Author(s): Zoe Deltombe; Guillaume Piton; Natacha Fructus; Samuel Pinjon; Laurent Borgniet; Andre Evette

Linked Author(s):

Keywords: Woody debris; Wood jam; Wood regime; Wood transport; Low tech

Abstract: During high magnitude flood events, large wood pieces are transported by flows in riverscapes. They contribute to create log jams increasing channel and floodplain habitat diversity, but they can also increase flood hazards when they clog bridges, culverts and weirs unable to allow their passage. In addition to common restoration operations changing riverscape geometry and vegetation to restore rivers and wetlands forms and processes, an increasing number of restoration projects use engineered or artificial log structures (ALSs) and beaver dam analogs (BDAs). Many scientific works are monitoring their effects on flow fields, sediment transport and terrestrial and aquatic habitats. However, much less is known about their capacity to trap and regulate the large wood pieces that are recruited and transported only for rare, strong flood events. In this on - going work, a small-scale model of a generic river whose channel and floodplain geometry were defined based on several restoration sites in France, was used to study this process. The riparian forest density was also defined based on the real standing tree density of the sites. Several flood events, from bank-full to largely overflowing discharges, with various wood transport intensity were tested without structures and with ALSs and BDAs. The amount of large wood pieces transiting through the system, being trapped and eventually released by the structures or moving to the floodplain and being trapped and eventually released by the riparian forest was documented by image analysis . The destabilization of the structures themselves was also analyzed. This work aims to determine under which flood conditions ALSs and BDAs may contribute to reducing flood hazards by enhancing the regulation and retention of large wood in restored river environments. The experiments are still on-going at the stage of this submission so we essentially explain the aim and scope of the study.

DOI: https://doi.org/10.64697/iahr.proc.ise2026.abs.187

Year: 2026