Three decades of monitoring in the Rio Cordon instrumented basin: Sediment budget and temporal trend of sediment yield

Abstract

This paper investigates nearly 30 years of monitoring of sediment fluxes in an instrumented Alpine basin (Rio\ud Cordon, Italy). The collected bedload and suspended sediment transport data allows sediment dynamics to be analyzed\ud at different time scales, ranging from short- (single event) to long-term (three decades). The Rio Cordon\ud monitoring station has been operating since 1986, continuously recording water discharge, bedload and\ud suspended load. At the flood event scale, a good relationshipwas found between peak discharges (Qpeak) andsediment\ud load (bedload and suspended load). The inter-annual sediment yields were analyzed, also assessing the\ud contribution of the single floods to the total sediment budget. The annual suspended load ranges from 10 to\ud 2524 t yr−1, while the bedload varies from 0 to 1543 t yr−1. The higher annual yields were recorded in the\ud years when large floods occurred, highlighting that the sediment budget in the Rio Cordon is strongly controlled\ud by the occurrence of high magnitude events. Investigation of the seasonal suspended load contribution demonstrated\ud that from 1986 to 1993 most fine sediments were transported during the snowmelt/summer seasons,\ud while autumn and snowmelt were the dominant seasons contributing to sediment yield in the periods 1994–\ud 2002 and 2003–2014, respectively. The mean annual sediment yield from 1986 to 2014 is equal to\ud 103 t km−2 yr−1, and overall, bedload accounts for 21% of the total sediment yield. The ratio between the sediment\ud transport and the effective runoff of the events allowed the temporal trends of transport efficiency to be\ud inferred, highlighting the existence of periods characterized by different sediment availability. In particular, despite\ud no significant changes in the hydrological variables (i.e. rainfall), nearly a decade (1994–2002) with high\ud transport efficiency appears to have occurred after an exceptional event (recurrence interval N100 years). This\ud event affected the sediment availability at the basin and channel bed scales, and provided a legacy influencing\ud the sediment dynamics in the basin over the long-term by increasing the transport efficiency for approximately\ud a decade. This work benefits from the long-lasting monitoring program undertaken in the Rio Cordon and is the\ud product of long-term data series. The quasi-unique dataset has provided detailed evidence of sediment dynamics\ud over about three decades in a small Alpine basin, also enabling the effects triggered by an exceptional event to be\ud analyzed

Morpho-textural implications to bedload flux and texture in the sand-gravel ephemeral Poveda Gully

“…nature is inaccurate owing to factors such as sediment supply and bed armoring (Recking, 2010(Recking, , 2012Rainato et al, 2017). Video cameras have been widely used in flume experiments but rarely in Nature (e.g., Drake et al, 1988;Garcia et al, 2007;Beylich and Laute, 2014).…”

“…In addition, the video recordings show why bedload transport equations cannot be accurate for actively changing channels (Rainato et al, 2017). The inclusion of bed surface material in bedload equations improves their predicting power (Recking, 2010) -the addition of information on the changing bed topography (e.g., bar formation and obliteration) during an event is paramount.…”

Suspended sediment transport analysis in two Italian instrumented catchments

“…Both are installed in correspondence to the water level gauges in order to simultaneously measure the water level and suspended sediment concentration (SSC). Several papers using the data monitored in the Rio Cordon monitoring station have been published (D'Agostino et al 1994;Lenzi et al 1997Lenzi et al , 1999Lenzi et al , 2004Lenzi and Marchi 2000;Mao 2003, 2004;Mao et al 2008;Picco et al 2012;Rainato et al 2013;Rainato et al 2016).…”

Coupling Climate Conditions, Sediment Sources and Sediment Transport in an Alpine Basin

“…This is particularly evident in small mountain basins, where the type and extent of sediment sources may strongly influence the nature, magnitude and efficiency of fluvial transport processes (Schuerch et al ., ; Rainato et al . ). The material supplied by the slopes may reach the channel network or not, depending on coupling/decoupling relationships between sediment sources and the channel network.…”