Many of Earth’s large lowland rivers are heavily impacted by land change and hydraulic engineering to support a range of societal demands. Dams and river engineering for flood control have disconnected rivers from floodplains, reduced coastal sediment flux, and driven land subsidence of deltaic wetlands because of reduced sediment loads. Structural modification of lowland rivers alters hydrologic and sedimentary processes, resulting in unintended geomorphic and environmental adjustments that require decades to unfold. Such problems not only degrade associated riparian ecosystems but also increase human vulnerability to flooding. Integrated approaches to lowland river management are needed to reduce flood risk, conserve and restore riparian environments, while ensuring that lowland rivers continue to meet societal demands.