中文摘要：

简要介绍了钱塘江河口含沙量、泥沙粒径的分布特性,建立了钱塘江河口泥沙起动流速和挟沙能力公式,分析了河床大冲大淤、大冲以后大淤、上游段洪冲潮淤、下游段洪淤潮冲等河床演变特性,研究了河床冲淤对洪水和潮汐的巨大反作用.分析研究表明,涌潮到达时,水流激烈冲刷河床,引起含沙量剧增,大多在涌潮过后的20min内达到极值,形成大含沙量区.在平水期和枯水期,涨潮输沙量明显大于落潮,加剧了河口上游的淤积,涌潮是钱塘江河口大冲大淤的机理之一.

英文摘要：

In this paper, the distribution characteristics of sediment concentration and sediment grain size are introduced in brief, and the formulas of the sediment incipient velocity and the sediment carrying capacity in the estuary are established. The characteristics of the large variation amplitude of the riverbed, the rapid deposition after rapid erosion, the flood-induced eroding and the tide-induced silting in the upper reach, and the flood- induced silting and the tide-induced eroding in the lower reach are analyzed. The riverbed variation has a great impact on flood and tides. When tidal bore arrives, the flows of the tidal bore violently erode riverbed and result in sharply increased sediment concentration, which mostly reaches a peak value after twenty minutes, thus forming a high sediment concentration region. In normal and dry periods, sediment discharge in flood tide is larger than that in ebb tide, resulting in silting in the upper reach. The tidal bore is one of the mechanisms for serious erosion and deposition of riverbed in the Qiantang estuary.