Dynamic conservation mechanism of temporal water area and its roles in preservation of riparian ecosystem

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(1)Formation process of "Wando" backwaterWe conducted field research at "Wando" backwater, which is an embayment opening to main river channel, at Kiso river's a series of grolyns. as the example case with tidal effect in downstream area. Two scale geography, one is large scale including main Wando's scouring and the other is sub channel in deposition area in smaller scale by field research, literature research, and numerical simulations.It is explained main depression at Wando is formed under flood, by bed load transport affected by of vegetation area's expansionsAnd subchannels are formed by daily tidal motion of sediment on deposition area of sand. Additionally, these channels take an important role to supply different water quality to Wando area from sand substrate during ebb-tide stage.(2)Water quality in backwater and subsurface waterWater movement in subsurfacewater surrounding backwater, i.e. Wando, pond, are significant for mechanisms of water quality formation. Field research and numerical simulation shows that subsurface flow is change by the existence of backwater and accelerated.In sandbar, water quality, especially in Nitrogen, of subsurface water is changed by both by denitrification and supply from surface layer, which include organic matter.(3)Growth and detachment of algaeWhen we consider water quality in backwater, the effects by argae production is important. We conducts field experiment and laboratory experiment on algae's production, competition between filamentous and non-filamentous periphyton, and debouchments. Additionaly, we made numerical simulation model on algae competition