Rivers and streams play a key role within the sediment cascade by transferring and buffering fluxes between active hillslopes and downstream alluvial environments (Fryirs, 2013). Mountains are important sediment sources for piedmont fluvial systems (Wohl, 2006). This analysis is proposed to remind how, conceptually, check dams may influence geomorphic systems, bearing in mind the knowledge represented in pioneer guidelines and recent works on the subject. Finally, the next steps and remaining research challenges toward a comprehensive analysis of check dams' efficiency in torrent hazard mitigation are presented.

The French experience is compared to other countries' pioneering works.

The second part of this paper synthesizes conceptual descriptions of the check dams' functions, in the light of more than 150 years of experience, with their implication on the features of the structures. In the nineteenth century, engineers developed a thorough empirical and conceptual knowledge of mountain soil erosion, torrential geomorphology, and sediment transport processes as well as check dam interactions with these natural processes. We first analyze chronologically how each function was theorized and applied in the field. To bridge this gap, this paper traces the purposes for which check dams were built, through a detailed analysis of French archives. The present understanding of these sometimes old structures' functions can be complicated because the societal and environmental contexts in which the original structures were built may have changed. The next steps concern quantitative assessments of each function on the flood features and combination of all effects. To help define their effectiveness and decisions concerning their maintenance or new project designs, a clear understanding of potential effects of check dams on river systems, i.e. Modern mountain societies have inherited thousands of these structures built in upland gullies and streams.

Check dams are likely the most emblematic civil engineering structures used in soil conservation programs. For more than 150 years, humans have tried to limit the geomorphic activity of mountain streams, and the related damage, using torrent control works.

Marc Antoine torrent