14106 research outputs found
Sort by
Directional Spectrum Estimation for Sea States Generated by the Single Summation Method
No full textThe influence of directional spreading of waves is significant for wave-induced loads, wave breaking and nonlinearity of the waves. For physical model testing performed at test facilities such as the Ocean and Coastal Engineering Laboratory at Aalborg University, it is crucial to validate if the test conditions match the target sea states by measurement and analysis of the generated directional wave field. Most of the existing methods assumes a double summation sea state to be present which is valid in the prototype. However, waves in the laboratory are usually generated by single summation. The current paper presents a method to analyse short-crested waves generated by the single summation method. Compared to similar methods oblique reflections are considered instead of only in-line reflections. The results show that the method successfully decomposes the incident and reflected wave fields in the time domain. Thus, for example the incident wave height distribution may be obtained. The sensitivity of the new method to additional reflective directions, noise, calibration errors and positional errors of the wave gauges was found small
Pfahl-Boden-Interaktion beim Rückbau von Rohrpfählen durch die Erzeugung eines hydraulischen Überdrucks im Pfahlinneren
No full textImpact and response of storm Babet from a Swedish perspective
No full textIn October 2023, storm Babet led to the most severe erosion in decades along the Swedish South coast. In this study we approach the affected coastal landscape as a coupled social-ecological system where environmental components (e.g. geology, bathymetry, waves) interact with social components (e.g. infrastructure, management, economic activities) to influence the outcome of an extreme event. We use observational data to analyse the meteorological and oceanographic conditions prior to and during Babet, and numerical modelling to create hindcast wave data covering 1959−2023. To understand Babet relative to other events we compare sea levels and waves during Babet to normal conditions and other extremes, especially focusing on the joint occurrence of high sea levels and large waves.
Using LiDAR data we quantify the morphological changes between 2019−2023 along approximately 220 km of coast. By interviewing stakeholders from municipal, regional and national level and from private and public sector, we analyse how Babet impacted coastal societies and how key authorities responded to the event. We also analyse how relevant stakeholders received, understood and acted on weather warnings issued by authorities.
Our findings show Babet to be an unusual but not unprecedented event. The high sea levels were caused by westerly winds pushing large amounts of water in to the Baltic basin prior to the event and wind setup during the event. We show the combination of high sea levels and large onshore waves seen during Babet to be unusual, explaining why Babet was more impactful than other events of similar sea levels. Weather warnings were available from October 17th, but many struggled to understand the combined risks associated to forecast high sea levels and easterly winds. Affected municipalities were differently organized before and during Babet, but mostly managed to deal with the event well. The larger organisational challenges were identified in the aftermath due to increased workloads and new types of tasks. As for the morphological changes they are in places significant. The total erosion is close to 1.3 million m3 and the total accretion close to 760 000 m3, resulting in a net loss of 510 000 m3. Expressed as normalized values in the longshore direction changes range from erosion surpassing 150 m3/m to accretion reaching almost 50 m3/m.
We identify parts along the coast where we believe most of the erosion between 2019−2023 stems form Babet, but also stretches where changes can only partially be attributed to Babet. We see that societal impacts during Babet were dictated more by coastal assets’ type and proximity to the sea then by the magnitude of morphological change
Future Needs in Estuarine Physical Processes Research from a Hydraulic Engineering Perspective
No full text
