钱塘江河口段动力沉积探讨

Dynamical Sedimentation in Qiantang Estuary

本文根据钱塘江河口水动力和沉积物分析成果,探讨钱塘江河口动力沉积特性.作者认为,钱塘江河口以潮动力作用为主,但洪季径流对河口段动力沉积有重要影响.钱塘江河口沉积物以跃移质为主,仅河口上段发育径流影响下沉积的推移质和悬移质.文章讨论了动力沉积的季节变化和沿程变化后认为,洪季常潮时受流域来沙的影响,河口上段沉积物中径较粗,分选较差,峰态宽平,正偏较弱;平水大潮季节,以海域来沙为主,潮水动力作用强劲,形成粒径较细,分选极佳,正偏较强,峰态尖陡的沉积.文章还简要讨论了细颗粒泥沙在钱塘江河口段的动力沉积,认为洪季河口上段受径流冲淡影响,在水动力掺混较弱处,可造成粘性细颗粒泥沙的絮凝沉积;其余时间和河段,强烈的涌潮掺混和强劲的水流剪切阻止了絮凝团的生成和沉积,并对洪峰作用时的絮凝沉积进行改造,在沉积地层中形成粘土质粉砂或粉砂质粘土镶嵌体.

The dynamical sedimentation characters are discussed based on the dynamical and sedimental analysed results in Qiantang Estuary of Zhejiang Province. It is pointed out that the tide flow is the major sedimentational dynamics but during the flood term, the runoff also play an important role on the sediments deposition. It is suggested that the sediments are majorly composed by leap load except in the upper section of the estuary where there are also solid and suspended load which were deposited under the runoff action during flood term. The grain size parameters analysis show that there are clear reversion dynamic sorting deposition which developed under the tidal dynamics in Qiantang Estuary, but it is modified by the sediments from river basin and the dynamics of runoff in the upper section of the estuary.