浚渫跡地の修復に関する施工上の影響と研究開発課題の抽出

Abstract

Sandminig for commercial construction aggregate and for landfilling projects has left borrow pits on the bottom in several coastal regions in Japan. The nation-wide survey revealed that the subaqueous borrow pits can be classified geomorphologically into a local depression type and a flatten-out type. As the local depression type of the borrow pits, for example, often cause severe deterioration of water quality such as formation of anoxia and blue tide, recontouring (raising the bottom) is expected to be effective to restore damaged ecosystems. In order to promote such geomorphological restoration effectively and to minimize negative effect, we summarized an impact-response flow diagram originated from such actions, displaying causal chains after placing materials into borrow pits. We also propose several research tasks on this matter; e. g., predictions of dispersion processes of particles and oxygen depleted water mass, fate and effects of fine chemicals contained or accumulated in the borrow pits, and propagation of restoration effects toward the whole basin-wide environment.