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Analysis of the Best Practices for the Flushing Operations of the Forni Barrage

Author(s): Alterach Julio; Peviani Maximo; Danelli Andrea; Sosio Sergio

Linked Author(s): Julio Alterach

Keywords: Reservoir sedimentation; Sediment transport; River morphology; Numerical modeling; Flushing; Reservoir management

Abstract: Alpine reservoirs are major vital components of water supply, renewable electric energy generation, recreation and flood protection for mountainous regions as well as large downstream piedmont areas. Due to sediment detachment processes in the basin, coming from surface erosion and large mass movements (bank erosion, debris flows, etc. ), commonly mountainous reservoirs have to deal with a considerable sedimentation. To guarantee the correct operation of the system, the sediment trapped inside the reservoir might be flushed to the downstream rivers. Sediment transport capacity, suspended sediment concentrations and morphological changes in the river are the major issues to be assessed, in order to avoid inconvenient environmental problems and the risk of flooding, as well. The MORIMOR GIS model (MOuntain RIver MORphology GIS), permits to evaluate all those parameters and to analyze different flushing operation scenarios in order to minimize the undesirable effects in the downstream river. The present paper describes the basis of the morphodynamic mathematical model, which is employed for the computations of sediment transport capacity and bottom changes, at basin space scale and for short and long-term calculations. The Forni barrage pilot application in Valtellina (Italy) is described, using the MORIMOR GIS model to simulate the morphological effects in the Frodolfo river, due to programmed and synthetic flushing operations. The flushing process parameters are tested and then optimized using the so-called “overflow hazard index”: an indicator which takes into account the relationship between the used and the overall conveyance of each cross section. Finally, it was derived the best operation flushing practice for the Forni reservoir.

DOI:

Year: 2007

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