河川流量管理のための河床付着物の視覚的評価に関する研究

抄録

Decrease of flow and reduction of disturbance affect river bed materials, periphyton and aquatic life. Fine sediments pile on riverbed and filament green algae proliferate. They impair visual appearance of riverbed. River flow management for restoring river ecosystem and visual appearance of riverbed needs knowledge of relationship between flow regime, visual estimation and periphyton.

In this study, experiments were performed and the relationship between visual estimation, quantity of periphyton, color of periphytic algael aseemblage was demonstrated. When the dry weight is little than 10 g/m², AFDM is little than 5g/m², fine sediment dry weight is little than 20g/m² and chlorophyll a is little than 30 mg/m² in periphyton, visual estimation is acceptable. It showed that human visual evaluation is affected by the color of periphytic algal assemblage. When relative abundance of green algae is higher (chlorophyll b /chlorophyll a is higher), periphytic algal assemble seems greenish. When diatom is dominant, it seems light brownish. Human evaluate that greenish assemblage is more beautiful than light brownish assemblage.