Ocean Sci. Discuss., https://doi.org/10.5194/os-2018-53 Manuscript under review for journal Ocean Sci. Discussion started: 3 May 2018 c Author(s) 2018. CC BY 4.0 License. Frictional interactions between tidal constituents in tide-dominated estuaries 1 2 3 1 Huayang Cai , Marco Toffolon , Hubert H. G. Savenije , Qingshu Yang , and 4 Erwan Garel 1Institute of Estuarine and Coastal Research, School of Marine Sciences, Sun Yat-sen University, Guangzhou 510275, China 2Department of Civil, Environmental and Mechanical Engineering, University of Trento, Italy 3Department of Water Management, Faculty of Civil Engineering and Geosciences, Delft University of Technology, Netherlands 4Centre for Marine and Environmental Research (CIMA), University of Algarve, Faro, Portugal Correspondence to: Erwan Garel (
[email protected]) Abstract. When different tidal constituents propagate along an estuary, they interact because of the presence of nonlinear terms in the hydrodynamic equations. In particular, due to the quadratic velocity in the friction term, the effective friction experienced by both the predominant and the mi- nor tidal constituents is enhanced. We explore the underlying mechanism with a simple conceptual 5 model by utilizing Chebyshev polynomials, enabling the effect of the velocities of the tidal con- stituents to be summed in the friction term and, hence, the linearized hydrodynamic equations to be solved analytically in a closed form. An analytical model is adopted for each single tidal constituent with a correction factor to adjust the linearized friction term, accounting for the mutual interactions between the different tidal constituents by means of an iterative procedure. The proposed method 10 is applied to the Guadiana (southern Portugal-Spain border) and the Guadalquivir (Spain) estuaries for different tidal constituents (M2, S2, N2, O1, K1) imposed independently at the estuary mouth.