The Gully Development Characteristics And Its Influencing Factor Analysis During Snowmelt Period In Black Soil Area Of Northeast China

The black soil region of northeast China is located in a high-latitude cold region that experiences seasonal snow cover.In addition to severe rainstorm erosion in summer,severe soil freezing and thawing occur in winter and spring.In certain areas,the amount of soil erosion caused by exogenic processes,such as freeze-thaw cycles and snowmelt runoff,is similar to the amount of soil erosion caused by rainstorms.Gully erosion is one of the main forms of soil erosion in this region.Current studies on gully erosion have primarily focused on the rainfall period and rarely investigated the snowmelt period.Furthermore,we explore gully development characteristics and the influencing factors in the black soil region during the snowmelting period and establish gully volume development model to provide an important reference for adjusting relevant measures to local conditions for the prevention and control of gullies during the snowmelting period in the black soil region of northeast China.Gully as one of the main types of erosion ditch and the main types of soil erosion for sloping farmland,which causes large amount of sediment production,therefore,the Differential Global Positioning System is used to monitor gullies developed in three typical soils of the study region in May and October every year.Combined with the spatial analysis function of geographic information system(GIS)software,we compare the gully parameters between October and the next May to obtain the gully length,area,and volume development parameters during the snowmelt period to explore its macro-development characteristics.On this basis,two gullies of the Guang Rong watershed is selected and the complete gullies are extracted by using the section method at intervals of 5m to get the depth,area,volume indicators to explore its development characteristics along the gully.Through the collection of the same period of snow to obtain the characteristics of the accumulation of snow,searching the Bureau of Meteorology official website and geospatial data cloud access to get precipitation and terrain characteristics,field investigation to obtain soil,vegetation,human activities,the collection of typical watershed corresponding provinces(autonomous regions)Census erosion erosion data and human activity intensity index,and then quantitative analysis the influence of precipitation,topography,soil,vegetation,human activities on gully development.In this paper,the effects of freeze-thawing on the development of gully during the snowmelt period are quantitatively analyzed by comparison of the developmental characteristics of the same basin during the rainfall period and the snowmelt period under the assumption that the precipitation is equal during the rainfall period and the snowmelt period.At the same time,the study will quantitatively calculate the human activities in order to provide a theoretical basis for the follow-up practice of human activities in the black soil area and the management of the gullies during the snowmelt period.The results show that:(1)In the typical watersheds significant regional variability in gully development occurrs.The regional heterogeneity is as follows:the development of the Wuyi basin with dark brown soil is the fastest,the length development of the gully is 14.23 m/a,which of the area is 147.62 m2/a,and the volume is 336.28 m3/a.The length development of the GuangRong basin is 3.37 m/a,which of the area is 82.19 m2/a,and the volume is 133.51 m3/a.The length,area and volume of the Jixing basin are 1.94 m/a,54.6 m2/a and 18.71 m3/a,respectively.Overall,gully development was characterized by a gradual decrease in gully development rates from northwest to southeast and changes from dark brown to albic soil in the typical watersheds in the black soil region of northeast China.The interannual variability was most evident in the Wuyi watershed,which primarily displays dark brown soil,followed by the Guangrong watershed which primarily displays black soil;however,this phenomenon was relatively weak in the Jixing watershed,which primarily displays albic soil.(2)The development characteristics along the gully in guang rong watershed are different,and the development from the gully head to the middle is relatively active,and from the middle to the tail is relatively slow.The width development in the middle of the gully is much more fluctuating,the depth development of G1 was significantly negatively correlated with area development rate(P<0.05,r =-0.500),and positively correlated with the volume development rate(P<0.05,r = 0.572),which indicates that the development of G1 owing to the main expansion of the gully bank,and erosion substances in the gully accumulation,and gully cross-section is a "V" font.The width development rate along G2 is significantly positive correlation with area development rate(p<0.05,r =0.412)and also significantly positive correlation with volume development rate.G2 development is also mainly to the expansion of the gully bank,the ditch under the weaker,the channel is relatively small accumulation,the channel depth is large,which cut the gully cross section into a "U" font.This shows that the expansion of the gully bank and erosion material accumulation in the channel,maybe one of the development model forgully in the black soil region during snowmelt period.(3)Slope length,catchment area,topographic factor(LS)and other terrain characteristics and human factors are the key factors that affect the regional differentiation of the gully development during smelt period.The gully length development rate was significantly correlated with slope length,catchment area and topographic factors(r1=0.761,r2=0.634,r=0.779,p<0.05);There is a significant positive correlation between human activity and the amount of gully development per unit area(r=0.937,p<0.05).because of the interannual variations in precipitation and freeze-thaw cycles among various watersheds gully development show differences.Precipitation characteristics are the critical factor affecting the interannual variability of gully development in the Wuyi watershed,whereas freeze-thaw cycles are the critical factor affecting the interannual variability of gully development in the Guangrong watershed.Freeze-thaw cycles have resulted in a gully head retreat rate of 0.58-5.5 m/a in the Guangrong watershed.