Effects of Sediment Transport on Survival of Salmonid Embryos in a Natural Stream: A Simulation Approach

A model is presented that simulates the effects of streamflow and sediment transport on survival of salmonid embryos incubating in spawning gravels in a natural channel. Components of the model include a 6-yr streamflow record, an empirical bed load-transport function, a relation between transport and infiltration of sandy bedload into a gravel bed, effects of fine-sediment infiltration on gravel properties, and functions relating embryo survival to gravel properties. High-flow events drive temporal variations in survival; cross-channel variations in bedload transport cause spatial variations. Expected survival, as a result, varies widely from year to year and between spawning runs in a single year. Alternative functions from previous research that relate survival to fine-sediment concentration in spawning gravel and to intergravel rates of flow yield categorically different results. The relative uncertainty of the components of this model indicates that the greatest research needs are to understand how sediment transport affects the intergravel environment and how these changes affect embryo development and survival.