| 跌水高度对元谋干热河谷冲沟沟头侵蚀产沙特征的影响初探 |
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| 引用本文： | 张宝军,熊东红,杨 丹,张 素,校 亮,苏正安,董一帆.跌水高度对元谋干热河谷冲沟沟头侵蚀产沙特征的影响初探[J].土壤学报,2017,54(1):48-59. |
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| 作者姓名： | 张宝军 熊东红 杨 丹 张 素 校 亮 苏正安 董一帆 |
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| 作者单位： | 1. 中国科学院山地灾害与地表过程重点实验室，成都 610041; 中国科学院水利部成都山地灾害与环境研究所，成都 610041; 中国科学院大学，北京 100049;2. 中国科学院山地灾害与地表过程重点实验室，成都 610041; 中国科学院水利部成都山地灾害与环境研究所，成都 610041 |
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| 基金项目： | 国家重点基础研究发展计划（973）项目(2015CB452704)、国家自然科学基金项目(41571277)和中国科学院“西部之光”重点项目(Y4R2060060)共同资助 |
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| 摘 要： | 元谋干热河谷冲沟侵蚀强烈,以沟头溯源侵蚀过程为主,陡立沟壁跌坎是活跃沟头的重要形态特征之一。采用野外原位放水冲刷试验,研究了25和50 cm两种不同跌水高度对侵蚀产沙过程的影响。结果表明:2种跌水高度下,(1)径流跌水冲刷力差异显著。跌水势能转化量平均值分别为4.89和9.78 J s-1,跌水剪切力平均值分别为25.9和53.5 Pa,均呈现倍数关系。(2)跌穴发育形态特征及下游侵蚀量差异大。2个小区跌水最大下切深度分别为7.38和7.50 cm,平均下切深度分别为3.87和5.16 cm;沟头沟壁及下游沟床部位侵蚀量累积贡献平均为41%和54%。(3)径流含沙量差异显著(p0.1)。整个试验中2个小区径流平均含沙量分别为7.51和18.76 g L~(-1),且径流经过沟壁跌坎后,含沙量分别平均增大6.25和25.49 g L~(-1)。初步认为沟壁跌坎高度差异影响径流冲刷力及其侵蚀产沙特征,但仍需进一步开展更多跌坎高度下的相关研究,为干热河谷区冲沟沟头溯源侵蚀动力学机制研究提供补充。
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| 关 键 词： | 径流冲刷力 侵蚀产沙特征 跌水高度 冲沟沟头 元谋干热河谷 |
| 收稿时间： | 2016/4/24 0:00:00 |
| 修稿时间： | 2016/7/18 0:00:00 |
Preliminary Study on Effects of Headcut Height on Soil Erosion and Sediment Yield at Gully Heads in Yuanmou Dry-hot Valley Region |
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| ZHANG Baojun,XIONG Donghong,YANG Dan,ZHANG Su,XIAO Liang,SU Zhengan and DONG Yifan.Preliminary Study on Effects of Headcut Height on Soil Erosion and Sediment Yield at Gully Heads in Yuanmou Dry-hot Valley Region[J].Acta Pedologica Sinica,2017,54(1):48-59. |
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| Authors: | ZHANG Baojun XIONG Donghong YANG Dan ZHANG Su XIAO Liang SU Zhengan and DONG Yifan |
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| Abstract: | Objective]Gully erosion is very severe in the Yuanmou Dry-hot Valley Region,dominated with headward erosion,which is characterized by steep gully headcuts. During the field investigations, headcut height is often regarded as one of the main indices of distinguishing the type of gully head activity. The abrupt drop of concentrated flow at headcut would cause a sudden change of the runoff in hydrodynamics, thus accelerating the headward erosion processes. It is,therefore,of great significance to carry out the preliminary study on effects of headcut height on characteristics of soil erosion and sediment yield in the gully headward processes,to the gully erosion research in this region as scientific supplement.Method]To simulate different step heights,based on an in-situ active bank gully head,two experimental plots were constructed with the headcut height of 25 cm and 50 cm,separately. And in November 2015 a series of in-situ scouring experiments were carried out with the flow set at 120 L min-1. The entire scouring test lasted 140 min,consisting of 5 test runs. During the scouring tests,cross-sections were set in the drainage area and along the gully bed at1 m intervals,for observation of changes of runoff in width,depth and velocity at regular intervals. Meanwhile,sediment samples were also collected at regular time intervals at the outlet of the drainage area and the plots,separately,for analysis of sediment content with the oven drying method. Besides,before and after the experiment,topographic data of the two plots were collected with the high-resolution close range digital photogrammetry measurements,for analysis of changes in landform, morphological parameters and net soil loss.Result]Results showed that:(1)The scouring power of jet flow differed significantly between the two plots. When surface runoff turned into impinging jets,the mean potential energy transformation in the two plots was about 4.89 and 9.78 J s-1,separately with shear stress reaching 25.9 and 53.5 Pa,on average respectively,both in multiple relations. And the velocity at the instance when the flow touched the bottom of the headcut reached as high as 2.28 and 3.18 m s-1, separately,which was 4.1 and 5.6 times larger than that at the brink point respectively.(2)The two plots also differed significantly in morphological characteristics of plunge pools and soil erosion volume at lower end. At the end of the experiment,the incision depth of jet flow reached 7.38 and 7.50 cm in maximum, and was 3.87 and 5.16 cm on average,separately,in the two plots. Especially,the growth of incision depth with the experiment going on varied sharply between the two plots. Furthermore,during the scouring tests, the soil erosion cumulative contribution rate at the gully headwall and in the bed at the lower end reached as high as 45.1% and 64.9%,and was 41% and 54% on average.(3)The two plots also differed sharply in runoff sediment concentration(p<0.1). Excluding the maximum concentration at the beginning of each test,the mean sediment concentration was 7.51 and 18.76 g L-1,separately,about 1.5 times in difference. Especially,during the first previous 80 min of the scouring tests,when runoff flew over the headcut,the runoff sediment concentration increased by 25.28 and 108.78 g L-1 in maximum and by 6.25 and 25.49 g L-1 on average,separately,in the two plots. Conclusion]This study has tentatively concluded that the effect of gully headcut height affecting runoff scouring force and characteristics of soil erosion and sediment yield is probably the key factor influencing the headward erosion process. However,it is still not very clear about how the effect would vary in the case of higher headcuts. More experiments with a variety of headcut heights should be conducted,in an attempt to supplement more complete meaningful theories to the study on dynamics and mechanisms of gully headward erosion in dry-hot valley regions. |
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| Keywords: | Runoff erosivity Characteristics of soil erosion and sediment yield Headcut height Gully head Yuanmou Dry-hot Valley Region |
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