scholarly journals Boulder accumulations related to extreme wave events on the eastern coast of Malta

2016 ◽  
Vol 16 (3) ◽  
pp. 737-756 ◽  
Author(s):  
Sara Biolchi ◽  
Stefano Furlani ◽  
Fabrizio Antonioli ◽  
Niccoló Baldassini ◽  
Joanna Causon Deguara ◽  
...  
Keyword(s):  
Radiocarbon Dating ◽  
Marine Organisms ◽  
Eastern Coast ◽  
Hydrodynamic Equations ◽  
Storm Events ◽  
Storm Waves ◽  
Intense Storm ◽  
Wave Heights ◽  
The Mediterranean ◽  
Very High

Abstract. The accumulation of large boulders related to waves generated by either tsunamis or extreme storm events have been observed in different areas of the Mediterranean Sea. Along the eastern low-lying rocky coasts of Malta, five sites with large boulder deposits have been investigated, measured and mapped. These boulders have been detached and moved from the nearshore and the lowest parts of the coast by sea wave action. In the Sicily–Malta channel, heavy storms are common and originate from the NE and NW winds. Conversely, few tsunamis have been recorded in historical documents to have reached the Maltese archipelago. We present a multi-disciplinary study, which aims to define the characteristics of these boulder accumulations, in order to assess the coastal geo-hazard implications triggered by the sheer ability of extreme waves to detach and move large rocky blocks inland. The wave heights required to transport 77 coastal boulders were calculated using various hydrodynamic equations. Particular attention was given to the quantification of the input parameters required in the workings of these equations, such as size, density and distance from the coast. In addition, accelerator mass spectrometry (AMS) 14C ages were determined from selected samples of marine organisms encrusted on some of the coastal boulders. The combination of the results obtained both by the hydrodynamic equations, which provided values comparable with those observed and measured during the storms, and radiocarbon dating suggests that the majority of the boulders have been detached and moved by intense storm waves. These boulders testify to the existence of a real hazard for the coasts of Malta, i.e. that of very high storm waves, which, during exceptional storms, are able to detach large blocks of volumes exceeding 10 m3 from the coastal edge and the nearshore bottom, and also to transport them inland. Nevertheless, the occurrence of one or more tsunami events cannot be ruled out, since radiocarbon dating of some marine organisms did reveal ages which may be related to historically known tsunamis in the Mediterranean region, such as the ones in AD 963, 1329, 1693 and 1743.

scholarly journals Boulder accumulations related to extreme wave events on the eastern coast of Malta

2015 ◽  
Vol 3 (10) ◽  
pp. 5977-6019 ◽  
Author(s):  
S. Biolchi ◽  
S. Furlani ◽  
F. Antonioli ◽  
N. Baldassini ◽  
J. Causon Deguara ◽  
...  
Keyword(s):  
Eastern Coast ◽  
Hydrodynamic Equations ◽  
Storm Events ◽  
Sea Waves ◽  
Extreme Waves ◽  
Extreme Wave ◽  
Storm Waves ◽  
Hellenic Arc ◽  
Intense Storm ◽  
Wave Heights

Abstract. The accumulation of large boulders related to waves generated either by tsunamis or extreme storm events has been observed in different areas of the Mediterranean Sea. Along the NE and E low-lying rocky coasts of Malta tens of large boulder deposits have been surveyed, measured and mapped. These boulders have been detached and moved from the seafloor and lowest parts of the coast by the action of sea waves. In the Sicily–Malta channel, heavy storms are common and originate from the NE and NW winds. Conversely, few severe earthquakes and tsunamis are recorded in historical documents to have hit the Maltese archipelago, originated by seismicity activity related mainly to the Malta Escarpment, the Sicily Channel Rift Zone and the Hellenic Arc. We present a multi-disciplinary study, which aims to define the characteristics of the boulder accumulations along the eastern coast of Malta, in order to assess the coastal geo-hazard implications triggered by the sheer ability of extreme waves to detach and move large rocky blocks inland. The wave heights required to transport coastal boulders were calculated using various hydrodynamic equations. Particular attention was devoted to the quantification of the input parameters required in the workings of these equations. The axis sizes of blocks were measured with 3-D digital photogrammetric techniques and their densities were obtained throughout the use of a N-type Schmidt Hammer. Moreover, AMS ages were obtained from selected marine organisms encrusted on some of the boulders in various coastal sites. The combination of the results obtained by hydrodynamic equations and the radiocarbon dating suggests that the majority of the boulders has been detached and moved by intense storm waves. Nonetheless, it is possible that some of them may have been transported by tsunami.

scholarly journals New Wind-Wave Climate Records in the Western Mediterranean Sea

2021 ◽  
Author(s):  
Khalid AMAROUCHE ◽  
Bilal Bingölbali ◽  
Adem Akpinar
Keyword(s):  
Mediterranean Sea ◽  
Global Climate ◽  
Kendall Test ◽  
Wave Climate ◽  
Western Mediterranean ◽  
Storm Events ◽  
Local Climate ◽  
Western Mediterranean Sea ◽  
Wave Heights ◽  
The Mediterranean

Abstract This study presents a detailed analysis of changes in wind and wave climate in the Western Mediterranean Sea (WMed), based on 41 years of accurate wind and wave hindcasts. The purpose of this research is to assess the magnitude of recent changes in wave climate and to locate the coastal areas most affected by these changes. Starting from the Theil-Sen slope estimator and the Mann Kendall test, trends in mean and Max significant wave heights (SWH) and wind speed (WS) are analyzed simultaneously on seasonal and annual scales. Thus, the new wave records observed since 2010 have been located spatially and temporally using a simple spatial analysis method, while the increases in maximum wave heights over the last decade have been estimated and mapped. This work was motivated by evidence pointed out by several authors concerning the influence of global climate change on the local climate in the Mediterranean Sea and by the increase in the number and intensity of wave storm events over recent years. Several exceptional storms have recently been observed along the Mediterranean coasts, including storm Adrian in 2018 and storm Gloria in 2020, which resulted in enormous damage along the French and Spanish coasts. The results of the present study reflect a worrying situation in a large part of the WMed coasts. Most of the WMed basin experiences a significant increasing trend in the annual Max of SWH and WS with evident inter-seasonal variability that underlines the importance of multi-scale analysis to assess wind and wave trends. Since 2013, about half of the WMed coastline has experienced records in wave climate, not recorded at least since 1979, and several areas have experienced three successive records. Several WMed coasts are experiencing a worrying evolution of the wave climate, which requires a serious mobilization to prevent probable catastrophic wave storms and ensure sustainable and economic development.

scholarly journals First evidence of accumulation of mega boulders on the Mediterranean rocky coast of Provence (southern France)

2011 ◽  
Vol 11 (3) ◽  
pp. 905-914 ◽  
Author(s):  
C. Vella ◽  
F. Demory ◽  
V. Canut ◽  
P. Dussouillez ◽  
T. J. Fleury
Keyword(s):  
Radiocarbon Dating ◽  
Mediterranean Coast ◽  
Storm Events ◽  
Wave Regime ◽  
Surface Appearance ◽  
Southern France ◽  
Modern Period ◽  
Fresh State ◽  
The Mediterranean ◽  
Rocky Coast

Abstract. An accumulation of boulders was recently discovered along the rocky coast of the Gulf of Fos located in Provence, in an area exposed to a south-westerly wave regime. The coast around this locality forms the western extremity of the calcareous Nerthe range between Marseille and the Rhône Delta. Several mega blocks are scattered to a distance of 30 m behind the coast line. The largest block (33.5 tonnes) has been transported about 39 m inland, up to about 2 m a.s.l. On the Mediterranean coast, the origin of such blocks is often attributed to tsunami-generated waves, but in the case examined here, although the origin is unclear, the differences in surface state between boulders indicates several events generated by south-westerly storms. Radiocarbon dating on several different shells collected from seven different boulders yields a wide dispersion of ages ranging from 4000 BP to the Modern Period. The differences in surface appearance, as well as the differences of fauna conservation and surface coloration, in some cases in a very fresh state, along with the dispersion of radiocarbon ages, suggest that historic storm events have affected these megablocks.

scholarly journals A Study of the Dynamics of Soil Erosion Using Rusle2 Modelling and Geospatial Tool in Edda-Afikpo Mesas, South Eastern Nigeria

2020 ◽  
Vol 0 (0) ◽  
Author(s):  
Joseph I. Amah ◽  
Okechukwu P. Aghamelu ◽  
Olufemi V. Omonona ◽  
Ikechukwu M. Onwe
Keyword(s):  
Soil Erosion ◽  
Soil Loss ◽  
Slope Failure ◽  
Liquid Limit ◽  
Storm Events ◽  
Remotely Sensed Data ◽  
Erosion Processes ◽  
Hill Slope ◽  
Intense Storm ◽  
Very High

AbstractThe Revised Universal Soil Loss Equation (RUSLE) was used to study the soil erosion processes in Edda-Afikpo mesas, Lower Cross River watersheds,Nigeria. The mesas occupy an area estimated at 60km2 on a surface relief of about 284m. DEM data, satellite images and basemap of the area were used. Remotely sensed data were ground-truthed through extensive field works. The results show that the process is facilitated by the Trifecta of hill slope hydrology, geology and land use practices. Steep hill Slope of values 78 % at the major hot spots, very fragile, dry and non-plastic sandy soils all aid sediment detachment. Analysis of the index properties which include Liquid Limit(LL) of 25-30, moisture content(w%) of 5.9-7.4, permeability of 1.541x10-3 – 1.636x10-3 cm/s and shear strength of 36-42 KN/m2 predispose the sediments to detachment and erosion. Based on the analysis, the amount of soil loss in the project area is about 1373.79 ton per year. Soil erosivity factor is high at the mesas(5023.83 MJ mm ha−1 h−1 yr−1 - 5069.51 MJ mm ha−1 h−1 yr−1) The sandy layer attain thickness of 50m-60m in places and with high pore pressure development, slope failure are triggered during intense storm events. In terms of vulnerability level in erosion risk, high to very high constitute 4.1% of the watershed which translate to 5.05km2 of the 59km2. The various processes occur simultaneously and are exacerbated by human factors through seasonal bush burning and development along drainage lines. The study reveals that 18.8% of the available land for development is at high to very high risk of erosion. The soil loss model has been validated and the hotspots from the map coincide with the gully sites. The results of this research can therefore be used for conservation and adaptation purposes.

scholarly journals The Relevance of Grated Inlets within Surface Drainage Systems in the Field of Urban Flood Resilience. A Review of Several Experimental and Numerical Simulation Approaches

2021 ◽  
Vol 13 (13) ◽  
pp. 7189
Author(s):  
Beniamino Russo ◽  
Manuel Gómez Valentín ◽  
Jackson Tellez-Álvarez
Keyword(s):  
Overland Flow ◽  
Drainage System ◽  
Critical Conditions ◽  
Hydraulic Efficiency ◽  
Storm Events ◽  
Urban Resilience ◽  
Urban Flood ◽  
Drainage Systems ◽  
Surface Drainage ◽  
Intense Storm

Urban drainage networks should be designed and operated preferably under open channel flow conditions without flux return, backwater, or overflows. In the case of extreme storm events, urban pluvial flooding is generated by the excess of surface runoff that could not be conveyed by pressurized sewer pipes, due to its limited capacity or, many times, due to the poor efficiency of surface drainage systems to collect uncontrolled overland flow. Generally, the hydraulic design of sewer systems is addressed more for underground networks, neglecting the surface drainage system, although inadequate inlet spacings and locations can cause dangerous flooding with relevant socio-economic impacts and the interruption of critical services and urban activities. Several experimental and numerical studies carried out at the Technical University of Catalonia (UPC) and other research institutions demonstrated that the hydraulic efficiency of inlets can be very low under critical conditions (e.g., high circulating overland flow on steep areas). In these cases, the hydraulic efficiency of conventional grated inlets and continuous transverse elements can be around 10–20%. Their hydraulic capacity, expressed in terms of discharge coefficients, shows the same criticism with values quite far from those that are usually used in several project practice phases. The grate clogging phenomenon and more intense storm events produced by climate change could further reduce the inlets’ performance. In this context, in order to improve the flood urban resilience of our cities, the relevance of the hydraulic behavior of surface drainage systems is clear.

scholarly journals Intermittent but Rapid Changes to Coastal Landscapes: The Tsunami and El Niño Wave-Formed Sea Arch at Laie Point, Oahu, Hawaii, U.S.A.

Geosciences ◽  
2021 ◽  
Vol 11 (3) ◽  
pp. 147
Author(s):  
Benjamin R. Jordan
Keyword(s):  
El Niño ◽  
El Nino ◽  
Sand Dunes ◽  
Tsunami Source ◽  
Tsunami Waves ◽  
Storm Waves ◽  
The Pacific ◽  
Coastal Landscapes ◽  
Wave Heights ◽  
First Time

Kukuiho’olua Island is an islet that lies 164 m due north of Laie Point, a peninsula of cemented, coastal, Pleistocene and Holocene sand dunes. Kukuiho’olua Island consists of the same dune deposits as Laie Point and is cut by a sea arch, which, documented here for first time, may have formed during the 1 April 1946 “April Fools’s Day Tsunami.” The tsunami-source of formation is supported by previous modeling by other authors, which indicated that the geometry of overhanging sea cliffs can greatly strengthen and focus the force of tsunami waves. Additional changes occurred to the island and arch during the 2015–2016 El Niño event, which was one of the strongest on record. During the event, anomalous wave heights and reversed wind directions occurred across the Pacific. On the night of 24–25 February 2016, large storm waves, resulting from the unique El Niño conditions washed out a large boulder that had lain within the arch since its initial formation, significantly increasing the open area beneath the arch. Large waves also rose high enough for seawater to flow over the peninsula at Laie Point, causing significant erosion of its upper surface. These changes at Laie Point and Kukuio’olua Island serve as examples of long-term, intermittent change to a coastline—changes that, although infrequent, can occur quickly and dramatically, potentially making them geologic hazards.

scholarly journals Storm Energy Flux Characterization along the Mediterranean Coast of Andalusia (Spain)

Water ◽  
2019 ◽  
Vol 11 (3) ◽  
pp. 509 ◽  
Author(s):  
Rosa Molina ◽  
Giorgio Manno ◽  
Carlo Lo Re ◽  
Giorgio Anfuso ◽  
Giuseppe Ciraolo
Keyword(s):  
Energy Flux ◽  
Wave Climate ◽  
Mediterranean Coast ◽  
Storm Events ◽  
Cumulative Energy ◽  
Weather Forecasts ◽  
Wave Energy Flux ◽  
The Mediterranean ◽  
Definition Of ◽  
Storm Characteristics

This paper investigates wave climate and storm characteristics along the Mediterranean coast of Andalusia, for the period 1979–2014, by means of the analysis of wave data on four prediction points obtained from the European Centre for Medium-Range Weather Forecasts (ECMWF). Normally, to characterize storms, researchers use the so-called “power index”. In this paper, a different approach was adopted based on the assessment of the wave energy flux of each storm, using a robust definition of sea storm. During the investigated period, a total of 2961 storm events were recorded. They were classified by means of their associated energy flux into five classes, from low- (Class I) to high-energetic (Class V). Each point showed a different behavior in terms of energy, number, and duration of storms. Nine stormy years, i.e., years with a high cumulative energy, were recorded in 1980, 1983, 1990, 1992, 1995, 2001, 2008, 2010, and 2013.

scholarly journals Statistics of Simulated Storm Waves over Bathymetry

2021 ◽  
Vol 9 (7) ◽  
pp. 784
Author(s):  
Arnida Lailatul Latifah ◽  
Durra Handri ◽  
Ayu Shabrina ◽  
Henokh Hariyanto ◽  
E. van Groesen
Keyword(s):  
Water Waves ◽  
Open Water ◽  
Storm Events ◽  
Extreme Waves ◽  
Marine Structures ◽  
Wave Statistics ◽  
Storm Waves ◽  
Different Types ◽  
Run Up ◽  
Good Agreement

This paper shows simulations of high waves over different bathymetries to collect statistical information, particularly kurtosis and crest exceedance, that quantifies the occurrence of exceptionally extreme waves. This knowledge is especially pertinent for the design and operation of marine structures, safe ship trafficking, and mooring strategies for ships near the coast. Taking advantage of the flexibility to perform numerical simulations with HAWASSI software, with the aim of investigating the physical and statistical properties for these cases, this paper investigates the change in wave statistics related to changes in depth, breaking and differences between long- and short-crested waves. Three different types of bathymetry are considered: run-up to the coast with slope 1/20, waves over a shoal, and deep open-water waves. Simulations show good agreement in the examined cases compared with the available experimental data and simulations. Then predictive simulations for cases with a higher significant wave height illustrate the changes that may occur during storm events.

scholarly journals Wave Height Distributions and Rogue Waves in the Eastern Mediterranean

2021 ◽  
Vol 9 (6) ◽  
pp. 660
Author(s):  
Sagi Knobler ◽  
Daniel Bar ◽  
Rotem Cohen ◽  
Dan Liberzon
Keyword(s):  
Wave Height ◽  
Eastern Mediterranean ◽  
Rogue Waves ◽  
Distribution Model ◽  
Storm Events ◽  
Order Model ◽  
Deep Seawater ◽  
Wave Heights ◽  
Storm Characteristics ◽  
Buoy Data

There is a lack of scientific knowledge about the physical sea characteristics of the eastern part of the Mediterranean Sea. The current work offers a comprehensive view of wave fields in southern Israel waters covering a period between January 2017 and June 2018. The analyzed data were collected by a meteorological buoy providing wind and waves parameters. As expected for this area, the strongest storm events occurred throughout October–April. In this paper, we analyze the buoy data following two main objectives—identifying the most appropriate statistical distribution model and examining wave data in search of rogue wave presence. The objectives were accomplished by comparing a number of models suitable for deep seawater waves. The Tayfun—Fedele 3rd order model showed the best agreement with the tail of the empirical wave heights distribution. Examination of different statistical thresholds for the identification of rogue waves resulted in the detection of 99 unique waves, all of relatively low height, except for one wave that reached 12.2 m in height which was detected during a powerful January 2018 storm. Characteristics of the detected rogue waves were examined, revealing the majority of them presenting crest to trough symmetry. This finding calls for a reevaluation of the crest amplitude being equal to or above 1.25 the significant wave height threshold which assumes rogue waves carry most of their energy in the crest.

Radiocarbon dating of individual foram tests show that alleged Lessepsian species are of Holocene age

2021 ◽  
Author(s):  
Paolo G. Albano ◽  
Anna Sabbatini ◽  
Jonathan Lattanzio ◽  
Jan Steger ◽  
Sönke Szidat ◽  
...  
Keyword(s):  
Mediterranean Sea ◽  
Red Sea ◽  
Native Species ◽  
Radiocarbon Dating ◽  
Suez Canal ◽  
Tropical Species ◽  
Indigenous Species ◽  
Last Interglacial ◽  
Sediment Depth ◽  
The Mediterranean

<p>The Lessepsian invasion – the largest marine biological invasion – followed the opening of the Suez Canal in 1869 (81 years BP). Shortly afterwards, tropical species also distributed in the Red Sea appeared on Mediterranean shores: it was the dawn of what would become the invasion of several hundred tropical species. The time of the Suez Canal opening coincided with an acceleration in natural history exploration and description, but the eastern sectors of the Mediterranean Sea lagged behind and were thoroughly explored only in the second half of the 20<sup>th</sup> century. Many parts are still insufficiently studied today. Baseline information on pre-Lessepsian ecosystem states is thus scarce. This knowledge gap has rarely been considered by invasion scientists: every new finding of species belonging to tropical clades has been assumed to be a Lessepsian invader.</p><p>We here question this assumption by radiocarbon dating seven individual tests of miliolids – imperforated calcareous foraminifera – belonging to five alleged non-indigenous species. Tests were found in two sediment cores collected at 30 and 40 m depth off Ashqelon, on the Mediterranean Israeli shelf. We dated one <em>Cribromiliolinella milletti </em>(core at 40 m, 20 cm sediment depth), three <em>Nodophthalmidium antillarum </em>(core at 40 m, 35 cm sediment depth), one <em>Miliolinella </em>cf. <em>fichteliana </em>(core at 30 m, 110 cm sediment depth), one <em>Articulina alticostata </em>(core at 40 m, 35 cm sediment depth) and one <em>Spiroloculina antillarum </em>(core at 30 m, 110 cm sediment depth). All foraminiferal tests proved to be of Holocene age, with a median calibrated age spanning between 749 and 8285 years BP. Only one test of <em>N. antillarum</em> showed a 2-sigma error overlapping the time of the opening of the Suez Canal, but with a median age of 1123 years BP. Additionally, a thorough literature search resulted in a further record of <em>S. antillarum</em> in a core interval dated 1820–2064 years BP in Turkey.</p><p>Therefore, these foraminiferal species are not introduced, but native species. They are all circumtropical or Indo-Pacific and in the Mediterranean distributed mostly in the eastern sectors (only <em>S. antillarum</em> occurs also in the Adriatic Sea). Two hypotheses can explain our results: these species are Tethyan relicts that survived the Messinian salinity crisis (5.97–5.33 Ma) and the glacial periods of the Pleistocene in the Eastern Mediterranean, which may have never desiccated completely during the Messinian crisis and which may have worked as a warm-water refugium in the Pleistocene; or they entered the Mediterranean Sea from the Red Sea more recently but before the opening of the Suez Canal, for example during the Last Interglacial (MIS5e) high-stand (125,000 years BP) when the flooded Isthmus of Suez enabled exchanges between the Mediterranean and the Indo-Pacific fauna. The recognition that some alleged Lessepsian invaders are in fact native species influences our understanding of the invasion process, its rates and environmental correlates.</p>

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