Two-Layer Non-Hydrostatic Model for Generation and Propagation of Interfacial Waves

When pycnocline thickness of ocean density is relatively small, density stratification can be well represented as a two-layer system. In this article, a depth integrated model of the two-layer fluid with constant density is considered,and a variant of the edge-based non-hydrostatic numerical scheme is formulated. The resulting scheme is very efficient since it resolves the vertical fluid depth only in two layers. Despite using just two layers, the numerical dispersion is shown to agree with the analytical dispersion curves over a wide range of kd, where k is the wave number and d the water depth. The scheme was tested by simulating an interfacial solitary wave propagating over a flat bottom, as well as over a bottom step. On a laboratory scale, the formation of an interfacial wave is simulated,which also shows the interaction of wave with a triangular bathymetry. Then, a case study using the Lombok Strait topography is discussed, and the results show the development of an interfacial wave due to a strong current passing through a sill.     

Changes in water quality and runoff in the Upper Oder River Basin

The aim of the study is the analysis of runoff and water quality changes in the Upper Oder River Basin above the Krapkowice gauging station (catchment area A = 10 720.6  km²).The issue of water quality is of particular importance to Poland, which has comparatively poor water resources compared with many countries of the European Union (EU). What is more, large pollutant loads in the upper course of the Oder pose huge problems for water consumers and users in its middle and lower course (including Germany) and pollute the Baltic Sea.Changes in 7 indices of water pollution, including BOD₅ and COD (synthetic indices), sulphates, chlorides and suspended matter (mineral substances) and nitrates and phosphates (biogenic substances), were investigated for 8 monitoring sites. The study spans the period before and after political transformation in Poland and the Czech Republic, which significantly altered the economies of these countries. In addition, the patterns of runoff changes were analysed at 3 gauging stations: Chałupki, Krzyżanowice and Miedonia, which were also water quality monitoring points. The analysis encompassed 2 periods: 1970–2000 and 1991–2000.The results demonstrated that poor water quality in the Oder improved significantly during the 1990s, as the result of closure of many industries and plants, improvement of sewage treatment and noticeable increases in runoff causing greater dilution of pollutants.As the EU Water Framework Directive is implemented, better water and sewage management can be expected that will contribute to further improvement of water quality in the Oder. However, problems that remain to be solved are the issues of saline mine waters and surface washings and the long-term accumulation of many hazardous substances in bottom sediments in rivers and reservoirs.     

Paleomagnetic study of Middle-Upper Jurassic sediments from the Polish segment of the Pieniny Klippen Belt

Middle-Upper Jurassic carbonates exposed in 7 separate fragments of three tectonic units were sampled in the Polish segment of the Pieniny Klippen Belt in 1981, before construction of the Niedzica-Czorsztyn dam. Demagnetization experiments performed about 20 years ago and analyzed lately with modern program package revealed the presence of Middle Miocene overprints acquired in the normal and reversed geomagnetic field, and pre-folding components of natural remanence acquired during the Middle-Upper Jurassic. A paleolatitude of 36N±7° was obtained for the studied area for this time on the basis of 3 normal and 1 reversed components. Three pre-folding pole positions are situated between pole positions of the normal and reversed Stable European Middle Jurassic field. The obtained paleomagnetic results imply several prefolding (pre-Upper Miocene) and postfolding (post-Upper Miocene) episodes of rotations of the studied fragments.     

Salt movements in the Northeast German Basin and its relation to major post-Permian tectonic phases—results from 3D structural modelling, backstripping and reflection seismic data

The NW–SE-striking Northeast German Basin (NEGB) forms part of the Southern Permian Basin and contains up to 8 km of Permian to Cenozoic deposits. During its polyphase evolution, mobilization of the Zechstein salt layer resulted in a complex structural configuration with thin-skinned deformation in the basin and thick-skinned deformation at the basin margins. We investigated the role of salt as a decoupling horizon between its substratum and its cover during the Mesozoic deformation by integration of 3D structural modelling, backstripping and seismic interpretation. Our results suggest that periods of Mesozoic salt movement correlate temporally with changes of the regional stress field structures. Post-depositional salt mobilisation was weakest in the area of highest initial salt thickness and thickest overburden. This also indicates that regional tectonics is responsible for the initiation of salt movements rather than stratigraphic density inversion.Salt movement mainly took place in post-Muschelkalk times. The onset of salt diapirism with the formation of N–S-oriented rim synclines in Late Triassic was synchronous with the development of the NNE–SSW-striking Rheinsberg Trough due to regional E–W extension. In the Middle and Late Jurassic, uplift affected the northern part of the basin and may have induced south-directed gravity gliding in the salt layer. In the southern part, deposition continued in the Early Cretaceous. However, rotation of salt rim synclines axes to NW–SE as well as accelerated rim syncline subsidence near the NW–SE-striking Gardelegen Fault at the southern basin margin indicates a change from E–W extension to a tectonic regime favoring the activation of NW–SE-oriented structural elements. During the Late Cretaceous–Earliest Cenozoic, diapirism was associated with regional N–S compression and progressed further north and west. The Mesozoic interval was folded with the formation of WNW-trending salt-cored anticlines parallel to inversion structures and to differentially uplifted blocks. Late Cretaceous–Early Cenozoic compression caused partial inversion of older rim synclines and reverse reactivation of some Late Triassic to Jurassic normal faults in the salt cover. Subsequent uplift and erosion affected the pre-Cenozoic layers in the entire basin. In the Cenozoic, a last phase of salt tectonic deformation was associated with regional subsidence of the basin. Diapirism of the maturest pre-Cenozoic salt structures continued with some Cenozoic rim synclines overstepping older structures. The difference between the structural wavelength of the tighter folded Mesozoic interval and the wider Cenozoic structures indicates different tectonic regimes in Late Cretaceous and Cenozoic.We suggest that horizontal strain propagation in the brittle salt cover was accommodated by viscous flow in the decoupling salt layer and thus salt motion passively balanced Late Triassic extension as well as parts of Late Cretaceous–Early Tertiary compression.     

The Elbe Fault System in North Central Europe—a basement controlled zone of crustal weakness

The Elbe Fault System (EFS) is a WNW-striking zone extending from the southeastern North Sea to southwestern Poland along the present southern margin of the North German Basin and the northern margin of the Sudetes Mountains. Although details are still under debate, geological and geophysical data reveal that upper crustal deformation along the Elbe Fault System has taken place repeatedly since Late Carboniferous times with changing kinematic activity in response to variation in the stress regime. In Late Carboniferous to early Permian times, the Elbe Fault System was part of a post-Variscan wrench fault system and acted as the southern boundary fault during the formation of the Permian Basins along the Trans-European Suture Zone (sensu [Geol. Mag. 134 (5) (1997) 585]). The Teisseyre–Tornquist Zone (TTZ) most probably provided the northern counterpart in a pull-apart scenario at that time. Further strain localisation took place during late Mesozoic transtension, when local shear within the Elbe Fault System caused subsidence and basin formation along and parallel to the fault system. The most intense deformation took place along the system during late Cretaceous–early Cenozoic time, when the Elbe Fault System responded to regional compression with up to 4 km of uplift and formation of internal flexural highs. Compressional deformation continued during early Cenozoic time and actually may be ongoing. The upper crust of the Elbe Fault System, which itself reacted in a more or less ductile fashion, is underlain by a lower crust characterised by low P-wave velocities, low densities and a weak rheology. Structural, seismic and gravimetric data as well as rheology models support the assumption that a weak, stress-sensitive zone in the lower crust is the reason for the high mobility of the area and repeated strain localisation along the Elbe Fault System.     

The Role of Dissolved Organic Carbon in a Shallow Lowland Reservoir Ecosystem — A Long‐term Study

Long‐term studies were conducted on the polymictic Siemianówka reservoir (SR), situated in a seminatural forest‐peat catchment in NE Poland. The studies were started on the second year of the reservoir's existence. The records showed dissolved organic carbon (DOC) concentrations gradually increasing up to 25…30 mg/L. The largest DOC pool in the reservoir comes from the spring load input, supplemented by the excessive development of phytoplankton with cyanobacteria dominance. The DOC limited the range of the photic zone, eliminated the occurrence of aquatic plants, and was a significant carrier of nutrients, which were gradually released to water, bringing about the “humoeutrophication” of the reservoir.     

Biomarkers of contaminant exposure: results of a field study with flounder (Platichthys flesus) from the southern Baltic Sea

The results of the present study are based on enzyme biomarker measurements in flounder (Platichthys flesus), a flatfish species that is widely distributed in Baltic coastal waters. The fish were collected from known pollution gradients and from reference areas regarded as relatively free of anthropogenic input. Muscular cholinesterases (ChEs), hepatic glutathione S-transferase (GST), and hepatic ethoxyresorufin-O-deethylase (EROD) activities were measured in each sampled specimen of flounder. Generalized linear models (GLM) were used to analyze the dependence of the enzyme activity on sampling year and area as well as on the biological parameters of the fish. Statistically significant differences in the activities of the measured biomarkers were observed between reference and contaminated sites. ChEs and GST activities differed with gender. The results of this study suggest that the location and year of sampling have a significant impact on the activity of all the measured biomarkers.     

Avalanche Hazard Mitigation Strategies Assessed by Cost Effectiveness Analyses and Cost Benefit Analyses—evidence from Davos,Switzerland

This paper demonstrates the application of cost effectiveness analysis and cost benefit analysis to alternative avalanche risk reduction strategies in Davos, Switzerland. The advantages as well as limitations of such analysis for natural hazards planning are discussed with respect to 16 avalanche risk reduction strategies. Scenarios include risk reduction measures that represent the main approaches to natural hazards planning in Switzerland, such as technical, organisational, and land use planning measures. The methodologies used outline how concepts and techniques from risk analysis, hazard mapping, Geographic Information System, and economics can be interdisciplinary combined. The results suggest important considerations, such as possible sources of uncertainty due to different choices in the calculation of cost effectiveness ratio and net present value. Given the parameters and assumptions, it seems as if the current approach to avalanche risk reduction in the study area approximates to economic and cost efficiency and serves the aim of reducing risk to human fatalities.