Surface deformation and displacement of bed elements during splash – Model tests.

• The initial location of the beads influenced the type and distance of their displacement. • The areas of various types of displacement overlapped each other. • The dry bed surface was more deformed by the impact of the drop. • Elements of the saturated bed were ejected over longer distances. • 97% of the beads ejected came from the first layer of the bed. The phenomenon of splash is connected with soil erosion, occurs commonly, and has a complex nature. The study presents the results of research in which glass beads (dry and saturated beds) with a diameter size range of 0.425–0.6 mm were used as a soil model. Patterns and layers of glass particles (beads), distinguished by their colour were placed on the surface of the samples. Displacements of the marked beads were used for the analysis of movement caused by splash. The measurements were supplemented with recordings made with high-speed cameras and photographs from an X-ray microtomograph. Three types of displacement for dry bed elements were distinguished: (i) displacement inside the surface area wetted with a falling drop of water, (ii) ejection and (iii) placement on the crater rim, as well as two types of displacement for elements from saturated beds: (i) displacement inside the deformation and (ii) ejection. The distance travelled by the beads was related to the specificity their displacement, which was associated with the initial location of the beads on the sample surface. In the case of dry beds, glass beads with an initial location equal to 14 mm or more from the centre of the drop impact were not moved. In the case of saturated beds, this distance was about 10 mm. More than 95% of the beads ejected from dry beds came from the surface layer of the sample. All the measurement methods applied show that the deformations of the dry bed surfaces were greater and more diversified than those of the saturated beds. The results presented in the study are important for understanding the mechanisms of transport of bacteria, fungi, and pollutants transferred with ejected soil particles during splash. The results can also be used for a physical description of the phenomenon for the computer modelling of both splash and water erosion. [ABSTRACT FROM AUTHOR]