Abstract

The Reno R. has been extensively affected by man activity for a long span of time. The first relevant interventions date back to the Romans time and were reiterated until present. After World War II, significant land use changes in the headwater, extensive exploitation of bed material, the construction of a downstream sluice gate for irrigation purposes and large withdrawal of fluids from the underground caused important channel and sediment budget changes, a marked reduction of bedload flux and, consequently, a worrying and fast retreat of a vast portion of the Adriatic coast. To understand such morphological changes and their causes, representative bed material samples were taken, the hydraulic geometry data of hundreds of cross sections, surveyed at different times, were analysed to quantify the streambed degradation and a field campaign of sediment transport measurement was started in 2003. Bedload transport rate resulted very low also during floods larger than bankfull and also those equations, known in the literature to underpredict bedload transport, overestimate the sediment transport of the Reno R. The river transport capacity always resulted by far larger than sediment supply and no significant relation was found between flow parameters and the bedload transport rates measured. The occurrence of cyclic peaks and lows of bedload rate and a clear sesonality were observed as well. The sediment deficit of the Reno river system results from many factors including an increase in foreset cover, vast bed material exploitation and likely a decrease in flood frequency.

Keywords: channel changes, streambed degradation, sediment transport, bedload yield