| Yuanmou Dry-hot Valley is an important ecological protection zone in China’s Jinsha River dry-hot valley area.Due to the increasingly severe erosion of its gullies,it poses a huge challenge to the ecological construction of the region.At the same time,due to the fact that properties of this regional soil are dry red soil and deformed soil,the spatial variation of soil moisture is uneven.Studying on the gullies’ TWI is an urgently scientific problem.With the increasing use of GIS and DEM in hydrology,more and more researchers have applied Topographic Wetness Index(TWI)to study the spatial distribution of soil moisture in different regions.In the study of gully,TWI can simulate the quantification of the spatial water content of gully soil in the dry-hot valley area.Existing research on TWI which based on Grid DEM are mainly concentrating on road slopes and terraces in river basins(small basins)and engineering geology.For different gullies those are at different stages of development,whether the existing research methods are in line with its research rules?Whether the existing research methods meet the research law?What are the impacts of different runoff algorithms?What are the differences in simulation of moisture content of soil that’s at different stages of development?In addition,based on high-precision point cloud DEM data,which scale meets the prediction of the gully TWI?These problems still needs further exploration and research.Based on this,the paper carries out a preliminary analysis.The typical gullies at different developmental stages in the dry-hot valley area were selected as the research area,and the high-resolution(0.5-m grid size)DEM was used as the basic data.I selected three aspects that including different runoff algorithms,different grid sizes and gutters in childhood,prime and old age to analysis the effect on TWI extraction.The results show that:(1)In the dry and hot valley area of Yuanmou,the TWI of the gully was extracted by the SAGA runoff algorithm,which is consistent with its topographic and geomorphic laws and could best simulate the soil moisture content.At the same time,the D∞ algorithm is superior to the D8 algorithm.(2)Based on the point cloud DEM(0.5m)of the gully in the Yuanmo Dry Hot Valley,and the gully point cloud DEM data(1m~2.5m)derived from ArcGIS platform,I study on the high precision gully point cloud DEM in-depth.With the continuous increasing of its grid,the gully slope average decreases,but the Specific Catchment Area(SCA)and TWI showing an increasing trend,which reflects the positive relationship.(3)Through the comparison of scale effect and topography,the maximum value of the gullies at different stages of development showed a downward trend within different grading ranges,and the minimum value showed a significant downward trend.The average value increases first and then decreases.The peak of the average occurs at a slope of 8-15 degrees.Under the SAGA algorithm,the maximum value of TWI appears,which indicates obvious superiority of the custom sinking area algorithm when used to calculating the TWI value of the gully,conforms to the topography and geomorphology of the development of the gully,and can effectively reflect the actual situation of the gully.The calculation results are in line with the topography and geomorphology of the development of the gullies and reflecting the actual terrain of the gullies.The research is based on high-precision data in order to indicate the spatial distribution characteristics of soil moisture in the hot dry river valley of Yuanmou more accurately,and this study is expected to provide some reference value for the study of soil moisture simulation in the ecological reconstruction of Yuanmou dry-hot valley area.At the same time,I hope this study result could provide a scientific theoretical basis for soil and water conservation,restoration of agricultural production,and reconstruction of the ecological environment in this area. |
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