1,720,974 research outputs found
Valutazione della morfodinamica di foce del torrente Bevano (RA): il ruolo del trasporto solido di fondo
No full textIl presente lavoro riguarda la stima del trasporto solido di fondo del Torrente Bevano, un
piccolo corso d’acqua che si trova in Emilia-Romagna, messa in relazione con le variazioni a
lungo e breve termine della foce e della spiaggia adiacente alla foce stessa.
E’ stato scelto tale torrente in quanto è sito, nel suo tratto terminale, in una delle poche aree
della costa Romagnola ancora priva di interventi antropici, poiché si trova all’interno di una
riserva naturale. Inoltre presenta dinamiche estremamente interessanti alla foce, essendo in
continuo e rapido movimento verso nord. Tale spostamento della foce genera l’erosione delle
dune che si trovano sulla spiaggia di Lido di Dante, con conseguente pericolo di ingressione
marina nella pineta retrostante.
Nello studio del Torrente Bevano è stato necessario valutare le caratteristiche dell’alveo, il tipo
di sedimenti del letto, il regime delle portate. La mancanza pressoché totale di dati misurati
del trasporto di fondo fa sì che esso sia stato valutato indirettamente, sulla base di modell
Processus de migration des barres intertidales sous l’impact du “swash”. Etudes en Adriatique septentrionale.
No full textSediment transport pattern and coastal evolution at lido di dante beach, Adriatic Sea
No full textInter-disciplinary medium term monitoring of a small coastal cell of the Northern Adriatic, Lido di Dante Beach, was undertaken starting from 2001. In association with the EU-CoastView Project, coastal state indicators were developed and surveyed. This paper presents the observations done during 3 years of surveys: beach morphodynamics, intertidal bars, dune morphology and vegetation, overwash observation and risk. Results evidence two areas with different dynamics: the Southern part of the beach is dependent on the Bevano River by-pass processes and all indicators are positive (stable vegetation, large beach) while the Northern part is very narrow, eroding (10m/year) and the dune is easily overwashed. This atypical behavior is though to be due to the groin that disturbs the protective function of the nearshore bar system. Copyright ASCE 2006
Bar changes due to storm events using argus: Lido di Dante, Italy
No full textIn this study sand bars were analyzed using remote sensing techniques. An Argus system was installed at Lido di Dante, a small village near Ravenna, in northern Italy. The study period is between April 2003 and May 2004. Timex video images were used to analyze bar dynamics. Pixel luminosity intensity was sampled along 15 cross-shore profiles, 50m spaced. The system was perturbed by a storm event occurred in December 2003. Before this event the bars were undulated with 2 wide crescents, after the event the crescents became 5. Before and after this event the system was stable and it maintained a constant configuration. A preliminary conceptual model is presented: the system is self-organized, by redistribution of sand within a delimited longshore area, even under low energy conditions. When an energetic event occurs, the system changes, but it recovers its stable configuration within a short time (6 days). Copyright ASCE 2006
An integrated study of shoreline variability using GIS and ARGUS techniques
No full textGIS techniques (Arcview) were used to study the long term (last 20 years) shoreline variation in the area of Lido di Dante, Ravenna, northern Italy. The shoreline was identified on the photos as the HighWater Line on 4 flights (1978, 1982, 1996, 1998). Evaluation of the error associated to the method (tidal range) indicates an horizontal variability of HWLin the order of 10-30 m, according to the beach slope typical of the different parts of the beach. This means that GIS techniques can be only used as a qualitative instrument for long-term assessments, as on short periods the noise can be high. In any case, the coastline can be broadly described by two segments: one in erosion affected by the presence of structures and one quite stable, dominated by natural process. To assess the correctness of the data extracted from the GIS, topographic surveys were carried out with aGPS in kinematic relative positioning and a total station. These surveys revealed that the area is eroding in the northern part, is oscillating in the central part and is in oscillation/ accretion in the southern one.AnARGUS station was installed in the area. Short-term (hours) shoreline surveys were carried out to compare the GPS data with the ARGUS ones after putting them in a GIS. This comparison revealed that the ARGUS and GPS shorelines are identified with a precision which is comparable
Relationship between bar migration and swash duration: field assessments at Lido di Volano beach, Adriatic Sea, Northern Italy
No full textMorphodynamics of intertidal sand bars: field studies in the northern Adriatic, NE Italy
No full textSwash bars onshore migration have been measured on intertidal area of two microtidal beaches of Northern
Adriatic during very low wave energy conditions. Bed microtopography was performed at every low tides, and
migration of features followed by rods in a cross-shore array. Very small swash bars (A<0.07m, 2<L<10 m) were
identified all over the intertidal zone, and their formation was always associated with a slack water tidal level.
Despite the virtual absence of waves (Hs of 0.04-0.08 m at the Volano site), a important landward migration was
measured (0.5-3 m/day). This migration is associated with an onshore sediment transport. The very low wave
energy permits to assess the action of swash processes alone on the bar morphodynamics. A direct relationship
was found between the bar migration rate and the duration of swash action over the bar crests. A similar study
was performed on a bigger intertidal bar at Lido di Dante, while it was exposed to swash processes. Despite
differences in bar nature and evolution, the landward bar migration also showed a strong relationship with the
duration of swash action, excepted when longshore currents were evidenced, decreasing the deposition on the
slip landward face, and thus the migration rate
Morphodynamics of intertidal sand bars: Field studies in the Northern Adriatic, NE Italy
No full textSwash bars onshore migration have been measured on intertidal area of two microtidal beaches of Northern Adriatic during very low wave energy conditions. Bed microtopography was performed at every low tides, and migration of features followed by rods in a cross-shore array. Very small swash bars (A<0.07m, 2<10 m) were identified all over the intertidal zone, and their formation was always associated with a slack water tidal level. Despite the virtual absence of waves (Hs of 0.04-0.08 m at the Volano site), a important landward migration was measured (0.5-3 m/day). This migration is associated with an onshore sediment transport. The very low wave energy permits to assess the action of swash processes alone on the bar morphodynamics. A direct relationship was found between the bar migration rate and the duration of swash action over the bar crests. A similar study was performed on a bigger intertidal bar at Lido di Dante, while it was exposed to swash processes. Despite differences in bar nature and evolution, the landward bar migration also showed a strong relationship with the duration of swash action, excepted when longshore currents were evidenced, decreasing the deposition on the slip landward face, and thus the migration rate
Geomorphic coastal vulnerability to storms in microtidal fetch-limited environments: Application to NW Mediterranean & N Adriatic Seas
No full textA methodology to compare in relative terms the coastal vulnerability to storm impacts is presented and applied to three sites in the Mediterranean Sea. The analysis separately evaluates the vulnerability to storm-induced processes (inundation and erosion) and, it quantifies the contribution of the forcing (storm properties) and receptor (beach geomorphology) to the overall vulnerability. Beach geomorphology affects calculated vulnerability by influencing process intensity and the ability of the beach to cope with the impacts (resilience). Results showed that regarding wave-induced inundation, the highest vulnerable area is the Ebro delta (Catalan coast) due to a combination of storm properties and the existence of a very low-lying profile. On the other hand, when considering the storm-induced erosion, Lido di Dante (Italy) is the highest vulnerable area because despite the fact that the estimated erosion is not the largest one, the beach width is narrower than in the other sites. In any case, actual beach width at the three sites exceeds the estimated shoreline retreat. According to the obtained results the main induced process affecting coastal vulnerability is inundation
Morphodynamique d’une embouchure tidale : le Bevano, Italie du NE. Apports de la technique de traçage fluorescent en domaine subtidal
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