Intensity and Spatiotemporal Evolution Characteristics of Loess Erosion in Dongzhi Tableland of Qingyang Area, Gansu, China Based on SBAS-InSAR Technology

The loess tableland region is characterized by intense gully development and frequent erosion, and quantitative monitoring of loess erosion-related deformation and its spatiotemporal variation is of great significance for the protection and management of loess tablelands. Dongzhi tableland in Qingyang area of Gansu, the largest tableland on the Loess Plateau, was selected as the study area; Sentinel-1 SAR data acquired from 2015 to 2024 were used with the SBAS-InSAR technique to derive time-series deformation related to loess erosion and deposition; by combining with rainfall data and micro-geomorphic analysis, the spatiotemporal evolution of the loess erosion-deposition process in Dongzhi tableland over the past decade was systematically analyzed. The results show that: ① the loess erosion-deposition process exhibits clear spatial zonation, characterized by strong erosion along gully margins, strong deposition in gully bottoms, and relative stability across the tableland surface; loess erosion is mainly concentrated on steep slopes within 0 - 0.1km of the gully edge line, accounting for 68.5 of the total erosion amount. ② The loess erosion-deposition process shows marked stage-wise temporal variation; loess erosion amount reaches a peak of 5.53× 10^6m^3 in 2015, indicating that loess erosion in the early stage is strongly controlled by intense rainfall; after 2019, overall loess erosion intensity weakens markedly; in 2024, despite relatively high rainfall, loess erosion amount remains only 1.53× 10^6m^3, suggesting that gully-slope stability has improved in recent years. ③ The loess erosion-deposition process also shows a pronounced temporal lag effect; after the severe erosion in 2015, deposition amount does not rise to 4.85× 10^6m^3 until 2016, indicating that slope material mobilized by extreme rainfall is not transferred immediately, but instead continues to accumulate and deposit in gully bottoms during subsequent years.