3.4 Estimation of ephemeral gully erosion volume and erosion rate
Ephemeral gully erosion volume was calculated based on the V–Lmodel using the length of 1,153 ephemeral gullies interpreted by remote sensing images in 2009, with the ephemeral gully erosion volumes in 2009 and 2012 summarized in Table 4. In 2009, the total erosion volume of 1,153 ephemeral gullies was 10,257.60 m3, with an average erosion volume of each ephemeral gully of 8.90 m3. In 2021, the total erosion volume of 2,312 ephemeral gullies was 19,175.95 m3, with an average erosion volume of each ephemeral gully of 8.29 m3. From 2009 to 2021, the ephemeral gully erosion volume change was mainly in the south of the watershed (Fig. 7), where the terrain is broken and has many steep slopes. In addition, the slope area has damaged soil structure and less vegetation coverage after the gully land consolidation project, so soil erosion can easily occur under extreme rainfall. The average erosion volume of each ephemeral gully increased by 3.54 m3 or 0.29 m3y–1, and the total erosion volume of all ephemeral gullies (except for those that disappeared) increased by 8,918.35 m3 or 743.20 m3y–1 from 2009 to 2021.
Table 4 Ephemeral gully volume from 2009 to 2021 in the Zhoutungou watershed.