Fringing intertidal flats are common features of elongated estuaries. We generalized the geometry of profiles of individual intertidal flats towards a common relationship, based on extensive measurement data of various estuaries. We found a strong linear relation between the width, slope and height of linear intertidal flat profiles, which also yields well for the mild-sloped upper part of convex-up profiles. Deviations of this linear relation at the lower steeper part of the flats are the result of dominating alongshore currents.@en

Three key factors that caused the erosion at the lower part of the intertidal area are identified: (1) the peak of the storm (with the highest waves) occurred during low water leaving the high elevations unexposed; (2) the storm surge induced unusually high flow velocities during low water; (3) the water depth at the lower part of the flat was small (±1 m) for several consecutive hours causing the waves to be highly effective. A low-water storm is therefore very effective in eroding the bed and should be considered as an important morphological event for specific parts of the tidal flats. Despite the fast recovery of the bed, the initial bed level was not reached. This implies that the storm has a longterm effect as well. Although long-term morphological consequences seem limited by the fast recovery, ecological consequences are expected to be substantial. @en