基于RTK监测的活跃花岗岩崩岗侵蚀过程与阶段性特征OA

[Objective]Benggang is the most severe soil erosion type in the red soil hilly regions of southern China,but due to its abrupt nature,long-term quantitative studies on its evolutionary processes remain scarce.This study aims to reveal the medium-to long-term erosion process characteristics and internal mechanisms of an active Benggang.[Methods]This study focused on a typical Benggang in the middle stage of development located in Tongcheng county.Through RTK in-situ monitoring,combined with spatial analysis and erosion volume calculations,the twelve-year evolution patterns of the Benggang were quantified.Four sequential high-precision RTK surveys were carried out between 2010 and 2022.Spatiotemporal analysis of geomorphic changes was subsequently performed using the Cut/Fill tool in the ArcGIS platform to quantify volumetric changes and calculate key erosion parameters across different monitoring intervals.[Results]The results revealed a distinct three-stage evolutionary pattern,including collapse-driven acceleration,rapid hydraulic response,and prolonged slow erosion.This pattern indicated that Benggang erosion was a non-equilibrium and episodic process.Following a major collapse event of 149.67 m3 between June and November 2010,erosion intensity peaked within one year.During this stage,the annual average soil loss rate reached 1 733.27 m3/a,which was 17.89 times higher than the 96.91 m3/a rate in the subsequent stable stage.This stage accounted for 58％of the total soil loss over the entire twelve-year period.Spatiotemporal analysis showed that freshly collapsed colluvial deposits played a dual role.They served as the primary sediment source for hydraulic erosion,while simultaneously aggrading the channel bed,reducing the longitudinal gradient,and dissipating flow energy through redistribution.The erosion-to-deposition ratio declined sharply from 14.33 during the collapse-driven stage from June to November 2010 to 2.03 in the subsequent stage of sediment redistribution,indicating a systemic transition from alternating source-sink dynamics to a continuous sediment transport channel.Deposition volume in the second stage reached 395.57 m3,effectively reshaping the gully morphology and reducing channel slope.[Conclusions]Benggang erosion is fundamentally an episodic process driven by intermittent collapse events,with sediment supply driven by collapse events and hydraulic processes controlling transport and redistribution.The newly formed colluvial deposits exhibit a critical dual functionality.They act as a short-term sediment source immediately after collapse,and subsequently function as a natural sediment trap through their redistribution,which reduces channel gradient and retards further erosion.This is a key self-regulating mechanism responsible for the sharp decline in erosion rate during the late stage.These findings advance the mechanistic understanding of coupled hydraulic-gravitational processes in Benggang erosion and sediment transport systems.