出水時における河川内草本類の破壊条件に関する基礎的研究

摘要

沿岸域に漂着する多量のゴミは，環境·海洋生物 に悪影響を及ぼすとともに，回収のための多くの労 力や処理費用を必要としている. そのため，こ れらの漂着ゴミは近年社会問題化しており，我が国 では海岸における良好な景観及び環境を保全することを目的とした「海岸漂着物処理推進法」がH21年 に施行された.%Although a main source of marine litter is known to be herbs grown thick in rivers, there were little information for flowing conditions of herbs due to fluid forces. The purpose of the present study is to clarify fracture conditions of herbs in rivers under flooding conditions. In this study, we conducted field measurements of the amounts of herbs and in-situ herb pulling tests in Edogawa and Oohorigawa Rivers. Fluid forces on herbs were also evaluated using numerical simulation. The results for leaves of herbs indicate that leaves were partially carried out in a flooding event mainly due to fluid forces. The results for caules of herbs revealed that the caules were also flowed in a flooding condition because caules broke due to bending moments from fluid forces.