110 research outputs found
Dynamics of a nearshore bar system in the northern Adriatic: A video-based morphological classification
No full textThe aim of this paper is to define a simplified morphodynamic classification suitable for low energy beaches exposed to microtidal conditions. The study site is located in the northern Adriatic (in Italy), it is an almost 2. km-long rectilinear beach bordered at the northern edge by coastal structures and at the southern end by a small river inlet. The mechanisms related to the evolution of the submerged part of the beach were derived from video-monitoring using Argus technology. The morphodynamic evolution of the system was studied using an automatic procedure on images for the characterisation of nearshore bars that showed good correspondence with hand-based (visual) interpretation. To apply this automatic procedure, the bar's plan crest shape was mapped using cross-shore pixel luminosity transects traced on time-averaged video images. A careful sensitivity analysis was undertaken to determine the best spacing between transects for the correct tracing of the shape of the bar crest. The error associated to a transect spacing every 25. m resulted in being comparable with the pixel resolution in the area and with the error found comparing the video interpretation with bathymetric surveys. From the study of a four and a half year dataset (February 2003-May 2007), the submerged beach was found to be characterised by the presence of a single bar in the area next to coastal protection structures. However, moving southwards of these, inner and outer bars were present. The morphodynamics of the outer bar and its plan shape modifications were dominated by rhythmic forms. Occasionally, after high energy events, the bar became rectilinear but during the following lower energy periods rhythmicity was re-established, supporting the hypothesis of self-organization mechanisms. The cross-shore position of the bar's crests only showed limited cross-shore mobility through time. © 2010 Elsevier B.V
Validation of the coastal storm risk assessment framework along the Emilia-Romagna coast
No full textThe Italian coasts are threatened by coastal flooding and erosion. The Emilia-Romagna region coastline is exposed to marine storms because of its low-lying nature and massive urbanization. Regional managers need comprehensive tools for coastal storm risk assessment. The RISC-KIT Coastal Risk Assessment Framework (CRAF) provides a conceptual framework, which includes hazard, exposure and vulnerability evaluation, to implement a screening process able to identify littoral zones that can be classified as hotspots (Phase 1) and to successively rank the identified hotspots to select the most critical ones (Phase 2). This study includes the results of the implementation of CRAF Phase 1 in the Emilia-Romagna coast. The method is based on a Coastal Index approach, calculated for 1 km length coastal sectors, applied taking into account both hazard and exposure indicators. The general methodology was partly modified thanks to the strong collaboration with the End-User (Servizio Geologico Sismico e dei Suoli, SGSS) which provided data, suggestions and comments at every step of the implementation. The SGSS also provided data to validate the outcomes of the CRAF methodology. Thus, the critical areas identified by the CRAF were compared with historical (1946–2010) storm impacts, resulting in a reasonable agreement between the identified hotspots
Evoluzione recente del sistema dunale di Lido di Dante-Foce Bevano (Ravenna): fattori naturali ed impatto antropico
No full textIl presente articolo descrive sei anni di monitoraggio della fascia dunale tra Lido di Dante e la Foce del torrente
Bevano, una delle poche aree naturali della costa dell’Emilia-Romagna. Il monitoraggio ha identificato uno
stato di degrado, ormai diventato irreversibile, di circa metà della fascia dunale, che tenderebbe a migrare verso
l’entroterra, attualmente occupata da una pineta costiera. I rilievi effettuati hanno identificato che, in seguito
alla progressiva riduzione dell’ampiezza della spiaggia a Sud delle opere di protezione di Lido di Dante, durante
le mareggiate si osserva il contatto tra l’azione del moto ondoso ed il fronte della duna. Il processo genera
una progressiva perdita di quota e la morte dell’ammofileto, esponendo quindi la duna stabilizzata all’azione
diretta delle onde e dello spray marino, in seguito all’obliterazione della duna mobile ad essa antistante. Sono
stati identificati due meccanismi di erosione della duna, in funzione della quota della cresta al di sopra del
l.m.m. e del volume in sezione: erosione del fronte della duna dovuta al crollo del lato esposto verso mare o
scavalcamento della cresta e progressiva formazione di morfologie “a collinetta”, che vengono erose lateralmente
fino alla loro obliterazione durante eventi di washover. Si pensa che l’indiscriminato accesso dei bagnanti alla
spiaggia attraverso i varchi presenti in punti dove il cordone è più basso sia un ulteriore fattore destabilizzante.
Nonostante siano stati tentati due ripascimenti della spiaggia (2005 e 2007), il volume di sabbia utilizzato non
è probabilmente stato sufficiente per dare respiro al sistema spiaggia-duna nelle zone più critiche, dove ad oggi
le dune sono ormai scomparse
A SIMPLIFIED METHODOLOGY FOR THE ESTIMATION OF WAVE RUNUP ON ARMOURED RUBBLE SLOPES FOR VULNERABILITY ASSESSMENT
No full textFrom Hazard to Consequences: Evaluation of Direct and Indirect Impacts of Flooding Along the Emilia-Romagna Coastline, Italy
No full textManaging coastal flood risk at the regional scale requires a prioritization of economic resources along the shoreline. Advanced modeling assessment and open-source tools are now available to support transparent and rigorous risk evaluation and to inform managers and stakeholders in their choices. However, the issues lay in data availability and data richness to estimate coastal vulnerability and impacts. The Coastal Risk Assessment Framework (CRAF) has been developed as part of the Resilience Increasing Strategies for Coasts - Toolkit (RISC-KIT) EU FP7 project. The framework provides two levels of analysis. In the first phase, a coastal index approach is applied to identify a restricted number of potential critical areas for different hazards (i.e., erosion and flooding). In the second phase, an integrated hazard and impact modeling approach is applied in the critical areas to assess the direct and indirect impacts of storm events using a matrix-based approach and a systemic analysis. The framework was tested on the coastline of the Emilia-Romagna region (northern Italy) for two probabilistic coastal storms with representative return periods of 10 and 100 years. In this work, the application of the second phase of the CRAF is presented for two sites, Lido degli Estensi-Spina (Ferrara province) and Milano Marittima (Ravenna province). The hazard modeling of floods was implemented using a coupling between XBeach and Lisflood-FP. The Integrated Disruption Assessment (INDRA) model was applied to quantify direct and indirect impacts. The impact assessment focused on household’s financial recovery, business disruption and financial recovery, transport network disruption and risk to life. The considered business sector comprised the key economic activities related to the sun-and-beach tourism, which is one of the main drivers of the regional economy. A Multi-Criteria Analysis was applied to support decision-makers to identify the most critical site. The importance of detailed physical and socio-economic data collected at the regional and local levels is highlighted and discussed, together with the importance to involve different stakeholders in the process (e.g., through interviews and surveys). The limitations of the applied approach due to data quality and availability and to the assumptions introduced in the hazard and disruption models are highlighted
Beach morphodynamics and types of foredune erosion generated by storms along the Emilia-Romagna coastline, Italy
No full textThe objectives of this study are to examine the response of a dune and beach system on the Adriatic coastline in northern Italy to the arrival of storms, compare it with seasonal (months) and medium-term (3-year) morphodynamic change, and evaluate results predicted by the numerical model XBeach. The studied coastline stretches 4. km from the Bevano River mouth to the north of the site to the township of Lido di Classe to the south, where the beach is protected by coastal structures. Fieldwork consisted of topographic profile surveys using RTK-DGPS technology (7 times over an approx. 3-year period). 103 samples of surface sediment were collected along 20 of the cross-shore profiles at 6 distinct cross-shore positions, selected on the basis of morphological beach characteristics. Data analyses of dune and beach slopes enabled the study area to be divided into 6 separate morphological zones using the spatial (longshore and cross-shore) variation of morphologies located on the backshore and intertidal beach observed in a preliminary survey of the area. Other criteria were a spatial consistency in beach slopes and/or presence/absence of intertidal morphologies identified in the aerial photographs and Lidar data. The swash zone slope did not show any significant variability for the entire area. A weak seasonal trend in the variability of the mean foredune slope was observed, with steeper slopes typically during winter and flatter slopes during summer. Analysis of grain size revealed that the beach sediment is well-sorted fine sand tending to medium, with a decreasing trend in size from the Bevano River mouth southwards towards Lido di Classe. According to the Masselink and Short (1993) classification, the natural part of the study site has an Intermediate Barred Beach (IBB) and following the Short (1999) classification, results in a modally LBT (longshore bar-trough) or LTT (low tide terrace) with a small section being TBR (transverse bar and rip). Storms are considered the main factor controlling changes in the beach and dune slope. The most significant storm was recorded in March 2010 with a peak significant wave height of 3.91. m. Contrary to the seasonal dune trend, several foredune slopes were observed to flatten following this event, which can be attributed to the action of dune slumping from the already weakened dune state. Modelling of foredune erosion, using a process-based model (XBeach), reproduced the erosion of the upper beach and dune toe reasonably well, but is currently limited by the acceptable slope value for dune stability, which does not account for biotic factors (e.g. plant roots). The comparison between the storm impact categories of Sallenger (2000) and the DSF (Dune Stability Factor) of Armaroli et al. (2012) shows a very good correspondence between the effects of the winter 2008-2009 storms and the vulnerability of the dune system predicted using both classifications.</p
An Airborne Lidar-Based 15-Year Study of Dune Reconstruction and Overwash Formation in a Microtidal and Fetch Limited Environment
No full textThis paper examines the long-term morphological evolution of the Bevano River sand spit (Ravenna, Italy) after an artificial intervention carried out in 2006 that artificially relocated the river mouth to improve the hydraulic efficiency, preventing flooding and reconstructing a local dune system. Using multitemporal Lidar data (2004–2019), combined with orthophotos and a storm dataset, this study analysed shoreline changes and morphological variations, highlighting the role of overwash processes in sediment transfer from the dunes to back-barrier areas. Based on the analysis, a set of washover fans was identified that began to form after a storm event in 2008 and accreted until 2015. These fans, which later coalesced into terraces and were colonised by vegetation, became stable after 2015. Despite an initial low resilience, due to insufficient nourishment and slow vegetation development, the barrier system eventually stabilised, with dunes growing higher and forming a continuous dune crest. The study illustrates the role of surge levels, waves, and low initial elevation in triggering and shaping overwash processes
Opportunities and constraints for managed retreat on exposed sandy shores: Examples from Emilia-Romagna, Italy
No full textManaged retreat is rarely implemented on exposed sandy coasts because of public interest in beach recreation and the great human-use value of existing beaches and dunes. The feasibility of retreat on the sandy coast of the Adriatic Sea in the Region of Emilia-Romagna was evaluated at a site with a single user facility (a beach concession) backed by public parkland. A conceptual scenario of changes to landforms and habitats was developed for the retreat option. Interviews with key stakeholders revealed perceptions of alternatives for addressing erosion and flooding by managed retreat or by protecting existing features in place.The beach concession occupies a segment of shore between an eroding (-9.3myr-1) washover barrier updrift and an accreting beach downdrift. Landward of the concession is a portion of the Po Delta Park, consisting of a brackish lagoon and marsh and an artificially-created freshwater lake. Shore protection projects have maintained the concession and the integrity of a dike protecting the lake. Allowing retreat to occur would cause (1) loss of the concession in its present location; (2) erosion of the dike, converting the lake to brackish habitat; and (3) migration of the shoreline to a pine forest, campground and residences that are now 500m from the shoreline. Freshwater and pine forest habitat would be lost, but salt water wetland and pioneer coastal species would be restored. The beach and campground could still be used as the shoreline migrates inland, but with less fixed infrastructure. Landward facilities could be protected by a ring dike.At issue is whether normally dynamic and short-term landforms and habitats should be protected as static features in perpetuity and whether human actions should be taken to protect human-created nature (lake, pine forest) against natural evolutionary processes. Stakeholders indicated that managed retreat should occur eventually but existing features should be protected now. The retreat option is compatible with Regional ICZM plans, but differs from the standard engineering designs actually suggested for implementation. The benefits of managed retreat on exposed sandy shores can only be presented in conceptual terms until demonstration projects provide concrete answers, so it is not surprising that the undocumented benefits of a more dynamic shoreline have little appeal relative to maintaining the status quo. •Managed retreat is evaluated on a coast where sandy beaches have recreational value.•Human-induced erosion is being countered by shore protection projects.•Normally dynamic landforms and habitats are being maintained as static features.•Managed retreat would reestablish natural features and still support beach use.•Stakeholders prefer maintaining the status quo but know that retreat should occur
Evaluation of XBeach predictions for a real-time warning system in Emilia-Romagna, Northern Italy
No full textThe ability to predict coastal hazards several days in advance is a valuable tool for coastal managers to carry out necessary hazard-reduction measures. The project MICORE aims to develop an early-warning system of coastal hazards at nine distinct sites across Europe using a train of numerical models from the prediction of forcing parameters to the localized hydro/morphodynamics. A vital component of this project is the evaluation of morphology predictions of storm erosion, using the recently-developed XBeach model. In this study, XBeach predictions of two storms events on the Emilia-Romagna coastline in Northern Italy are assessed against measured beach response. This site is unique in that as well as consisting of relatively pristine natural areas, it also contains a series of offshore breakwaters protecting urban settlements and hence represents the first time XBeach has been run in such a setting. 1DH model runs at a natural section of the site predict the relatively minor dune erosion relatively well, with best results obtained by increasing the critical avalanching slope below water. For the section with offshore breakwaters, a 1DH model is found to be inappropriate due to the unreasonable increase in water levels modeled in lee of the structures. Water levels are observed to reduce significantly when running the model in 2DH, where return flow currents through the gaps in breakwaters are also included
Studio della variazione della linea di riva tramite l’analisi di immagini video e strumenti GIS
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