基于势能信息熵的黄土小流域沟谷网络演化特征研究

Study on Evolution Characteristics of Valley Network in Small Loess Watershed Based on Potential Energy Information Entropy

沟谷网络是黄土高原流域地貌的重要侵蚀产沙区和最主要的产沙运移通道,深入了解沟谷网络的形成过程和演化特征,对黄土高原小流域的水土保持综合治理、生态恢复和流域地貌演化过程研究具有重要意义。然而,流域内部沟谷网络的发育演化过程与整个流域地貌演化过程的相互作用机制尚未得到有效揭示。该文基于室内人工降雨试验条件下获取的9期人工模拟黄土小流域DEM数据,提出一种表征流域地貌系统内部沟谷网络演化有序程度的方法,并利用小流域地貌系统的势能信息熵及其熵变规律对沟谷网络演化过程及其变化特征进行研究。结果表明:在该实验条件下,以侵蚀为主的均质黄土小流域在地貌发育的幼年期,势能信息熵呈不断减小态势,沟谷网络有序性不断增强,在幼年期末达到最高;进入壮年期后,势能信息熵呈缓慢增加态势,沟谷网络有序性受到一定程度破坏,演化特征与该系统势能信息熵的熵变特征及流域地貌侵蚀发育阶段高度一致,流域地貌的势能信息熵和沟谷网络有序演化特征能有效指示流域地貌的侵蚀发育阶段。

The valley system is an important erosion and sediment-producing area and the most important sediment-producing migration passage of the Loess Plateau watershed.An in-depth understanding of the formation process and evolution characteristics of the valley network is of great significance to the study on the comprehensive management of water and soil conservation,ecological restoration and the evolution process of the watershed landform in the small watersheds of the Loess Plateau.However,the interaction mechanism between the development and evolution of the valley network within the watershed and the geomorphic evolution of the entire watershed geomorphic system(WGS)has not been effectively revealed.To this end,based on the 9-phase digital elevation model(DEM)data of artificially simulated small loess watershed terrain obtained by indoor artificial rainfall experiment,this paper proposes a method to characterize the orderly degree of the evolution of the internal valley network of the WGS,and uses the potential energy information entropy(PEIE)and its entropy change law of the small WGS to study the evolution process and change characteristics of the valley network within the WGS.The results show that under the experimental conditions(the small watershed of homogeneous loess dominated by erosion),in the young stage of watershed landform development,the PEIE shows a trend of decline,the orderliness of the valley network continues to increase,and the degree of orderliness is highest at the end of the young stage.After entering the maturity stage,the PEIE shows a slow increase trend,the orderliness of the valley network suffers a certain degree of destruction.This means that the orderly evolution characteristics of the valley network within the WGS are highly consistent with the PEIE change characteristics of the system and the erosion development stage of the watershed landform.The PEIE of the watershed landform and the ordered evolution characteristics of the valley network can effectively indicate the erosion development stage of the watershed landform.