FUNDAMENTAL STUDY ON FRACTURE CONDITIONS OF HERBS IN RIVERS UNDER FLOODING

Abstract

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.