Existing numerical models simulating the vertical growth of tidal marshes have only, to a very limited degree, been validated using observed data. In this study, we describe a refined zero-dimensional time-stepping model, which is based on the mass balance approach of Krone [in: Coastal Sediments '87, 1987, pp. 316-323], Allen [Mar. Geol. 95 (1990) 77-96] and French [Earth Surf. Process. Landforms 18 (1993) 63-81]. The model is applied and evaluated, using field data on suspended sediment and tidal regime as input and the historical growth of a specific minerogenic tidal marsh in the Scheldt estuary (Belgium) as independent data for model testing. First, the historical rise of the marsh surface during the past 55 years is reconstructed based on land use and vegetation cover changes, which are dated using aerial photographs and which are recognised in sediment cores. After marsh formation, the marsh surface builds up very quickly and asymptotically to an equilibrium level relative to the tidal frame. Second, temporal variations in suspended sediment concentration (SSC) were measured above the actual marsh surface during a 1-year period. These measurements show that the SSC, in the water that floods the marsh surface at the beginning of an inundation, increases linearly with maximum inundation height. The application of existing models, which assume a constant incoming SSC, leads to an underestimation of the observed historical growth and to biased predictions under scenarios of future sea-level rise. However, after incorporation of the relationship between SSC and inundation height, the observed vertical growth is successfully simulated. This leads to the conclusion that not only the decrease in tidal inundation, but also the decrease in SSC with decreasing marsh inundation height, is of great importance to fully explain and successfully simulate the long-term vertical morphodynamics of tidal marshes. (C) 2002 Elsevier Science B.V. All rights reserved.