Gully morphology is an important part of loess landform research. Along with gully development, the variation of its cross section is the most significant, and it can intuitively reflect the characteristics of the lateral widening of the gully slope. Therefore, in-depth research of the variation of the cross-sectional morphology of the gully is helpful to understanding the development process of the loess gully. Based on the DEMs (Digital Elevation Model) of nine periods of an indoor simulated loess small watershed, this paper studies the evolution model of a complete branch ditch in the watershed using the digital terrain analysis theory and method. Results show that with the development of the gully, the average gradient of the gully slope continuously decreases, and the slope morphology is mostly a concave slope along the slope direction. The degree of downward concave first increases and then gradually tends to be gentle. The gully erosion mode is gradually transformed from downward cutting erosion to lateral erosion. The more mature the gully development, the lower the depth of gully bottom cutting is compared with the width of gully widening. Furthermore, the surface cutting depth tends to be stable and the slope is stable. Then, the transformation law of the slope morphology of the gully cross section with the development of the gully is studied, and the prediction model of the transformation of the slope morphology of the gully cross section is established by using the Markov chain. The Markov model can better reflect the dynamic change of the slope morphology of the gully cross section, which is of great significance to revealing the external performance and internal mechanism of the gully morphology.

沟壑形态是黄土地貌研究的重要组成部分。随着冲沟的发育，其断面变化最为显着，可以直观地反映冲沟坡度横向展宽的特征。因此，深入研究沟谷断面形态的变化，有助于认识黄土沟谷的发育过程。基于室内模拟黄土小流域九期DEM(Digital Elevation Model)，运用数字地形分析理论与方法，研究流域内完整支沟演化模型。结果表明，随着冲沟的发育，冲沟坡度平均坡度不断减小，坡面形态多为沿坡向的凹坡。下凹的程度先增大后逐渐趋于平缓。冲沟侵蚀方式由下切侵蚀逐渐转变为侧向侵蚀。沟谷发育越成熟，沟底切割深度相对于沟谷加宽宽度越小。此外，表面切削深度趋于稳定，坡度稳定。然后,研究了冲沟断面坡度形态随冲沟发育的变化规律,利用马尔可夫链建立了冲沟断面坡度变化的预测模型。马尔可夫模型能较好地反映沟谷断面坡度形态的动态变化，