Understanding the physical processes of the past is fundamental to our current understanding and management of the coastline. Depositional landforms, such as back-barrier marsh, are at particular risk from rising sea levels and therefore need to be managed effectively and sustainably. This study aimed to use particle characteristics to identify the role of coastal barrier progradation and high-magnitude low-frequency events, on the development of the back-barrier marsh at Budleigh Salterton, Devon. Particle characteristics plotted onto the bivariate plot model of Lario et al. (2002) revealed that barrier progradation did lead to a decrease in particle size. Following this initial decrease, particle size tended to increase up-core. This study indicates that this is the result of higher energy fluvial activity depositing larger sediments during lateral migration. Further, the plots revealed little evidence that high-magnitude low-frequency events have been significant in the marsh development, however further analysis is recommended.