砂鉄川ショートカット区間における水辺域修復工法の導入効果

抄録

We developed and implemented new shoreline rehabilitation techniques in the short-cut channel of the Satetsu River of the Kitakami River system in Japan. The river channel in the altered section had been straightened, causing habitat degradation only in the shore areas, which are indicated as biodiversity loss of the fish assemblage structure, steep bank slope, fast-flowing water and a monotonous riverbed. In order to restore this river section, we reduced the flow velocity by installing a group of wooden piles and we created gaps and slow-flowing backwaters by installing stone groynes. Within a year of completing the project, we confirmed that the fish diversity was similar to that in the natural sections of the Satetsu River. In addition to the restoration of the physical environment, the retention of woody debris and fine particulate organic matter and the establishment of the macroinvertebrate community in the rehabilitation area, are factors that contributed to a relatively rapid recovery of the fish community system.