Channeling Floodwaters

The impacts of our restoration work can take years to manifest. Sometimes, it happens overnight.

In July 2015, Columbia Land Trust completed a major step in restoring a historic floodplain of the Lower Hood River that had been cut off 90 years ago by the Powerdale Hydroelectric Project. After removing a half-mile of a 10-foot-diameter pipeline from the site in 2014, the Land Trust perforated the levee that was built to protect the pipeline from floods. Three sections of the levee, totaling 500 linear feet, were excavated down to the level of a five-year flood event. We also placed roughly 100 large logs and nearly 100 boulders in the floodplain, with the goal of slowing flood waters and providing fish habitat.

Amazingly, the five-year flood event we planned for happened just five months after we completed the project.

Last week, when heavy rains drenched the Columbia River region Stewardship Lead Kate Conley visited our Hood River floodplain restoration site. The roiling Hood River had slowed down to around 7,000 cubic feet per second (CFS) after peaking at 14,700 CFS on Monday, December 7th. These flow levels were high enough for water to spill across the levee excavation sites and into the floodplain.

Note how the main river channel is rushing at high velocity at the beginning of the clip, but as the camera pans left to the newly activated side channel, flows are much calmer. Flood conditions like these demonstrate why we restored the river’s access to the side channel. The logs and boulders we placed throughout the floodplain help slow flood waters and offer vital refuge for fish and other wildlife.

Without access to side channels and historic floodplains, flooding rivers rage downstream at high speeds, conditions that can be costly to humans and wildlife alike. Just look at this channelized portion of the Hood River for comparison.

In 2016, the Land Trust will turn its Hood River restoration efforts to riparian revegetation (replanting the riverside). We’ll replant the three-acre floodplain area that we reconnected to the river by removing the pipeline. In the meantime, we’re hopeful that our side channel restoration efforts will help support salmon and other fish in the soggy months ahead.