Author(s): Huayang Cai, Peng Yao, Suying Ou, Qingshu Yang

Linked Author(s): Huayang Cai

Keywords: Residual water level, tidal rivers, overtide, tidal asymmetry

Abstract: As river flow debouches into the sea, it is affected by the fluctuation of tide at the estuary mouth, resulting in a backwater zone where the residual water level (averaged over a lunar day) tends to rise in landward direction. It is known that backwater hydrodynamics, especially the variation of residual water level, is controlled by the river-tide interaction, while it follows the traditional stage-river discharge relation in the upstream river-dominated region. However, the contribution made by tidal asymmetry due to the generation of overtides and their interplay with river flow is poorly understood. This present study aims to understand the impact of nonlinear M4 overtide on the increase of residual water level in tidal rivers. To quantify the contribution made by nonlinear M4 overtide, the numerically computed subtidal friction is decomposed into different components representing contributions by the river flow alone, the river-tide interaction, and the tidal asymmetry due to internal generation of M4 overtide. Numerical results show that the influence of nonlinear M4 overtide on residual water level becomes important with increasing tidal amplitude to depth ratio and its relative importance can be represented by a tidal asymmetry term, which depends on the sign of the phase relation between M2 and M4

DOI:

Year: 2017