Figure 4. Recognition results of the SegNet model in the Zhoutungou
watershed in 2021. Ephemeral gully recognition results at (a) the
watershed scale and (b) the sampling area.
The SegNet model extracted 1,153, 2,045, 2,413, and 2,312 ephemeral
gullies encompassing 34.32, 60.86, 71.82, and 68.81
km2 in 2009, 2012, 2018, and 2021, respectively, with
a frequency development rate of 2.87 km2y–1 (Table 2). Most of the ephemeral gullies were in
the southern half of the Zhoutungou watershed (Fig. 5), which has
complex landforms and large slope gradients. From 2009 to 2012, many new
ephemeral gullies formed in the northeast and south of the watershed,
but some disappeared. From 2012 to 2018, new ephemeral gullies formed in
the middle south and southeast regions of the watershed, while others
disappeared in the northeast and southwest regions. From 2018 to 2021,
only a few regions formed new ephemeral gullies, with many disappearing
in the western region.
Table 2 Statistical characteristics for ephemeral gully number and
frequency in the Zhoutungou watershed from 2009–2021.