Human influence on the morphological adjustment of river channels: The evolution of pertinent concepts in river science

Abstract

Whereas 6 decades ago little attention was accorded to the influence of human activity on affecting river channel adjustment, great progress has been made subsequently, with many contributions published in River Research and Applications. Many concepts have been involved, and this paper considers how they have arisen and developed during a sequence of complementary research stages. The first stage during the 1970s and 1980s, including research by Geoff Petts, involved “recognition of change” and saw the emergence of two separate research strands focused on different timescales: over shorter timescales river channel adjustments affected by the impacts of dams and reservoirs, channelization, land use changes, and urban effects; over longer timescales investigations of river metamorphosis. The second “realization” stage involved significant advances in understanding by considering interaction between these two timescales, more detailed investigations of changing processes, a more holistic catchment‐based approach, and incorporation of ecological changes. These advances led into the third stage, “application” of results, stimulated by analysis of the effects of hard and soft engineering, development of international drivers such as the Water Framework Directive, and concern for what is “natural.” This paper evaluates this sequence of stages, the concepts that have emerged, the extent to which they are consistent and sustainable, and how they can provide the foundation for evaluation of channel adjustments. The effects of urbanization in Fountain Hills, Arizona, USA provide an illustration. Finally, the future requirement for adaptation of existing concepts and the possible development of new ones is briefly considered in the context of global environmental changes.

An index to assess the extent and success of river and floodplain restoration: Recognising dynamic response trajectories and applying a process‐based approach to managing river recovery

“…If restoration is to generate a more natural river character in better balance with sediment and water fluxes in a contributing catchment, it is imperative to understand how rivers have been altered by human activity, specifically by channel and floodplain engineering (Gregory, 2019; Wohl & Merritts, 2007). If a “natural” (neo‐quasi‐equilibrium) river state is to be restored, that state must be understood, which defines what may be feasible in restoring a river and how that might be best achieved (Wohl & Merritts, 2007).…”

“…Provision of an “erodible corridor” (Piégay, Darby, Mosselman, & Surian, 2005), “fluvial territory” (Ollero, 2010), freedom space (Biron et al, 2014; Buffin‐Bélanger et al, 2015), “room to move” (Reid & Brierley, 2015) making “room for the river” (Rijke, Van Herk, Zevenbergen, & Ashley, 2012) to “heal itself” (Kondolf, 2011) are gaining recognition. The development of these ideas arises as part of a “third stage” in concept development within river science (Gregory, 2019). This “application stage” follows naturally from the stages of “recognition” and “realisation” (see Gregory, 2019).…”

“…The development of these ideas arises as part of a “third stage” in concept development within river science (Gregory, 2019). This “application stage” follows naturally from the stages of “recognition” and “realisation” (see Gregory, 2019). In New Zealand, river managers have now moved along this same trajectory.…”

Degradation and Improvement of Urban River Water Quality

“…Current analysis by Gregory [7] and Maklin and Lewin [8] suggest a more holistic paradigm for river change. Time has elapsed since early urbanization impacted river systems and researchers now incorporate time scales into thinking about human impact on these systems.…”

GRAINet: Mapping grain size distributions in river beds from UAV images with convolutional neural networks

“…However, the fluvial morphology of many streams is heavily affected by human activity and construction along the river. Gravel extractions, sediment retention basins in the upper catchments, hydro power plants, dams or channels reduce the bed load and lead to surface armouring, clogging of the bed, and latent erosion (Surian and Rinaldi, 2003;Simon and Rinaldi, 2006;Poeppl et al, 2017;Gregory, 2019). As a consequence, the natural alteration of the river bed is hindered, eventually deteriorating habitats and potential spawning grounds.…”