Adding Habitat Complexity to Aid Fish Recovery Efforts within the Channelized Okanagan River, BC

To aid in flood control, the Okanagan River in British Columbia was completely channelized in the 1950’s with the exception of a small portion flowing through tribal land. In an effort to return portions of the channelized Okanagan River back to a more natural condition and regain the habitat quality and quantity that has been lost, the Okanagan River Restoration Initiative (ORRI) concept was conceived.  ORRI is a collaborative ecosystem approach involving a steering committee as well as several Canadian and American partners and funding contributors which addresses the habitat concerns of the Okanagan River approximately 17 km upstream of Osoyoos Lake.

The ORRI project is divided into phases. Phase I was completed in 2009 and consisted of removing 1.2 km of dyke and 0.5 km of river re-meandering. For economic and habitat preservation reasons, a split channel design was selected. This design re-connects two isolated oxbows to the Okanagan River. The Okanagan River flow was designed to be equally split between the main stem and the re-connected oxbows. There are potentially two other phases that could be completed as part of ORRI.

During the winter of 2008, the dyke located along the west side of the Okanagan River was removed, reconnecting the river to 15,000 m² of contiguous floodplains. During the summer of 2009, the river was re-connected with its two historic meander loops following the original naturally formed channel. Spawning platforms and boulder clusters were placed in the excavated channels to enhance the habitat quality for sockeye salmon (Oncorhynchus nerka), steelhead/rainbow trout (O. mykiss) and potentially Chinook (O. tshawytscha). Another spawning platform and a rock riffle were built in the main stem channel replacing the existing uniform bottom by pool/riffle sequences. Five gravel bars were built in order to increase the water depth in the main stem river and to minimize egg loss during winter lower flows. Boulders and logs were placed in the oxbows to enhance the habitat for the Western painted turtle (Chrysemys picta bellii). Re-vegetation of disturbed areas started during the fall of 2009. Intensive outreach activities were conducted prior, during and after construction.

On-going aquatic and terrestrial monitoring activities are measuring the biological impacts of the restoration. Spawning substrate, wetted depths and Froude numbers were improved for salmonids. Sockeye and Chinook were observed using the spawning structures created only a month after they were built.