POLLUTION OF GRAVEL SPAWNING GROUNDS DUE TO FINE SEDIMENT.

Salmon and related species of fish use the structure of natural gravel-bed rivers for the purpose of spawning. Of all the factors that could adversely affect spawning success, fines accumulation in the gravel-bed streams is one of the most important. Laboratory experiments which model gravel-bed streams with poorly-sorted material were conducted in two parts: first, results were obtained from experiments during which no fine material was externally fed into the flume: and second, fine material was introduced into the channel and the experiments were repeated. An attempt was made to derive a relation predicting the characteristics of retention of fines in the substrate as a function of fines input and other factors.