基于三维激光扫描技术的冻结黑土细沟发育模拟

为探究融雪径流与冻结状态对黑土细沟网络发育的影响，该研究开展了冻结与非冻结处理黑土坡面的融雪径流模拟冲刷试验，利用三维激光扫描技术获取多次定时径流冲刷并直至侵蚀形态稳定的坡面点云，结合数字表面模型差异（digital surface model of difference, DoD）微地形变化监测方法与点云逆向工程，获取细沟网络发育过程的侵蚀面积、侵蚀体积、细沟长度和细沟密度等侵蚀参数。结果表明，冻结因素与温度变化对细沟网络发育过程与程度有重要影响：1）冻结处理的黑土坡面更容易发展出细沟网络，达到坡面侵蚀形态基本稳定后的侵蚀面积、侵蚀体积以及侵蚀细沟长度是非冻结处理黑土坡面的291%、557%和437%。2）冻结处理与非冻结处理沿坡面细沟截面形态变化差异明显。冻结坡面细沟交叉时宽深比R_W/D快速减小，下切速度加快，随后宽度与深度呈比例稳定增加；非冻结坡面汇水处的R_W/D随冲刷次数增加而增大，侧蚀速度加快，其他截面R_W/D随着冲刷次数的增加而减小，下切速度加快。3）采用ArcGIS与点云逆向工程模型联合获取的冻结状态下细沟形态参数与发育过程DoD相对误差范围为-12.70%～4.42%，提取精度在95%以上。该联合方法在冻结土体条件下获取细沟参数具有较高精度，可作为土壤侵蚀参数高精度提取的一种手段。

Simulating rill development in frozen black soil using 3D laser scanning

Snowmelt runoff and soil freezing have been combined to seriously exert on the rill networks and soil erosion intensity in the black soil region of northeastern China. The dynamic development of rill networks can be used to quantitatively extract the parameters of erosion. Previous studies have focused primarily on the runoff erosion caused by rainfall. Only a few studies were to consider the combined effects of snowmelt runoff and freezing. Currently, available methods cannot fully meet the high precision of rill morphology. Therefore, it is very necessary to systematically investigate the rill erosion under combined effects using high-precision extraction. This study aims to simulate the snowmelt runoff scouring on the frozen (-20°C freezing) and non-frozen slopes (10°C), refilled with black soil from northeastern China. A 0°C ice-water mixture was used to simulate the snowmelt runoff scouring. Meanwhile, three-dimensional laser scanning was employed to obtain the point cloud data of the slope surface after different times of scouring, until the eroded surface stabilized. The Digital Surface Model (DSM) of Difference (DoD) with point cloud reverse engineering was used to detect and parameterize the micro-topographic pattern (e.g., development of rill networks and erosion area, erosion volume, rill length, and rill density). The results show that there was a significant impact of freezing-induced temperature on the development of rill networks: (1) The frozen slope was more prone to develop the rill networks. The erosion rate after each scouring was significantly higher than that on the non-frozen slopes. Upon reaching stability, the erosion area, erosion volume, and rill length were 291%, 557%, and 437% of those on the non-frozen slopes, respectively; (2) The cumulative erosion volume of the frozen and non-frozen slopes showed similar patterns during the rill development. But there were noticeable differences along the cross-sectional direction of the rills. On the frozen slopes, the width-depth ratio (R_W/D) of the rill cross-sections decreased rapidly at the rill intersections with accelerated downcutting, whereas, the width and depth of rills increased linearly and stably. On the non-frozen slopes, the R_W/D at the mid-slope cross-sections increased with the number of scouring events, thus accelerating lateral erosion, while the R_W/D at other sections decreased with the number of scouring events with accelerated downcutting; (3) The relative error range was -12.70% to 4.42% for the Differential Digital Surface Model (DoD) with ArcGIS hydrological processing and GeoMagic point cloud reverse engineering models for the frozen slopes, with an absolute mean relative error of 5.48%, and an extraction accuracy of over 94%. The combined extraction with GeoMagic and ArcGIS showed a great contribution to obtain the rill parameters on the freeze-treated slopes. The finding can serve as a promising potential to the rill development under complex eroding settings.