钱塘江河口古海塘塘前滩地冲刷研究

Scour mechanism of the seawall beach of the ancient seawall in the Qiantangjiang Estuary,China

利用2010年以来钱塘江河口海宁古海塘塘前滩地地形精细化监测资料,结合河口洪水、潮汐以及宏观河床地形等资料数据,分析了古海塘塘前滩地冲刷机理。结果表明:(1)古海塘所在的强涌潮河段,潮强流急、河床冲淤变化剧烈,年际河床呈现丰冲枯淤,年内呈现洪冲枯淤、大潮期或冲或淤的特征;(2)塘前滩地高程对洪潮动力响应复杂,其中大缺口河段位于潮水上溯顶冲河段,塘前滩地以潮水冲刷为主,最低高程出现在梅汛后的秋季大潮期,洪水对该段滩地的影响主要是梅汛期冲刷河槽,江道容积越大,进而潮动力越强滩地冲刷越剧烈;尖山河段塘前滩地以洪水冲刷为主,梅汛期后的大潮期亦有一定的冲刷。成果揭示了塘前滩地高程对洪潮动力宏观层面的响应机理和时空差异性。

Based on terrain refinement monitoring data since 2010,land erosion mechanisms in Qiantangjiang Estuary were analyzed by combining flood,tide,and river regime data.The results present the following conclusions:(1)in the tidal reach where the ancient seawall is located,the tidal current is strong and rapid and the riverbed scours and silts violently,showing the characteristics of high flow,low flow,and siltation during the spring tide period.(2)the elevation of the beach in front of the pond has a complex response to flood and tide dynamics with temporal and spatial differences;the reach with a large gap is located in the reach with the top scour upstream of the tide,beach in front of the pond is primarily scoured by the tide,and lowest elevation occurs in the autumn spring tide period after the plum rains season flood.The primary impact of flooding on the beach is the scouring of the river channel during plum rains in the flood season.The larger the flood,the greater the volume of the river channel,tidal power of the reach,and intensity of the beach scouring.(3)the results discussed the relationship between macro riverbed erosion,deposition,and local beach changes and revealed the response mechanism of the scour elevation of the beach to flood and tide dynamics in the strong tidal reach.Short term erosional and depositional changes at the beach micro level must be further discussed through real-time dynamic observation and model tests.