1,721,015 research outputs found
Testing coastal DRR in current and climate change scenarios – Artificial winter dune system in a highly touristic beach in the Northern Adriatic
No full textArtificial dunes are common features built along the coast of the Emilia-Romagna region (Italy) that act as temporary protections during the stormy season in order to prevent damages and inundation to the structures located on the backshore. The RER coast is in fact characterised by low sandy beaches that are exploited for tourism and where beach huts are permanently present on the rear part of the beach. While scientists and regional managers already provided proofs of the capacity of the artificial dunes to lower the hazard component, any study has never investigated their direct impacts in the current (CS) and climate change scenarios (CCS). The RISC-KIT project (www.risckit.eu) provided a methodology for testing DRRs at local level integrating hydro-morphological numerical modelling with a Bayesian Network to assess the consequences of extreme events for different scenarios. The approach was applied at the beach of Lido degli Estensi and Spina (Comacchio, Italy) in the Emilia-Romagna coast. It is a highly touristic area with concessions directly facing the sea, providing sun-and-beach tourism services during summer time, and private residences, commercial activities and hotels at the seafront. The flooding and erosion hazards were analyzed, along with their impacts. A 2DH XBeach model was built and forced with a large number of triangular storms, representative of many different representative combinations of waves' and total water level's ranges observed at regional level. Flooding and erosion results were input into a Bayesian Network which included, as feeding variables categories, deep water boundary conditions (including the CCS trigger), receptors (type and location of assets at the coast), hazard intensity affecting the receptors, impacts and DRR. Therefore, it was possible to integrate a flood damage curve and an erosion potential damage function for the analyzed receptors (beach concessions and residential/commercial buildings), in order to calculate the direct impacts. The artificial dune system was implemented, as representative of the DRR scenario, modifying the topography through the DuneMaker 2.0 Matlab tool. The CCS was implemented through a predicted RSLR under RCP8.52050. The results evidenced that the DRR positively influenced both flooding and erosion hazard intensities distributions. The impacts for the CS showed that, potentially: 20% of residential and commercial buildings and 90% of concessions will be preserved from flood impacts; more than 50% of concessions will be preserved from erosion impacts. The impacts of the CCS evidenced that, potentially: 65% of residential and commercial buildings and 95% of concessions will be preserved from flood impacts; more than 30% of concessions will be preserved from erosion. The positive effect on coastal extreme storm impacts of the implementation of the artificial dunes was evidenced and quantified in comparison with current and climate change scenarios without any DRR implemented. Ongoing studies on the artificial winter dunes, comparing field drone observations and numerical modelling, are being implemented starting from October 2016. Besides, the methodology, if properly adapted, can be applied for any type of DRR, as demonstrated by the RISC-KIT project. It is able to help managers in comparing DRR solutions or strategic alternatives
Morphodynamic evolution of a microtidal barrier, the role of overwash: Bevano, Northern Adriatic Sea
No full textThis study discusses the morphological changes of the Bevano "microtidal barrier" and the washover dynamics and evolution in response to several storm surges recorded during one year between September 2008 and September 2009. This barrier corresponds to the old Bevano river spit (characterised by a northward migration) which was abandoned after the relocation of the river mouth some 600 m to the south of the previous inlet position. The first overwash event was recorded in this barrier just after one of the highest surges recorded in the last 100 years (01 December 2008) with a high a surge level of 0.97 m, combined with an offshore significant wave height of 1.45 m (measured at Cesenatico). Seven separate washover fans were identified together with severe damages to fences and dune vegetation. The washover fans had different dimensions, the most important one being around 18 m wide, and generating a ∼ 9 m landward migration of the back-barrier limit. The study area was therefore subjected to a series of storm-surges during the study period with surge values fluctuating between 0.6 m and 0.8 m. The overwash processes and particularly the exceptional surge of 01 December 2008 was the instigator of initial morphological changes which then facilitated successive morphological changes caused by the subsequent storm surges and, as a result, generating the complete change of the morphologic configuration of the microtidal setting
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 mitigation measures. The MICORE project aims to develop an early warning coastal hazards system at nine distinct sites across Europe using a suite 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 storm 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 represents the first time XBeach has been run in such a setting. 1DH model runs at a natural section of the site predict the minor dune erosion relatively well, with best results obtained by increasing the critical avalanching slope below water. For the section containing offshore breakwaters, a 1DH model is found to be inappropriate due to the unrealstic 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 incorporated
Sedimentation at River Mouths bounded by Coastal Structures: A Case Study along the Emilia-Romagna Coastline, Italy
Full text linkBeach retreat in the Emilia-Romagna coast, facing the north Adriatic Sea, is well-known since decades and several factors are behind this phenomenon: a scarcity of natural sediment supply by rivers, natural and anthropogenic subsidence, and a strong urbanization of the coastal zone. Several bedload measurement campaigns in one representative river of the Ravenna province (Savio River) have been carried out since 2017. At the same time, seasonal surveys of bathymetry were undertaken at the river outlet to correlate changes in sedimentation with river input. The river mouth is constrained by artificial embankments that possibly funnel out sediment offshore during river floods. However, monitoring of bedload transport correlated with bathymetric changes between July 2017 and November 2018 still found a positive budget of almost 5000 cubic meters. Local authorities in Ravenna are planning to dredge 20000 cubic metres from the river mouth to supply small nourishments outside the studied coastal cell. According to the measurements of bathy-metric changes, the Savio mouth will need almost six years to recover, assuming the occurrence of a particularly efficient rate of sediment transport, like the one observed in the monitored period. Notably, the analysed period included a very large river flood that could overshadow the modal sediment transport operated by the river. Furthermore, with deepening of the mouth, the two villages adjacent to the outlet are likely to become more exposed to sea flooding, due to the propagation of surges inside the river mouth. The paper concludes that dredging activities should be reconsidered in view of the precarious equilibrium of the system
Sediment 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
Using high‐spatial resolution uav‐derived data to evaluate vegetation and geomorphological changes on a dune field involved in a restoration endeavour
No full textNowadays, the employment of high‐resolution Digital Surface Models (DSMs) and RGB orthophotos has become fundamental in coastal system studies. This work aims to explore the potentiality of low‐cost Unmanned Aerial Vehicle (UAV) surveys to monitor the geomorphic and vegetation state of coastal sand dunes by means of high‐resolution (2–4 cm) RGB orthophotos and DSMs. The area of study (Punta Marina, Ravenna, Italy), in the North Adriatic Sea, was considered very suitable for these purposes because it involves a residual coastal dune system, damaged by decades of erosion, fragmentation and human intervention. Recently, part of the dune system has been involved in a restoration project aimed at limiting its deterioration. RGB orthophotos have been used to calculate the spectral information of vegetation and bare sand and therefore, to monitor changes in their relative cover area extension over time, through the using of semi‐automatic classification algorithms in a GIS environment. Elevation data from high‐resolution DSMs were used to identify the principal morphological features: (i) Dune Foot Line (DFL); (ii) Dune Crest Line (DCL); Dune seaward Crest Line (DsCL); Stable Vegetation line (SVL). The USGS tool DSAS was used to monitor dune dynamics, considering every source of error: a stable pattern was observed for the two crest lines (DCL and DsCL), and an advancing one for the others two features (DFL and SVL). Geomorphological data, as well as RGB data, confirmed the effectiveness of planting operations, since a constant and progressive increase of the vegetated cover area and consolidation of the dune system was observed, in a period with no energetic storms. The proposed methodology is rapid, low‐cost and easily replicable by coastal managers to quantify the effectiveness of restoration projects
Run-up computation behind emerged breakwaters for marine storm risk assessment
No full textFlood vulnerability assessment due to marine storms is very important for integrated coastal zone management. The case study site is a highly developed area (Rimini) along the Emilia Romagna coastline, facing the north Adriatic sea in Italy. This area is composed of low sandy beaches and is completely protected by emerged breakwaters. Rimini was chosen in order to assess the vulnerability of a very important tourist resort that represents one of the most significant revenue for the regional economy. For the vulnerability assessment it was decided to consider the worst scenarios, using a joint probability of occurrence for a 1, 10 and 100 years return period storm, happening at the same time as an atmospheric surge and with the maximum spring tidal level of +0.45 m above MSL (run-up + surge + tide). The beach slope of different profiles was calculated using the a 2004-DTM (Lidar-based). The attenuation effect of the breakwaters was considered inside the run-up formula using the following method: (i) a 1-d model was used to evaluate the wave height at the seaward foot of each structure; (ii) the Van der Meer formula was applied to calculate the wave height behind structures; (iii) the calculated wave height was transported back to deep water conditions using a 1-d model. Different damage categories were created. The results reveal that, even with the one year event, most of the infrastructures are damaged and the areas behind the beach are flooded
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