Dams and geomorphology: Research progress and future directions

Dams impose changes of flow and sediment transfer that drive changes of channel form along the downstream regulated river. These changes have been described for more than 50 years but process-form relationships have only been advanced with the establishment of a conceptual framework during the 1970s, and then the extension of monitoring data and advancement of remote sensing technologies, particularly over the past 20 years. This paper reviews these developments and identifies three influential themes: (i) channel dynamics, (ii) the role of riparian vegetation, and (iii) channel change as the driver of ecological change. Changes can be rapid in semi-arid regions but elsewhere relaxation periods may extend to millenia. In these latter cases regime or steady-state models should be replaced by models of transient states applied to the reach scale in order to respond to the needs of river managers over decadal timescales.