Numerical modelling of bedload transport in torrents and mountain streams / presented by Michael Chiari

TL;DR: In this paper, a sediment routing model for steep torrent channel networks called SETRAC has been developed at the University of Natural Resources and Applied Life Sciences, Vienna, which is the acronym for Sediment TRansport in Alpine Catchments.

Abstract: Floods with substantial bedload transport have a high potential for damage. In particular inhabited fans are often heavily affected by deposits of sediment. Aim of the study is to improve an existing sediment transport model and to evaluate numerical simulations of bedload transport at steep slopes with field observations. A sediment routing model for steep torrent channel networks called SETRAC has been developed at the University of Natural Resources and Applied Life Sciences, Vienna. SETRAC is the acronym for Sediment TRansport in Alpine Catchments. The main purpose of the model is the simulation of bedload transport at steep channel slopes. The SETRAC model has been further developed in collaboration with the programmer of the original version. Flow resistance and bedload transport equations appropriate for torrents and mountain streams are implemented. To take form roughness losses into account several approaches are available to modify the calculated transport capacity to better match observations on bedload transport. Armouring effects can also be considered. In addition it is possible to calculate fractional bedload transport by taking grain sorting effects in combination with mobile bed conditions into account. Flow hydrographs are routed through the channel network by using the kinematic wave approach. The improved sediment routing model for steep torrent channel networks is presented. The model has been tested with two flume studies to examine the models ability to simulate morphologic changes as well as sorting effects. In addition, SETRAC has been applied to well documented case studies on flood events in torrential catchments with substantial sediment transport in the Austrian, Swiss and French Alps. The simulation results show the importance of form roughness losses when computing bedload transport in torrents and mountain streams. Neglecting form drag in rough steep channels often results in an overestimation of the calculated bedload transport.