Study On Soil Erosion Of Typical Slope Farmland Gully Catchment Units In Huifa River Basin

The Huifa River Basin,which is located in the southeast of the black soil region of northeast China,has typical soil,topography and climate characteristics of the black soil region of northeast China.In the basin,the seasonal variation is obvious,and the soil erosion varied significantly within a year.The regularity and continuity of inter-annual soil erosion are strong,In order to further explore the characteristics of soil erosion in different seasons,the Jixing small watershed in the southwest of the Huifa River Basin was selected as the research object.Through the observation of typical gully catchment area in small watershed and runoff plot of Jixing soil and water conservation monitoring field,and by analyzing differences in soil erosion and slope-gulley erosion relationship caused by seasonal changes,the difference and continuity of soil erosion in time and space were revealed.By analyzing the differences in soil erosion in different seasons within the basin,it is found that during the seasonal variation,the soil erosion is mainly divided into hydraulic erosion caused by rainfall,melting water erosion caused by melting snow and ice,and soil erosion caused by freezing and thawing.By dividing rainfall period and freezing-thawing period,the erosion environment and sediment yield characteristics of study area were analyzed,and the variation of erosion gully length,area and volume in gully catchment area was studied to explore the seasonal variation characteristics of slope and gully erosion.This study found that the runoff and erosion volume in the runoff plot during the rainfall period were larger than those in the freeze-thaw period,while the sand content was smaller than those in the freeze-thaw period.The length and volume of erosion gully increased significantly in rainfall period compared with freeze-thaw period,while the area of erosion gully increased significantly in freeze-thaw period.In addition,the erosion characteristics of different parts of erosion gully are different in rainfall period and freezing-thawing period,and the transport paths of runoff and sediment are basically the same.There are both differences and consistency in soil erosion in different periods.In the same period,the slope and gully erosion in the catchment area are continuous in space,and the slope erosion and gully erosion affect each other.The ridge direction of the slope directly affects the runoff confluence path and gully entry path.CCHE(Center for Computational Hydroscience and Engineering)model simulation shows that under the condition of ridge cultivation,the water depth in the catchment channel is relatively large;The flow velocity,runoff shear force and Froude number are small;the potential erosion capacity is relatively weak.The runoff confluence,ridge-breaking and transport paths are more complex and variable under the condition of diagonal ridge cultivation.The potential erosion capacity of ridge runoff to the middle and lower part of the trench is strong;under the condition of contour tillage,the retention effect of slope runoff is betterthe potential erosion capacity of slope runoff is weaker than that of the other ridge directions.The potential erosion capacity of the upper and middle furrows is larger than that of other furrows,and the potential erosion capacity of the lower and middle furrows is weaker.In addition,the potential erosion capacity of single ridge facing tillage slope is different at different positions of erosion ditch.A single ridge tillage method could not show absolute superiority in soil erosion control.Various ridge orientations should be arranged according to furrow development and practical cultivation needs to restrain erosion furrow development.Through WEPP(Water Erosion Prediction Project)model simulation,it is found that the erosion of gully can increase the amount of sediment in slope runoff and enhance the connectivity of sediment.The erosion ditch and the expansion of the ditch bank within the headward erosion caused the increasing soil erosion in the ditch.But whether these two forms of ditch erosion can cause the increase of the slope erosion amount depends on the slope area and the slope change caused by the increase of the ditch area in specific situation.Overall,the development of erosion ditches can lead to corresponding changes in slope erosion in the trench catchment area,as well as improving the connectivity of runoff and sediment in the catchment area.This study analyzes and compares the characteristics of soil erosion in different seasons,and explore the erosion relationship in the process of seasonal succession,which has good innovation value in theory.The relationship between slope and gully erosion was analyzed by the simulation modeling,and the connectivity of runoff and sediment in the catchment area was investigated.This study can provide a theoretical basis for the optimal configuration of soil and water conservation measures in the slope-ditch system.