龛沟是崩岗早期发育的形态标志

Niche-like Ephemeral Gully is A Morphological Symbol of the Early Development of Benggang

为探究我国南方花岗岩红壤地区崩岗的起始标志和发育阶段。在湖北省通城县和广西岑溪市2个典型崩岗区调查崩岗的发育过程。结果表明,2个调查区都存在一种细沟发育而来的龛状浅沟,将其命名为龛沟。龛沟具有3个特征:上游有明显细沟,沟壁陡峭且具有上窄下宽的宽深梯形形态。龛沟主要发生在砂土层裸露、具有一定汇水面积和局地坡度>30°的裸露坡面。龛沟是一种特殊形态的浅沟,其定义、形态和侵蚀营力都不同于常规浅沟、切沟和Amphitheatershaped canyons等沟蚀地貌。龛沟是沟道侵蚀从水力侵蚀为主变为水力和重力复合侵蚀的过程,是崩岗起始发育的启动标志,其发生原因与花岗岩红壤上红(黏)下砂的土层结构有关。以龛沟出现为标志,将崩岗的发育阶段重新划分为早期准备阶段、初期启动阶段、中期发展阶段和后期成熟阶段。龛沟的特点和研究区的崩岗治理效果表明,削坡开级的治理方式不适合在红土层较薄的花岗岩红壤地区使用。龛沟的发现将推进对崩岗早期发育的研究,并为崩岗的预防和治理提供新的理论依据。

In order to explore the initial sign and development stage of Benggang in granite red soil area in South China,field investigations were conducted in two typical Benggang areas in Tongcheng,Hubei and Cenxi,Guangxi to investigated the development process of Benggang.The results showed that there was a special niche shaped ephemeral gully developed from a rill in both survey areas,named niche-like ephemeral gully(NEG).The morphology of the NEG had the following characteristics:a distinct rill in the upstream,steep banks,a narrow upper bank and a wide,deep gully bed.The NEG was formed on slopes without plant cover where sandy soil layers were exposed,with a small contribute area and a slope steeper than 30°.The NEG was a special morphological ephemeral gully,its definition,morphology,erosion forces were different from the ephemeral gully,permanent gully,Amphitheater shaped canyons and so on.The NEG was the process of gully erosion changed from being dominated by hydraulic erosion to being highly coupled by hydraulic and gravity erosion.The NEG is the launching marker for the Benggang.The formation of the NEG is related to the soil configuration of granitic red soil with upper red clay and lower sandy soil layers.Taking the emergence of NEG as a sign,the development stage of Benggang is re-classified into the early preparation stage,initial launching stage,middle development stage and late maturation stage.The characteristics of the NEG and the management effect of the study area show that the terrace is not suitable for the area with a thin red soil layer.The discovery of the NEG will promote the study of the early development of Benggang and provide a new theoretical basis for the prevention and management of the Benggang.