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Surface sediment data acquired by the grab sampling technique were used in the present study to produce a high-resolution and full coverage surface grain-size mapping. The objective is to test whether the hypothetically natural relationship between the surface sediment distribution and complex bathymetry could be used to improve the quality of surface sediment patches mapping. This is based on our hypothesis that grain-size characteristics of the ridge surface sediments must be intrinsically related to the hydrodynamic condition, <i>i.e.</i> storm-induced currents and the geometry of the seabed morphology. The median grain-size data were obtained from grab samples with inclusive bathymetric point recorded at 713 locations on the high-energy and shallow shelf of the Spiekeroog Barrier Island at the German Bight of the Southern North Sea. The area features two-parallel shoreface-connected ridges which is situated obliquely WNW-SSE oriented and mostly sandy in texture. We made use the median grain-size (<i>d</i>₅₀) as the predictand and the bathymetry as the covariable to produce a high-resolution raster map of median grain-size distribution using the Cokriging interpolation. From the cross-validation of the estimated median grain-size data with the measured ones, it is clear that the gradient of the linear regression line for Cokriging is leaning closer towards the theoretical perfect-correlation line (45°) compared to that for Anisotropy Kriging. The interpolation result with Cokriging shows more realistic estimates on the unknown points of the median grain-size and gave detail to surface sediment patchiness, which spatial scale is more or less in agreement with previous studies. In addition to the moderate correlation obtained from the Pearson correlation (r = 0.44), the cross-variogram shows a more precise nature of their spatial correlation, which is physically meaningful for the interpolation process. The present study partially contributes to the framework of habitat mapping and nature protection that is to fill the gaps in physical information in a high-energetic and shallow coastal shelf

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The death toll and economic impact of an earthquake are greatly exacerbated when landslides are triggered by strong ground motion. These slides typically occur in two different contexts: localized failure of steep slopes that pose a major threat to life in areas below; and lateral spreading of nearly flat sediment plains due to shaking-induced liquefaction, which can damage large areas of critical infrastructure. Catastrophic landsliding triggered by the September 28, 2018 earthquake at Palu, Indonesia did not occur in either context, but produced both outcomes. Here, we show that major alluvial landsliding was a direct consequence of irrigation that activated a previously nonexistent liquefaction hazard. Aqueduct-fed wet rice cultivation raised the water table to near ground level, saturating sandy alluvial soils that liquefied in response to strong ground shaking and enabled extensive and large-displacement lateral spreads on slopes less than 1.5°. On slopes steeper than 1.5°, lateral spreads sourced long-runout landslides and debris flows that swept through villages below. This damage and loss of life would not have occurred in the absence of aqueduct-fed wet rice cultivation. Landsliding of gentle, irrigated alluvial slopes is an unrecognized anthropogenic hazard, particularly in seismically active, rice-growing areas of Asia.