The vertical heterogeneity of soil detachment by overland flow on the
water-level fluctuation zone slope in the Three Gorges Reservoir, China
Submersion and exposure from the operation of the Three Gorges Reservoir
(TGR) can alter soil properties and plant characteristics at different
elevations of the water level fluctuation zone (WLFZ), possibly
influencing soil detachment capacity (Dc), but the vertical
heterogeneity of this effect is uncertain. Soil samples were taken from
6 segments (5 m elevation per segment) along a slope profile in the WLFZ
of the TGR to clarify the vertical heterogeneity of Dc. Scouring
experiments were conducted at 5 slope gradients (17.63%, 26.79%,
36.40%, 46.63%, and 57.74%) and 5 flow rates (10, 15, 20, 25, and 30
L min–1) to determine Dc. The results indicate that the soil properties
and biomass parameters of the WLFZ are strongly affected by elevation.
Dc fluctuates with increasing elevation, with maximum and minimum
average values at elevations of 145-150 m and 165-170 m, respectively.
Linear equations accurately describe the relationships between Dc and
hydrodynamic parameters. τ, ω, and E perform much better than U.
Furthermore, a clear improvement is seen when using the general index of
flow intensity to estimate Dc. Dc is significantly negatively correlated
with MWD (p < 0.05) and organic matter (p < 0.01)
but not significantly correlated with other soil properties (p
> 0.05). At elevations of 145-150 m and 170-175 m, rill
erodibility was greater than at other elevations. The critical hydraulic
parameters were highest in the 165-170 m segments, both showing
obviously fluctuation in the vertical direction of slope surface. This
research highlighted the vertical heterogeneity of the soil detachment
and was helpful to understand the mechanisms of soil detachment
processes in the WLFZ of the TGR.