186
11 Detecting Fingerprints of Gravity Erosion Drivers …
with the maximum volume of the individual mass failures was the Uc scar, although in
the experiment L10 it was the Dc scar (Table 11.2). Generally, the above-mentioned
individual mass failures occurred during the third or fourth rainfall events for each
model. This implies that multiple mass failures after two or three rainfalls may
decrease the initial slope gradient and lead to the occurrence of mass failure with
the Uc and Dc scars. Indeed, the mass failures with Dc and Uc always occur on
the relatively gentle slope rather than a nearly vertical slope. Lohnes (1991) also
found that the mass failure with the scar Tf always occurred on steep gully banks,
and that with the arc-shaped scar (Uc and Dc) they generally happened at the low
slope angles where the surfaces of slab or planar failure unlikely exist. Moreover,
a Dc scar with low stability tends to cause subsequent mass failures. For example,
the concave-shaped failure generally formed a spoon-shaped cavity on the slope, as
shown in Fig. 11.1j, and then the soil block on top of the cavity surface may fall due
to its own gravity.
In addition to the damages mentioned above, the mass failure also caused the
channel to widen because mass failure was a frequent and successive process of
geomorphic evolution. If the mass failures on the gully bank were not controlled, the
process of gully expansion would reach its maximum size, forcing farmers to retreat
and reduce the cultivated area around the gullies (Yitbarek et al. 2012). From this
perspective, gravity erosion is an important geomorphic natural hazard that affects
livelihoods in a catchment, especially on the Loess Plateau of China.
11.4 Conclusions
The experimental results obtained here provide a morphogenic insight into a mechanism analysis of the gravity erosion on the gully banks. In an event of rainfall, various
scar morphologies of mass failure might emerge in the same period. The scars Tf,
Uc, and Lc were the three major types of scars occurring in the processes of gravity
erosion on the steep loess slope, among which the Tf was the most crucial.
Climate-driven factors and topography triggers prominently influenced the distribution of the scar morphologies. Whether for the total amount or total number
in the experiments, the largest sensitivity parameter of the influential factors was
rainfall duration. The distribution of the scar pattern was highly susceptible to the
slope gradient. In comparison, slope height was relatively less influential.
References
Basharat M, Rohn J, Baig M S, et al. 2014. Spatial distribution analysis of mass movements triggered
by the 2005 Kashmir earthquake in the Northeast Himalayas of Pakistan. Geomorphology, 206(1):
203–214.
11 Detecting Fingerprints of Gravity Erosion Drivers …
with the maximum volume of the individual mass failures was the Uc scar, although in
the experiment L10 it was the Dc scar (Table 11.2). Generally, the above-mentioned
individual mass failures occurred during the third or fourth rainfall events for each
model. This implies that multiple mass failures after two or three rainfalls may
decrease the initial slope gradient and lead to the occurrence of mass failure with
the Uc and Dc scars. Indeed, the mass failures with Dc and Uc always occur on
the relatively gentle slope rather than a nearly vertical slope. Lohnes (1991) also
found that the mass failure with the scar Tf always occurred on steep gully banks,
and that with the arc-shaped scar (Uc and Dc) they generally happened at the low
slope angles where the surfaces of slab or planar failure unlikely exist. Moreover,
a Dc scar with low stability tends to cause subsequent mass failures. For example,
the concave-shaped failure generally formed a spoon-shaped cavity on the slope, as
shown in Fig. 11.1j, and then the soil block on top of the cavity surface may fall due
to its own gravity.
In addition to the damages mentioned above, the mass failure also caused the
channel to widen because mass failure was a frequent and successive process of
geomorphic evolution. If the mass failures on the gully bank were not controlled, the
process of gully expansion would reach its maximum size, forcing farmers to retreat
and reduce the cultivated area around the gullies (Yitbarek et al. 2012). From this
perspective, gravity erosion is an important geomorphic natural hazard that affects
livelihoods in a catchment, especially on the Loess Plateau of China.
11.4 Conclusions
The experimental results obtained here provide a morphogenic insight into a mechanism analysis of the gravity erosion on the gully banks. In an event of rainfall, various
scar morphologies of mass failure might emerge in the same period. The scars Tf,
Uc, and Lc were the three major types of scars occurring in the processes of gravity
erosion on the steep loess slope, among which the Tf was the most crucial.
Climate-driven factors and topography triggers prominently influenced the distribution of the scar morphologies. Whether for the total amount or total number
in the experiments, the largest sensitivity parameter of the influential factors was
rainfall duration. The distribution of the scar pattern was highly susceptible to the
slope gradient. In comparison, slope height was relatively less influential.
References
Basharat M, Rohn J, Baig M S, et al. 2014. Spatial distribution analysis of mass movements triggered
by the 2005 Kashmir earthquake in the Northeast Himalayas of Pakistan. Geomorphology, 206(1):
203–214.