Geomorphological Processes and Human Impacts in River Basins (Proceedings of the International Conference held at Solsona, Catalonia, Spain, May 2004). IAHS Publ. 299, 2005, 154-160

1 Dipartimento di Ingegneria Civile, Università degli Studi di Firenze, via Santa Marta 3, 50139, Firenze, Italy

2 Centro de Geologia de Costas y del Cuaternario, Universidad Nacional de Mar del Plata, Funes 3350,
Mar del Plata 7600, Argentina

3 Dipartimento di Scienze della Terra, Università degli Studi di Ferrara, Corso Ercole I d’Este n.32,
44100 Ferrara, Italy

Abstract The aim of this work was to identify the geomorphological units within the drainage network of the Rio Quequén Grande low relief basin, situated in the southeast section of the province of Buenos Aires, and to quantify the present sediment transport rate. For this purpose field surveys and satellite images were analysed. The former included measurement of bed material grain size and channel hydraulic geometry, in order to set up a bed and a suspended load measurement programme. Six main geomorphic units were identified: Ranges, Perirange Aeolian Hillocks, Hillocks with Lagoons, Relic Hills, a Poor Drainage Alluvial Plain and an Alluvial Plain. Bed load discharge and suspended sediment concentration measured during a bankfull flood are very low, given the relatively high stream power of 287 W m^-1. The measured bed load discharge was three to five orders of magnitude lower than six applied bed load equations, presumably due to low sediment availability.

Key words Argentinian Pampas; geomorphology; sediment transport