James Buttle Review: Bed, Banks and Beyond: River Flood Dynamics

Abstract

Floods are amplified and attenuated by features and processes across spatial scales, defined here as flood dynamics. We review and synthesise these influences at the catchment, river network and reach scales as a means of integrating understanding of controls on flood dynamics and identifying key questions that arise because of differences in techniques of investigation and disciplinary emphases between spatial scales. Catchment-scale influences include catchment area, topography, lithology, land cover, precipitation, antecedent conditions and human alterations such as changing land cover. Network-scale influences on flood dynamics include network topology, longitudinal variations in the geometry of successive river corridor reaches, lakes and wetlands and human alterations including flow regulation and cumulative changes in channel-floodplain connectivity in multiple reaches across a network. Reach-scale influences on flood dynamics include water sources, river corridor geometry and connectivity and human alterations such as artificial levees, channelisation, bank stabilisation, changes to floodplain land cover and drainage, dike operation, process-based river restoration and urban stormwater management. Our review and synthesis of relevant literature suggest that the relative importance of these multiple influences on flood dynamics varies across spatial scales. Hillslope response may dominate hydrograph characteristics in smaller catchments, for example, whereas network geometry and flow dynamics exert progressively stronger influences on flood dynamics with increasing catchment size. Scale-specific advances in understanding flood dynamics, including rainfall-runoff analyses of water movements from uplands into channel networks (catchment-scale), analyses of flow dynamics along networks of multiple channel reaches (network-scale) and investigations of biophysical feedbacks and the influences of river corridor geometry and hydraulic roughness (reach-scale), have largely contributed to understanding flood dynamics, but there remain important disconnects between these diverse bodies of research and outstanding questions related to the cumulative effects on flood dynamics across scales.