Study On Runoff And Sediment Yield Process Of The Cross Ridge And Longitudinal Ridge Slope Under Natural Rainfall

Slope cultivated land is an important land resource in our country and the main site of soil erosion.Due to natural rainfall,runoff and sediment production on the slope surface and rill erosion process are important components of soil erosion as well as the issues that affecting the global ecological environment.Carrying out the object of runoff and sediment yield can provide a scientific basis for soil and water conservation planning and construction,land resource utilization and sediment disaster control,and lay a foundation for the study of soil erosion process model and runoff and sediment theory also promote the scientific development of soil erosion.At present,the research on the process of runoff and sediment production of Longitudinal ridge and Cross ridge under the natural rainfall is rare.Through two years of field experiment,studied the time to runoff initiation,runoff and sediment yield process,and the shape of rill erosion in the Bare land,Longitudinal ridge and Cross ridge.The results provide a theoretical basis for the prevention and control soil erosion on slope.From July 26 to August 10(2015),the influencing factors of the time to runoff initiation of Bare land,Cross ridge and Longitudinal ridge were determined at Sujiatun Soil and Water Conservation Monitoring Station in Shenyang.The measured indices include surface stratification soil water content,vegetation quantity,plant coverage,plant height,stem diameter,canopy density.From July 20 to August 20(2016),the runoff and sediment yield of the Bare land,Cross ridge and Longitudinal ridge were determined,and the shape of rill slope was analyzed.The main indicators included runoff and sediment concentration,rill morphological,etc.The main conclusions are as follows:(1)Impact factors of the time to slope runoff initiation on the Bare land,Cross ridge and Longitudinal ridge mainly included soil water content,rainfall intensity,and plant indicators.There was a negative correlation between the soil water content at the 0 ~ 5 cm layer and the time to runoff initiation,and the plant index was positively correlated with the time to runoff initiation.The rainfall intensity was negatively correlated with the time to runoff initiation of Bare land and Longitudinal ridge,but Cross ridge not show negative correlation.According to correlation analysis and principal component analysis,the comprehensive factor of soil water content was the main factor affecting the time to runoff initiation.The second principal components of Bare land,Cross ridge and Longitudinal ridge were rainfall intensity comprehensive factor,plant comprehensive factor,rainfall and plant comprehensive factor respectively.(2)Runoff and sediment yield process of the Bare land,Cross ridge and Longitudinalridge slope mainly include the three aspects of the total amount,shape and peak time under Continuous rainfall and intermittent rainfall.Under Continuous rainfall,The runoff and sediment yield process of Bare land was overall W-type or M-type,with 1 or 2 peaks,peak time of 1 ~ 3 min;Cross ridge and Longitudinal ridge runoff process was W-type or inverted V-type,sediment yield process was W-type or M-type;only Cross ridge and rainfall intensity exist peak shifting phenomenon,delay 1 min.Under intermittent rainfall,Bare land runoff and sediment yield process as a whole was inverted V-type or M-type,with 1 or 2 peaks,the peak time of 1 ~ 4 min;Cross ridge and Longitudinal ridge runoff inverted V-type pattern,sediment yield process Inverted V-type or M-type.Both the Cross ridge and Longitudinal ridge had a peak phenomenon.The runoff and sediment yield along the Longitudinal ridge were delayed by 1 ~ 4 min and the Cross ridge delayed by 1 min.(3)The characteristics of rill erosion on the Bare land,Cross ridge and Longitudinal ridge mainly included rill morphology,overall rill parameters and rill erosion segmentation parameters.In the four rains,the rill of Bare land showed three kinds of patterns on the whole,which were in strip type,V-type and twig type distribution respectively.Cross ridge rill expressed broken ridge bar type and compound long branches type,and Longitudinal ridge rill pattern also showed long branches type.The average rill density of Bare land showed an increasing trend.The rill density and width-to-depth ratio of the Cross ridge express an increasing trend.The cumulative rill length of the Bare land changed as follows: the first slope section > the second slope section > the third slope section,the average rill width of Bare land was the largest on the first slope,and the minimum value is distributed on the third slope section,the changes of average rill depth was the first slope section;The accumulative rill length of the first slope section on the Cross ridge is the smallest,the average rill width of the third slope section is the least,and the average rill depth of is the largest.