Field measurement and numerical simulation are carried out for an artificial flush flood in 2010 in the downstream reach of Haizuka dam located at the Jouge River to quantify the effect of flush flood on the exfoliation of attached algae. Measured items are water level, chlorophyll a (Chl-a), SS and attached algae at several locations. The relation between Chl-a attached to riverbed stones and velocity at the same location before the flood and the relation between detached rate of the algae and accumulated bed shear stress during the flood are obtained based on the field observation and 2-D numerical simulation. Based on these relations the total amount of supplied algae to water over the measurement reach during the flood is estimated to around 15.0kg in which the total amount of exfoliated algae is estimated to around 9.4kg.
