In the Lower Lhasa River basin of the Tibetan Plateau, gully erosion poses a threat to alluvial fans (AF), which are the main available land resource for agriculture. Runoff from the whole contributing catchment is concentrated in AF, which makes influencing factors of AF gully erosion more complex than it is for hillslopes. There is a lack of quantitative research about the influencing factors and mechanisms of AF gully erosion. The main objectives of this study were to: (1) quantify gully erosion on AF; and (2) identify the controlling factors of gully erosion on AF. The gullies of 12 AF were investigated by unmanned aerial vehicle (UAV). To help understand better the gully erosion on AF, nine morphological parameters were measured, four gully quantitative characteristics were calculated, and 16 factors affecting the gully erosion on AF were analyzed. The gully width–depth ratio of over 20 on the studied AF is larger than that usually seen in other regions. The mean value of gully amount density (GAD), gully density (GD), the degree of gully dissection (GDD), and gully volume modulus (GVM) were 26.51 km⁻², 4.93 km·km⁻², 7.16%, and 1.28 × 10⁻⁴ km³·km⁻², respectively. Linear correlations showed a significant (p < 0.05) relationship between the gully quantitative characteristics of AF and the catchment gully density. So, catchment gully density may indirectly affect gully erosion on AF by influencing hydrological connectivity and then changing generation and confluence processes of runoff in catchment. Therefore, gully erosion on AF can be mitigated by shifting hydrology pathway on AF and reducing hydrological connectivity in contributing catchment.

中文翻译：

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通过改变冲积扇和贡献流域之间的水文连通性可以减轻冲积扇的沟侵蚀：拉萨河流域的一项研究

在青藏高原拉萨河流域下游，冲积扇（AF）是可用于农业的主要土地资源，冲积扇（AF）面临着冲积的威胁。整个贡献流域的径流都集中在AF，这使得AF沟侵蚀的影响因素比山坡更复杂。房颤冲沟的影响因素及机制尚缺乏定量研究。本研究的主要目的是：（1）量化 AF 的沟壑侵蚀；(2)确定AF沟蚀的控制因素。通过无人机（UAV）对12个AF的沟壑进行了调查。为了帮助更好地了解 AF 的冲沟侵蚀，测量了 9 个形态参数，计算了 4 个冲沟数量特征，分析了影响房颤冲沟侵蚀的16个因素。所研究AF的沟壑宽深比超过20，大于其他地区常见的沟深比。沟量密度（GAD）、沟密度（GD）、沟剥离程度（GDD）、沟体积模量（GVM）的平均值为26.51 km^{− 2}、4.93 km·km ^{− 2}、7.16%和1.28 × 10 ⁻⁴  km ³ ·km ^{− 2}。线性相关表明AF的沟壑定量特征与集水沟壑密度之间存在显着( p  <0.05)关系。因此，流域沟壑密度可能通过影响水文连通性进而改变流域径流的产生和汇合过程来间接影响AF的沟壑侵蚀。因此，可以通过改变 AF 的水文路径和减少贡献流域的水文连通性来减轻 AF 的沟壑侵蚀。