Landslide Toe Habitat Restoration Engineering and Permitting

The Clackamas River Basin Council is taking the lead on the Landslide Toe Restoration Project on behalf of the Clackamas Partnership. The Clackamas River is a priority river for the recovery of native and trout populations in the Lower Columbia Basin. The proposed project will address primary limiting factors by increasing off channel habitat, improving floodplain connectivity and increasing habitat quantity and quality and large wood abundance along the mainstem Clackamas River. The proposed project is located at Clackamas River Mile 17.3, on public land managed by Bureau of Land Management (BLM), Oregon Parks and Recreation Department (OPRD) and Clackamas County, and private parcels, located near Eagle Creek, Oregon in Clackamas County. The area targeted for reconnection was occupied by the mainstem river as recently as 1996, when major flooding cut-off the meander bend. The relic channel is located immediately upstream of the Eagle Creek Confluence project and is a key opportunity for off-channel habitat reconnection. The goal for this project is to complete the engineering, modeling, and permitting work required to undertake restoration actions for this large floodplain and off-channel restoration project. Project Partners include Oregon Department of Fish and Wildlife (ODFW), Oregon Parks and Recreation Department (OPRD, landowner), Bureau of Land Management, Clackamas County, members of Clackamas Partnership, and the Johnson Creek Watershed Council.

Clackamas River basin focal fish species (i.e. spring and fall Chinook, coho and winter steelhead, Pacific lamprey) are negatively impacted by loss of habitat, impaired water quality and lack of access to historic spawning areas. This project will restore habitat elements, including a lack of mainstem and off-channel rearing habitat, that are identified as primary limiting factors for the survival of anadromous salmonids in the Clackamas River. The project will increase the amount of available side-channel habitat in a reach currently lacking adequate thermal and flow refuge, as well as providing access to the Eagle Creek Confluence complex of multi-threaded channels, a large wetland and alcove, and year-round rearing habitat. The project includes hydrologic re-connection of up to 5,080 feet of side channel habitat, 24 acres of off-channel wetland complex, improved hydrologic connection to the floodplain, and improvement of riparian conditions. The design focus will be on improving juvenile rearing conditions for coho salmon, and with surreptitious benefits to winter steelhead and spring Chinook salmon. Reconnecting these habitats, including side channels, wetlands, ponds and alcoves, will provide critical habitat for not only juvenile salmonids, but will have significant benefits for a suite of wildlife species that either use or indirectly benefit from such habitats (e.g., amphibians as refuge and reproductive habitat, birds as foraging habitat, waterfowl, etc).

The presence of side channels, especially a series of side channels in various stages of succession, increases the diversity of aquatic habitat available within a stream corridor. Also, during flood events, side channels will offer aquatic species refuge from adverse mainstem conditions while attenuating flood flows. Temperatures are moderated in side channels, offering cooler rearing conditions in summer months and during the winter months will provide more preferred (slightly warmer) temperatures for rearing. Juvenile coho are known to actively and preferentially migrate from mainstem rearing locations to off-channel habitats (that would be off mainstem channels) in both fall and spring for protection from winter freshet activity and where they experience high survival rates.

The project area would be reconnected to perennial flows. Seeps and springs have been identified through the relic channel, as well as extensive hyporheic flow, providing cooler rearing water conditions in the summer and warmer rearing conditions in the winter. Springs have been identified in multiple locations along side channel 2 that were contributing flow in July and August 2021, a notably dry year. The Clackamas River temperatures during winter months have been shown to be less than ideal (i.e., too cold) for growth and health of rearing juveniles. The improved hydrologic connection is important because of the diversity of fish species and life cycles in the mainstem lower Clackamas River; and improved hydrologic connection should improve on the overall survival rate as opposed to fish rearing in the mainstem Clackamas River.

The Pacific Northwest is expected to see dramatic increases in temperatures due to climate change, with more rain in winter and spring, increased variability in peak flows, reduced snow-packs and drier summers. The Partners’ planning documents recommend actions that will recover natural river processes and riparian function by reactivating the floodplain and naturally aggrading the river; which will disperse flood flows providing high velocity refuge and attenuating downstream flooding, increasing hyporheic flows and decreasing water temperature, and providing cold water refuge and carbon sequestration in healthy native riparian stands that exclude invasive plants.