"Sediment Dispersion in Salmon Spawning Streams: The Influence of Floods and Salmon Redd Construction," by Allen S. Gottesfeld, Marwan A. Hassan, Jon F. Tunnicliffe and Ron W. Poirier?

The article presents a discussion on the research paper "Sediment Dispersion in Salmon Spawning Streams: The Influence of Floods and Salmon Redd Construction," by Allen S. Gottesfeld, Marwan A. Hassan, Jon F. Tunnicliffe and Ron W. Poirier. According to the author, it is surprising that the researchers did not discuss the contradiction between their conclusion that salmon spawning increases the mobility of streambed gravels and the contrary conclusion supported by other investigators that bioturbation of streambed sediments by salmonids and other organisms, while mobilizing significant quantities of gravel and fine sediments during periods of biological activities decreases gravel mobility in subsequent high flows. It has been widely observed that bioturbation of streambed gravels increases the geometric mean or median particle size and reduces the proportion of fine sediments. According to the author Gottesfeld and others also speak of a positive feedback with sediment transport from floods, noting that optimum spawning habitat requires the vertical mixing and winnowing of fines that result from spawning activity, and conclude that recovery of normal sediment transport processes will be problematic in the many streams that now have depressed salmon spawning populations.