崇明东滩不同部位的季节性沉积研究

A STUDY ON SEASONAL EROSION-ACCRETION CYCLE OF CHONGMING EAST TIDAL FLAT,THE YANGTZE ESTUARY

2002年4月至2003年4月,通过对崇明东滩南部、中部和北部的标志桩观测以及实地观测分析,发现崇明东滩在一年中不同季节冲淤变化过程存在很大差异:春季到夏季,南部以冲刷为主,中部和北部以淤积为主;夏季到秋季,南部和中部以淤积为主,北部表现为冲刷;秋季到冬季,南部、中部和北部都以冲刷为主;头一年冬季到次年春季,南部和北部以淤积为主,中部则表现为冲刷。在同一观测路线上,不同季节高、中、低潮滩冲淤也存在一定差异。通过对沉积物粒度、水体含沙量等指标的测试,并借助潮差等资料,探究了影响潮滩季节性沉积的因素,发现潮滩季节性沉积与潮滩基础地貌、水体含沙量、水动力、潮流等有密切关系;但在不同部位不同季节,各因素对潮滩冲淤影响程度各不相同。

During the period from April 2002 to April 2003,mark-stakes and field observations were conducted on tidal flats in eastern Chongming Island of the Yangtze Estuary. The seasonal erosion and deposition cycle differed in southern part, east part and northern part. From spring to summer, the southern part was eroded,other parts were deposed;from summer to autumn, the northern part eroded, other parts deposed;on the contrary, from autumn to winter the erosion and deposition was different from other seasons; from winter to the following spring,the middle part was eroded,other parts deposed. Erosion and deposi- tion were very much different in high tidal flat,middle tidal flat and low tidal flat in the same researching route. Based on the analysis of sediment grain size, suspended matter concentration in the water and other indicators, and on the examination of tidal variation data in the Yangtze Estuary, we found that the seasonal erosion and deposition cycle is closely linked to the morphology, suspended matter concentration in the water,hydrodynamics, tidal variation, wind direction, etc. But different effects may be observed in different parts and different seasons.