FORCED DETACHMENT OF ATTACHED ALGAE IN DOWNSTREAM REACH OF DAM BY ARTIFICIAL FOOD

Abstract

Laboratory experiment on relation between bed load and algal detachment revealed that bed load with the diameter of 5-15mm is most effective to remove attached algae. A prediction model of detachment of the attached algae, which consists of flow equation and the relation between tractive force and algal detachment, was constructed and applied to a riverine section in about 1 km downstream reach from Miyagase dam, Kanagawa, Japan, where serious proliferation of filamentous algae occurs. The result shows that the artificial flood with the smaller discharge, compared with the present flush discharge, is enough to remove the attached algae when the bed load with the diameter of 10.4mm was supplied with sufficient.