The Study On The Development Characteristics And Influencing Factors Of Erosion Gullies In Typical Areas Of The Northeastern Hill

The black soil area in Northeast China is an important commercial food production base and ecological barrier in China,and is known as"the giant panda of arable land".Due to the long-term high-intensity agricultural development and predatory management,which emphasizes the use rather than nourishment,and the topographic characteristics of long and gentle slopes,the water and soil erosion in the Northeast Black Soil Region has been increasing.Soil erosion on the slope induces the formation of erosion gullies,which not only eat up arable land,but also cause soil nutrient"depletion",reduce soil quality,accelerate agricultural non-point source pollution,and cause serious impact on agricultural production,ecological security,water environment security and regional sustainable development.However,quantitative studies on the development of erosion gullies in northeastern black soil areas are limited,and most of them are concentrated in the flat topography of rolling hill area,and few of them are reported in the hill areas where sloping farmland is widely distributed.In this study,106.5 km²area in the upper reaches of the Dongliao River was selected as the research object,and the basic geometric parameters of the erosion gullies in the study area were measured and the distribution characteristics and development pattern of the erosion gullies in the study area were analyzed by using3S technology,based on indoor predictive reading and interpretation,and field review;The same erosion gully,which was surveyed twice,was extracted from the first national water census erosion gully vector database（2011）for comparative analysis,and the rate of gully erosion was estimated for 2011-2021;Various mathematical and statistical analysis methods and techniques,including Pearson correlation analysis,multiple linear regression analysis（MLR）,redundancy analysis（RDA）and landscape pattern analysis,were used to reveal quantitative relationships between erosion gully morphological features and environmental factors,and to identify the main drivers of erosion gully development;The amount of soil erosion and agricultural nonpoint source pollution load were estimated;the influence of the main influencing factor,topography,on the development of erosion gullies on sloping farmland was explored.The main findings of this paper are as follows:1)A total of 322 erosion gullies were found in the study area,with an average length of 261.8 m,an average width of 14.9 m,an average depth of 3.1 m,a distribution density of 3.0 gullies/km²,a gully density of 0.8 km/km²,and a cut-off degree of 1.4%,which has belonged to the area of serious gully erosion in the northeast black soil area.2)In the 1st national water census（2011）,the identification rate of erosion gully interpretation was 47.2%,and the accuracy of remote sensing image interpretation in this survey in 2021 was 73.6%.Soil erosion caused by gully erosion accounted for21.3%of the total erosion,while surface erosion accounted for 78.7%.3)The analysis results shown that linear gully retreat rate in the study area from2011 to 2021 ranged from 4.3 to 8.4 m y^-1(mean:6.3 m y^-1),areal gully retreat rate ranged from 90.7 to 1224.4 m²y^-1(mean:339.2 m²y^-1).Linear gully headcut retreat(about 3.8 m y^-1)was the main form of gully length change,while gully side-wall retreat(about 56.8 m²y^-1)dominated the gully area change.4)All changes in erosion gully morphological characteristics can be predicted by environmental factors,and natural factors have more influence on linear development of erosion gullies than anthropogenic factors,while anthropogenic factors are more closely related to lateral expansion of erosion gullies.The catchment area,elevation and landscape pattern index（PD and ED）are the main drivers of erosion gully morphological changes.Using erosion ditch catchment area as the evaluation unit and elevation as the discriminant index can improve the accuracy of identifying high risk areas of gully erosion in the hill areas of northeastern black soil area.The influence of slope gradient and elevation on gully density shows a pattern of increasing and then decreasing,with elevation values peaking at 330～345 m and slope values peaking at 8°～10°.The gully density on the slopes of sunny slopes and semi-sunny slopes（SE,S,E）exceeds 750 m/km²,and the morphological parameters of erosion gullies on the slopes of sunny slopes and semi-sunny slopes are significantly higher than those on other slopes,and erosion gullies are more likely to be formed on the slopes of sunny slopes and semi-sunny slopes.The gully density of sloping farmland is not proportional to the topographic area.The research results provide scientific data for understanding the occurrence and evolution of erosion gullies in the northeastern hill areas.