Kootenai River Assessment

As part of a collaborative effort, the Kootenai Tribe of Idaho, Montana Fish Wildlife and Parks, and the U.S. Army Corps of Engineers retained RDG to identify restoration opportunities on a 62-mile reach of the Kootenai River between Libby Dam, Montana and Moyie Springs, Idaho. Riparian and aquatic habitat conditions on the Kootenai River downstream of Libby Dam are influenced by the dam’s effects on natural riverine processes. Libby Dam operations have altered flow and sediment regimes downstream of the dam by reducing peak flow magnitude, changing the timing (seasonality) of the hydrograph, and retaining the upstream sediment supply. Kootenai River temperature and nutrient regimes, which support primary productivity of the food web, have also been modified. The net result of these changes is a less dynamic river and an altered ecosystem that affects fish and wildlife resources along the river corridor.

A restoration suitability analysis was conducted, with emphasis on vegetation communities which support Kootenai River food web ecology. A hydraulic model was completed for the study area, and riparian vegetation communities were surveyed at reference locations. Existing vegetation categories were then compared with flow magnitude and flow duration, target flows for vegetation recruitment and establishment were identified, and mapping of riparian habitat potential and restoration opportunities was completed.