漢江下流의 河中島에 對한 考察

Abstract

This paper has two aims; one is to find out the factors for forming sand-bars, and the other is studies of the shapes and landform on the Han River. The area of this study includes from Yangsoo-Ri, the point where North Han River and South HanRiver meets, to Shinpyoung-Ri, about 75Kms down from the Yansoo-Ri. This study concentrates, especially, 10 sand-bars in this district with a special reference to load, discharge, velocity, slope, meandering rate, width and depth of stream channels. In order to understand the whole picture of landform of this area, maps of summit level, gradient, relief and degradation on the Lower Han River are made. The changes of stream channel during 1916-1966 are studied through topographic sheets of 1916 and aerial photographs taken in 1966. Also meandering rate is measured by curvimater. Due to the condition of velocity, slope and discharge of this area of Han River, the most of sand-bars in the Han River are distributed in this district. Tide effect made little sand-bars on the down stream of Shinpyoung-Ri though other conditions are favorable for forming sand-bars on the Lower parts of Han River. There are three main types of sand-bars: delta shape sand-bars on the stream confluence, oval shaped sand-bars Located on the diverging points of streams, elongated ones formed at the former narrow stream channels. The Structure of sand-bars are usually belted by natural levee, back marsh or swamp material, and sometimes old rivers such as ox bow lakes. However, depositional materials are usually coarser than the flood plain materials because there are formed by turbulent flows during the flood season.