Abstract
At the Keisei Dentetsu Oshiage line, which locates in the downstream of the Ara river, the new bridge construction is under way to secure the flowing capacity. As the construction proceeded, conservation groups were strongly worry about the survival of the rare animate beings, Mortonagrion Hirosei, which ranged in the phragmites field near the site. Taking the conservation of the habitat into consideration, we chose the landing bridge form instead of the banking form to make the temporary road for the beam construction. Also, to maintain the phragmites field and the revetment as the new habitat, “The Conservation Study Committee” was established. It followed that the phragmites field was designed as its ground height is adequate to the habitat and the revetment allows moderate inflow of river water to secure the wetness. We will conduct a follow-up research, and make conservation of nature in which Mortonagrion Hirosei can survive.
