An Experimental Study On Loessial Hillslope Gully Erosion Development Process

Research on loessial hillslope gully erosion process has important significance to understanding soil erosion process mechanism and providing valuable information for soil loss control at Loess Plateau.By using the research methods of simulated rainfall and gully erosion process dynamic monitoring,this thesis, through building initial gully model, quantified hillslope gully erosion development process, analyzed relationships between gully erosion process and sediment yield, and established statistical equations of gully dynamic development process.The main research results were as follow:1. The gully erosion development process without human disturbance were researched.The gully erosion development process experienced three stages of rill erosion development,process from rill erosion to gully erosion,and gully erosion development process.Headward erosion was the main erosion pattern in the stage of rill erosion and sediment yield tended to increasing trend;then the gully erosion entered active stage,gully-wall collapse and deep-cutting were very significant, and sediment yield abruptly increased;late on, the gully erosion developed to the stable development stage and sediment yield tended to stable-state.2. The relationship between the gully erosion development process and sediment yield process were researched.In the initial stage of gully erosion,headward erosion was the main erosion pattern,and the rill length increase fast but the width and depth increase slowly.So the sediment yield tended increasing trend;gully-wall collapse and the deep-cutting developed rapidly as the gully erosion entered active stage,the gully width and depth increased fast,and the sediment yield greatly increased.As the gully erosion develop to the stable stage,the increasing rate of length,width and depth of the erosion gully are decreased,and the sediment yield also entered stable stage.3. The relationship of rainfall intensity and gully erosion development process were researched.Increasing the rainfall intensity speeded up the gully erosion develop rate,decrease the time of gully erosion formation process.And the time of every erosion stage of gully erosion development stages is also decreased.4. Statistical equations of gully erosion dynamic development process.The gully length increased as the time of rainfall and expressed as a power function. The gully width also increased as the rainfall duration and showed the cubic relationship in 50 mm/h rainfall intensity and the liner relationship in 100 mm/h rainfall intensity, respectively.The gully depth change with rainfall duration showed different trends, it was the cubic relationship in 50 mm/h rainfall intensity and the power function relationship in 100 mm/h rainfall intensity.