Conceptual framework and interdisciplinary approach for the sustainable management of gravel-bed rivers: The case of the Drôme River basin (S.E. France)

Abstract

Geomorphic responses to changes in bedload transport in gravel-bed rivers are complex. Such responses occur over long time scales and vary as a function of distance from sediment sources and local channel characteristics. As a result, different types of cascading ecological and social consequences are observed in different parts of a drainage network. This paper presents the results of an interdisciplinary research project, conducted by geomorphologists, ecologists, social scientists, and river managers that focused on changes in bedload transport in the Drôme River catchment in south-eastern France. Our objective was to document a general conceptual framework of the historical and current physical, ecological, and social implications of human-caused bedload transport changes in the Drôme River watershed that could be used to develop sediment management plans for similar gravel-bed river catchments. First, we synthesized the historical trajectory of the Drôme River over the past two centuries from a geomorphic perspective in relation to the evolution of socio-economic activities. Then, we summarized typical ecological responses to gravel-bed channel adjustment. Third, we reviewed how the problems of water and sediment management in the Drôme have been addressed over the past 20 years. We identified the best technical solutions for the replenishment of incised reaches by considering practical interdisciplinary questions including each techniques juridical feasibility, ecological impacts, and its degree of acceptance by managers and the public. Finally, we integrated geomorphic processes, ecological dynamics, and socio-economic values into a functional river reach typology that was used to map target restoration reaches and potential sediment sources throughout the Drôme River catchment.

Geomorphological Approaches for River Management and Restoration in Italian and French Rivers

“…The use of local known physically based processes in the extrapolations that we can do at catchment scale is therefore a new scientific frontier to provide data for sustainable scenarios. Prospective geomorphology is a new application, where important uncertainties must be identified and time scales of channel adjustments need careful consideration if we really want to move from a local-scale traditional expertise to the promotion of long-term sustainable options [Pont et al, 2009]. Thinking process rather than form is easy to say, but it is difficult to apply.…”

Socio-environmental implications of process-based restoration strategies in large rivers: should we remove novel ecosystems along the Rhône (France)?

“…The Rhône restoration conducted to more lotic environments and diverse aquatic communities and renewed social links with the river human pressures. This requires a common conceptual framework and an interdisciplinary effort as highlighted by Pont et al (2009). Based on this strategy, we aim to assess potential consequences and the sustainability of such an ambitious restoration policy focused on Casiers Girardon removal.…”

“…It is a complex question within fluvial socio-ecosystems, requiring an interdisciplinary research approach to address the different issues. To do so, we first identified the pros and cons of such a policy, following the approach of Pont et al (2009). We then produced scientific expertise to reduce gaps in understanding.…”

Did you say reference conditions? Ecological and socio-economic perspectives on the European Water Framework Directive

“…In contrast, for rivers that continuously experience flooding and chemical inputs from upstream, the millennial transformation of watersheds by humans (including changes to forest cover) make it impossible to define an ecosystem state that has not been impacted. A recent case study of the Drôme River, southeast France, shows the temporal succession of interactions between land drainage and river basin dynamics (Pont et al, 2009). Gunderson and Holling (2002) proposed the concept of panarchy to account for the complex natural and human dynamics of watersheds.…”