Analysis on residual coarse sediment transport in estuaries

The analytical expression for residual coarse sediment transport of Van de Kreeke and Robaczewska (1993) is extended for estuaries. The major extension concerns the contribution to sediment transport by residual current, which is ignored by Van de Kreeke and Robaczewska (1993). Tidal constituents M-0, M-2, S-2, N-2, M-4, MS4, MN4, M-6, K-1 and O-1 are used to represent the collinear tidal current. It is shown that interactions of Mo and all tidal constituents contribute to residual sediment transport when M-0 is not negligible. Thus, a representative tide based on M-2 and its overtides only is not sufficient to drive morphodynamic models in this case. The present analysis also reveals that triad interactions of compound tides with their basic constituents, i.e. MS4 with M-2 & S-2 and MN4 with M-2 & N-2, contribute to residual sediment transport, besides interactions of M-0 and M-2, and of M-2 and its even overtides M-4 and M-6. The extended analytical expression is applied to determine residual sediment transport in the Yangtze Estuary. It is demonstrated that a single representative tide does not exist for morphodynamic models in this case. This conclusion is likely to also apply to other estuaries in which residual flow is not negligible. (c) 2015 Elsevier Ltd. All rights reserved.