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 Drome 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 Drome 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 Drome 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 Drome 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 technique’s 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 Drome River catchment.