Sandy beach ridge system profiles as indicators of changing coastal processes

Abstract

Many prograded coastal plains, barriers and spits in mid-latitude swell wave environments have a surface topography which consists of sandy beach ridges. These ridges are some- times termed parallel dunes because they develop successively parallel to a prograding shoreline. Sandy beach ridges in New Zealand and southern Australia originate as foredunes and can be contrasted with gravel beach ridges which are formed by the action of storm waves. Hesp (1984a, b) has suggested that 'relict foredunes' is a more appropriate term for beach ridges formed by eolian deposition. The development and form of foredunes is influenced by a number of factors including wind and wave energy, beach profile, sediment characteristics and supply, and vegetationidde type and cover. Some of these influences vary laterally along the shore of an embayment but have been relatively uniform through time along single transects normal to the shore- line. However, the sediment budget has varied considerably along many coasts during Holocene time with onshore sediment transport having been particularly pronounced following the post-glacial transgression but slowing or ceasing during more recent Holocene time. Irregular coasts with pronounced littoral drift may also experience abrupt variation in the sediment budget owing to changing coastal outline.