AbstractIn order to maintain an elevation in the intertidal zone at which marsh vegetation can survive, vertical accretion of the marsh surface must take place at a rate at least equal to the rate of relative sea‐level rise. Net vertical accretion of coastal marshes is a result of interactions between tidal imports, vegetation and depositional processes. All of these factors are affected, directly or indirectly, by alterations in marsh hydrology which might occur as a result of sea‐level rise. The overall response of coastal marshes to relative sea‐level rise depends upon the relative importance of the inorganic and organic components of the marsh soil and the impact of increased hydroperiod on net accumulation. The varied combination of factors contributing to sediment supply, and their complexity at the scale of individual marshes, means that predicting the response of suspended sediment concentration in marsh floodwater to any changes which may occur as a result of sea‐level rise, at anything other than the local scale is unlikely to be accurate. The impact of sea‐level rise on net below‐ground production is also complex. The sensitivity of certain species to waterlogging and soil chemical changes could result in a change in species composition or the migration of vegetation zones. Consequently, predicting the net impact of sea‐level rise on organic matter accumulation is fraught with difficulties and requires improved understanding of interactions between vegetation, soil and hydrolo