4. Discussion
This study combined remote sensing imagery and the SegNet model to
analyze the morphological features of temporal and spatial distribution
law in gullies at a watershed scale. Jiang et al. (1999) analyzed
the distribution characteristics of gullies using W-B aerial photographs
to identify 4,495 gullies in the Zhoutungou watershed in 1999. We found
that the number of gullies in the watershed decreased sharply from 4,495
in 1999 to 1,153 in 2009 (Fig. 7) due to China’s returning farmland to
forest project that has significantly improved vegetation coverage on
the Loess Plateau and reduced the occurrence of slope soil erosion (Chenet al. , 2019; Dou et al. , 2020; Liang et al. ,
2019), inhibiting the formation and development of slope gullies.
However, the number of gullies increased slightly after 2009 due to (1)
extreme rainfall on the Loess Plateau, increasing soil erosion (Huet al. , 2019; Li et al. , 2022; Wang et al. , 2020a;
Zhao et al. , 2021); (2) the gully land consolidation project
implemented in 2011 increasing the cultivated land area and, despite
reducing watershed erosion to a certain extent (Chen et al. ,
2020; Han et al. , 2018; Kang et al. , 2021b; Li et
al. , 2016; Zhao, 2014; Zhao et al. , 2019), its associated
engineering involving topsoil stripping and ridge construction has
damaged the slope vegetation (increased slope) and soil environment
(loosened soil structure), forming new gullies on the slope; (3)
returning farmland to forest on the Loess Plateau has resulted in lush
vegetation, making it difficult to see some gullies in the remote
sensing images. Soil erosion on the Loess Plateau will gradually decline
to achieve the strategic goal of protecting and controlling the
ecological environment of the Loess Plateau, and ‘green water and green
mountains are golden mountains and silver mountains’.