Stability Evaluation Of Gullies In The Loess Hilly Area Of The Loess Plateau Of China

Based on the three remote sensing images of 1968,2004 and 2018,the study area was divided into two geomorphic units:intergully land and gully land.Meanwhile,the data of land use,fraction of vegetation cover and engineering measure of soil and water conservation were extracted as the backside of erosion gully change.On this basis,the spatial and temporal characteristics of erosion gullies(gullies and larger channels)in the Loess Hilly and gully region in recent 50 years are analyzed,and the influencing factors are quantitatively analyzed by using geographic detectors.Finally,the stability of erosion gullies is evaluated.The main results are as follows:(1)The interpretation results of the shoulder-line based on high-resolution remote sensing images are in good agreement with the actual geomorphological characteristics.Combined with the information of land use,water conservation measures and fraction of vegetation cover,it can be used to analyze the spatial and temporal dynamic changes of erosion gully.(2)Erosion gullies in the study area have been changing for 50 years,but the change rate is slowing down.From 1968 to 2004,the erosion gully lateral erosion and headward erosion were widespread.The average advance distance of the whole area was 56.84 m/(km~2.a).From 2005 to 2018,the erosion was relatively weakened.The main erosion forms were headward erosion.The average advance distance of the whole area was 30.17 m/(km~2.a),and the change rate of erosion gully was significantly slowed down.Downward erosion analysis with 5m resolution non-homologous DEM can not meet the accuracy requirement,so it is necessary to use more accurate homologous DEM data for downward erosion research.(3)The dynamic change of erosion gully is mainly affected by the change of land use and vegetation coverage in the early stage of the study period(1968-2004).The continuous decrease of cultivated land and the rapid increase of fraction of vegetation are the main factors to slow down the change of erosion gully.In the later stage of the study period(2005-2018),the increase of engineering measure of soil and water conservation and the continuous improvement of fraction of vegetation have a common impact.LS factor has a weak influence on the dynamic change of erosion gully in single factor analysis,but its explanatory ability to the dynamic change of erosion gully is obviously enhanced under the condition of satisfying certain land use change.(4)Evaluating the stability of erosion gully shows that the increasing rate of erosion gully density has slowed down in the past 50 years.The increase of erosion gully density in 1968-2004 and 2005-2018 is mainly distributed in 0.1-0.2 km/(km~2.a)and 0-0.1 km/(km~2.a),respectively.The evaluation of erosion gully stability by land use,catchment area and engineering measure of soil and water conservation shows that from1968 to 2004,the area of sub-unstable region is the largest,followed by the basic stable region;from 2005 to 2018,erosion gully is stable and basically stable,the area of sub-unstable region is obviously reduced,and the unstable region is characterized by centralized distribution.