新安江大洪水对钱塘江涌潮的影响研究

Impact of extreme flood in Xin’an River on tidal bore in Qiantang River Estuary

新安江水库首次九孔泄洪,恰逢下游大潮,涌潮汹涌,洪水与涌潮相互顶托,九孔泄洪对涌潮的影响研究具有重要学术意义,并对两岸防洪调度和海塘安澜具有工程实际意义。该文通过分析实测资料和平面二维涌潮数学模型,研究了泄洪对涌潮的影响。结果表明,泄洪对涌潮的影响显著,存在直接影响和间接影响。直接影响为仓前站上游的涌潮基本不出现,盐官站下游沿程涌潮高度增加,涌潮流速和传播速度均减小;“一线潮”会更加平顺,“交叉潮”难以出现。间接影响为泄洪冲刷河床,增大河床容积并降低沙坎高程,增加进潮量有利于涌潮传播和加强。总体而言,泄洪增加了盐官以下河段的涌潮高度,但涌潮流速减弱且到达时间滞后,涌潮的气势减弱,交叉潮难以出现,降低了涌潮的观赏价值。

The first nine-hole discharge from the Xin’an River Reservoir coincides with the spring tide at the downstream.There is mutual supporting force between the flood and the tidal bore. It is of greatly theoretical and practical significance in the study of the effect of nine-hole discharge on the tidal bore, the management of flood control operation and seawall safety. In this study, a two-dimensional mathematical model of tidal bore, combining with the field data analogy analysis for run off, sand ridge elevation and channel volume, are used to identify the influence of flood release on the tidal bore in Qiantang Estuary. The study results indicate that the effect of discharge on the tidal bore is remarkable, there are direct and indirect effects. The direct effect is that the tidal bore upstream of the Cangqian station barely appears, the tidal bore height increases, the tidal current velocity and the propagation velocity decrease downstream of the Yanguan station, and the "shape-line tidal bore" becomes smoother, and the "cross-tidal bore" rarely appear. The indirect effect is the river bed erosion caused by the flood discharge, results in increasing the channel volume and decreasing the sand ridge elevation, therefore, promoting the flood tidal volume and contributing to the propagation and strengthen of the tidal bore. Overall speaking, the discharge increases the tidal bore height downstream of the Yanguan station but the tidal current velocity decreases and the arrival time is delayed, and the tide momentum decreases, making it difficult for the cross-tides to appear, reducing the viewing value of the tide.