福州盆地内闽江洪水和潮汐作用的关系

A CORRELATION OF THE MIN RIVER FLOOD AND TIDE IN THE FOOCHOW BASIN

本文研究的目的是了解福州盆地内闽江洪水和潮汐的关系,初步探讨两者关系的一般规律,作为闽江下游水文地理教学上和下游地区进行经济建设方面,提供一些参考.内容包括:1、福州盆地闽江概况和闽江出口形势的简介.2、年最大流量和潮汐关系.本文研究的重点是福州盆地内的闽江下游河段.1、福州盆地闽江的概况和闽江出口形势的简介本文所指的福州盆地闽江是闽江干流总流量的水文站——竹岐——算起。

This paper is a preliminary study of the laws concerning the variations of the water level or the tide level under the influence of the interaction of the floods and the tides. The purpose is to furnish data for exploring the possibilities of greater utilization of hydrologic resources of the basin and of further improvements of the Min River waterways.During the flood period, the amount of water flowing from the main valley of the Min River into the South Channel is two to three times greater than into the North Channel. But the rising of the water level in the whole length of the South Channel is one to two meters lower than that of the North Channel. The range between them is greater with larger floods. Since the construction of the Min River dike, the above mentioned phenomena become more obvious. After the confluence of the flood of the North and South channels at Pogoda Anchorage the anount of the flood becomes the fullest especially during the uplifting effect of the high tide of the Spring tide. However, the highest flood level or tide level of Pagoda Anchorage is lower than that of the South Channel. At Pagoda Anchorage the range of the high tide level during the flood period and also the low water period is within half a meter. In general, the flood level is the highest at the North Channel. The south Channel ranks second. Pagoda Anchorage has the least. The Min River dike causes water to rise according to the above mentioned orders. But the effect of the dike at Pagoda Anchorage is not felt. The reasons for these variations are due to the differences in the width, length and depth of the river bed at the upper and lower parts of the channels, and also of the South and North channels.In time of flood, the limit of the changes of the tide leval tends to move toward the lower part of the channels. The greater the flood, the more is the shift. In comparison, with the low water period, the limit is shortened between two-seventh to three-seventh meter in length. At the North Channel the maximum limit reaches the place below the Kiangnan and Wanshou bridges, but the maximum limit at the South Channel is only several kilometers above eichou.Furthermore, the water level of the South Channel during the flood period tends to decrease gradually toward the lower part of the channel. For comparision, with the South Channel the range of the water level of the North Channel is over one meter changing abruptly just a little way above and below the bridge on account of the damping effect of the bridge olumns. The range increases with the increasing amount of the flood especially during the ebb tide. Since the construction of the dike this range is more obvious.In summation, the formation of the annual high water or high tide level at the South and the North channels appears during the moment of the annual flood peak. The height of the level of the middle and lower part of these channels is determined by the interaction between the tide height and the flood peak. In contrary, at Pagoda Anchorage the height of the level is dominantly influenced by the factor of the Spring tide. The flood is only a minor factor.The differences of the interactions of the flood and the tide in the upper and the lower parts of the channels as well as in the South and the North channels, cause the discrepancies in the amount of suspended sediments and the sediment discharge as well as the nature of the deposit. For instance, the amount of the suspended sediments and the sediment discharge is the greatest during the flood period. In the meantime, the amount of deposit in different sections of the river channels is also different. The process of the deposit is most obvious in the South Channel where sand bars and sand beaches are more widely distributed and the percentage of the deposit is the greatest. The Nortth Channel ranks second. The Pagoda Anchorage section has the least. The variations in the deposit of the different sections of the river channels affect the condition of the river navigation. The benefit of the river navigation at the Pagoda Anchorage section surpasses both the South and the North channels, but the North Channel is better than that of the South Channel.