Culvert performance in steep streams under sediment transport conditions

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Jochen Aberle, Harald Norem, Joakim Sellevold, Fanni Terlaky

Monday 29 june 2015

17:48 - 17:51h at North America (level 0)

Themes: (T) Flood risk management and adaptation, (ST) Adaptation measures, Poster pitches

Parallel session: Poster pitch: 2I: FloodRisk - Adaption

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Culverts are important hydraulic structures providing cross-drainage during normal and extreme hydrologic conditions for transportation routes such as roads or railway lines. Most of the available guidelines for the hydraulic design of culverts have been derived under clear water conditions, and several recent studies have focused on the improvement of fish passage in culverts during low flow conditions in order to address ecological needs. On the other hand, the effect of sediment deposits at culvert sites has been rarely considered in the design process. Such deposits can lead to partial blockage and hence to a reduction of the effective culvert cross section so that the design discharge may no longer be safely conveyed during flood events which can result in the failure of transportation This paper presents results from an ongoing laboratory study which is carried out in the framework of the research project “Natural hazards – Infrastructure for floods and Landslides (NIFS)” coordinated by the Norwegian Public Roads Administration (NPRA), the Norwegian National Rail Administration (NNRA), and the Norwegian Water Resources and Energy Directorate (NVE). Focusing on small streams with steep slopes, experiments were carried out in the NTNU hydraulic laboratory in a generalized single barrel culvert scale model (1:10) with a barrel diameter of 10 cm. The hydraulic efficiency of different three culvert inlet types (projecting barrel, cut inlet, and wing-walls) was tested for different headwater basin geometries under clear water and sediment transport conditions. For the latter, coarse material (d = 8 – 16 mm and 16 -32 mm) was added at different feeding rates in order to mimic sediment entrainment in mountainous areas. Performance curves (flow rate vs. headwater depth) will be presented and discussed with regard to inlet type and headwater geometry, sediment transport rate, and sedimentation patterns.