Evaluation and modeling of scouring and sedimentation around check dams in a Mediterranean torrent in Calabria, Italy

The effectiveness of check dams on channel morphology of managed torrents is rarely assessed. Therefore, there is a need for studies that focus on the impacts of existing engineering check dams on the planoaltimetric characteristics of the torrent, particularly in Mediterranean areas, where the hydrological regime of ephemeral channels is dynamically unsteady. The quantitative evaluation of the effects of the check dams on channel morphology after many years (i.e., at least four or five decades) helps introduce innovations to the usual analysis of check dam efficacy which have often been limited to qualitative observations for only a few years after installation. As a contribution to make up these shortcomings, this paper investigates the geomorphologic asset of a torrent in southern Italy containing 10 check dams (installed in the 1950s to 1960s) and analyzes the dynamics of the scouring and sedimentation processes upstream and downstream of selected check dams after 8 rainfall events; moreover, the capability of the model by Castillo (2007) to predict scouring/ sedimentation in proximity to these check dams is assessed. Sediment stored upstream of each check dam (where lower channel gradients and wider channel sections formed very long and wide sedimentary wedges) is more than one order of magnitude higher compared to scouring downstream. The morphological analysis revealed that the check dams installed in the headwater reach play a function of bed stabilization (due to the longitudinal slope reduction) and flood lamination (because of the wider channel section) rather than a role of sediment collectors as their sediment storage capacity has already been completed. Scouring/ sedimentation dynamics depend mainly on the channel slope and width in proximity to the check dams rather than on structure height. Finally, Castillo’s model showed an acceptable performance in predicting scouring/sedimentation in the channel bed close to check dams after the monitored rainfall events, the model efficiency being satisfactory and the differences between the mean observed and simulated values low. This investigation improves the understanding about morphological effects of check dams in Mediterranean torrents based on field observations and quantitative analysis.