Summary: One of the main targets of river regulation with dams and dykes is the stabilization of highly fluctuating water tables. While there is information about the overall impact of such regulation measures on plant species composition and richness, far less is known about specific species’ response patterns to reduced water level fluctuations. The response of 30 common grassland species to soil moisture and water level fluctuations was assessed. Floristic data were collected from the floodplain of the Elbe River, Germany, from 182 plots, 99 within the recent floodplain and 83 in an older floodplain, separated from one another by dykes. Hydrological data were collected weekly over 2 years at 37 water level wells. Using logistic regression, the patterns of species’ responses to hydrological regulation were predicted. The majority of species responded significantly to water level fluctuations. Species of high elevation habitats occurred at lower elevations where water level fluctuations were reduced, indicating increasing drought at high elevation habitats. However, species that occurred in floodplain depressions tended to shift from lower to higher elevations to avoid permanent inundation. Almost half of the species showed a significant preference for either highly fluctuating water tables, characteristic of the recent floodplain, or for stable water tables, characteristic of the older floodplain. The probability of their occurrence was either reduced or increased along a gradient of reduced fluctuations. These species’ responses could be partly explained by altered flooding regimes, although other factors, such as disturbance and dispersal processes, were also involved. Synthesis and applications. This study demonstrates that reduced water level fluctuations caused by the construction of dams and dykes lead to substantial changes in the spatial distribution of floodplain plant species and in species composition. The methodology reported here allows accurate prediction of shifts in floodplain vegetation in response to human‐induced alterations in floodplain landscapes. This can be used as a tool to assess river regulation measures and for floodplain restoration purposes, such as dyke relocations.

Throughout Europe the demands for improved flood protection on the one hand and the requirements to maintain and enhance floodplain forests on the other are perceived as conflicting goals in river‐basin management, revealing the urgent need for strategies to combine both issues. We developed an interdisciplinary approach for floodplain‐forest restoration identifying sites suitable for reforestations from both an ecological and hydraulic point of view. In the ecological module, habitat‐distribution models are developed providing information on ecologically suitable sites. In the hydraulic module, a two‐dimensional hydrodynamic‐numerical model (2D‐HN model) delivers the requested hydraulic information. The output of the two models is intersected. Subsequently, in an iterative procedure, the potential of plantings without exceeding critical water levels can be identified by hydraulic evaluation using the 2D‐HN‐model. The approach is exemplified using two reforestation scenarios at the Elbe River, Germany, showing considerable potential for softwood forest establishment without negative hydraulic effects.The approach reported here provides a solution for a severe conflict in river‐basin management that hampers the reestablishment of the strongly threatened floodplain forests in Europe. Alternative measures to enhance floodplain‐forest regeneration feasible under certain preconditions are discussed in the context of the current state of European large rivers.