Increasingly, the importance of vegetation in influencing the structure and function of riparian zones has been recognised (e.g. Bendix and Hupp, 2000; Tabacchi et al., 2000). This thesis explores vegetation dispersal and establishment in the riparian zones of two contrasting river systems, with a focus upon Salicaceae. Dispersal, hydrochorous transport, deposition and establishment of vegetation along the River Frome (UK), was investigated over one year. The study demonstrated the importance of hydrochory for dispersing propagules to new environments and for promoting diversity within the riparian zone. The role of hydrochory changed seasonally and with the hydrological regime, highlighting the importance of high flows for structuring and creating diversity in riverbank vegetation.