Mason Meadow Restoration

In order to restore meadow hydrology and improve downstream habitat for steelhead trout (Oncorhynchus mykiss, ESA-listed threatened), Latah Soil and Water Conservation District (Latah SWCD) implemented this project to improve hydration of the meadow system by retaining flows in the project reach and improving floodplain access and interaction. The project removed the northeast channel (ditch), 0.25 miles, from the flow path and diverted the flow into the abandoned southwest channel, 0.36 miles. Length of stream protected was 0.36 miles and the size of the work site is approximately 20 acres.

Instream Habitat:
Stream treatment occurred on 0.36 miles of West Fork Big Bear Creek. To remove flow from the active ditch, one habitat structure and one channel diversion structure were constructed at the top of the ditch. The ditch was plugged with five earthen structures (ditch plugs) leaving the channel intact between plugs. These intact reaches retain spring flood flows in wetland pools that hold water throughout the growing season and provide hyporheic flow across the meadow. Two 50-foot persuasion channels were dug above the first two ditch plugs to help reduce pressure on the ditch plugs during peak flows. Approximately 16.5 acres of floodplain were reconnected following project implementation.

In total, five log structures and eight faux beaver dams were constructed in the historic channel to provide grade control and for pool creation. In the southeastern portion of the project area, 0.3 acres of the floodplain were regraded to correct previous earthwork that was disrupting the floodplain hydrology in the meadow. Two stick berms were constructed on site to slow overland flow and captures debris and sediment during high flow events. The entire treated stream length (0.36 miles) was treated for invasive weeds. Weed species for control included: Reed Canarygrass (Phalaris arundinacea), Sulfur cinquefoil (Potentilla recta), Orange hawkweed (Hieracium aurantiacum), Yellow hawkweed (Hieracium caespitosum), Houngstongue (Cynoglossum officinale), Canada thistle (Cirsium arvense), and Tansy (Tanacetum vulgare).

Riparian Habitat:
In total, approximately 2.5 acres of the site were revegetated with local native riparian and meadow plant species. The length of the historic channel, 0.36 miles, was revegetated with a mix of native trees, shrubs, grasses, grass-likes, and forbs. Total area planted along the historic channel with a 20-foot buffer on both sides is 1.74 acres. All areas disturbed during construction were decompacted if needed, revegetated, and reshaped with embedded wood and slash to promote roughness, retain sediment, and trap native seed stock. Directly following construction in fall 2016, all disturbed areas were seeded with a native grass and forb mix and mulched with certified weed-free straw mulch to improve germination rates. Channel diversion structures and ditch plugs were revegetated using a combination of purchased sedge mats, native grass and forb seed, cuttings, and container plants. A diverse mix of native grasses, grass-likes, forbs, shrubs and trees were planted to provide a variety of rooting depths for soil stability, increased ground coverage to prevent weed encroachment, and to increase wildlife and pollinator habitat. Planting and weed control efforts continued through spring 2019.

This project will restore hydration of the meadow complex, increase the amount of groundwater stored, improve hyporheic water exchange, extend base flows, and enhance meadow/riparian vegetation all of which will improve downstream steelhead habitat. The fish impacted by the results of this project are part of the lower mainstem Clearwater population of the Clearwater Major Population Group of the Snake River steelhead Distinct Population Segment. A (partial) fish passage barrier exists approximately 9 miles downstream of this project; IDFG have sampled steelhead immediately above the barrier and below the barrier. IDFG intends to restore passage at this site and has had several alternative engineering designs for the site. The IDFG has identified Big Bear Creek as the highest priority for restoration in the Potlatch River (Potlatch River Watershed Management Plan, 2007).