3.2 Development rate of ephemeral gully morphological features
In 2009, 2012, 2018, and 2021, ephemeral gully lengths ranged from 7.00–209.50, 5.00–228.00, 5.00–230.00, and 5.00–209.50 m (average 48.39, 46.58, 45.75, and 45.84 m) (Table 3), with total ephemeral gully lengths of 55.79, 95.26, 110.40, and 105.98 km and densities of 1.66, 2.84, 3.59, and 3.15 km km–2, respectively, and development rates of 1.66 m y–1 (length) and 0.12 km km–2 y–1 (density). From 2009 to 2021, ephemeral gully width ranged from 0.50 to 2.50 m, with more than 99% between 0.50 and 1.50 m and an average width development rate of 0.04 m y–1. The proportion of ephemeral gully widths 2.00–2.50 m decreased from 0.67% in 2009 to 0.05% in 2021. In 2009, 2012, 2018, and 2021, ephemeral gully area ranged from 6.50–230.71, 4.64–246.86, 4.64–230.00, and 5.36–209.50 m2(average 49.12, 47.34, 46.05, and 46.36 m2), total area was 0.0566, 0.0968, 0.1111, and 0.1072 km2, and dissection degree was 0.17%, 0.29%, 0.33%, and 0.32%, respectively, with development rates of 4,213.39 m2y–1 (total area) and 0.0125% y–1(dissection degree). This study found that the development rate of all ephemeral gully morphological parameters gradually decreased over time.
Table 3 Ephemeral gully morphological features from 2009 to 2021 in the Zhoutungou watershed.