The paper presented the impact of dredging on the vegetation of a regulated section of a lowland river based on the example of the Krąpiel River (NW Poland). The field research with pre-investment monitoring was conducted over three vegetation seasons in the years 2008–2010. Mechanical dredging and alignment of the river bed caused changes in vegetation structure. Reducing the diversity of habitat contributed to observed impoverishment of plant communities and species that build them. In the first year after dredging, communities from class Bidentetea tripartitae (Chenopodietum rubri) were dominant along the flood terrace covered with a layer of dredging material. In the second year after dredging, terophytes were again replaced by rush communities, dominated by Phalaridetum, Phragmitetumand locally Riparian tall herb communities.