Salt marshes play a vital role in estuaries and coastal lagoons, by offering intertidal storage space that influences the tidal prism and tidal asymmetry. Survival of salt marshes depends on feedbacks between plant growth and sediment accumulation, which in turn are governed by marine boundary conditions. On a global scale, these boundary conditions are subject to changes dominated by sea level rise and intensified storms. Storms play an ambivalent, understudied role in the salt marsh sediment balance by delivering sediment and causing lateral salt marsh erosion. Detailed processes controlling the long-term residual sediment exchange between salt marshes and the adjacent tidal basin are still poorly understood. Consequently, it is unclear whether salt marshes will act as a source of sediment, or as a sink. This work package takes up the challenge to simulate and predict salt marsh development governed by changing boundary conditions and human influence, and, ultimately, to determine prerequisites for salt marsh survival and the resulting coastal protection.