Quantifying gully erosion in the black soil region of Northeast China by long-term RTK GPS survey

Gully erosion is a severe form of soil erosion but has not been studied adequately as other types like interrill and rill erosion. Commonly used remote sensing approaches can only deal with the areal characteristics of gullies while the gully erosion rates rely on the determination of the volume changes. In this study, RTK (Real Time Kinetic) GPS was used to measure seven typical gullies over a period of 13 years in the black soil region of Northeast China to spatial-explicitly quantify the erosion rates and identify in the main influencing factors. Results showed that six of the seven gullies were seriously eroded, and the average volume increased 1911.35 m 3 which is 42% of the gullies. Four gullies elongated by 35 to 57m, averaging 44 m, due to gully headcut retreat. Larger drainage areas facilitate gully erosion. A significant positive correlation exists between erosion rate and slope gradient. Headcut retreat is most active in farmland, and erosion is most severe in gullies along with roads. Gully conservation measures show diverse effects. Check dam as an engineering measure can conserve soils but can also exacerbate erosion when the construction is damaged by extreme events. Vegetation measures can effectively inhibit the deterioration on gully development. This emphasizes the importance of integrating ecological conservation strategies to control gully erosion in the black soil region. These findings rely on the reliable volume data of the gullies over a long time span which highlights the merits of the long-term RTK GPS survey. Such long-term efforts should be strengthened in future studies to improve erosion assessment and support effective conservation strategies.