DESCRIPTION
The Chewuch River has been slow to recover from the removal of wood in the early half of the 1900's. Many of the forest stands along the project area provide low rates of natural wood recruitment due to low stand densities. In addition, channel and streambank alterations have reduced the ability of stream channels to effectively retain wood once it has been recruited. Recreation and road development have also reduced the potential for new wood to fall into the river. These factors have led to a decrease in pool habitat in the river; beyond what would occur naturally. The Chewuch River Watershed Analysis (USDA 1994), Upper Columbia Salmon-Steelhead Recovery Plan (UCSRB 2007), and the MVRD's Draft Lower Chewuch Watershed Action Plan (USDA 2010) each identify the lack of habitat diversity in the Chewuch River as limiting fish productivity for fish in the Methow sub-basin. Each plan identified the need to increase large wood quantities, pool frequency and quality, and to re-establish side- and off-channel habitat in the Chewuch River.
TheYakama Nation's, Phase 1 (River Mile, (RM) 15.5-17), of the Chewuch River Mile 15.5 to 20 Fish Enhancement Project was completed on November 10, 2017. Permitted work of phase 1 included 5 LWD Apex Structures, 3 LWD Bank Structures, 1 LWD Cover Habitat, and 1 historic side channel connection that measures 0.90 miles in length. The project also included decommissioning 1.3 miles of historic road located within the riparian management zone of the
The Chewuch River RM 10R Project has been identfied as a critical area of concern in the Chewuch Rvier Reach Assessment. The project area is a moderately confined reach. Bedrock outcrops on both sides of the valley provide the primary constraints on valley width. Glacial deposits overlay the bedrock in most areas and form the low-surface boundary except for at a few locations. The glacial terrace has been eroded and a wide floodplain has developed along the west side of the valley. This surface contains wetlands, but only limited evidence of frequent flood inundation or high flow channels.
The channel forms one large amplitude half-meander. The upstream end of the reach has a large mid-channel bar that creates split flow and pool-riffle development. Downstream, the channel simplifies and is essentially a long run with coarse cobble/boulder bed material. As the channel swings west to complete the half-meander, a deep scour pool is formed on the outside of the bend. At the downstream end of the reach, the channel flows through a tight bedrock constriction where another deep scour pool has formed.
The objective focuses first on protecting existing conditions from further impairment. This objective is followed by reconnecting the fundamental bio-physical processes that will create and maintain habitat conditions over the long-term. Off-channel habitat enhancement (rehabilitation) is also included; these projects occur in conjunction with long-term process reconnection and are also applied in cases where long-term process reconnection is constrained by existing human uses. The primary objectives suggested by the USBR are to "restore wetland or high-flow network", or to "restore primary side channel and wetland". The restoration concepts behind achieving these goals are restoring cleared areas, assessing connectivity, removing riprap, and excavating to enhance side-channel connectivity. The USBR also suggests that addition of LWD throughout the reach may be beneficial.
