No abstract

<p>With an area of almost 10,000 km², the project area represents the tidal flats on Germany’s North Sea coast. The tidal flats and their channels as well as morphologically highly active estuarine systems undergo significant erosional and sedimentational processes that prove difficult the assessment of sedimentological composition based on relatively few and temporally far stretched field measurements. The holistic databased simulation of both the internal structure of the soil itself and its sedimentary composition is based on around 21,000 measured surface sediment samples (from 1949 until recent) and yearly consistent digital bathymetric models, starting 1950, spatiotemporally interpolated in a 10 m grid resolution by the Functional Seabed Model. By utilizing the high temporal and spatial resolution of the bathymetric models, it is possible to quantify the seabed depth evolution (sedimentation and erosion) and to solve a differential equation to capture sedimentary evolution, a consistent and continuous three dimensional model of both the surface and the subsurface structures and sedimentary compositions can be generated. To further extend the volumetric extent of the model, around 16,000 sedimentary core samples are used to fill the spatial and consequently the temporal void between the lowest altitudinal range of validity of the aforementioned model segment to the lower boundary of the target model volume. This boundary is set to be the lower limit of the morphologically active or activatable space, which contains the volume of sediment that could be eroded in current climate conditions. The limit, generally speaking, can be expected to somewhat coincide with the base of Holocene sediments, as Pleistocene sediments – especially subglacial tills – generally take higher amounts of bottom shear stress to erode than unindurated Holocene sediments, which usually form tidal flat sediments. The purpose of the generated three dimensional model is to be able to derive sedimentological information in both custom spatial resolution as well as custom sedimentological classification as base and validation data for process based morphodynamic simulation models. With these enhanced models, the quality of the prognosis of morphological developments and stability of coastal areas as a tool for planning processes for coastal protection and maritime economy is expected to be increased.</p>

Abstract. The German Bight located within the central North Sea is a hydro- and morphodynamically highly complex system of estuaries, barrier islands and part of the world’s largest coherent tidal flats, the Wadden Sea. To identify and understand challenges faced by coastal stakeholders, such as harbor operators or governmental agencies, to maintain waterways and employ numerical models for further analyses, it is imperative to have a consistent data base for both bathymetry and surface sedimentology. Current commercial and public data products are insufficient in spatial and temporal 15 resolution and coverage for recent analyses methods. Thus, this first part of a two-part publication series of the German joint project EasyGSH-DB describes annual bathymetric digital terrain models in a 10 m gridded resolution for the German North Sea coast and German Bight from 1996 to 2016 (Sievers et al., 2020a, https://doi.org/10.48437/02.2020.K2.7000.0001), as well as surface sedimentological models of discretized cumulative grain size distribution functions for 1996, 2006 and 2016 on 100 m grids (Sievers et al., 2020b, https://doi.org/10.48437/02.2020.K2.7000.0005). Furthermore, basic morphodynamic and sedimentological 20 processing analyses, such as the estimation of e.g. bathymetric stability or surface maps of sedimentological parameters, are provided (Sievers et al., 2020a, 2020b, see respective download links).

<p>In the awareness of the increasing conciousness regarding the sensitivity, vulnerability, and<br>complexity of near coastal marine ecosystems, including tidal flats, it is imperative to improve the<br>understanding of its individual elements. One of these elements are organisms habitating the<br>seabed, such as mussels.<br>Bivalves - specifically blue mussels (Mytilus edulis) and pacific oysters (Magallana gigas) - besides<br>other smaller organisms are an integral part of the seabed fauna. On the one hand they serve as a<br>basic food resource for a large number of higher trophic level predator. On the other hand they<br>affect the surface structure, stability and composition of the seabed.<br>To better understand the large fluctuations the mussel stocks underwent during the last decades, it is<br>of great benefit to know the environmental conditions of their habitats. Based on the analysis of<br>different physical parameters at known mussel beds, prototypical automated algorithms were<br>developed and used to identify other tidal flat regions with favorable conditions for epibenthic<br>mussels. The input parameters originate from different morphological, hydrodynamical,<br>sedimentological and hydrochemical numerical models. Morphological factors include<br>morphological activity and gradient conditions of the ground surface, hydrodynamical factors<br>include stream velocities, bottom shear stress, wave orbital velocities, energy of wave breaking and<br>duration of tidal flats falling dry during low tide, sedimentological factors include sediment<br>composition and hydrochemical factors include salinity. These parameters were available as<br>products of the mFUND project EasyGSH-DB and were supplemented with additional evaluations.<br>It is expected that the approach of habitat modeling will allow to determine the possibility of initial<br>and long-term settlements of epibenthic mussels by ruling out intertidal or subtidal seabed areas<br>where environmental parameter combinations do not fulfill the necessary requirements.</p>

Abstract. The German Bight located within the central North Sea is a hydro- and morphodynamically highly complex system of estuaries, barrier islands, and part of the world's largest coherent tidal flats, the Wadden Sea. To identify and understand challenges faced by coastal stakeholders, such as harbor operators or governmental agencies, to maintain waterways and employ numerical models for further analyses, it is imperative to have a consistent database for both bathymetry and surface sedimentology. Current commercial and public data products are insufficient in spatial and temporal resolution and coverage for recent analysis methods. Thus, this first part of a two-part publication series of the German joint project EasyGSH-DB describes annual bathymetric digital terrain models at a 10 m gridded resolution for the German North Sea coast and German Bight from 1996 to 2016 (Sievers et al., 2020a, https://doi.org/10.48437/02.2020.K2.7000.0001), as well as surface sedimentological models of discretized cumulative grain size distribution functions for 1996, 2006, and 2016 on 100 m grids (Sievers et al., 2020b, https://doi.org/10.48437/02.2020.K2.7000.0005). Furthermore, basic morphodynamic and sedimentological processing analyses, such as the estimation of, for example, bathymetric stability or surface maps of sedimentological parameters, are provided (Sievers et al., 2020a, b, see respective download links).