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Research content This poster presents selected findings from the article Unsteady linearisation of bed shear stress for idealised storm surge modelling of 2021 for the participants in the NCK Days 2022, the yearly get-together of the Netherlands Centre for Coastal Research. The summary underlying the poster is available from the event's Book of Abstracts both as web page and as PDF document. The poster is open-access under a Creative Commons Attribution 4.0 International. Document design: structure and styling The conference organisers required the production of a paper-based poster in A0 format with portrait orientation. The document has been designed in A4 format, as available from the copy shared in this website. A resolution of 1200 dpi produced sharp enough images when printing in A0 size a document in PDF format. The whole document has been composed as a three-column table of a Google Doc document, with row-wise column merges which produce a well-marked layout consisting of stacked rows. In order to favour speed-reading, two font types and sizes produce a contrast between headings and narrative. Likewise, the text blocks are made of short and clearly spaced paragraphs, easy to point to and scan. The font size in the text body was readable when printed in A0 and, in retrospect for the specific venue the poster has been presented in, could still have been reduced to the same effect. Test prints confirmed that an additional margin would have been present around the page. The poster promotes a study published in a journal article, whereby the methods and results on display are already established. The audience is assumed to have been attracted by the poster title, thus to have been moved by an affinity for the topical area and to nurse a potential curiosity about reading the article in depth. As a result, the slant of this poster is intendedly descriptive, if not unimaginative; visuals are not especially meant or positioned to catch the eye. Document design: narrative and presentation The findings selected for the poster are those encapsulating the novelties of the article most compactly. This content selection provides maximum integration between narrative and scientific advances within the limited space of the document and of the interactions in a poster session. The table cells organise information progressively more detailed in the reading direction, broadly following a general-to-specific or abstraction-to-implementation order. During a poster session, the poster presenter could illustrate the content either in a bottom-up fashion starting from the results, supported by cartoons and graphs; or top-down, starting from the generalities presented as textual narrative. Outside the poster session, interested passerbys may find essential guidance into the topic scanning the poster in normal reading direction. Document design: on-line dissemination Hyperlinks to further resources, aimed at the digital poster version, are in blue. The DOI of this document has been reserved upon creating an unpublished Zenodo entry while drafting the poster. The DOI is shown in the poster so as to inform the viewers of the possibility to download the document after the conference. The poster has been uploaded ahead of the event and embargoed until the planned day of the off-line presentation. The publication date is the date of the poster session. Description authored by Giordano Lipari, {"references":["Roos PC, Lipari G, Pitzalis C, Reef KRG, Campmans GHP, Hulscher SJMH. Unsteady Linearisation of Bed Shear Stress for Idealised Storm Surge Modelling. Journal of Marine Science and Engineering. 2021; 9(11):1160. https://doi.org/10.3390/jmse9111160"]}

We investigate the influence of wind waves and wind-driven flow on sand wave dynamics using a two-model approach. Using a linear stability analysis, we find that waves decrease sand wave growth and wind causes sand wave migration. Combining linear stability analysis with a typical North Sea wave and wind climate explains variability in sand wave migration rates. Using a nonlinear sand wave model we show that waves reduce sand wave height and wind causes sand wave asymmetry as well as migration.

Observations from the field show that the spatial distribution of benthic organisms is strongly correlated to the morphological structure of tidal sand waves. In particular the troughs of sand waves are typified by a large benthic community, in contrast to the crest. In this paper, we present an idealised process-based model to study these patterns of biota and sand waves. Our model results agree with the observations that these phase-related patterns can arise on the seabed. Moreover, we show that local topography disturbances may lead to spatial patterns of both sand waves and biomass.

Tidal sandwaves form a prominent bed pattern in shallow sandy shelf seas. Here the class of idealised process-based models, aimed at obtaining generic insight in sandwave dynamics, is reviewed. Since many model studies focus on the instability underlying sandwave formation, first an outline of linear stability analysis is given. Then, an overview of model results is presented, highlighting two ongoing research projects (SMARTSEA and SANDBOX) and followed by suggestions for future research.

Flow velocity measurements in rivers and coastal areas are often collected at cross-sections where velocity is measured at multiple locations and over certain period of time. Subsequent data processing often involves temporal averaging and spatial smoothing of the raw velocity data. This process of spatial smoothing and temporal averaging is motivated by spatial and temporal behavior we expect to be present in the data, such as coherent velocity patterns at the scale of the water depth and temporal coherence at the scale of for instance tides. The process of smoothing and averaging, however, is often arbitrary, and the consequences of averaging windows in space and time on the resulting velocity patterns are often obscure. In this contribution we investigate a method based on spectral analysis to analyze the spatial patterns in a cross-section. This allows to identify the dominant spatial patterns that are present in the velocity data leading to a more grounded choice for spatial smoothing. Furthermore, the choice of basis function allows to include some physically based constraints such as no-slip at the bed and banks. The method consists of computing the components and location of the velocities measured in a cross-section. These locations are transformed to a normalized coordinate system. For each velocity component a set of basis function is selected and higher order function are progressively included and fitted to all the velocity data measured at a cross-section. The process is repeated until there is no spatial structure in the residuals. The method is applied to velocity measurements collected in a sharp bend. The analysis allows to identify dominant spatial patterns present in the data and results in continuous functions that describe the velocity field in detail, and that meet the requirement of no slip at the boundaries. Future work will extend the analysis to include different of basis functions, to include more physical constraints, such as continuity.