河口河槽季节性冲淤变化及其对河流来水来沙响应的统计分析——以长江口南槽为例

利用长江口南槽1989年12个月的实测地形图和大通站相应的水沙资料,采用GIS技术和数理统计技术分析了南槽的地形变化与河流来水来沙的关系。结果表明:南槽水深与大通站各月平均流量、输沙率和含沙量之间有明显的相关性,说明河口冲淤对流域水沙变化有敏感响应;河槽的响应具有1~1.5月的滞后性。

The Statistical Analysis of Response of the River Mouth Passage to Water and Sediment Discharges from the Changjiang River

Based on the data of the south passage of the Changjiang River Mouth and the data of water and sediment in Datong Gauging Station, and with the technology of GIS and mathematical statistics, this article analyzed the relationship of the change of the topography of south passage in the Changjiang River Mouth and water and sediment discharges from the Cangjiang River. The results are as follows: (1) There is a law of accretion in flood season and erosion in dry season in the south passage of the Changjiang River Mouth. The mean thickness of erosion and accretion is biggest in August and smallest in March. The biggest thickness of accretion is in August and the biggest thickness of erosion is in December. (2) There is good negative correlation between the monthly mean water depth in the south passage and the monthly mean riverine discharge, the monthly mean rate of the sediment discharge and the monthly mean suspended sediment concentration. The correlation is best when the monthly mean water depth is lagged about one month or one and half months from the monthly mean riverine discharges, the monthly mean rate of the sediment discharge and the monthly mean suspended sediment concentration. The reason may be that there is a distance about 640 km from Datong Gauging Station to the estuary and it must take some time for the river to reach the estuary from Datong Gauging Station. In fact, the negative correlation between the monthly mean depth and the monthly mean riverine discharge is false,for there is evident positive correlation between the riverine discharges, the rate of sediment discharge and the suspended sediment concentration. (3) In their correlation, the correlation between the monthly mean depth and the monthly mean suspended sediment concentration is best and the correlation between the monthly mean depth and the monthly mean riverine discharge is worst. This shows that the factor of sediment is more important than that of water for the erosion and accretion in the river passage. (4) According to the examination of F, the relationships between the monthly mean riverine discharges, the monthly mean rate of sediment discharges and the monthly mean suspended sediment concentration and the monthly mean depth of the south passage lagged about one month, one and half months and two months are linear correlation. The correlation is significant under the level of 0.01 or 0.05. (5) The human activities in the valley may affect the change of erosion and accretion of the estuary passage by changing the condition of water and sediment. We can select a best correlation equation to forecast the seasonal changes of the South Passage according to the condition of water and sediment in the future. Then we can make the groundwork in establishing the critical value of erosion and accretion. The critical value of erosion and accretion is significant to the forecasting of the change of erosion and accretion in the estuary passage. When the variable is the erosion-accretion value of the consecutive two months, we can get a critical value by the corresponding equation. It is indicated that the erosion and accretion in the estuary is very sensitive to the changes of the condition of water and sediment discharges from the valley and there is of special significance to recognize the correlation and create the correlation when the sediment discharge from the river to the sea is generally decreasing in the globe range.