长江口北支的涌潮及其对河口的影响

The Tidal Bore on the North Branch of Changjiang Estuary and Its Effects on the Estuary

根据现场踏勘、实测并结合历史资料,阐述了长江口北支涌潮的发育、种类、形态和特点,并利用流体水跃现象的Froude数判别,解释了涌潮成因。进一步研究表明,河槽束狭加大涨潮流速,河床淤浅则减缓潮波传速。北支在自然和人为的影响下,河槽不断束狭、河床逐渐淤浅是近年来涌潮发生次数增多、潮头增大的原因。随着涌潮潮头的推进,大量水沙上溯,这对北支和南支上段的滩、槽变化和河口环境有着深刻的影响。

The development, characteristics and cause of the tidal bore on the North Branch of Changjiang Estuary are expounded based on survey and measured data. The hydraulic jump can be distinguished using the Froude number. When the flood tidal current velocity exceeds the propagation velocity of tidal wave, the water particles transfer the kinetic energy to the potential energy, therefore the water level abruptly jump and forms bore. Further analysis suggests that narrowed river channel increases flood current velocity and silted riverbed slows down tidal wave propagation velocity. The river channel of the North Branch of Changj iang Estuary has been narrowed and its bed has been silted for recent years because of natural processes and artificial actions, which are the main causes of increased bore frequency and strength. With the bore head advance, a great amount of saltwater and sediments flow upstream. It has profound effects on the river channel evolution and environment of the estuary.