Clatskanie River Floodplain Restoration

The Clatskanie River Floodplain Restoration Technical Assistance grant provided funding to the LCRWC to hire an engineering firm and collect environmental data for the development of a restoration design for 23-acres of floodplain located between River Mile 5 and 6 on the Clatskanie River. In particular, data was collected on water temperature, vegetation communities, hydrology, historical context, and geomorphology of the river reach. Using this information the hired engineering firm, Waterways Consulting, created a hydraulic model and plan set to 65% completion that restores the sites ecological processes. A strong emphasis was placed on the restoration of rearing habitat for coho and spawning habitat for chum in the restoration design. Designed habitat restoration actions include the excavation of some existing side channels to increase their connectivity with the Clatskanie River, placement of large wood within the side channels and on the floodplain, control of exotic invasive vegetation, exclusion of cattle from the project area, and restoration of the floodplains native plant community. The plan set will be used to seek additional funding to implement the proposed restoration actions and seek federal and state permits. Partners on the project include USFWS, ODFW, Columbia SWCD and the project site landowners.

The Clatskanie River watershed supports wild stocks of coho, steelhead, Chinook, cutthroat trout and, historically, chum. An ODFW fish trap installed just downstream of the restoration site has a preliminary estimate of the watersheds populations to be 36,850 (+1- 9,068) coho smolts, 71,075 (+1- 24,280) coho fry, and 10,648 (+1- 7,910) Chinook fry for the 2011-2012 year (Kristen Homel personal communication Oct 2012). Our project would design the restoration of -1,900 In. ft. of stream, 26-acres of floodplain, and the enhancement of -4,000 In. ft. of off-channel habitat to help augment these existing populations. Currently, the stream reach experiences extreme streambank erosion, is lacking in large woody debris, and is only connected to existing off-channel habitat at extremely high flows. In addition, the riparian buffer is dominated by reed canarygrass, suppressing the recruitment of native vegetation and allowing significant exposure of solar radiation to the stream channel. We would address these impacts by designing a project that restores the reachs ecological processes, thereby enhancing critical rearing habitat for juvenile salmonids and increasing their survival. In addition, we would restore spawning habitat for chum, which would improve their potential for reintroduction into this basin. Specific habitat restoration actions would include the placement of large wood, replanting of the riparian buffer to a diverse native mix of trees and shrubs, stabilization of the eroding streambank, installation of cattle exclusion fencing, and encouraging flows through the existing network of secondary and tertiary channels on the floodplain. The installation of large wood would enhance habitat and aid the reachs recovery by forming deeper pools, recruiting spawning gravel, supporting healthy macroinvertebrate populations, increased in-stream complexity, and enhanced over wintering habitat for juvenile salmonids. In addition, by replanting the riparian buffer and re-grading the stream bank, we will increase stream shade, detrital inputs supporting the food web, and reduce fine sediment inputs into important Chinook and chum spawning habitat.