Shoreface morphodynamics along the Holland Coast

Abstract

AbstractThe morphodynamic behaviour of the shoreface of the Holland coast has been investigated over the medium- and large-scales (years to decades). This is a wave-dominated, uniform coastline backed by dunes and uninterrupted by tidal inlets. The work takes a data-orientated approach using the ‘long’ profiles in a data set extending over 32 years and covering 81 km of coast. These profiles are spaced every 1 km alongshore and extend to a maximum offshore distance of 3 km (approximately 16 m water depth).Previous work based upon cross-shore profiles suggests that there is a seaward limit to significant depth change, or activity, on the upper shoreface over the small- and medium-scales (termed ‘depth of closure’). Examination of the data set shows that the middle and lower shoreface is also morphologically active in many instances, with the activity increasing with timescale. Many profiles exhibit closure on the upper shoreface, and then reopen on the middle/lower shoreface, exhibiting morphological activity. This deeper shoreface morphodynamics appears to be related to onshore supply of sand to the active zone. Hence, the analysis shows that the upper, middle and lower shoreface are coupled, as widely assumed, and has widespread significance for understanding long-term coastal evolution.