INVESTIGATION OF SEDIMENT DYNAMIC CHARACTERISTICS FOR THE ARIAKE SEA AT THE TIME OF FLOODING

Abstract

 In the Ariake Sea, the events of heavy rainfall have caused a large amount of river water and sediment to flow into the sea in recent years, resulting in salinity decrease and sediment accumulation. Additionally, a lot of bivalves such as clams and pen shells die. This study developed a sediment transport simulation model with the unstructured-grid system in the Ariake Sea and performed the simulation during the past heavy rain period. As a result, in the Chikugo and Kikuchi Rivers, sedimentation of 40 cm or more occurred near the estuary, and sedimentation of 5 cm reached a maximum of 3.7 and 1.0 km, respectively. The dependence of the sedimentation area on the timing of the outflow of water at the mouth of the Kikuchi River was investigated. The results showed that the sedimentation trend was different when the outflow of water was at high tide and low tide, with the sedimentation distribution from the mouth of the river spreading westward and southeastward, respectively.