臺灣西南部河口地區之地形學研究

Abstract

The vincinity of the estuaries is one of the most populated area in the world. In order to ultilize the resource of this area more reasonably, the understanding of geomorphogical, hydrological and sedimentary characteristics becomes a main and basic task. Since estuary is located on the interface of river and sea, the morphology of estuary is influenced by the factors coming from both environments. The drainage basin area, shoreline length, shape factor, channel gradient, opening form, runoff, sediments, and monthly discharge etc. coming from the land. While the wind current, wave and tide etc. coming from the sea. This study area focuses on 20 estuaries of the south-western coast of Taiwan. The five of them are gravel estuaries and the rest are sandy. By correlation grain size of sandy estuaries has relationship with channel gradient below 100m, width of opening and shape factor. The forms of sand bar on estuaries are changed seasonly. Most of them has a tendency migrating southward due to northern moonsoon. The 20 estuaries can be classified into the wave dominated type, the tide dominated type and the runoff dominated type according average wave height, specific discharge and tidal range. Comparing the location of 20 estuaries during the period from 1904 to 1990(85 years). Most estuaries tend to migrate westward. The changes of estuaries are controlled by the intensity of wave and precipitation, the influence of reservior and hydraulic engineering and the changes of land use.