Study On Snowmelt Erosion Of Slope On Soil And Water Conservation Measures In Low Mountain Area Of Northeast China

The snowfall in the northeastern mountainous area is higher than other regions,and the temperature is increasing rapidly with the spring snowmelt.The surface soil is not completely thawed,and the water infiltration is poor,Therefore,the runoffs formed by the snow-melt eroding the soil produce erosion,and the freeze-thaw action effect the soil property.The snow cover is poor in the period of snow-melting,and the snowmelt erosion can not be ignored,So the situations in regional area is even worse than those in the flood season.Therefore,it is of great significance to study the effect of soil and water conservation measures on erosion in snow-melting period,which is important for strengthening the infiltration of melt water and mitigating the snowmelt erosion.At present,the research on soil and water conservation measures at home and abroad mainly focuses on the prevention and control of summer rainfall erosion,and lacks pertinent research on water conservation measures to control snowmelt erosion.So our research on snowmelt erosion mainly focuses on seven different measures in the runoff observation field of Jixing small watershed in Meihekou,Jilin Province are selected as the research object in total.The results indicate that the snowmelt characteristics,erosion characteristics and soil and water conservation measures factors of different water security measures are calculated and analyzed,which provides a theoretical basis for the prevention and control of snowmelt erosion in seasonal frozen soil area.The following conclusions are drawn:(1)Study on snow characteristics of snowmelt periodThe change in snow depth over time reflects the different snowmelt rates of each measure.The rate of melting snow was the highest in the upper part of the bare slope,and the snowfall rate was the fastest in the middle and lower part of the horizontal slope.Tillage measure(tillage factor for counter ridge combing with vegetation stripes?contour tillage,up-down slope tillage with soybeans)snow melting the fastest,followed by biological measures(biological-control factor of shrubs,the natural ecosystem rehabilitation)and engineering control measures(engineering-control factor for terrace).When there is no runoff in the plot,the volumetric moisture content of the upper and lower layers of snow area shows the same trend.The rate of snow and snow is gradually higher than that of the upper layer,and the rate of snow melting is also accelerated,and the water content of the snow cover is also increasing until the snow is completely ablated.The total water content of snow slope in the snow slope is the largest in the upper part of the slope,and the snow density in the upper part of the slope is stable,and the snowmelt process is in the trend of"increasing and decreasing-increasing" The density of the measures is larger and the slope density of the lower part of the slope is the largest.(2)Study on the characteristics of snowmelt erosionFrom the characteristics of runoff,the engineering-control factor for terrace is the first time that it has delayed the melting time of the snow.The natural ecosystem rehabilitation have the characteristics of quick runoff and short cycle.Compared with the forest land,The results showed that the natural ecosystem rehabilitation in grass land had the strongest ability to resist the snowfall runoff during snowmelt period,and the level of the lake was the same as that of the bare land.Sediment production rises with increasing runoff,therefore,the most direct way to prevent and control snowmelt erosion is to control runoff.The soil moisture content in the initial stage of thawing was saturated,about 53.02%averagely.With the soil thawing,the water content of topsoil decreased,and then the water content decreased with the decrease of surface water content,The level of pit measures;the thawing depth of each measure showed a steady upward trend,the thawing depth of the tillage measures was higher for the ridge plant,and the defrosting depth of the biological-control factor of shrubs in the biological measures was larger,and the engineering measure was thawed compared with other measures depth is small.(3)Factor analysis of soil and water conservation measures in snow meltingThe effect of the measures on the control of the snow melt is as follows:biological measures>engineering measures>farming measures;under the conditions of snow melting,the conditions of the natural ecosystem rehabilitation are better than other measures;the engineering measures are mainly reflected on the effect of soil and water conservation in snowmelt.The erosion modulus and the runoff depth of the tillage factor for counter ridge combing with vegetation stripes in the farming scheme were higher than that of the transverse ridge contour tillage under the snowmelt conditions.Because of the high vegetation coverage,the biological control measures have the best effect of snowmelt erosion control The engineering measures are better than the tillage measures that change the surface micro terrain by changing the local topography.The study of the snowmelt erosion process on the slope in runoff plots is the first time to used as a test facility for the quantitative description in the snowmelt erosion prevention and control.Combined with the typical measures in the northeastern low mountain area,the different soil and water conservation measures effect the control of snow melt erosion is quantitatively studied,and the optimal control measures are put forward to prevent the snowmelt erosion in seasonal frozen soil area and provide a theoretical basis.However,there are still some problems in the study of mitigation measures,such as the influence factors of snowmelt erosion,regional scale and so on,which should be studied in the future,and the two types of erosion(snowmelt and rainfall)should be taken into account in the planning and design of soil and water conservation measurements in the snow melting erosion area(especially the farmland).