崩岗侵蚀沟的时空侵蚀特征及预测

Spatio-temporal Erosion Features and Prediction for the Erosion Gullies on Collapsing Hills

崩岗是水力和重力复合的土壤侵蚀类型,严重危害我国南方地区的农业生产和生态环境。侵蚀沟对崩岗的侵蚀过程以及地貌变化起着关键作用。本研究以福建省安溪县龙门镇一处崩岗为研究区,以无人机获取的正射影像和高程数据为基础,通过采点重构坡面提取出侵蚀沟,然后对其进行时空动态分析,得到侵蚀沟的时空侵蚀特征;然后将其侵蚀特征与CA-Markov模型耦合,通过修正转移概率矩阵以及制定空间分配规则,构建崩岗侵蚀沟模拟模型。研究结果表明:降雨量与侵蚀沟的侵蚀强度呈正相关,强降雨利于侵蚀沟的下切侵蚀,弱降雨则有利于沟沿的重力崩塌;坡度对侵蚀沟的侧切和下切具有促进作用,沟道距离和坡面高度则对下切和堆积具有抑制作用;由面积差异率0.18和Kappa系数0.81验证了崩岗侵蚀沟模拟模型的精度;在对该崩岗侵蚀沟2018-12-02空间分布预测的基础上,得到其年侵蚀量和侵蚀模数,分别为653.9 m^3和340 606 t·km^(-2)·a^(-1)。研究结果为探索崩岗侵蚀过程提供了新思路,并为崩岗侵蚀的防治工作提供了参考。

Gully erosion on collapsing hills is a common type of soil erosion in Southern China,that is severely detrimental to agricultural production and ecological environment.Erosion gullies play a key role in understanding the erosion process and landform development of a collapsing hill.This study investigated a collapsing hill at Longmen Town (Anxi County,Fujian Province,China).Digital Orthophoto Maps (DOMs) and Digital Elevation Models (DEMs) of the area were collected by an unmanned aerial vehicle on 11 March 2017,21 July 2017,and 2 December 2017.Based on the DOMs and DEMs,erosion gullies were identified by reconstructing the slope surface in the study area.A spatio-temporal analysis of the erosion features for gullies was performed by subdividing the changed patches into three main types: the expanded patch that was the result of side-cutting,the deepened patch indicated down-cutting,and the accumulated patch indicated soil depositing.An erosion gullies simulation model was developed by coupling the recognized spatio-temporal erosion features with Cellular Automata (CA)-Markov model,by refining transition probability matrixes according to rainfall amounts and intensity,and,finally,by regulating cellular allocation rules based on the influence mechanism for each type of changed patch.The study results indicated: 1) Rainfall amounts had a positive correlation with gully erosion,while rainfall intensity increased down-cutting and decreased gully edge collapse;2) Increase in slope gradient promoted gully side-cutting and down-cutting,whereas both the channel distance and slope height restricted down-cutting and soil depositing;3) Area difference ratio (0.18) and the Kappa coefficient (0.81) validated the accuracy of the model;4) Gully erosion simulation model developed on 2 December 2018 showed that the amount and modulus of annual gully erosion in the study area were 653.9 m^3 and 340 606 t·km^-2 ·a^-1 ,respectively.The current study provides a novel way to characterize the process of gully erosion on collapsing hills,and provides data for gully erosion prevention and control measures.