riffles picture


 As an alternative to natural meanders, Newbury has suggested creating riffles in creeks to generate substrate complexity and enhance the availability of spawning gravel for kokanee salmon. In 2000 an experimental riffle was constructed in Mission Creek at the intake for the spawning channel water. Study of substrate changes for two years showed some improvement in gravel. During spring runoff in 2002, key rocks in the riffle appear to have dropped deeper into the substrate causing rocks that form the trough in the riffle to tumble downstream. Given the apparent vulnerability of the riffle to high spring floodwaters, this technique has been abandoned as a mechanism for efficiently improving substrate quality and quantity for kokanee.