CHARACTERISTICS OF SAND TRANSPORT BY FLOOD FLOWS IN THE ESTUARY OF THE CHIKUGO RIVER WITH COMPLEX RIVER BED LAYERS

Abstract

A series of environmental issues in the Ariake sea has been believed to be caused by a lack of sand supply from the Chikugo river to the Ariake sea on the basis of few investigations of characteristics and amount of sediment transport in the the Chikugo river estuary . To make clear the characteristics of river bed material, the core sample survey and supersonic echo sounding has been conducted .Its shows that the sand and gata-soil are exiting with complex layer structure of sand and gat-soil respect to depth. And authors applied unsteady quasi three-dimensional river bed variation analysis using observed temporal changes in water surface profiles of 2009 flood. The result of analysis demonstrated that bed variation occurred in the river channel and sand was transported from the Chikugo river to the Ariake sea. In addition, the river bed movement and deformation was ascertained by 3D laser scanner data measured in the ordinary flow under the daily tide change.