Modeling embryo survival affected by sediment deposition into salmonid spawning gravels: Application to flushing flow prescriptions

This paper presents a framework for predicting embryo survival in salmonid spawning gravels as a function of sediment deposition. This framework integ rates three quantitative relationships modeling the variations of substrate permeability with sediment deposition, apparent velocity with substrate pe rmeability, and embryo survival rate with apparent velocity. The model allo ws evaluation of the impacts of sediment deposition on embryo survival. The relative sensitivity of embryo survival to three selected environmental fa ctors is investigated. The model results indicate that embryo survival is m ost sensitive to the composition of fine sediments (or sediment-gravel size ratio). The maximum influences of the hydraulic pressure head and the leng th of intragravel flow path are similar to 60 and 35% of the value influenc ed by size ratio. The proposed model is applied to determine the timing of flushing flows. The results that suggest that the interval between flushing flows should be reduced when higher levels of embryo survival are prescrib ed or higher near-bed sediment concentrations are imposed.