Author(s): Richard Mcdonald; Jonathan Nelson; Vaughn Paragamian; Gary Barton
Linked Author(s): Jonathan Nelson
Keywords: Rivers; Habitat; Substrate; Morphodynamics
Abstract: White sturgeon in the Kootenai River, Idaho, USA, spawn successfully within an 18-kilometer reach of river every year since long-term monitoring began in 1991. Despite successful spawning, there has not been successful recruitment of a juvenile year class documented since operations of Libby Dam, upstream of the spawning habitat, began full flow management in 1975. Operations of Libby Dam reduced the mean annual peak flow by approximately 70 percent from 2000 m3/s to 600 m3/s. Where sturgeon spawn successfully in other rivers, the spawning substrate consists of gravel and larger sized material. Under current flow management conditions on the Kootenai River, the substrate in the spawning reach consists of sand. However, coring studies indicate there is suitable substrate buried under a meter or more of sand; following a 1600 m 3 /s high flow in 2006, m3/s a video survey revealed a sand free substrate containing gravel and cobble material. A multi-dimensional flow and sediment-transport modeling study of the entire spawning reach is conducted to gain insight into the effects of flow magnitude and duration on scour. Model predictions suggest scour of a meter occurs in the location of buried gravel within the spawning reach with a discharge of1300 m3/s over 14 days or 1600 m3/s over 6 days.
Year: 2010