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Misura delle portate solide, in sospensione e al fondo, del F. Reno e inquadramento geomorfologico e sedimentologico dell’alveo
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Land use changes, torrent control works and sediment mining: effects on channel morphology and sediment flux, case study of the Reno River (Northern Italy)
No full textAs with most Italian rivers, the Reno River has a long history of human modification, related also to morphological changes of
the lower Po River since Roman times, but in the last decades, significant land use changes in the headwaters, dam construction,
torrent control works and extensive bed material mining have caused important channel morphology and sediment budget
changes. In this paper, two main types of channel adjustment, riverbed incision and channel narrowing, are analysed. Riverbed
degradation is discussed by comparing four different longitudinal profiles surveyed in 1928, 1951, 1970 and 1998 in the
120 km long reach upstream of the outlet. The analysis of channel narrowing is carried out by comparing a number of
cross-sections surveyed in different years across the same downstream reach. Field sediment transport measurements of seven
major floods that occurred between 2003 and 2006 are compared with the bedload transport rates predicted by the most
renowned equations. The current low bedload yield is discussed in terms of sediment supply limited conditions due to land
use changes, erosion-control works and extensive and out of control bed material mining that have affected the Reno during
the last decades
Channel morphology evolution and bedload transport of the Reno river in northern Italy
No full textThe Reno R., as many other Italian rivers, has been significantly affected by man activity since Romans time, but in the last decades significant land use changes in the headwater, extensive bed material mining, dams construction, torrent-control works and large fluids extraction from the underground caused important channel morphology and sediment fluxes changes.
To better understand such morphological changes and their causes, the hydraulic geometry data of several cross sections and the longitudinal profile data of the Reno river, surveyed at different times, were analysed emphasizing a dramatic streambed incision that took place between 1950s and 1980s, with a volume of sediment lost of about 18 x106 m3.
At the same time a field campaign was started in 2003 collecting representative bed material samples and sediment transport measurements with Helley-Smith bedload sampler to assess the present river dynamics and evolution.
Bedload transport rate resulted very low also during floods larger than bankfull stage and even those equations renown in the literature to underpredict bedload transport overestimate the sediment transport of the Reno R. Among the equations used those predicting transport rates closer to the actual surveyed values are modified Meyer-Peter & Muller equation
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 seasonality were as well.
Sediment deficit of the Reno river system results from many factors including an increase in forest cover, presence of dams for agricultural and hydroelectric purposes, engineering works on the watershed and on the river channel, large bed material exploitation and likely a decrease in flood frequency
Sediment supply and morphological evolution of a small river mouth (fiumi uniti, ravenna, italy): should river management be storm-driven?.
No full textLo studio riporta l'analisi delle relazioni tra apporti solidi a mare e dinamica della costa prospiciente la foce dei Fiumi Uniti
Valutazione della vulnerabilità intrinseca alle perdite d'acqua e di azoto attraverso l'approccio deterministico e l’analisi di regressione
No full textUno dei principali problemi che riguarda i sistemi ambientali è la vulnerabilità delle acque sotterranee e superficiali alle perdite di prodotti chimici utilizzati nelle pratiche agricole. Per quantificare queste perdite, provenienti da terreni agricoli, è diffuso l’utilizzo di modelli matematici che descrivono il movimento dell'acqua, il trasporto e la trasformazione delle specie disciolte attraverso il profilo del terren
Valutazione della vulnerabilità intrinseca e specifica ai nitrati di origine agricola nella Provincia di Ferrara
No full textLe perdite di azoto, soprattutto derivanti da pratiche agricole, sono diventate, recentemente, una seria minaccia per la qualità sia delle acque superficiali che sotterranee. Con lo scopo di raggiungere un “buono stato” ecologico e chimico di tutte le acque comunitarie entro il 2015, l’Unione Europea ha iniziato una politica di contenimento dell’inquinamento dell’azoto, a partire dalla Direttiva Comunitaria 91/676 CEE, chiamata Nitrate Directive e successivamente con la Direttiva 2000/60/CE Water Framework Directive (WFD), con le quali si stabiliscono una serie di misure e di limitazioni da applicare in quelle aree dichiarate “vulnerabili ai nitrati di origine agricola”. E’ stata fatta trasposizione della direttiva a livello nazionale, attraverso l’approvazione del D. Leg. 3 n.152 del 7 aprile 2006, entrato in vigore il 29 aprile 2006 e poi con i Piani Regionali di Tutela delle Acque (PTA), che definiscono tutta la Provincia di Ferrara ZVN, cioè Zona Vulnerabile da Nitrati di origine agricola
Implementazione di un metodo di separazione granulometrica gravitazionale
No full textIn questo studio è stato testato un metodo per separare le diverse frazioni granulometriche senza l’utilizzo di agenti chimici, quindi mantenendo inalterate le caratteristiche chimico-fisiche delle varie frazioni separate. Il metodo si avvale del classica separazione umida per dividere la frazione sabbiosa da quella fine (<63 μm).
Mentre le frazioni siltose vengono separate da quelle argillose utilizzando il metodo di separazione gravitazionale in cilindri immersi in un bagno termostatico a 20 °C. Come fase disperdente è stata utilizzata solo acqua deionizzata, il surnatante contenente le particelle di argilla in sospensione è stato sifonato dopo che le frazioni più grossolane hanno sedimentato sul fondo. Il calcolo del tempo di sedimentazione è stato effettuato tramite la legge di Stokes. La procedura è stata testata su 3 repliche di suolo granulometricamnete eterogeneo. I risultati ottenuti confermano il buono grado di riproducibilità del metodo, in quanto la deviazione standard normalizzata risulta inferiore al 5% ed il grado di purezza delle frazioni granulometriche più fini è risultato del 90% per il silt e del 95% Per l’argilla. Questo metodo, semplice ed economico può quindi essere applicato in esperimenti sull’adsorbimento di contaminanti su diverse frazioni granulometriche data l’elevato grado di purezza raggiungibile
Seismic induced variation of hydraulic conductivity distribution in a large tank
No full textA large tank (4x8x1.4 m) equipped with 26 standard piezometers and filled with sandy sediments (35 m3), was characterized via slug tests and grain size distribution analysis in 2006. The characterization via slug tests was repeated in 2013 after the seismic events of May 2012 near Ferrara (IT) characterized by a maximum Mw of 5.9 to infer the hydrological response of the tank's hydraulic conductivity field to the stresses induced by the earthquake. Results show a general decrease in hydraulic conductivity values, due to compaction phenomena, and a variation in the spatial distribution of hydraulic conductivity values, directly correlated to the presence of the finer fraction of the sediments within the large tank. In particular, the lenses, prevalently made of sandy sediments showed a negligible reduction, while the lenses constituted prevalently by silt displayed a larger decrease. The differential hydraulic conductivity reduction inhibited the flow linkages between the sandy lenses, provoking a four times decrease in the bulk hydraulic conductivity of the tank. This laboratory experiment highlights that pronounced hydraulic conductivity shrinkages should be expected after important seismic events in heterogeneous fine alluvial units
Groundwater flow modelling of a tunnel-drained fractured aquifer: validation through creek base-flow continuous monitoring
No full textThis paper concern the implementation and validation of a numerical flow model based on the data collected and related to the bored section of a base tunnel through the Appenninic chain (Veccione watershed, Upper Reno basin, Tuscany, Northern Italy). The hydrologic input data employed in the simulation are the results of an hydrogeological program based on a discontinuous monitoring of springs, creeks discharges and tunnel’s drainage rate from 1995 to 2001. Moreover a detailed geological survey of the area was developed to identify the main tectonic patterns.
Three different numerical models were set up, all based on the numerical code Modflow: the first one is a steady-state model calibrated on piezometric levels, springs and creeks discharge in undisturbed conditions; the second one is a transient model relative to the time span between 1999 and 2004 calibrated with the tunnel drainage to nowdays; the third is a transient model to verify the long term effects (till 2015). To improve the validation of the second transient model, were compared data coming from continuous stream stage monitoring systems with model outputs . The study focus on tunnel’s interference with groundwater flow system and the possibility to employ a finite differences code as a predictive tool in fractured aquifer
Intrinsic vulnerability uncertainties due to climatic variability and soil permeability in the Fucino plain (IT)
No full textReactive nitrogen losses from agricultural activities are a global problem and its management requires an integrated interdisciplinary approach. Throughout the world, alluvial plains are usually the most impacted regions by nitrate pollution and especially by nitrate groundwater contamination. This study shows that climatic variability in this small alluvial plain affects LOS indices results less than ks uncertainties. The application of LOS indices showed its aptitude to adequately represent the intrinsic vulnerability to nitrogen and water losses in agricultural alluvial plains
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