Robust methods for the decomposition and interpretation of compound dunes applied to a complex hydromorphological setting
Creators: name: Scheiber, Leon
name: Lojek, Oliver
name: Götschenberg, Axel
name: Visscher, Jan
name: Schlurmann, Torsten
Publisher: name: New York, NY [u.a.] : Wiley
Year: 2021
Subjects: subject: bedform identification
subject: German North Sea
subject: Jade fairway
subject: morphodynamics
subject: subaqueous compound dunes
subject: Marine engineering
subject: Silicate minerals
subject: Earth surface process
subject: Integrated approach
subject: Marine scientists
subject: Morphodynamic analysis
subject: Morphological features
subject: Morphological process
subject: Sediment changes
subject: Tracking algorithm
subject: Scales (weighing instruments)
subject: aggradation
subject: bedform
subject: coastal morphology
subject: coastal sediment
subject: decomposition analysis
subject: dune
subject: Atlantic Ocean
subject: German Bight
subject: North Sea
subject: Dewey Decimal Classification::900 | Geschichte und Geografie::910 | Geografie, Reisen

description: Underwater dunes are a morphological feature that are explored by marine scientists and coastal engineers alike. This study presents new methodologies in order to simplify bedform identification and morphodynamic analyses. Specifically, subaqueous compound dunes are decomposed with a simple yet extensive tracking algorithm, which relies on a repeated evaluation of unfiltered bed elevation profiles according to five predefined length classes. In a second step, morphological trends are assessed in the form of bed migration rates, bed slope asymmetries and net sediment changes, in which all parameters are referred to equidistant sections of the examined fairway stretch. This integrated approach not only avoids the challenges in weighting the varying size and abundance of dunes of different scales but also ensures comparability between dune-specific and areal parameters, which significantly improves the interpretation of the morphological setting as a whole. The developed methods are applied to the Outer Jade fairway, an anthropogenically influenced and regularly maintained waterway in the German Bight, and allow scrutiny of spatio-temporal trends in this region. Based on a unique data set of 100 sequential high-quality echo-sounding surveys, various types of bedforms are identified, comprising large-scale primary as well as superimposing secondary dunes that are assumed to interfere with each other. Temporal trends show a long-term rise of the troughs of major bedforms and constant maximum crest elevations near the official maintenance depth, which matches the observed long-term aggradation of sediments. The spatial distribution of integrated morphodynamic parameters reflects a previously described zone of primary dune convergence and facilitates the precise localization of this geophysical singularity. The presented findings both confirm the robustness of the proposed methodologies and, in return, enhance the understanding of morphological processes in the Outer Jade. © 2020 The Authors. Earth Surface Processes and Landforms published by John Wiley &amp; Sons Ltd. © 2020 The Authors. Earth Surface Processes and Landforms published by John Wiley &amp; Sons Ltd