Evolution Characteristics And Comprehensive Utilization Of Debris Flow Fans In Xiaojiang River Basin

Although the fan caused by debris flows is an important field for residents' production and life in Xiaojiang River Basin,the residents are still under the threat of debris flow.The research on the risk of these fans and the potential for development and utilization can maximize the development of these fans' land resources.Meanwhile,the research on the evolution of the fans can protect the people life and property security.The fans,which is a deposition of debris flow,is mainly affected by the internal characteristics of the basin and the characteristics of the accumulation area.In this study,the internal characteristics of the basin are discussed from the topographic conditions,source mass and excitation conditions.The influence of the deposition on the formation and development of these fans is analyzed according to the topographic features of the debris flow outlet,the main river width and the main river energy.The field survey data,DEM data and remote sensing image data were used to extract debris flow gullies and fans,and to obtain the distribution characteristics and morphological characteristics of debris flow depositions.Based on the shape index of the longitudinal profile of the gully and the principle of geomorphic information entropy,the development of the debris flow gully is divided into four stages.At the same time,the morphological,distribution and evolution characteristics of the fans at different developmental stages are described,and the influence of the debris flow gully development on the fan evolution is explained.According to the development stage of the debris flow,the fan is divided into three stages: youth stage,strong stage and old stage.The number of debris flows in the development phase,the boom phase and the recession phase were 46,82 and 14,respectively.The debris flow fan area increased by 2.52,3.47 and 5.04 km2 from 2010 to 2017.Using the two-phase remote sensing image interpretation data of Dabaini,the impact of the single debris flow on the evolution of the fan is analyzed to verify the debris flow's development stage.Using the transfer matrix to analyze the land use situation of the two stages of debris flow fan in Xiaojiang River Basin to obtain the characteristics of fan's land use.It is found that the area of these fan in the study area is expanding continuously,and the land use trend of the constant area on the fans is: the land use area of cultivated land,residential land,forest and grassland is increasing.And the growth rates were 0.04,0.23 and 0.04 respectively.The general trend of land use for these fans is: the transfer of bare land to forest grassland,residential land and cultivated land.According to the land use situation of these fans,land use change trends and land use predictions,it can be concluded that the bare land on the fans has the potential to be exploited and utilized on a large scale.The research results can provide reference for the development and utilization of debris flow fans,and provide reasonable suggestions for urban site selection,highway line selection and cultivated land development.