Boulders as a signature of storms on rock coasts

This paper is the first review of coastal boulder studies; it serves as a peer-reviewed introduction to a special issue on the topic of ‘Boulders as a signature of storms on rock coasts’. Since 2004 and the Indian Ocean tsunami, most coastal boulder research has been focused on using boulders as sedimentary signatures of palaeo-tsunami events and the most commonly used transport equations typically suggest that large boulder deposits are products of tsunami rather than storms. There is growing empirical evidence demonstrating (on inter-annual to century timescales) that storm waves are capable of transporting and depositing boulders of significant size at elevations well above sea level. Current process studies of how boulders are eroded, transported and deposited have not received wide attention by rock coast geomorphologists or palaeoenvironmental reconstruction scientists. This special issue is framed around the goal of highlighting our current understanding of the role of storm waves as a driving mechanism for boulder erosion, transport and deposition. Here, we review the current state of knowledge about boulder dynamics, boulder responses to storms and boulders as sedimentary signatures of storm events. We identify gaps in our conceptual and quantitative understanding. Lastly, we propose means of addressing research gaps, improving consistency between researchers and collecting multi-purpose data. This review and the papers contained within the special issue provide an improved understanding of coastal dynamics; particularly the role storms can play in influencing erosion rates and depositional patterns of coarse material (i.e. boulders or larger), which has hitherto been under represented in the literature