Browsing by Author "Lenzi, Mario A."
Now showing 1 - 6 of 6
Results Per Page
Sort Options
- ItemA 2D hydrodynamic-sedimentological model for gravel bed rivers. Part II, Case study: The Brenta River in Italy(2013) Kaless, Gabriel; Moretto, Johnny; Delai, Fabio; Mao, Luca; Lenzi, Mario A.A 2D depth average model has been used to simulate water and sediment flow in the Brenta River so as to interpret channel changes and to assess model predictive capabilities. The Brenta River is a gravel bed river located in Northern Italy. The study reach is 1400 long and has a mean slope of 0.0056. High resolution digital terrain models has been produced combining laser imaging detection and ranging data with colour bathymetry techniques. Extensive field sedimentological surveys have been also carried out for surface and subsurface material. The data were loaded in the model and the passage of a high intense flood (R.I. > 9 years) was simulated. The model was run under the hypothesis of a substantial equilibrium between sediment input and transport capacity. In this way, the model results were considered as a reference condition, and the potential trend of the reach was assessed. Low-frequency floods (R.I. » 1.5 years) are expected to produce negligible changes in the channel while high floods may focalize erosion on banks instead than on channel bed. Furthermore, the model predicts well the location of erosion and siltation areas and the results promote its application to other reaches of the Brenta River in order to assess their stability and medium-term evolution.
- ItemA 2D hydrodynamic-sedimentological model for gravel-bed rivers. Part I: Theory and validation(2013) Kaless, Gabriel; Lenzi, Mario A.; Mao, LucaThis paper presents a novel 2D-depth average model especially developed for gravel-bed rivers, named Lican-Leufú (Lican=pebble and Leufu=river, in Mapuche’s language, the native inhabitants of Central Patagonia, Argentina). The model consists of three components: a hydrodynamic, a sedimentological, and a morphological model. The flow of water is described by the depth-averaged Reynolds equations for unsteady, free-surface, shallow water flows. It includes the standard k-e model for turbulence closure. Sediment transport can be divided in different size classes (sand-gravel mixture) and the equilibrium approach is used for Exner’s equation. The amour layer is also included in the structure of the model and the surface grain size distribution is also allowed to evolve. The model simulates bank slides that enable channel widening. Models predictions were tested against a flume experiment where a static armour layer was developed under conditions of sediment starvations and general good agreements were found: the model predicted adequately the sediment transport, grain size of transported material, final armour grain size distribution and bed elevation.
- ItemDynamics and management alternatives of in-channel large Wood in mountain basins of the southern Andes(2013) Luca Mao; Andreoli, Andrea; Iroume, Andrés; Comiti, Francesco; Lenzi, Mario A.
- ItemLinking riparian woody communities and fluviomorphological characteristics in a regulated gravel-bed river (Piave River, Northern Italy)(2016) Picco, Lorenzo; Sitzia, Tommas; Mao, Luca; Comiti, Francesco; Lenzi, Mario A.
- ItemMedium-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.
- ItemThe response of a gravel‐bed river planform configuration to flow variations and bed reworking : a modelling study(2015) Kaless, Gabriel; Mao, Luca; Moretto, Johnny; Picco, Lorenzo; Lenzi, Mario A.