The role of climate in determining foredune types and modes

Foredune morphology can be influenced or controlled by multiple natural factors including sediment supply, wind regime, vegetation cover and distribution, species presence/absence, plant morphology, surfzone-beach type, wave erosion and storm frequency and magnitude, and barrier dynamics (e.g. prograded, aggraded, or retrograded barrier types). The role of climate in controlling foredune type and morphology, as well as foredune mode (continuous ridges, discontinuous ridges or nebkha) has been poorly investigated to date. This paper examines the role of climate, and, in particular, rainfall, in controlling vegetation cover, and foredune type and mode. In general, as rainfall declines the vegetation percent cover declines, tree species disappear, and foredunes tend to be less and less regular symmetrical ridges and more discontinuous foredune/blowout complexes. As annual rainfall falls below ~300 mm, nebkhas become more common and eventually only nebkhas can form in arid coastal environments. Multiple examples of foredune types and modes in various climate settings are examined to show that climate, and especially rainfall is indeed a major driver of foredune type and mode. However, shoreline progradation rate or shoreline stability may exert an influence especially where the shoreline has been stable for a long period of time.