Event-induced sediment yield from mountain valley slopes to rivers may represent a problem for landscape safety if the total sediment volume supplied is larger than the transport capacity of the water courses, leading to riverbed aggradation and increased water levels. Multiple sediment sources are normally present in mountain basins; the former are characterized by different spatial and temporal scales, which makes a global analysis hardly possible. On the other hand, modeling of sediment yield furnishes the necessary boundary condition for that of sediment transport in rivers. In this study, several types of sediment sources were separately analyzed with reference to the Tartano basin, located in Northern Italy. A detailed analysis of the sediment volume from soil erosion and some preliminary analyses of a faulted valley were performed. The transport capacity of the major water courses was computed around the confluence among them, for comparison with the estimated yields. The analysis showed that not all the sediment sources contribute significantly to the solid volumes that must then be transported by the rivers. This enables simplified models to be used considering only the yields that are expected to represent a major load. It is hypothesized that such fi nding be valid for other basins, of course considering the specific features of each.
hydro-geological risk, mountain basin, sediment transport, sediment yield
 De Vente, J. & Poesen, J., Predicting soil erosion and sediment yield at the basin scale:
scale issues and semi-quantitative models. Earth-Science Reviews, 71, pp. 95–125, 2005.
 Chikita, K., Sedimentation by river-induced turbudity currents: fi eld measurements and interpretation. Sedimentology, 37(5), pp. 891–905, 1990.
 Lajczak, A., Modelling the long-term course of non-fl ushed reservoir sedimentation and estimating the life of dams. Earth Surface Processes and Landforms, 21(12), pp. 1091–1107, 1996.
 De Cesare, G., Schleiss, A. & Hermann, F., Impact of turbudity currents on reservoir sedimentation. Journal of Hydraulic Engineering, 127(1), pp. 6–16, 2001.
 Elçi, S., Work, P.A. & Hayter, E.J., Infl uence of stratifi cation and shoreline erosion on reservoir sedimentation patterns. Journal of Hydraulic Engineering, 133(3), pp. 255–266, 2007.
 Lane, S.N., Tayefi , V., Reid, S.C., Yu, D. & Hardy, R.J., Interactions between sediment delivery, channel change, climate change and fl ood risk in a temperate upland environment. Earth Surface Processes and Landforms, 32, pp. 429–446, 2007.
 Reid, S.C., Lane, S.N., Berney, J.M. & Holden, J., The timing and magnitude of coarse sediment transport events within an upland, temperate gravel-bed river. Geomorphology, 83, pp. 152–182, 2007.
 Sear, D.A., Newson, M.D. & Brookes, A., Sediment-related river maintenance:
the role of fl uvial geomorphology. Earth Surface Processes and Landforms, 20, pp. 629–647, 1995.
 Klaassen, G.J., FRIMAR: Flooding RIsks in Mountain Areas, available at http://www. hrwallingford.co.uk/Mitch/papers/klaassen.pdf, 1997.
 Wasson, R.J., What approach to the modelling of catchments scale erosion and sediment transport should be adopted? Modelling Erosion, Sediment Transport and Sediment Yield, eds. W. Summer & D.E. Walling, Technical Documents in Hydrology, 60: UNESCO, Paris, pp. 1–11, 2002.
 Williams, J.R. & Berndt, H.D., Sediment Yield production with the universal equation using runoff Energy factor. Present and Prospective Technology for Predicting Sediment Yield and Sources, USDA, ARS-S-40, pp. 244–252, 1975.
 Gavrilovic, S., Bujicni tokovi i erozija, Gradevinski kalendar, Beograd, Serbia, 1976.
 Wischmeier, W.H. & Smith, D.D., Predicting Rainfall Erosion Losses, Agric. Handb. 537, USDA, Agricultural Research Service: Washington, DC, 1978.
 Mandelli, M., Longoni, L., Papini, M., Roncoroni, F. & Radice A., Modellazione del trasporto di sedimenti sul bacino del Tartano (Valtellina). GEAM, Anno XLVI, n. 2, pp. 53–63, 2009.
 Ballio, F., Brambilla, D., Giorgetti, E., Longoni, L., Papini, M. & Radice, A., Evaluation of Sediment Yield From Valley Slopes: a case study. Proc. Debris Flow, Milan, Italy, 2010.
 Ramsay, J.G. & Huber, M.I., The Techniques of Modern Structural Geology. 2: Folds and Fractures. Academic Press: London, 1987.
 Wolman, G., A method of sampling coarse river bed material. Transactions of the American Geophysical Union, 35(6), pp. 951–956, 1954.
 Kellerhals, R. & Bray, D.I., Sampling procedures for coarse fl uvial sediments. Journal of the Hydraulics Division, American Society of Civil Engineers, 97(HY8), pp. 1165–1180, 1971.
 Nash, E., Systematic determination of unit hydrograph parameters. Journal of Geophysical Research, 64, pp. 111–115, 1957.
 Giandotti, M., Previsione delle piene e delle magre dei corsi d’acqua italiani. Memorie e studi idrografi ci, Pubb.2 del Servizio Idrografi co Italiano, Vol. VIII, p. 107, 1934.
 Schoklitsch, A., Handbuch des Wasserbauers, 3rd edn, Springer-Verlag: Vienna, 1962.
 Franzetti S. & Ballio F., Studio su modello fi sico della confl uenza dei torrenti Val Lunga e Val Corta in comune di Tartano. Modello idraulico: relazione fi nale, Politecnico di Milano, 2004.
 Meyer-Peter, E. & Müller R., Formulas for bed-load transport. Proc. II Meeting of IAHR, Stockholm: Sweden, 1948.
 Smart, G., Sediment transport formula for steep channels. Journal of Hydraulic Engineering, 110, pp. 267–276, 1984.
 Rickenmann, D., Comparison of bed load transport in torrents and gravel bedstreams. Water Resources Research, 37, pp. 3295–3305, 2001.
 Gomez, B., & Church, M., An assessment of bed load sediment transport formulae for gravel bed rivers. Water Resources Research, 25, pp. 1161–1186, 1989.
 Martin, Y., Evaluation of bed load transport formulae using fi eld evidence from the Vedder River, British Columbia. Geomorphology, 53, pp. 75–95, 2003.
 Chanson, H., The Hydraulics of Open Channel Flow: An introduction. Elsevier Butterworth-Heinemann, 1999.
 Van Rijn, L.C., Sediment transport, part I: Bed load transport. Journal of Hydraulic Engineering, 110, pp. 1431–1456, 1984.