M. Chiari

A one-dimensional bedload transport model for steep slopes

A sediment routing model called SETRAC has been developed to simulate bedload transport in torrents and mountain streams. SETRAC is the acronym for Sediment Transport in Alpine Catchments. Flow resistance is modelled using an approach proposed by Smart and Jäggi, and bedload transport is predicted with an equation by Rickenmann. Form roughness losses are accounted for by an empirical approach which is based on flow resistance observations in mountain streams. It is possible to compute fractional bedload transport taking grain sorting effects into account. Flow hydrographs are routed through the channel network by using the kinematic wave approach. An application of the model is discussed for an extreme flood event of August 2005 in the Chiene catchment, Switzerland, which mobilized 120,000 m3 of bedload along the mountain stream. The simulation results underline the importance of form resistance when modelling bedload transport in steep and rough channels.

Debris flow impacts on masonry arch bridges

Debris flows are a mountain hazard and present a risk to bridges in mountainous areas. Designers of modern bridges are able to consider loads related to debris flows but the designs for historical arch bridges lack this possibility. Although historical arch bridges still form a substantial amount of the total number of bridges in mountainous areas, most research investigations for this bridge type have considered vertical loadings; a few studies consider horizontal longitudinal loads but there are no reported investigations into horizontal transversal loads, which is the debris load direction. The research reported in this paper investigated, firstly, the impact force of debris flows against solid structures in terms of miniaturised laboratory tests. A variety of debris parameters was systematically investigated and an impact–force relationship was developed. Secondly, different horizontal transversal impacts on a slightly miniaturised arch were carried out in the laboratory. The behaviour of the arch und...