近年の小集水域における湿地環境の形成と河川流域におけるその役割

抄録

Abandoned paddy fields are increasing in Japan nowadays, especially in micro drainage basins in suburbs and mountainous regions, where some specific kinds of stream-swamp systems have formed to produce interesting features of ecosystem. We have continued observations of environmental changes in abandoned paddy fields in order to clarify their roles in river basin environment and rainfall runoff, measuring flow velocities and water qualities in a stream-swamp system there, monitoring discharge at the downstream end and collecting rainfall data near there. It was found out that the stream flows interact with topography, vegetation, soil properties and organic matters as same as ordinary rivers, that three species of freshwater fish, two of loach and one of carp, live there and that their inhabitation is strongly influenced to by changes in flow conditions caused by strong rainfalls, and that correlations between rainfall and discharge show quick runoff responses and changes due to cultivation abandonment.