Splashed material as a measure of detachment
According to Zhang et al. (2020), the amount of splashed material collected in the slot is directly related to the amount of material mobilized by raindrop impact. When drops impacts cause detachment in rain-impacted flows, part of the material lifted into the flow from the soil surface results from detachment by the raindrops impacting at that time and part results from the lifting of loose material sitting on the surface. Loose material is present on the surface because when soil particles are transported by splash or raindrop induced saltation, coarse material falls back on the soil surface where it waits until moved again by a subsequent drop impact. When loose material sits on the surface, some of some of the energy that could be used to detach soil is used to move the loose particles so that MM , the mass of material lifted vertically, is given by
MM = MD (H -1) +H MPD (1)
where MD is the mass detached directly by the current drop impact if no loose material is present,MPD is the mass of the loose material sitting on the surface lifted when the loose material completely protects the underlying soil surface from detachment, and H is the degree of protection provided by the loose material sitting on the surface (Kinnell, 2005). H varies from 0 to 1. MD varies with the resistance to detachment associated with the surface of the soil matrix (Kinnell, 2020a), raindrop size and velocity, and flow depth (Kinnell, 2020b).