Abstract
Recently, importance of river environment is getting recognized in Japan, so that river improvement taking river ecology into consideration, the nature-oriented method is one of which, is carried out. However, in present stage, relationships between habitat and living creatures are not clear. The purpose of this study is to make clear whether nature-oriented method distorts river ecology or not. Particularly, in this study, we evaluated physical environment and existence of aquatic insects around the nature-oriented bank and the concrete bank in a improved river (Gogyou river in Ibaraki Prefecture), based on those in a natural river (Kinu river in Tochigi Prefecture). As a result of comparing existence of aquatic insects around the nature-oriented bank with those around the concrete bank in Gogyou river, existence of aquatic insects around the concrete bank is more than those around the nature-oriented bank. One of the reasons is that the depth of water around the concrete bank is lower than those around the natureoriented bank. Consequently, to keep the depth of water shallow should be considered in river improvement on the flat low lands.
