To predict the changes of natural systems like estuaries and tidal lagoons as a consequence of human interferences often numerical models are applied. An important aspect is the erosion and transport of sediment. Therefore, these models require formulations that describe the erosion of the sediment bed consisting of sand, mud and organic matter. A physically founded and validated process-based description of these mixed sediments is still missing. Recently, a theoretically derived formulation for erosion of mixed sediments has been proposed. However, a proper validation of this new formula is lacking. Therefore, a systematic study has been undertaken. First, studies have been executed to investigate the individually physical properties in this formula. Next, erosion tests have been executed on a large number of varying sample compositions using a straight, re-circulating flume. The effect of sediment structures and cohesiveness of the sediment bed has been investigated, from which the new formulations could …