This dataset contains the data presented in the article: L. Cornacchia, J.P. Bakker, E.C. Koppenaal, et al., Spatial and temporal variation in long-term sediment accumulation in a back-barrier salt marsh, Geomorphology (2024), https://doi.org/10.1016/j.geomorph.2024.109191.The aim of this research was to investigate the spatial and temporal variation in sediment accumulation within the back-barrier salt marsh of Schiermonnikoog (The Netherlands). We conducted field measurements focusing on two parameters: elevation and thickness of the salt-marsh deposits. Elevation was measured with an optical levelling instrument before 2005, and a Trimble Spectra Precision laser from 2005 onwards. For the thickness of the deposits, we collected soil samples using a narrow auger. These measurements were conducted at two spatial scales: at the landscape scale, we covered the area from the base of the dunes to the intertidal flats with a grid of 820 points (sampled only in 2010). At the sub-catchment scale, we established six small-scale permanent