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
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