Distribution and constructed morphology of artificial foredune notches

Foredune notches are a contemporary management intervention on coastal sand dunes, which aim to create and enhance bare sand and transitional habitats and/or increase resilience to climate change. These features consist of an excavated depression within the coastal foredune, designed to facilitate aeolian sediment transport from the beach into the inter- and back dune areas. Despite their increasing use by site managers and conservation organisations, foredune notches are under-researched, with existing analysis being almost entirely site-specific and descriptive. In this study, we present the first comprehensive, global study of these features; 133 notches were identified across the Netherlands, United Kingdom, France and New Zealand using peer-reviewed and grey literature. These notches were then verified using aerial imagery. The dimensions of 132 notches were measured using aerial imagery captured shortly after construction to understand the constructed morphology of these anthropogenic landforms. The results show that there is significant variability in constructed morphology both within and between sites. At a national scale, notches in France (average length 14.48 m, width 7.62 m, slot width 8.39 m) and New Zealand (average length 14.58 m, width 8.47 m, slot width 5.49 m) were characteristically smaller than those in the United Kingdom (average length 113.83, width 51.11 m, slot width 22.67 m) and the Netherlands (average length 109.81 m, width 81.02 m, slot width 24.67 m). There was also a large degree of variation in the relationship between landform length, landform width and ‘slot’ width, further demonstrating the diversity of current notch design. These results demonstrate that the current practice of referring to all these excavated landforms as ‘notches’ without further qualification is ineffective in communicating the diversity of size and shape of constructed foredune notches. Here, we propose a systematic classification scheme that standardises notch morphology, improving comparability across studies and enabling future research to better assess and communicate the influences of differing constructed morphology on aeolian, sediment and vegetation processes.