Elevation-related accretion-erosion rates in the period of 1996 to 2022 in the Wadden Sea

Supplementary Information for: Pineda Leiva, D., Lorenz, M., Kösters, F., Winter, C. & Lepper, R. Asymmetric morphodynamics of the Wadden Sea. Commun. Earth Environ. 6, 354 (2025). DOI: https://doi.org/10.1038/s43247-025-02340-y This dataset contains: - Yearly values in columns represent the elevation values mapped back from the quantile regression, along with min, mean, and max values derived from the conversion spread for each percentile (quantile) during the years, - ESRI Shapefiles of the extended morphological units derived from Baptist et al. (2019) (see Shapefile properties for source) Abstract: Shallow coastal systems with tidal flats and barrier islands are valuable assets to coastal protection and unique habitats with thriving biodiversity. Sea level rise threatens to diminish these systems unless sediment accretion compensates submergence. To quantify these dynamics for the world’s largest channel-shoal system, the Wadden Sea, an observed geomorphological time series was created and assessed over three decades. We found how (i) accretion-erosion was asymmetric from deep to shallow, (ii) topographic steepening occurred, and (iii) the morphological evolution was systematic across tidal basins. Peak accretion was observed below tidal low and above tidal high water, while the greatest erosion was found at intermediate subtidal elevations. Most intertidal areas accreted faster than sea level rise, and accretion was prominent at the channel-flat and flat-marsh interfaces. The simultaneous deepening of tidal channels leads to topographic steepening. Overall, the current net sediment import of the Wadden Sea is 19.7 Mm³/yr. Additional Info: In contrast to ordinary least squares (OLS) linear regression, which would describe the change of the mean elevation with time in our application, quantile regression describes the elevation change of the respective quantile over time. As the latter can be done for numerous quantiles, the temporal evolution of the elevation distribution can be statistically estimated to reveal detailed information on how the topography evolved. In statistical terms, quantile regression allows a separate behavior within the explanatory variable at different points in its distribution. This way, a different evolution of morphologic hotspots, e.g., the intertidal flats was detected, contrary to being masked in the OLS regression of averages.