problems Stefano Calappi**, Andrea Maffio*, Mario Gallati** 2nd SPHERIC Workshop – ETSIN Madrid, 23 maggio 2007 *CESI RICERCA **Dept. Hydraulics and Environmental Eng., University of Pavia Reservoir sedimentation may give rise to safety hazards for population and infrastructures where the scheme is located, related to equipment malfunctioning (due to clogging of dam bottom outlets) and increase in dam static load. Numerical modeling may provide an useful tool to make predictive simulations of hydrodynamics and sediment transport problems associated with the above issues, to assess sediment scour and transport induced by outlet opening maneuvers for different operational strategies (e.g. reservoir elevation, opening duration, etc.). Hence, a research activity is in progress to develop a SPH software tool (SPHERA code) to simulate local sediment scour and hydrodynamics in reservoir sedimentation problems. Reservoir sediment bed is included in the computational domain and modeled as a granular pseudo-fluid with the same set of equation used for water dynamics, provided a relationship is used to define and apparent viscosity (considering Mohr-Coulomb criteria) as a function of friction angle. To evaluate SPH modeling response, numerical simulations are carried out for a two-dimensional test case, based on a laboratory flume schematizing a simplified vertical section of a dam with a bottom outlet and non-cohesive sediment bed. By opening the bottom outlet flume drawdown and local scour (with sediment flushed downstream) are induced. SPH results in terms of bed profile variation are compared to flume experimental measures. As research is aimed at developing tools to be used in engineering applications, emphasis is placed on evaluating SPH from the point of view of both accuracy and computational cost (SPH results are compared to others numerical techniques, e.g. CFD).