水保所知识产出(1956---)知识库

Thespatiotemporalchangesinflowhydraulicsand
energy consumption and their associated soil erosion remain
unclear during gully headcut retreat. A simulated scouring
experiment was conducted on five headcut plots consisting
of upstream area (UA), gully headwall (GH), and gully bed
(GB) to elucidate the spatiotemporal changes in flow hy-
draulic, energy consumption, and soil loss during headcut
erosion. The flow velocity at the brink of a headcut increased
as a power function of time, whereas the jet velocity entry to
the plunge pool and jet shear stress either logarithmically or
linearly decreased over time. The jet properties were signif-
icantly affected by upstream flow discharge. The Reynolds
number, runoff shear stress, and stream power of UA and
GB increased as logarithmic or power functions of time, but
the Froude number decreased logarithmically over time. The
Reynolds number, shear stress, and stream power decreased
by 56.0%, 63.8%, and 55.9%, respectively, but the Froude
number increased by 7.9% when flow dropped from UA to
GB. The accumulated energy consumption of UA, GH, and
GB positions linearly increased with time. In total, 91.12%–
99.90% of total flow energy was consumed during head-
cut erosion, of which the gully head accounted for 77.7%
of total energy dissipation, followed by UA (18.3%), and
GB (4.0%). The soil loss rate of the “UA-GH-GB” system
initially rose and then gradually declined and levelled off.
The soil loss of UA and GH decreased logarithmically overtime, whereas the GB was mainly characterized by sediment
deposition. The proportion of soil loss at UA and GH is
11.5% and 88.5%, respectively, of which the proportion of
deposited sediment on GB reached 3.8%. The change in soil
loss of UA, GH, and GB was significantly affected by flow
hydraulic and jet properties. The critical energy consumption
initiating soil erosion of UA, GH, and GB is 1.62, 5.79, and
1.64Js −1 , respectively. These results are helpful for deep-
ening the understanding of gully erosion process and hydro-
dynamic mechanisms and can also provide a scientific basis
for the construction of gully erosion model and the design of
gully erosion prevention measures.