Morphological modelling of intertidal mudflats: The role of cross-shore tidal currents

We describe a mathematical model of the sediment transport resulting from cross-shore tidal currents on an intertidal mudflat. The model is integrated numerically to determine the long-term ("equilibrium") behaviour of the morphodynamic system, and to investigate how the morphology of the flats depends on tidal range and sediment supply. Under a sinusoidal tide, the equilibrium flat is approximately linear below mean sea level (MSL) and convex above MSL, and advances seawards over long timescales. The cross-shore width of the flat is independent of tidal range, and increases with increasing sediment supply. Tidal asymmetry (flood- or ebb-dominance) leads to a steeper flat, and ebb-dominance can cause the flat to retreat landwards in the long term. Under a spring-neap tidal cycle, the shape of the equilibrium profile is very similar to that for a fixed tidal range, but the rate of accretion is significantly reduced.