Coupling Effects of Unsteady River Discharges and Wave Energy on Mouth Bar Morphodynamics

Abstract

As a key morphological unit at delta front, the evolution of mouth bar is of critical importance to channel bifurcation and the formation of deltaic distributaries and have received wide attention (Fagherazzi et al., 2015 and references therein, Wright, 1977). However, those studies were mostly carried out under the assumption that most of the sediments were delivered to the ocean during bankfull discharge stages, so was the most significant deltaic morphological evolution, and neglected periods of relative low river discharge. As such, the effects of unsteadiness of river discharge are largely elusive (Fagherazzi et al., 2015, Shaw and Mohrig, 2014). In natural deltas, the occurrence of maximum river discharge could be in-phase or out-ofphase with the occurrence of maximum wave energy, which further complicates their coupling effects (Wright and Coleman, 1973). Therefore, different combinations of flow regime and wave energy over a hydrologic period need to be considered, to fully explore the coupling effects of river discharge and wave on the estuarine morphological evolution. In this study, numerical experiments adopting different combinations of flow regime and wave energy were carried out to investigate the coupling effects of river discharge and wave on the evolution of mouth bar. We focused on the formation of mouth bar during high flows and the reworking processes of wave during low flows.