臺灣東部河口地形的變動時距與循環

林雪美; 張喬盛

臺灣東部河口地形的變動時距與循環

Date

2001-05-??

Authors

林雪美

張喬盛

Publisher

地理學系
Department of Geography, NTNU

Abstract

The estuary represents a very unique environment. It's influenced by forces from the rivers, the land, and the sea. Within the dynamic system, the estuary is located at the transition zone in which sediment-laden flows both from the river and the sea. The estuarine landforms may change due to the vaious combinations of wave, river discharge and tidal conditions. This study focuses on three estuaries in eastern Taiwan. The main aim is to outlook the change of the estuarine landforms in the different time span. It is expected that better understanding of the estuarine behavior may be helpful when conducting the development schemes regarding to the estuaries. The depositional forms of estuaries have significant daily, monthly and annual change due to the river discharge, wind, tidal range, wave, and typhoon frequency. First, the forms of estuaries are stable in the long-germ scale. Three estuaries have only slight change during the period from 1904 to 1989, moving back and forth within the distance of few hundreds meters. Second, the forms of the estuaries in eastern Taiwan have significant annual change due to the seasonal differences of discharge and monsoon. In summer, the channels usually become wider and sandbars are gentler and extended seaward. In winter, however, these sandbars become narrower, steeper and extend toward right bank. There is an obvious cycle of the change in the moderate time span. Third, the form of the three estuaries has most significant change due to the typhoon and storm. The mouth of channels will be narrowed or even closed when typhoon comes. But, the recovery time is different among the three estuaries.