基于三维激光扫描技术的喀斯特地表微地形特征及其侵蚀响应

Micro Topography Characteristic of Karst Slope and Its Response to Soil Erosion Based on 3D Laser Scanning Technique

为了探究喀斯特黄壤坡面微地形变化特征及其与土壤侵蚀的关系,基于人工模拟降雨试验,结合三维激光扫描技术,分析了坡面地表粗糙度和坑洼体积的变化特征及其与土壤侵蚀的响应关系。小区坡度25°,共有3种雨强(30,60,90 mm/h)和4种块石出露度(0,5.4%,13.1%,42.9%)处理。结果表明:(1)坡面块石出露在小雨强下(30 mm/h)可明显促进产流,产流时间较裸土坡面提前18.0%~57.2%,但大雨强下的影响被弱化。产流产沙随块石出露度的增大呈先增后减,最大值处块石出露度在小雨强和大雨强下分别为5.4%~13.1%和13.1%~42.9%。(2)裸土坡面地表粗糙度和坑洼蓄积量由坡上到坡下呈递增趋势,而块石出露坡面地表粗糙度沿坡面的分布规律不明显,坑洼蓄积量总体上也表现为由坡上到坡下逐渐增大。相同雨强下,块石出露坡面地表粗糙度较雨前的变幅大于裸土坡面,坑洼蓄积量较雨前增大的倍数随块石出露度的增大而减小。(3)当块石出露度小于42.9%时,坑洼体积与产流率、产沙率有良好的线性关系。地表微地形因子可作为侵蚀结果预测的重要参数,也可为特大暴雨事件中漏测数据的补充提供理论基础。

To explore the variation of micro topography condition and its relationship with soil erosion on slope of yellow soil in karst region,we analyzed the variation of surface roughness and depression storage as well as its response to soil erosion by means of simulated rainfall experiments and 3D laser scanning technology.The experiments were all implemented on the plots with 25°slope gradient.Three levels of rainfall intensity(30,60,90 mm/h)and four grades of boulder outcropping(0,5.4%,13.1%,42.9%)were designed as the treatments in experiments.The results show that:(1)under the light rainfall with intensity of 30 mm/h,the existence of boulder outcropping could promote runoff initiation,and the runoff-yielding time was brought forward by 18.0%~57.2%.However,this phenomenon was not obvious under heavy rainfalls.The production of surface runoff and soil loss tended to increase and then decrease with the increase of boulder outcropping;in light(30 mm/h)and heavy rainfall cases(60,90 mm/h),the production of surface runoff and soil loss reached the maximum when the boulder outcropping was in the range of 5.4%~13.1%and 13.1%~42.9%,respectively;(2)the surface roughness and depression storage tended to increase from the top to the bottom of the non-boulder outcropping slope.However,the distribution of surface roughness along the boulder outcropping slope was in a random.On the whole,the depression storage also tended to increase from the top to the bottom along the boulder outcropping slope.Under the same rainfall effect,the variation amplitude of surface roughness on boulder outcropping slope was greater than that of non-boulder outcropping slope.Compared with before the rain,the multiple of depression storage decreased with the increase of boulder outcropping;(3)there were good linear relationships between depression storage and runoff and sediment rate when the boulder outcropping was less than 42.9%.Surface micro topography factors can be regarded as the important parameters for soil erosion prediction,and can provide theoretical basis for the supplement of missed data in heavy rainstorm events.