We experimentally tested the effect of a  largerange in helical flow intensity and  sedimentmobility on equilibrium transverse  slopes,which resulted in a function for slope  effectsdepending on bed state and  sedimenttransport mode, that deviates from  linearfunctions with sediment mobility in  literature.Furthermore, we obtained basic  relationsfor sorting patterns as a function of  transverseslope and sediment mobility 

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The use of photogrammetry based on UAVs allows to survey long distances of riverbanks with a resolution capable of identifying detailed bank erosion features and quantifying retreat rates with an accuracy of centimetres. The identification of these features would be missed in slower and more expensive GPS profiling. Moreover, moving terrestrial laser scanning would require significant greater times and costs for comparable results.

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Lateral sorting (= bend sorting) is observed in  natural meanders, where the inner and outer  bend are fairly fine and coarse, respectively  (e.g. Julien and Anthony, 2002; Clayton and  Pitlick, 2007). This is caused by the mass  differences between grains on a transverse  slope, leading to coarser grains being dragged  down net more than finer grains (Ikeda et al.,  1987). The slope of the transverse bed  influences the degree of bend sorting greatly.  Also vertical sorting occurs. Grainflows at  the lee side of dunes result in a net fining  upward trend (Kleinhans, 2005). The degree of  vertical sorting depends on flow velocity and  sediment mixture characteristics.  Most previous studies focused on the  development of the transverse slope using  small ranges of uniform sediment, so spatial  sorting was absent. Yet, it was argued that  there is a feedback mechanism between bend  sorting and the transverse slope (Ikeda et al.,  1987). So, it is of key importance to attain  better understanding of how sorting in river  bends comes about, which can improve current  numerical models.  It is the objective of this study to examine  experimentally the effect of transverse bed  slope and sediment mobility on spatial sorting  of bed load in a meander. 

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We experimentally tested the effect of a large range in helical flow intensity and sediment mobility on equilibrium transverse slopes, which resulted in a function for slope effects depending on bed state and sediment transport mode, that deviates from linear functions with sediment mobility in literature. Furthermore, we obtained basic relations for sorting patterns as a function of transverse slope and sediment mobility.@en

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Granular materials avalanche when a static angle of repose is exceeded and freeze at a dynamic angle of repose. Such avalanches occur subaerially on steep hillslopes and wind dunes and subaqueously at the lee side of deltas. Until now it has been assumed that the angles of repose are independent of gravitational acceleration. The objective of this work is to experimentally determine whether the angles of repose depend on gravity. In 33 parabolic flights in a well‐controlled research aircraft we recorded avalanching granular materials in rotating drums at effective gravitational accelerations of 0.1, 0.38 and 1.0 times the terrestrial value. The granular materials varied in particle size and rounding and had air or water as interstitial fluid. Materials with angular grains had time‐averaged angles of about 40° and with rounded grains about 25° for all effective gravitational accelerations, except the finest glass beads in air, which was explained by static electricity. For all materials, the static angle of repose increases about 5° with reduced gravity, whereas the dynamic angle decreases with about 10°. Consequently, the avalanche size increases with reduced gravity. The experimental results suggest that relatively low slopes of granular material on Mars may have formed by dry flows without a lubricating fluid. On asteroids even lower slopes are expected. The dependence on gravity of angle of repose may require reanalysis of models for many phenomena involving sediment, also at much lower slope angles. @en