of the River Protection Overlay, whichever is greater, plus adjacent wetlands and meadows.

The river corridor boundaries established in the Merced River Plan are based on the existing river channel. Although the river is a dynamic natural system, boundaries depicted in the Merced River Plan’s maps will not be changed to account for every future fluctuation in the river channel. However, in the interests of allowing natural processes to prevail, the National Park Service will consider changing the delineation of river corridor boundaries if there is a major shift in the river channel. Boundaries may also be redrawn if significant new information regarding the river channel becomes available and the National Park Service’s ability to protect and enhance the Outstandingly Remarkable Values is inhibited. If changes are deemed necessary, an environmental compliance process will be initiated (including future opportunities for public involvement) and the Merced River Plan will be amended or updated as appropriate.

For more detail regarding the determination of boundaries, refer to Appendix E of the Merced Wild and Scenic River Comprehensive Management Plan/FEIS, and the Revised Record of Decision dated November 2000 (see Appendix A).