Development of hierarchical model of river ecosystem for its conservation and restoration-analyses on interrelations amongst sediment dynamism, channel geomorphology and ecological functions.

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Hierarchical structure of river ecosystems : Geomorphological features of each hierarchy in the river systems were reviewed. Segment classification was conducted for the Kizu River based on stream geomorphology and riparian vegetation patterns. Physico-chemical structure of hyporheic zones in the sandy bar was studied in the Kamo River in Kyoto City and changing patterns of water quality and water temperature in the sandy bars were presented. A distributed rainfall-runoff prediction system was developed for assessing flood attenuation under the dam operation in the Yodo River system.Interrelations between sediment dynamism and river morphology : Sediment amount accumulated in the channel was investigated in relation to the geomorphology and microhabitat structure in the Yoshino River in Nara Prefecture. Effects of sediment flushing from dams on the SS concentration and stream geomorphology were studied in the Kurobe River and the Takahara River. Monitoring system for erosion process of … More sediment in the reservoir bed during the flushing work was developed in the Kurobe Dam.Relations of hierarchical structure to habitat function : Determinant factor for distribution of oviposition sites in fish and aquatic insects were investigated was elucidated to be a feature of reach scale which is caused by oxygen supply through a set or physical factors such as hydraulic gradient, Froude number, and permeability of the streambed.Relations of hierarchical structure to material cycling function : Longitudinal changes in size and source composition of SPOM were investigated in Uji River and Kizu River under different flow conditions and the results indicate that sandy bar structure functions as both fifterer of drifting SPOM and provider of SPOM derived from riparian vegetation to the river ecosystem. Results of a series of field experiments on bioassay of epilithon in seventeen rivers indicated that production of the epilithon depends more on supply of organic matter, current velocity and water temperature than on nutrient supply.Amount of sediment supply required for restoration of ecological function in the river ecosystems : Benthos community was compared among rivers different in sediment load and found that the species diversity was the highest in the rivers with intermediate sediment supply. Effects of artificial sediment supply with flushing flow from the reservoir dams were studied in the Abukuma River and the Kuzuryu River, resulted in recovery of sediment moving which promoted a renewal of epilithon on the stone surface. Less