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Investigation of the Wave Field around a Monopile due to Long Crested Irregular Waves in Moderate Steepness
No full textMonopile foundations are the most built foundations in the offshore wind industry. The diameter is also expected to increase in the near future to accomodate for larger wind turbines in deeper water depths. The large monopile diameter imposes additional challenge in planning the marine operations near the monopile, as the monopile can no longer be treated as a transparent monopile (i.e. the monopile gives negligible impact on the incident waves). Proper wave field estimation around the monopile that also accounts for the monopile existence is needed to assure the safety of the operations. Investigation of the wave field around a monopile due to long crested irregular incident waves is provided in the present study. Experimental study was performed with different irregular wave properties, varying the wave steepness and wave diffraction number. The present study explores further the available experimental studies that focus mostly on the runup of the monopile. Initially, Linear Transfer Function (LTF) of the wave field around a monopile from the experimental study is compared to the linear theory, which is found to match well in the high energy frequency range. The LTF differs with the linear theory in the low and high frequency ranges, indicating pronounced nonlinear effect in those frequency ranges. Further, time series analyis is also performed via exceedance probability analysis and significant value computation. It is found that the nonlinearity appears in the crest properties of the wave field around a monopile, while the wave height properties can still be predicted well with the linear theory. Moreover, Wave Type II, wave that travels in the clockwise/anti-clockwise direction around a monopile and not in radial direction, is seen to influence the crest properties
Beyond the 2023 surge: Quantifying shoreline dynamics in the German Baltic Sea with Sentinel-2
No full textMonitoring coastal zones is essential for evidence-based coastal management. Commonly applied methods and technologies like beach surveys, aerial imagery, and Light Detection and Ranging (LiDAR) provide highly accurate data but are often limited in spatial coverage or monitoring frequency due to high costs. Satellite remote sensing has emerged as a promising and cost-effective alternative, offering frequent, large-scale shoreline observations. To facilitate rapid and precise satellite-based shoreline change analysis across large regions, we developed the Shoreline Extraction and Change Analysis Tool (SEaCAT). This Python-based toolkit leverages cloud technology to semi-automate key stages of data processing, including scene selection, shoreline extraction, and change analysis. We employ SEaCAT to assess the impact of the October 2023 storm surge on coastal morphology in two regions along the German Baltic Sea coast. By analysing the entire Sentinel-2 archive (July 2015 to June 2024), we contextualize the event within broader morphodynamic trends and observe post-storm recovery. Our findings reveal that due to differences in the surges’ duration and intensity, it had a significantly higher morphodynamic impact in Angeln, Schleswig-Holstein, compared to Mönchgut, Mecklenburg-Vorpommern. Despite this, recovery processes in the months after the surge mitigated the surge's effects along most coastal sections. However, the Schleimünde sand spit emerges as an erosion hotspot, experiencing continued coastal recession for approximately six months post-surge due to a dramatically altered spit profile. Our study demonstrates that, although satellite-based shoreline monitoring may not achieve the accuracy of commonly employed methods, its frequent observations and low costs make it a valuable complement to existing monitoring strategies
Das Regelungssystem der Grenzoder – Unterhaltung und Entwicklung
No full textDie Oder wurde in mehreren Etappen seit Mitte des 18. Jahrhunderts umgestaltet und ausgebaut [1, 2]. Das heute vorhandene Stromregelungssystem ist auf der Grundlage von Gesetzen, die Anfang des 20. Jahrhunderts verabschiedet wurden, entstanden. Der etwa 160 km lange Bereich der Grenzoder ist freifließend und zum Großteil mit Buhnen geregelt. Für den Grenzfluss gab es lange keine einheitlichen Regel- und Unterhaltungsgrundsätze,
zudem sind viele Regelungsbauwerke marode oder zerfallen und erfüllen nicht mehr ihre bestimmungsmäße Funktion. Eine unregelmäßige Streichlinie sowie schlechte Fahrrinnenverhältnisse erschweren die Schifffahrt und führen zu einem erhöhten Gefahrenpotenzial bei Hochwasser und Eisgang. In
diesem Artikel werden die Entwicklung des Regelungssystems seit den 1950er Jahren und die seit 1990 durchgeführten Unterhaltungsarbeiten beschrieben. Seit 2014 liegt eine einheitliche, zwischen Polen und Deutschland abgestimmte Regelungskonzeption vor. Erste Maßnahmen wurden bereits umgesetzt
A review of TELEMAC-2D numerical schemes for modelling two-dimensional free surface flows
No full textWater column optical properties influence in satellite-derived bathymetry
No full textSatellite-derived bathymetry (SDB) has become increasingly recognised for its effectiveness in acquiring bathymetric data in recent decades. This method heavily relies on water properties to estimate depths accurately, assuming minimal backscatter from the water column and focusing mainly on seabed backscatter. In this study, we explore the potential benefits of incorporating water column properties information by calculating the absorption and scattering coefficients of remote sensing reflectance. By doing so, we aim to differentiate between the direct backscatter of the water column and that of the seabed. Our investigation focuses on Chrissi Island in Greece, known for its clear waters and distinctive geological and environmental features. Using SDB, we analyse changes in seabed morphology throughout the year 2022, revealing seasonal variations that influence water properties
