A permeability study on salmonid spawning riffles in the Little River drainage and Canon Creek in Northern Humboldt County, California

I determined if local coho salmon (Oncorhynchus kisutch), Chinook salmon (O. tshawytscha), and steelhead trout (O. mykiss) redd location is dependent upon permeability of the streambed. The study took place in four coastal drainages in northern Humboldt County, California. The sampling period extended over a sixteen month period from June 2004 – October 2005. This period covered pre- and post-spawning conditions, as well as changes in seasonal flow. Surveys were conducted to determine if permeability affected redd placement, or if redd placement affected permeability. Sampling grids were established at each site to allow for repeatable permeability measurements. The number of measurements taken ranged from 37 to 105, depending on site and wetted width of the channel. Permeability measurements were taken using a battery operated pump to draw water through a perforated standpipe driven into the streambed at a depth of approximately 25 cm. I found that permeability was not significant in predicting redd location. In addition, permeability measurements varied in orders of magnitude at sample points only 30 cm apart. The results of this study support the need for further investigation of sampling methods that will be able to accurately assess condition of spawning gravel with consideration of extreme spatial variation while providing minimal disturbance to the streambed.