千曲川におけるワンドの実態とその特徴に関する基礎的研究

抄録

Separation zone is a type of backwater that occurs on banks of the main stream or on sandbars where water is pooled (M. Church, 1993). Flow diverges into these pools, with declining velocity and energy gradient. Thus, separation zones is suitable for the refuge for aquatic organisms (hydrobionts) such as small fish. This is called wando* in Japanese. Until recent days separation zones (wando) have been decreasing due to the old type river improvement or the development of river basin area. With these backgrounds, several activities to restore the separation zone have started. However, it is difficult to control the river dynamics and to keep the land in a form of a separation zone.
In this study, the Chikuma River was selected as a study river and we analyzed that causes the creation of the separation zone based on river characteristics in order to effectively restore the separation zone. As a result, separation zones were classified into four types and the features of each type of separation zone were recognized.