The Placerville Ranger district, El Dorado National Forest and project stakeholders are seeking to restore the natural hydrologic functions of Cody Meadow to provide improved water quality, timing of flows and enhanced aquatic and terrestrial habitats onsite and downstream.
Prior to the 1950s, surface flows likely sheeting across the meadow surface or occupied multiple small channels. The present incised (downcut) channels have resulted from over 100 years of land use (including channel modification, interactive grazing, and road building) which diminished the vegetative armor of the meadow soil. With reduction in soil protection, any small channel, livestock trail, or other bare linear feature became vulnerable to erosion. Despite having very small draining areas, these features gradually deepened and widened to the incised conditions that exist today. Roads within and around the meadow are also currently affecting the meadow. A road constructed across the meadow channelizes flow through a culvert and blocks subsurface flow. Another road (10N04) parallels the meadow, limiting the lateral migration of the stream channel.
These changes to surface topography have not only altered the flow regime of the meadow, but also the vigor and resilience of the vegetative community and suitability of the aquatic habitat. Sierra Nevada yellow-legged frogs (Rina sierra) listed as a Endangered Species under the Endangered Species Act, were documented in Cody Meadow in 2004 and 2005. Repeated surveys since 2005 have not found Sierra Nevada yellow-legged frogs in Cody Meadow. Currently, Cody Creek supports a population of rainbow trout (Oncorhynchus mykiss). The project intends to restore the natural flow regime of Cody Meadow as well as improve aquatic, riparian, and meadow habitat.
Ultimately, the design concept for the Cody Meadow project area is to implement near-complete gully fill. The fill material would be excavated from 7 small borrow ponds along the margins of the meadow. Given meadow slopes of 3% complete gully fill significantly reduces risk associated with concentrated flow over plugs.
The principle function of the borrow ponds is to provide native fill material for plug construction. Since the ponds will fill the groundwater and maintain ponded water year-round, habitat features and diversity are incorporated into the construction. These include varying water depths, islands, peninsulas, basking logs, etc., which are determined as fill needs are met. Topsoil is removed and stockpiled adjacent to the plug fill zone to top dress the completed plug. All plugs and borrow ponds are sited and configured to accommodate surface and subsurface through flow as well as adjacent hillslope surface and groundwater inflows. The plugs would be constructed with a track loader to minimize impacts to undisturbed meadow areas. Plug compaction is intended to match the porosity/transmissivity of the native meadow soils. This allows moisture to move freely within the plug soil profile and support erosion resistant meadow vegetation for long term durability as well as prevent preferential pathways for subsurface flow, either in the plug or the native material.
All vegetation and larger woody material (lodgepole pine) from either the borrow ponds or the plug fill areas will be salvaged. Meadow sod and willow transplants will be planted into the plug surfaces, with particular emphasis on securing seams and reducing flow velocity of overland flows. Wood material, though limited, would be used for habitat features in the borrow ponds and added surface roughness in key areas of plug fill.
The lower end of the project will require 7 rock riffles to raise the base level of the channel, in lieu of gully fill, in its existing alignment. The project will be anchored with a valley grade structure at the end of the riffle reach. At the downstream end of the project this will allow a seamless transition of the new meadow gradient to the existing channel. It is expected that approximately 250 yds of onsite rock will be required for the riffles, valley grade structure and removing the road across the meadow (by filling it to meadow grade).
Upon completion, all plug surfaces are ripped to a depth of 12" to facilitate rainfall infiltration, with the recovered topsoil spread and seeded with native seed. All native vegetation recovered from fill and borrow sites will be transplanted to plug edges, surfaces and key locations on the remnant channel. All access for equipment and materials will be on existing open or closed roads and skid trails.