Towards a better understanding of the today French torrents management policy through a historical perspective

Abstract

Abstract. Protective measures against torrential floods and ORZODQGV ¶ IORRGV have been set up since the 19 th century in mountainous areas. To help decide on maintenance of numerous existing structures, a better understanding of their objectives and technical functions is needed. Nevertheless, that remains tricky in torrent management context, due to several changes for more than 150 years, either in terms of natural torrential risk (e.g. land-use changes), scientific understanding of complex phenomena (e.g. hillslope-streambed coupling

Why do we build check dams in Alpine streams? An historical perspective from the French experience

“…why the structure was built in the first place. Our present expectation of the structure's functions can also be complicated by changes in the socio‐economic and environmental contexts (Dufour and Piégay, ; Carladous et al , ): for instance, our understanding of sediment continuity processes has evolved, and many watersheds have been spontaneously or artificially reforested since the structures' construction.…”

“…To make the decision problem on maintenance of existing structures even more complicated, the decision context has changed over time since the nineteenth century (Carladous et al , ): (i) exposed elements have evolved from a native permanent population to a touristic temporary one (de Crécy, ; Brugnot and Cassayre, ; Comiti, ); (ii) torrent activity and catchment morphodynamics have changed due to spontaneous or planned reforestation or to the implementation of check dams which fundamentally impact upon the geomorphic functioning of landscapes; (iii) new alternatives to old torrent control techniques emerged with the advent of earth‐moving machinery (e.g. direct torrent bed mechanical dredging) and open check dams (Piton and Recking, ); (iv) the importance of the sediment cascade and continuity within the river system is now better understood and is taken into account in various policies, e.g.…”

Reported Occurrence of Multiscale Flooding in an Alpine Conurbation over the Long Run (1850–2019)

“…Torrential floods have the peculiarity of triggering active sediment transport, an aggravating factor of risk that was conceptualized as soon as the 19th century with, in France, the creation in 1860 of a national service for the management of the Alpine and Pyrenean mountainous areas-RTM [45]. As part of the forest administration (Office National des Forêts), this national service had the central objective of curtailing sediment production in torrent headwaters through the active protection of tree planting (3800 km 2 ) and civil engineering works (ca.…”

Managing protection in torrential mountain watersheds: A new conceptual integrated decision-aiding framework

“…Evaluation scales for a device's capacity and effect have been established in Carladous et al (2016a). In the same way, evaluation criteria are established at the scale of structures.…”

“…5) has determined concepts pertaining to the effectiveness assessment. Functions, associated objectives and means of capacity and effect assessment have been specified (Carladous et al, 2016a) for the different scales of control systems. An evaluation process, broken down and sequential, is thus established in Fig.…”