Browsing by Author "Rainato, Riccardo"

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    Coupling Climate Conditions, Sediment Sources and Sediment Transport in an Alpine Basin
    (2018) Rainato, Riccardo; Picco, Lorenzo; Cavalli, Marco; Mao, Luca; Neverman, Andrew J.; Tarolli, Paolo
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    Medium-term fluvial island evolution in a disturbed gravel-bed river (Piave River, Northeastern Italian Alps)
    (2014) Picco, Lorenzo; Mao, Luca; Rainato, Riccardo; Lenzi, Mario A.
    River islands are defined as discrete areas of woodland vegetation surrounded by either water-filled channels or exposed gravel. They exhibit some stability and are not submerged during bank-full flows. The aim of the study is to analyze the dynamics of established, building, and pioneer islands in a 30-km-long reach of the gravel-bed Piave River, which has suffered from intense and multiple human impacts. Plan-form changes of river features since 1960 were analyzed using aerial photographs, and a LiDAR was used to derive the maximum, minimum and mean elevation of island surfaces, and maximum and mean height of their vegetation. The results suggest that established islands lie at a higher elevation than building and pioneer islands, and have a thicker layer of fine sediments deposited on their surface after big floods. After the exceptional flood in 1966 (RI > 200 years) there was a moderate increase in island numbers and extension, followed by a further increase from 1991, due to a succession of flood events in 1993 and 2002 with RI > 10 years, as well as a change in the human management relating to the control of gravel-mining activities. The narrowing trend (1960-1999) of the morphological plan form certainly enhanced the chance of islands becoming established and this explains the reduction of the active channel, the increase in established islands and reduction of pioneer islands.
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    Surprising suspended sediment dynamics of an alpine basin affected by a large infrequent disturbance
    (2023) Pellegrini, Giacomo; Mao, Luca; Rainato, Riccardo; Picco, Lorenzo
    In many environments, climate change causes an increase in the frequency and magnitude of Large Infrequent Disturbances (LIDs). LIDs make fragile areas, as mountain basins, even more vulnerable, along with local communities that could be severely affected by extreme events. Among all LIDs, windthrows are one of the most relevant and yet rather unpredictable disturbances affecting the Alpine region. Windthrows can affect the forest cover and morphological settings at the basin scale, changing the supply of sediments to river networks and affecting the sediment cascading processes. This work aims at (i) identifying the contribution of Suspended Sediment Load (SSL) from a windthrow-managed-affected area induced in an Alpine basin by a recent LID (Vaia rainstorm, 2018), (ii) assessing the annual, seasonal and monthly variation in the SSL, and (iii) analysing the changes in SSL fluxes and dynamics in the 2nd and 3rd year after the LID in comparison to those detected after a similar high magnitude event occurred in 1994. To do so, two multiparameter sondes measuring the water level and the turbidity were installed upstream and downstream the windthrow-affected area. Discharge measurements and water samples were collected to obtain the rating curves and calibrate the turbidity meters in order to derive suspended sediment loads (SSL). The results show that the windthrow-affected area was significantly contributing suspended sediment during events occurring two years after Vaia (2020) but less intensively in those occurred three years after the event itself (2021). Both the events average intensity rainfalls and the total precipitation appear to be the best predictors of both the peak of suspended sediment concentration (SSCp), the total suspended sediment (SSL) and the suspended sediment percentage variation among the two cross-sections. The seasonal and monthly analysis revealed to be in line with those detected prior the disturbance. The analyzed LID affected the transport efficiency for near-bankfull events but not the annual sediment yield as it was found after the previous high magnitude flood event recorded in 1994. Unexpectedly, the mean rate of SSL (42 t km(-2) yr(-1)) is indeed comparable with what monitored during the decade before Vaia (2004-2014) (40 t km(-2) yr(-1)). Such surprising results may be explained by the fact that the Rio Cordon basin have had an alluvial response rather than colluvial during the Vaia rainstorm event and that the basin's resilience may be in a different stage as compared to the one of 1994, when the catchment featured different cascading processes that completely overturn the suspended sediment dynamics and fluxes for about a decade.