Morphological characteristics and volume estimation model of permanent gullies and topographic threshold of gullying in the rolling hilly Mollisols region of northeast China

Gully erosion is an essential source of soil loss in the world, severely causing land degradation and threatening food security. It is essential to explore the gully morphological characteristics and identify the topographic threshold for gully initiation for the control and prevention of gully erosion. However, limited information about the gully morphological characteristics, volume (V) estimation model and topographic threshold model of gully initiation is available in the rolling hilly Mollisols area of northeast China where gully erosion is prevalent. Herein, a detailed field investigation was carried out in a region of 121.5 km2 to obtain morphological pa-rameters of each gully and the slope (S) and contributing area (A) of each gully head. The results showed that 383 permanent gullies were identified, with the mean length, top width and depth of 511.12 m, 7.84 m and 2.34 m, respectively. Most values of length, top width and depth were in the range of 50-250 m, 1.0-5.0 m and 0.5-3.0 m, respectively. The gully density is 1.61 km km-2 with 1.6% of land disappearing. These gullies are longer, narrower and shallower in this study than other regions of the world. Gully volume showed the optimal relationship with gully surface area (Ag). An optimized power piece-wise models of V-Ag, classified by gully top width (TW) using threshold iteration method provided a better predicted result. Topographic threshold model (S = 0.033A-0.171) of gully initiation was established by the quantile regression. This study highlights the severity of gully erosion in this major grain producing area of northeast China and proposed a new method for gully volume estimation, which could provide scientific reference for the design and plan of gully erosion control measures and the prevention of gully erosion.

Automated summary

Gully erosion is a common landform in the rolling hilly Mollisols area of northeast China. The gullies in this area are characterized by longer length, narrower width, and shallower depth compared to other regions. This study conducted a detailed field investigation to determine the morphological parameters of the gullies and established an optimized relationship between gully volume and surface area. A topographic threshold model for gully initiation was also established using quantile regression. The findings of this study provide scientific reference for the design and planning of gully erosion control measures in northeast China.