Simonetto, Anna Caratteristiche morfologiche di alcuni fiumi ghiaiosi antropizzati e naturali e studio della stabilitÃ del fiume Brenta tra Bassano e Carturo. [Laurea specialistica biennale]
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This work analyses morphological and hydrological processes of gravel-bed rivers located in different geographic contexts: the North Eastern Italian region (Brenta River) and the central Patagonic region. Within the study reaches, the grain size distribution of the sediments is significantly different between riffles and pools, being coarser in the former. The downstream fining tendency is evident as well, whereas the armour ratio seems more influenced by differences in sediment supply conditions rather than the downstream trend. A comparison of cross sections measured in 1997 and 2009 revealed an incision trend in the upper part of the study reach (which is 21 km long) and a sedimentation tendency in the lower part. This trend is confirmed by a numerical simulation which reveals a downstream reduction of shear stress, thus allowing sediment erosion (bank erosion and slight incision) in the upper portion of the reach and sedimentation downstream. On the other hand, the hydrological analysis reveals that overall the building of the dam system in the upper part of the basin has not changed the recurrence of moderate to high flows, keeping the formative bankfull discharge at the same value is analyzed before and after the dam closure.
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