Hydraulic Structure and Material Transport in an Irrigation Channel with a Side-Cavity for Aquatic Habitat

摘要

Due to the growing concern for natural environment conservation in Japan, agricultural channels have recently been required to provide structures for an aquatic habitat. Following such request, an irrigation channel running in To-on, Ehime, was reconstructed for aiming to create the aquatic habitat by widening a part of the channel. This paper deals with the flow and material transport in the channel with a side-cavity, by means of field observation and numerical experiment. The field observation revealed a clock-wise eddy in the cavity. The average velocity in the cavity was less than10 cm/s and flow in the cavity was always calm, not so depend on the discharge in the channel. To simulate the flow and then investigate the material transport in thechannel,a horizontally 2-D shallow water flow model combined with quadtree numerical grids was used. The materials were modeled to be transported horizontally with the same speed as water flow. At the same time, however, they settle down following the Stokes law of resistance. The computed result showed that the material having small settling velocity is easy to be transported into inner part of the cavity.