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.

The final chapter on human impacts to lowland rivers logically ends at the basin terminus, at the coast. Large flood basins and deltas are the most challenging environments to manage because of being impacted by ground subsidence and coastal storm surge events, particularly large populations in delta cities. Artificial floodwater diversion mirrors natural flood pulses, although it also disturbs aquatic ecosystems that requires further management. Challenges with floodwater diversion for environmental management of the lower Sacramento basin links to historic hydraulic gold mining. A major geomorphic phenomenon that influences flood basin environments is channel avulsion, which can be set up by embanked floodplain sedimentation and subsidence. Ground subsidence problems are particularly acute as regards flood control infrastructure, increasing the risk of dike failure during coastal storm surge events. Urban flood basin subsidence and flood control challenges is examined in a review of the epic 2011 Chao Phraya River flooding of Bangkok and the 2005 coastal storm surge flooding of New Orleans by Hurricanes Katrina-Rita.