EasyGSH-DB: Porosity (1996, 2006, 2016)

Definition: The measure of porosity “n” (dimensionless from 0 to 1) provides information about the volume fraction of a sediment sample that is or can be filled with liquids or gases (Wilson et al., 2018). This volume is the total pore space. A high pore content of the sediment results in a high value for porosity “n”. Porosity can be used as a measure for estimating further sedimentological properties, including permeability and consolidation, and is therefore a significant parameter in predicting the mechanical and hydraulic behavior of the sediment. Data generation: The basis for sedimentological evaluations are surface sediment samples, which were interpolated in the context of the EasyGSH project by means of anisotropic interpolation methods and taking into account hydrodynamic factors and erosion and sedimentation processes from individual samples of different years to a grid valid for one year. At each of these grid nodes, the sediment distribution is therefore available as a sum curve. For Deutsche Bucht, this basic product is available for 1996, 2006 and 2016 in a 100 m grid, for the exclusive economic zone of Germany for 1996 in a 250 m grid. From these sum curves, the median grain diameter d50 and the sorting can be determined. Wilson et al (2018) have determined a logistical regresson function based on the d50 from the homogenisation of analysis results from four sedimentological measurement campaigns in the North Sea. This approach has been extended (unpublished) by smile consult GmbH to reduce porosity with increasing — and thus worsening — sorting. This expansion is based on the fact that poor sorting results in higher grain size variability and that the pore space between particles of larger equivalent diameter can thus be filled by smaller sediment grains, thus reducing porosity. Product: 100 m grid of the German Bay (1996, 2006, 2016) or 250 m grid of the Exclusive Economic Zone (1996), where the porosity “n” is deposited at each grid node with a value of 0 to 1. The product is provided in GeoTiff format. Literature: Wilson, R. J., Speirs, D.C., Sabatino, A., & Heath, M. R. (2018). A synthetic map of the north-west European Shelf Sedimentary environment for applications in marine science. Earth System Science Data, 10(1), 109-130. For further information, please refer to the information portal (http://easygsh.wb.tu-harburg.de/) and the download portal (https://mdi-de.baw.de/easygsh/).