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Comment on “Zhang, X. C. (2019). Determining and Modeling Dominant Processes of Interrill Soil Erosion. Water Resources Research, 55(1), 4-20. doi:10.1029/2018wr023217”
  • Peter Kinnell
Peter Kinnell
Canberra Univ.

Corresponding Author:[email protected]

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Abstract

Zhang (2109) presented results from experiments where 4 sections in 1.8 m long flumes were sequentially exposed to rainfall during 15 minute periods during an hour where rainfall intensity and slope gradient remained constant. The upslope areas were protected by a tarp in one treatment, and a screen placed 5 cm above the soil surface to provide sheet flow protected to some degree from raindrop impact in another treatment. Zhang presented two equations, one for the screen experiments, one for the tarp experiments, for estimating the soil loss rates in the sections under steady state conditions. The equation used for the screen experiments is shown here to produce results that do not conform to well known long established rules that apply to the determination of erosion in a section. In terms of modelling sediment discharge, Zhang applied an equation developed by Zhang and Wang (2017). It is shown here that that equation was not well suited to predicting the discharges in the screen treatment. Zhang also observed sediment discharges were well correlated to stream power even though sediment concentrations were influenced by rainfall intensity. Considerable insights exists in respect to the detachment and transport mechanisms that operate in rain-impacted flows a few millimetres deep but the closeness of the flow surface to the soil surface has a major impact on sediment transport by saltation and rolling. Further study of sediment transport by very shallow rain-impacted flows is warranted