Active Gully Head Erosion Rates Characteristics on the Loess Plateau: InSAR-Based Calculation and Response to Extreme Rainfall

Quantitative analysis and prediction of gully head erosion hold paramount importance for terrain evolution studies and risk mitigation effort. However, previous findings could not reconcile high temporal resolution with long time series coverage, particularly at the watershed scale. In this study, a calculation method for the active gully head erosion rate (AGHER) was proposed on the basis of interferometric synthetic aperture radar (InSAR) technology, thereby combining the historical climate data to estimate the annual AGHER. Additionally, we investigated the relative importance of extreme rainfall events on erosion rates. The results indicated that the long-term annual AGHER in the study area ranged from 51.83 to 89.50 mm year⁻¹ from 1980 to 2023 on the Dongzhi Plateau (DZP). Extreme rainfall events (rainfall amount ≥ 150 mm) emerged as the foremost erosion-causing factor, accounting for a contribution rate ranging from 69.8% to 75.0%. Furthermore, through field surveys, we identified 21 gully heads that represent potential hazards to high-speed railways (HSRs). Although the proportion of gullies affecting rail infrastructure may be relatively modest in century-long projections, it notably increases against the background of worldwide escalation due to the occurrence of extreme precipitation events. This study establishes a robust foundation for gully erosion management and risk assessment on the Loess Plateau.