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River Protection Overlay
The areas immediately adjacent to the river channel, along with the river channel itself, are particularly important to the health and proper functioning of the river ecosystem. These areas allow for the main channel to link with backwater areas, tributaries, and groundwater systems; provide for increased channel diversity; and contribute sources of needed nutrients and woody debris to the river. In most circumstances, trees or other large woody debris falling into the river are recognized as part of the natural processes and will be left in the river to aid in the recovery of aquatic and riparian habitat. Additionally, the areas immediately adjacent to the river channel can help protect surrounding development from potential flood damage and can be used to filter runoff water draining into the river.
To ensure that the river channel itself and the areas immediately adjacent to the river are protected, the Merced River Plan includes a management tool called the River Protection Overlay. It is intended as a primary mechanism to achieve the goals of the Merced River Plan. The River Protection Overlay is also intended to identify the location of highest priority for restoration of hydrologic processes and biotic habitats within the river corridor. This critical zone would provide a buffer area for natural flood flows, channel formation, riparian vegetation, and wildlife habitat and would protect riverbanks from human-caused impacts and associated erosion. The River Protection Overlay is intended to apply the requirements of the Wild and Scenic Rivers Act, including the protection and enhancement of the Outstandingly Remarkable Values and the preservation of the free-flowing condition of the river, at a higher standard than that of the underlying management zones. However, the River Protection Overlay does not apply to private property within the river corridor.
RIVER PROTECTION OVERLAY
National Park Service staff developed the technical framework for the River Protection Overlay in a series of internal workshops beginning in 1993 and continuing into 1999. Staff reviewed technical studies by various agencies, including the U.S. Forest Service and the U.S. Fish and Wildlife Service. Many of these studies confirmed the importance of ensuring the contribution of inputs to the river from upland vegetation as a guide for setting the width of riparian protection areas. See, for example, Murphy and Meehan 1997; U.S. Forest Service 1990; Klein, Sonnevil, and Short 1987; Elser 1968; and Bilby and Likens 1980.
Rivers are dynamic systems. As the movement of the river channel shifts over time, so would the specific areas included within the River Protection Overlay. Regardless of the location of the water’s edge on any given day throughout the year, the River Protection Overlay is measured from the ordinary high water mark, as defined by the Army Corps of Engineers in 33 CFR Section 328.3 (see Glossary, Appendix C).
The width of the River Protection Overlay is determined by site topography and vegetation and includes the area needed to encompass riparian and adjacent upland vegetation and habitat. In areas above 3,800 feet, the River Protection Overlay includes the river channel itself and extends 150 feet on both sides of the river measured from the ordinary high water mark; and in areas below 3,800 feet includes 100 feet on both sides of the river measured from the ordinary high water mark. (On the main stem of the Merced River, the 3,800-foot elevation point occurs near the Cascades Powerhouse. On the South Fork, the 3,800-foot elevation point occurs approximately one mile downstream of Squirrel Creek.) Generally, a wider band is required along the river in the flatter, open valleys, while a narrower buffer provides adequate protection in the steeper, V-shaped river gorges of the lower elevations (see figure 3). This transition occurs approximately at the 3,800-foot elevation mark, in the gorge area below Yosemite Valley on the main stem of the Merced River, and downstream of Wawona on the South Fork. Approximately 70 miles of the river has a 150-foot River Protection Overlay, including Yosemite Valley and Wawona. Approximately 11 miles of the river has a 100-foot River Protection Overlay, including the El Portal Administrative Site.
Projects occurring within the bed or banks of the river and that affect the free-flowing condition of the river are considered water resources projects under the Wild and Scenic Rivers Act and must also go through a Section 7 determination process.
Within the River Protection Overlay, future actions shall be consistent with the following conditions:
Nonessential facilities (including, but not limited to, riprap, levees, diversion walls, impoundments, bridges, bridge abutments, roads, campsites, buildings, utilities, and other structures) should not be located in the River Protection Overlay, except when they meet the following two criteria: (1) where required for access to or across the river, for health and safety, or for the maintenance of historic properties; and (2) where it is impractical to locate them outside the River Protection Overlay.
Existing facilities meeting these criteria may remain, and they may be replaced, repaired, or relocated within the River Protection Overlay, but only if the replacement, repair, or relocation does not directly and adversely affect the Outstandingly Remarkable Values.
New facilities and development may be constructed in the River Protection Overlay only when meeting these criteria and when located where they do not materially impair the natural function of the river, impede linkages to tributary inflow and backwater areas, or disrupt contribution of woody debris to the river, and where they do not have a direct and adverse impact on the Outstandingly Remarkable Values.
Actions within the bed and banks of the river to construct, replace, repair, or relocate essential facilities (i.e., primary roads and bridges, wastewater collection and treatment, domestic water supply, electrical distribution, and similar facilities required to keep the park operating) and facilities that directly protect and enhance the Outstandingly Remarkable Values (e.g., raft launch facilities to preserve the spectrum of recreational experiences and to concentrate use in a hardened area) may be permitted provided that:
Project design minimizes impacts to the free-flowing condition of the river, interference with linkages to tributary inflow and backwater areas, and disruption of contribution of woody debris to the river.
The project incorporates mitigation measures to avoid or reduce impacts.
Facilities and development covered by paragraphs 1 or 2, above, that occur within the bed or banks of the river and that affect the free-flowing condition of the river must also comply with Section 7 of the Wild and Scenic Rivers Act.
Other existing facilities that are not addressed by paragraphs 1 or 2 should be removed, and must be removed at the earliest practicable opportunity when major rehabilitation is needed or when a facility is no longer of use.
Facilities proposed in the River Protection Overlay must meet the stringent requirements of its prescriptions. However, existing facilities in the River Protection Overlay are allowed to remain even if they do not conform with prescriptions. The National Park Service may address an existing, nonconforming facility in the River Protection Overlay at any time, such as through a planning effort.
