Dealing with river complexity

Posted on March 27, 2017

Hydromorphology is a relatively new field that deals with the structure of hydrological systems and changes in their form over time. Many such changes are influenced by human-induced pressures. Realistic attempts to conceptualize hydromorphological forms and processes reflect the fact that rivers are complex multidimensional systems with longitudinal, lateral, vertical and temporal components, as well as being hierarchically organized, with fine-scale elements embedded within reaches, segments and river networks. Although several indicators of river hydromorphology have been proposed, most of them have focussed on a single component, such as flow regime or the riparian zone, without considering interactions with other components or effects at different spatial scales. A new analytical framework has been developed as part of the European Union’s REFORM Programme for sustainable river management. In this system, river reaches are assigned to a river type based on valley confinement, planform and bed material. River assessments are based on three types of indicators, which are selected to represent key processes and features at each spatial scale. Contemporary indicators at reach and sub-reach scales relate to processes, forms and human pressures, which feed assessments of present function and alteration in a given reach. Indicators at catchment to segment scales investigate water and sediment production and delivery to reaches and how these are affected by human pressures. And historical indicators at reach and sub-reach scales are used to construct the trajectory of reach-scale changes. The three types of indicators are then combined to examine how different river reaches behave in response to changes at all spatial scales, and to generate predictions of their responses to future scenarios (change in climate or land cover; channel interventions). The authors draw on information for the River Frome in southern England to illustrate this approach to stream management.

Gurnell, A.M. et al. 2016. A multi-scale hierarchical framework for developing understanding of river behaviour to support river management Aquatic Sciences 78, 1–16.

Tanago, M.G. et al. 2016. Indicators of river system hydromorphological character and dynamics: understanding current conditions and guiding sustainable river management. Aquatic Sciences 78, 35-55.