(c) 2012–2018 (d) 2018–2021
Fig. 4 Spatial variation of gully distribution from 2009–2021
3.2.2 Length and density of gullies
Figure 5a shows the length distribution of gullies from 2009 to 2021. In
2009, 2012, 2018, and 2021, gully lengths ranged from 7–209.5, 5–228,
5–230, and 5–209.5 m (average 48.39, 46.58, 45.75, and 45.84 m), total
gully lengths were 55.79, 95.26, 110.4, and 105.98 km, and gully
densities were 1.66, 2.84, 3.59, and 3.15 km km–²,
respectively, with a length development rate of 1.66 m
y–1 and density development rate of 0.12 km
km–² y–1.
The length variation in gullies is clear and normally distributed. From
2009 to 2012, 65.82% of gullies increased in length, 22.86% decreased,
and 11.32% did not change, with >64% of the length
changes between 0 and 50 m. From 2012 to 2018, 56.49% of gullies
increased in length, and 43.07% decreased, with >62% of
the length changes between –20 and 40 m. From 2018 to 2021, 47.81% of
the gullies increased in length, and 51.40% decreased, with
>52% of the length changes between –20 and 20 m. From
2009 to 2021, the proportion of length decreases gradually increased,
and the proportion of the length increases gradually decreased,
indicating that gully development is under control.