Morphological characteristics of permanent gullies and their relationship with topography in two typical agro-geomorphic regions of Northeast China

Abstract

Gully erosion poses significant challenges to land degradation and food security. The Mollisols region of Northeast China (MNC) is the main grain-producing region in China. The low mountainous and hilly region (M_FI) and the rolling hilly region (R_FI), as the prominent topographic units in MNC, have suffered significantly from severe gully erosion. However, the actual situation and influencing factors of gully erosion in both regions are still unclear. Thus, we selected two field investigation regions of 103.4 km² in M_FI and 123.9 km² in R_FI to obtain a detailed inventory of gullies. Results showed that the gully number density in M_FI was 25.7 No. km⁻², 8.3 times greater than in R_FI. Conversely, the gully average gully length (511.7 m), width (7.8 m) and depth (2.8 m) in R_FI were 156.8%, 112.6% and 37.4% greater than those in M_FI, respectively. The three types of gullies, developed in different land uses (GF, farmland; GW, woodland; GR, unpaved road), had significantly varying morphologies. In R_FI, GF was the longest, and GW was the widest and deepest. Conversely, in M_FI, GR was the longest but exhibited the least width and depth. Notably, farmland posed the highest risk of gully erosion in both M_FI and R_FI, with 74.4% and 89.6% of the gullies developed there, respectively. Topography was the critical factor influencing the differences in gully erosion between the two regions. To effectively control gully erosion, topographic conditions most susceptible to gully erosion should be prioritized for attention, e.g., slopes of 8–10° and 2–4° were the slope intervals most likely to contribute to gully development in M_FI and R_FI, respectively. We provide the potential for large-scale prediction of gully erosion. Corresponding prediction models based on gully area were provided and the effectiveness of the predictions was improved by separating different land uses. The study's findings could serve as a valuable foundation for gully erosion control and prediction for MNC.