狭长小型河口冲淤特征与演变机制

Scouring and Silting Characteristics and Bed Evolution Mechanism in Narrow Small Estuary

摘要:

基于Mike21软件建立狭长小型河口——风河河口的二维潮流、波浪和泥沙输运数学模型，并运用验证合理的模型研究风河河口及其邻近海域的水沙动力特征，探讨50年一遇风暴浪作用下狭长小型河口冲淤演变的响应特征.结果表明,纯潮流作用下，河道总体呈现“上淤下冲”的演变态势，潮不对称输沙是风河河口地貌演变的主要原因；河口冲淤在正常天气下受潮流控制，在极端天气下受风暴浪控制；常浪与潮流耦合作用下，河道内冲淤分布与纯潮流相似；50年一遇波浪耦合潮流作用下掀沙能力显著增强，其中SE向和E向波浪影响最大，近岸海域主要呈冲刷态势，河口河道呈淤积态势，并且淤积厚度比纯潮流作用下高一个量级.

Abstract:

A two-dimensional hydrodynamic and sediment transport numerical model for a narrow small estuary, i.e. Feng River Estuary, was established based on Mike21 and well validated by field measured data. The model was used to study the characteristics of hydrodynamics and sediment dynamics in the Feng River Estuary and its adjacent coastal water. The response characteristics of sediment evolution in the narrow small estuary under a designed one in 50-year storm wave were mainly discussed. The results indicate that under the action of pure tidal current, the estuarine channel generally presents the evolution trend of “silting up and scouring down”, mainly caused by tidal asymmetric sediment transport. The sediment evolution in the estuary is controlled by tidal currents in the normal weather, while it is controlled by storm waves in extreme weather condition. Under the normal wave-current interaction, the sediment evolution in the estuary is similar to the one under the pure tidal current. The sediment suspension is significantly enhanced under a designed one in 50-year storm wave coupled with tidal current, especially for SE and E direction incoming waves. The erosion mainly appears in the coastal area, while the deposition emerges in the estuarine channel and the siltation thickness is one order of magnitude higher than that under the pure tidal current action.