Analytical investigation of superimposition between predominant M2 and other tidal constituents in estuaries

Huayang Cai, Marco Toffolon, Hubert H. G. Savenije

Wednesday 1 july 2015

11:15 - 11:30h at Amazon (level 1)

Themes: (T) Water engineering, (ST) River and coastal engineering

Parallel session: 9C. Coastal engineering

Analytical solutions for tidal hydrodynamics developed to date mainly focus on one predominant tidal constituent (e.g., semidiurnal M2), which fails to explain the tidal asymmetry when tide propagates upstream due to the fact that the tidal spectrum consists of different tidal constituents. Hence it is important to understand the superimposition between the predominant M2 and other tidal constituents. In this study, we apply a linear analytical model to the Guadalquivir estuary in Spain for given different tidal constituents (M2, S2, K1, O1) imposed independently at the estuary mouth. Although the linear model cannot reproduce the internal generation of overtides by means of non-linear interactions among the different modes, however it is able to reasonably capture the correct wave behavior (i.e., wave damping and celerity) for the different tidal constituents. To this end, a correction factor needs to be used for frictional dissipation to adjust the linearized friction term accounting for the interaction of minor constituents (e.g., S2, K1, O1) with the predominant tide. The underlying mechanism is explored with a simple conceptual model, where this interaction is analyzed by assuming that the velocities of the different tidal constituents can be summed up in the friction term.