Sediment routing model for steep torrent channels

In steep streams with gradients larger than about 0.05 there are only very few measurements of sediment transport. During flood events, large sediment loads can be moved through steep torrent channels. Post-event geomorphologic documentations of the main sediment transfer processes are the basis to evaluate sediment routing models in such channels. SETRAC is a sediment routing model specifically developed for steep torrent channel networks. It can be linked with a rainfall-runoff model. The flood hydrograph is translated through the channel network using a kinematic flow routing. A selection can be made among different sediment transport formulae suitable for steep channels and water flow resistance approaches. The sediment is transferred through the channel network by a considering a reachwise sediment budget. Initial sediment stock can be assigned for each channel reach. The project aims at assessing the suitability of SETRAC and other sediment transfer models in torrent channels during flood events. For this purpose the following tasks will be performed: (i) Application of the model to well documented case studies on flood events in torrent catchments with substantial sediment transport in the Austrian Alps; (ii) Comparison of the model results with other models simulating sediment transfer with different approaches such as ETC, PROMAB-GIS, and FLUMEN; (iii) Expansion of the SETRAC code to allow for a more refined analysis of sediment transport and transfer conditions, by including effects of bed armouring, form resistance losses, and a more complex channel sediment routing; (iv) Sensitivity study on the relative importance of changing input and model parameters. The tested and refined version of the SETRAC model can be a useful tool supporting practical hazard assessment in torrent catchments.