Our results are confirmed by field observations in small streams (Fig. 1) in Western Europe. The calculated time scales suggest that bed erosion in rivers with formerly mill activity may continue for several hundreds of years. A comparison between water mill systems in Western Europe and the USA shows that, even though there are fundamental differences in water mill design, the morphological processes caused by the construction and the removal of water mills on both continents result in net incision of the river bed into the valley bottom, a reduced trapping efficiency of floodplains for suspended sediments, a terraced landscape, a disconnection of the floodplains from the river bed, and reduced floodplain inundation rates