Onshore migration and subsequent destruction of an intertidal slip-face bar was documented during a 1-day field experiment at Skallingen, Denmark, in August 2010. The experiment coincided with an unusual summer storm that was associated with a 40–50 cm storm surge and offshore waves that were significantly larger than the 5% annual exceedance wave height at the site. High-resolution measurements of morphological change were obtained at a spatial scale of 2 m and a temporal scale of 15 minutes and these were complemented by measurements of inshore waves, longshore currents and wave runup. The measurements demonstrated an example of positive morphodynamic feedback. Once the bar crest elevation started to decrease because of wave overtopping and sediment transport into the runnel on the rising tide, the bar crest lowered and overwash frequency increased, leading to enhanced crest erosion, even under conditions of constant or slowly falling tide conditions. Due to the relatively small spatial scale of slip-face bar systems and the occurrence of positive
feedback, they can be destroyed over a single tidal cycle.