Wyniki wyszukiwania - Biblioteka Nauki

1

Defining a single set of calibration parameters and prestorm bathymetry in the modeling of volumetric changes on the southern Baltic Sea dune coast

100%

Bugajny N. , Furmańczyk K.

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2022

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tom No. 64 (1)

160--165

EN

The studies described herein aimed to estimate the accuracy of determination of the volumetric changes on the dune coast of the southern Baltic Sea through the application of the XBeach numerical model, which is crucial for coastal engineering. In the first phase of the study, the profile (1D) mode of the model was adapted to 19 cross-shore profiles located along the Dziwnów Spit. The model was calibrated with a storm event in 2009 that caused significant changes to dunes and beaches. Cross-shore profiles were measured approximately one and a half months before and after the storm. An evaluation of model performance was made based on the Brier skill score (BSS), the visual match of the profile shape (VMS), the absolute volumetric change error (m3/m) and the relative volumetric change error (%). In this study, parameters related to the asymmetry transport (facua) and the dune erosion algorithm (wetslp) were taken into account. The best results for model calibration on all 19 cross-shore profiles were obtained with facua values ranging from 0.16 to 0.40 and wetslp values from 0.35 to 0.60. The calibration of individual profiles yielded good results, with an average absolute error of approximately 4 m3/m and an average relative error of ca. 20%. The poorest results were collected for the profiles situated near coastal engineering structures, where the average absolute error was 10 m3/m and the relative error was 60%. The possibility of accepting one set of parameter values for all the profiles at once was also investigated. These studies revealed that the application of one set of facua and wetslp values for all profiles simultaneously resulted in a relative volumetric change error of ca. 25% on average, with the maximum of about 40%. Due to the difficulty of collecting data just before and after the storm event, complex studies using all available bathymetric data were performed. Using a joint dataset composed of prestorm topography recorded before that storm and bathymetry from different years, a simulation of the 2009 storm event was carried out. The studies revealed that the prestorm bathymetry and the randomness of the selection of calibration parameters have similar effects on the accuracy of volumetric changes. Moreover, the impact of the nearshore bathymetry (to a depth of 2 m) on modeling the volumetric changes in the terrestrial part of the shore is evident. A change in the sea bottom inclination and a successive change in the nearshore sediment volume can increase the difference between modeled and actual volumetric changes.

2

Coastal cliff erosion as a source of toxic, essential and nonessential metals in the marine environment

88%

Bełdowska M. , Bełdowski J. , Kwasigroch U. , Szubska M. , Jędruch A.

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2022

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tom No. 64 (4)

553--566

EN

Due to the rising environmental awareness, emissions and releases of pollutants, including metals, have been considerably reduced in the last decades. Therefore, the remobilization of natural and anthropogenic contaminants is gaining importance in their biogeochemical cycle. In the marine coastal zone, this process occurs during the erosion of a shore, especially the most vulnerable cliffs. The research was conducted in the Gulf of Gdańsk (southern Baltic Sea) from 2016 to 2017. The sediment cores were collected from four cliffs; additionally, marine surface sediments were also taken. The concentrations of essential (Cr, Mn, Fr, Cu, Zn) and nonessential (Rb, Sr, Y, Zr, Ba) metals were analyzed using the XRF technique. The levels of the analyzed metals were relatively low, typical of nonpolluted areas. However, considering the mass of eroded sediments, the annual load of metals introduced into the sea in this way is significant. In the case of Cu, Zn, and Y the load can amount to a few kilograms, for Cr and Rb – over ten kilograms, for Mn, Sr, and Zr – several tens of kilograms, for toxic Ba – over 100 kg, and in the case of Fe – 4.8 tonnes. During strong winds and storms, when the upper part of a cliff is eroded, especially the load of Zn and Cr entering the sea may increase. The content of Cr, Zr, and Ba in the cliffs was higher compared to marine sediments from the deep accumulation bottom, which indicates that coastal erosion may be an important source of these metals.

3

Baltic Sea coastal erosion; a case study from the Jastrzębia Góra region

63%

Uścinowicz G. , Kramarska R. , Kaulbarsz D. , Jurys L. , Frydel J. , Przezdziecki P. , Jegliński W.

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tom Vol. 20, No. 4

259--268

EN

The coastline in the Jastrzębia Góra area can be divided into three major zones of general importance: a beach and barrier section, a cliff section, and a section protected by a heavy hydrotechnical construction. These areas are characterised by a diverse geology and origin, and hence different vulnerability to erosion. In addition, observations have demonstrated a different pace of erosion within each zone. Based on the results obtained by remote sensing methods (analysis of aerial photographs and maps), it has been determined that the coastline in the barrier area, i.e., to the west of Jastrzębia Góra, moved landwards by about 130 m, in a period of 100 years, and 80 m over about 50 years. A smaller displacement of the shoreline could be observed within the cliff. Between the middle of the twentieth and the start of the twenty-first centuries the shore retreated by about 25 m. However, in recent years, an active landslide has led to the displacement of the uppermost part of the cliff locally up to 25 m. Another issue is, functioning since 2000, a heavy hydrotechnical construction which has been built in order to protect the most active part of the cliff. The construction is not stable and its western part, over a distance of 50 m, has moved almost 2 m vertically downwards and c. 2.5 m horizontally towards the sea in the past two years. This illustrates that the erosional factor does not comprise only marine abrasion, but also involves land-based processes determined by geology and hydrogeology. Changes in the shoreline at the beach and barrier part are constantly conditioned by rising sea levels, the slightly sloping profile of the sea floor and low elevation values of the backshore and dune areas. Cliffs are destroyed by mass wasting and repetitive storm surges that are responsible for the removal of the colluvium which protects the coast from adverse wave effects. Presumably, mass movements combined with groundwater outflow from the cliff, plus sea abrasion cause destabilisation of the cliff protection construction.

4

Geological structure of the southern Baltic coast and related hazards

51%

Uścinowicz S. , Zachowicz J. , Graniczny M. , Dobracki R.

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tom Vol. 15

61-68

EN

Polish coast of the Baltic Sea has a total length of 498 km (without internal lagoons coasts). Quaternary deposits dominate coastal zone, similar to central and northern Poland. According to morphology and geological structure, three types of coast are distinguished: cliffs (c. 101 km), barriers (380 km) and coast similar to wetlands (salt marshes) (c. 17 km). Generally, three types of mass movements can be distinguished on cliff coast: eboulements (rock falls) dominated on the cliffs built mainly by tills, talus and landslip, dominated on sandy cliffs, and typical landslides occurred on cliff stretches with a complex structure where the main role play clay layers being initial slide layers for other deposits. Serious risks are related to erosion of low and narrow barriers, which could be easy broken during storm surges. Storm floods in case of barrier being broken threaten lowlands behind the barriers. Similar flood hazard exists also on lagoon coasts located behind large and relatively stable barriers. It is caused by barographic high water stands, which in extreme cases reach up to 2 m above the mean sea level, and water back flow into straits connecting lagoons with the sea.

PL

Długość polskiego wybrzeża morskiego wynosi 498 km (bez linii brzegowej Zalewów Wiślanego i Szczecińskiego). W budowie geologicznej strefy brzegowej, podobnie jak środkowej i północnej Polski, dominują osady czwartorzędowe. Biorąc pod uwagę geomorfologię i budowę geologiczną wyróżniono trzy zasadnicze typy wybrzeży: klify o łącznej długości ok. 101 km, wybrzeża wydmowe (mierzeje) o łącznej długości ok. 380 km oraz wybrzeża nizinne typu Wetland o długości ok. 17 km. Na wybrzeżach klifowych wyróżniono trzy typy ruchów masowych: obrywy dominujące na klifach, w których występuje glina zwałowa, zsuwy i osypiska dominujące na klifach zbudowanych głównie z osadów piaszczystych oraz typowe osuwiska występujące na klifach o złożonej strukturze geologicznej, gdzie główną rolę odgrywają warstwy ilaste będące powierzchnią poślizgu dla warstw wyżej ległych. Poważne zagrożenia związane są też z erozją niskich i wąskich mierzei, które łatwo mogą być przerwane w czasie sztormów. Nisko położone obszary zaplecza mierzei w takim wypadku zagrożone są powodziami sztormowymi. Podobne zagrożenia powodziowe istnieją też na zapleczu mierzei relatywnie stabilnych - szerokich z wysokimi wałami wydmowymi. Powodzie mogą wystąpić w przypadku wysokich stanów wody spowodowanych spiętrzeniami sztormowymi i barycznymi, dochodzącymi maksymalnie do 2 m ponad średni poziom morza, kiedy dochodzi do wlewów wód morskich do Zalewów i jezior przybrzeżnych.

5

Effects of human activities in the coastal zone of Laizhou Bay

51%

Wang M. , Han M. , Hui H. , Li Y.

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2021

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tom Vol. 28, nr 2

219--227

EN

The serious destruction of resources and environment in Laizhou Bay has attracted extensive attention of researchers. This study mainly analysed the changes of fish structure and environment in the coastal zone of Laizhou Bay caused by human activities. By consulting literatures and field measurements, the changes of dominant fish species, coastline and sea water intrusion were analysed. The results showed that dominant fish species in Laizhou Bay change from high-economic species to low-economic species under the influence of human activities, and the coastline erosion was serious, and the area of sea water intrusion was also increasing year by year. It is concluded from the research results that human activities had a significant impact on the structure of fish school and the environment. It is necessary to arrange human activities in an appropriate amount to reduce the overexploitation of resources in order to restore the fishery resources and environment in Laizhou Bay.

6

Texture and composition of the Rosa Marina beach sands (Adriatic coast, southern Italy): a sedimentological/ecological approach

38%

Moretti M. , Tropeano M. , van Loon A. J. , Acquafredda P. , Baldacconi R. , Festa V. , Lisco S. , Mastronuzzi G. , Moretti V. , Scotti R.

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2016

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tom Vol. 22, No. 2

87--103

EN

Beach sands from the Rosa Marina locality (Adriatic coast, southern Italy) were analysed mainly microscopically in order to trace the source areas of their lithoclastic and bioclastic components. The main cropping out sedimentary units were also studied with the objective to identify the potential source areas of lithoclasts. This allowed to establish how the various rock units contribute to the formation of beach sands. The analysis of the bioclastic components allows to estimate the actual role of organisms regarding the supply of this material to the beach. Identification of taxa that are present in the beach sands as shell fragments or other remains was carried out at the genus or family level. Ecological investigation of the same beach and the recognition of sub-environments (mainly distinguished on the basis of the nature of the substrate and of the water depth) was the key topic that allowed to establish the actual source areas of bioclasts in the Rosa Marina beach sands. The sedimentological analysis (including a physical study of the beach and the calculation of some statistical parameters concerning the grain-size curves) shows that the Rosa Marina beach is nowadays subject to erosion.