黄土丘陵沟壑区浅沟发育动态监测与形态定量研究

Dynamic Monitoring of Ephemeral Gully Development and Its Morphology Quantification in Loess Hilly-gully Region

基于测尺法对野外浅沟发育过程进行长历时动态监测,并结合三维激光扫描和立体摄影测量技术,定量刻画了坡面浅沟集水区3条具有不同上方汇水面积的浅沟形态,揭示了浅沟发育动态变化过程,建立了浅沟沟槽跌坎间距与坡度的关系。结果表明:在2003—2015年观测期间,上方汇水面积分别增加34. 8%和159. 6%时,浅沟长度分别增加39. 6%和138. 8%,沟槽平均宽度分别增加19. 7%和75. 3%,沟槽平均深度分别增加32. 4%和71. 4%,说明上方汇水面积对浅沟发育具有重要影响。浅沟形态监测表明,与2003年相比,2015年3条浅沟长度分别增加26. 4%、12. 1%、29. 4%,增加速率分别为0. 82、0. 55、0. 52 m/a;浅沟沟槽断面面积分别增加22. 5%、65. 1%、45. 9%,增加速率分别为5. 0、15. 8、4. 1 cm^2/a。浅沟集水区春季的横向犁耕将沟槽两侧的表层土壤带入沟槽,使得沟槽两侧坡面高度每年平均下降2 cm;浅沟沟槽宽度和深度随坡长呈先增大后减小的趋势,且在距坡底约20 m处达到最大值。70%的浅沟沟槽跌坎间距均分布在10～25 cm之间。浅沟沟槽坡度主要分布在15°～40°之间,跌坎间距和坡度呈负指数关系。研究结果可为浅沟侵蚀防治提供科学依据。

Dynamic quantification of field ephemeral gully development and morphology on natural hillslope has great significance on ephemeral gully erosion control and ephemeral gully erosion modelling. Due to the difficulty of dynamically monitoring field ephemeral gully catchments and limitation of measurement method, quantification of ephemeral gully morphology and its dynamic evolvement process is still lacking. Thus, based on the long-term field ephemeral gully development investigation data, three-dimensional laser scanning and photogrammetry techniques were used to quantify the ephemeral gully morphology of three ephemeral gully catchments with different upslope drainage areas (1 012 m 2 , 995 m 2 and 424 m 2 ). The dynamic evolution processes of ephemeral gully were revealed, and the relationship between drop-sills distance of headcuts and slope gradient was also analyzed. The result showed that during the monitoring period from 2003 to 2015, when upslope drainage area was increased by 34.8% and 159.6%, ephemeral gully length was increased by 39.6% and 138.8%, average ephemeral gully width was increased by 19.7% and 75.3%, and average ephemeral gully depth was increased by 32.4% and 71.4%, respectively. Dynamic monitoring illustrated that ephemeral gully length was increased by 26.4%, 12.1%,29.4% from 2003 to 2015 and the increasing rate was 0.82 m/a,0.55 m/a,0.52 m/a;the cross-section areas of ephemeral gully in 2015 was increased by 22.5%, 65.1%, 45.9% compared with those in 2013, and the increasing rate was 5.0 cm 2 /a, 15.8 cm^2 /a, 4.1 cm 2 /a. Tillage in spring brought the lateral topsoil into the ephemeral gully channel which induced 2 cm decrement of soil layer around the channel. With the increase of slope length, ephemeral gully width and depth were increased first and then decreased, with maximum value in the location of about 20 m to the slope bottom. Totally 70% of drop-sills distances of headcuts in ephemeral gully channel were distributed in 10~25 cm, while slope gradients were distributed in the range of 15°~40°. A negative exponent relationship can be found between drop-sills distance and slope gradient. The research results enhanced the understanding on ephemeral gully erosion processes, which could provide scientific bases for ephemeral gully erosion control.