Rainfall simulation to identify the storm-scale mechanisms of gully bank retreat   总被引：1，自引：0，他引：1  

Vincent Chaplot  Jacqueline BrownPhesheya Dlamini  Tarryn EusticeJean-Louis Janeau  Graham JewittSimon Lorentz  Lauren MartinCharmaine Nontokozo-Mchunu  Ernest OakesPascal Podwojewski  Sylvain RevilCornelia Rumpel  Nhlakanipho Zondi 《Agricultural Water Management》2011,98(11):1704-1710

Gully erosion is one of the main causes of soil loss in drylands. Understanding the dominant mechanisms of erosion is important to achieve effective erosion control, thus in this study our main objective was to quantify the mechanisms involved in gully bank retreat as a result of three processes, falling of entire soil aggregates, transport of soil material by splash and by water running along gully banks (runoff), during rainfall events. The study was conducted in the sloping lands of the KwaZulu-Natal province, a region that is highly affected by gully erosion. Artificial rain was applied at 60 mm h⁻¹ for 45 min at the vertical wall of a gully bank typical to the area. The splash material was collected by using a network of 0.045 m² buckets. The sediments in the running water were assessed by sampling the runoff collected from a microplot inserted within the base of the bank, and collecting the fallen aggregates after the rainfall simulation was complete. Results indicated that the overall erosion for the simulation was 721 g m⁻² h⁻¹. Runoff erosion proved to be the dominant mechanism and amounted to 450 g m⁻² h⁻¹, followed by splash and fall down of aggregates (about 170 g m⁻² h⁻¹). Gully bank retreat occurred at a rate of 0.55 mm h⁻¹ and assuming that the soil bulk density is 1.3 g cm⁻³, this corresponds to a retreat of 8.8 mm y⁻¹. Extrapolations to the watershed level, where about 500 m² of gully bank are observed per hectare, would lead to an erosion rate of 4.8 t ha⁻¹ y⁻¹. These limited results based on a simulated storm show that the three main mechanisms (runoff, splash and fall down of aggregates) are responsible for the retreat of gully banks and that to mitigate gully erosion, appropriate measures are required to control all three mechanisms. Further research studies are needed to confirm and to scale up, both in time and space, as these data are obtained at one location and from a single artificial storm.  相似文献   

“8·13”碱坪沟泥石流形成机理及特征研究     

褚胜名  余斌  李丽  马煜  吴雨夫  亓星 《中国水土保持》2011,(8):52-54

2010年8月13日在强降雨的作用下,四川省都江堰市龙池镇碱坪沟沟床启动并带动沟道两侧固体物质运动,形成大规模泥石流,冲毁沟口农家乐、龙池公路及沟口一处居民供水设施。碱坪沟泥石流是典型的震区沟谷型泥石流,通过分析泥石流的形成机理及容重、流速、流量、冲出量等动力学参数,得出泥石流的危险范围和威胁对象,并根据沟道中大量崩滑体等各类物源的堆积情况,在降雨作用下对其再次暴发泥石流的可能性进行了分析预测,还根据沟口现场堆积情况提出了防治建议。  相似文献   

碱坪沟地震次生泥石流形成特征与发展趋势     

杨成林  陈宁生  邓明枫  邓虎  佘涛 《水土保持通报》2011,31(6):59-63

＂5.12＂汶川地震后,龙溪河碱坪沟流域内堆积了大量的松散固体物质,成为参与泥石流形成的主要物源。碱坪沟于2009—2010年先后3次暴发大规模泥石流灾害。通过对碱坪沟的地形、水源和物源条件的分析发现,该流域地形和水源条件满足泥石流形成的条件,且在地震前后未发生显著变化,而物源条件已经成为影响该区域泥石流形成与发展的主要因素。基于流域物源量与物源固结效应的研究结果表明,在5a内碱坪沟泥石流灾害较活跃,可能暴发大规模泥石流灾害。5～10a后,在降雨条件不发生较大变化以及不暴发大地震的情况下,流域内泥石流规模和频率会逐渐减小,只有在低频率暴雨作用下才可能暴发大规模泥石流灾害。  相似文献   

Evaluating gully erosion using Cs and Pb/Cs ratio in a reservoir catchment     

Y. Li  J. Poesen  J. C. Yang  B. Fu  J. H. Zhang   《Soil & Tillage Research》2003,69(1-2):107-115

Water erosion in the hilly areas of west China is the main process contributing to the overall sediment of the Yellow River and the Yangtze River. The impact of gully erosion in total sediment output has been mostly neglected. Our objective was to assess the sediment production and sediment sources at both the hillslope and catchment scales in the Yangjuangou reservoir catchment of the Chinese Loess Plateau, northwest China. Distribution patterns in sediment production caused by water erosion on hills and gully slopes under different land use types were assessed using the fallout ¹³⁷Cs technique. The total sediment production from the catchment was estimated by using the sediment record in a reservoir. Sediment sources and dominant water erosion processes were determined by comparing ¹³⁷Cs activities and ²¹⁰Pb/¹³⁷Cs ratios in surface soils and sub-surface soils with those of sediment deposits from the reservoir at the outlet of the catchment. Results indicated that landscape location had the most significant impact on sediment production for cultivated hillslopes, followed by the terraced hillslope, and the least for the vegetated hillslope. Sediment production increased in the following order: top>upper>lower>middle for the cultivated hillslope, and top>lower>upper>middle for the terraced hillslope. The mean value of sediment production declined by 49% for the terraced hillslope and by 80% for the vegetated hillslope compared with the cultivated hillslope. Vegetated gully slope reduced the sediment production by 38% compared with the cultivated gully slope. These data demonstrate the effectiveness of terracing and perennial vegetation cover in controlling sediment delivery at a hillslope scale. Averaged ¹³⁷Cs activities and ²¹⁰Pb/¹³⁷Cs ratios in the 0–5 cm surface soil (2.22–4.70 Bq kg⁻¹ and 20.70–22.07, respectively) and in the 5–30 cm subsoil (2.60 Bq kg⁻¹ and 28.57, respectively) on the cultivated hills and gully slopes were close to those of the deposited sediment in the reservoir (3.37 Bq kg⁻¹ and 29.08, respectively). These results suggest that the main sediment sources in the catchment were from the surface soil and subsoil on the cultivated slopes, and that gully erosion is the dominant water erosion process contributing sediment in the study area. Changes in land use types can greatly affect sediment production from gully erosion. An increase in grassland and forestland by 42%, and a corresponding decrease in farmland by 46%, reduced sediment production by 31% in the catchment.  相似文献   

Coupling between hillslopes and channels in upland fluvial systems: implications for landscape sensitivity, illustrated from the Howgill Fells, northwest England     

A. M. Harvey 《CATENA》2001,42(2-4)

The sensitivity of upland fluvial systems depends on the magnitude and frequency of sediment and flood producing events, modified by the internal coupling characteristics of the system. This paper assesses the role of hillslope/channel coupling for the sensitivity of upland geomorphic systems, using evidence from a 30-year monitoring programme of geomorphic change in the Carlingill valley, Howgill Fells, northwest England. In the hillslope zone, there is little sediment supply to the stream system. Locally, slope failures occur in response to extreme events (six such events in 30 years within the ca. 6 km² Carlingill valley). In the footslope coupling zone, basally induced gullies are major sediment sources to the stream. Sediment-production events occur ca. 30 times per year, feeding sediment to basal debris cones. Stream floods which can entrain these sediments occur once every ca. 2–5 years. Stream channel morphology is adjusted to this regime. Downstream of gullies, channels are wide and braided; elsewhere they are narrow and single-thread. As the gullies develop, however, this coupling weakens and the eroding slopes eventually stabilise by revegetation. Over the 30-year monitoring period, there has been a progressive trend towards gully stabilisation, and an associated reduction in channel instability. Massive destabilisation may occur in response to rare extreme flood events. Such an event (return period >100 years) occurred in neighbouring Langdale and Bowderdale valleys in June 1982. That event destabilised the system, causing slope failures, fan deposition, and in some places, a switch in channel style to wide braided channels. Since 1982 there has been a progressive recovery by slope stabilisation and single-thread sinuous channels have become reestablished. A different style of extreme event occurred in Carlingill in October 1998, in response to the wettest week in the 30-year period. A slope failure fed debris flows 400 m downslope, almost coupling with the channel system. Future climatic change could render the system prone to destabilisation, through either extreme flood events or through major slope failures.  相似文献   

延河流域沟壑密度统计学特征及影响因素分析   总被引：2，自引：0，他引：2  

丁琳  刘辉 《安徽农学通报》2016,22(14)

为研究延河流域沟壑密度统计学特征,该文基于延河流域DEM数据及Arc GIS软件,运用水文分析法及均值变点法提取最佳沟谷网络,并在Excel中进行沟壑密度统计分析。结果表明:研究区总沟壑密度为1.16km/km2,各分区沟壑密度趋势为D1区D2区D3区D4区;不同分区,不同等级沟谷的平均长度及沟壑密度均存在较大差异;同一等级的沟谷在不同分区中的空间分布不同,沟壑密度也存在空间分异性;这些沟壑密度特征是地貌因素及土壤性质等耦合作用的结果。本研究将有助于揭示土壤侵蚀的空间差异性,深入理解沟壑密度的影响因素,从而为有针对性地提出水土保持综合防治措施提供理论依据。  相似文献   

近50年平凉黄土高原沟壑区气温和降水变化趋势分析     

王若安 《安徽农业科学》2009,37(35):17564-17566

[目的]研究平凉黄土高原沟壑区气温和降水变化,全面了解当地气候变化特点和未来发展趋势。[方法]采用线性倾向估计法对平凉黄土高原沟壑区近50年的年平均气温和年降水量的变化特点进行分析,用累积距平法和Mann—Kendall法对气候突变进行分析检测,并用重标极差（R-S）法对其未来气候变化趋势进行分析。[结果]近50年平凉黄土高原沟壑区气温呈上升趋势,气温变化率为0．26℃／10年,降水呈减少趋势,降水变化率为-20．2Mm／10年;气温的Hurst指数为0．90,降水量的Hurst指数为0．62．预示未来气温上升和降水减少的趋势还将持续;气温的突变发生在1997年,而年降水量的突变发生在1991年,二者的突变时间不同步。[结论]以气温升高降水减少为主要特征的气候变化将对平凉黄土高原沟壑区农业生产产生不利影响。  相似文献   

黄土丘陵区沟谷地植被恢复群落特征研究   总被引：4，自引：1，他引：3  

张健  刘国彬  许明祥  王兵  王翼龙  齐智军 《草地学报》2008,16(5):485-490

对黄土丘陵区2个不同沟向沟谷地植被群落特征进行样方调查,统计分析沟谷地植物物种频度和植物种群相似系数。调查共记录植物81种,隶属31个科,菊科、禾本科和豆科物种分别占物种总数的19.75%、16.05%和14.81%;封禁20年左右的沟谷地植被演替表现出良性演替的趋势;目前该沟谷地植物群落生活型中草本植物仍占主导地位,尤其是多年生草本,而灌乔生活型植物也已占有重要地位。灌乔木树种对植物群落多样性和结构等方面具有重要影响,沟谷地植被分布的斑块格局较为突出,不同沟向沟谷地的灌乔植物种的重要值构成格局存在一定差异,南北沟向较西东沟向分配均匀;沟向不同,沟谷地所形成的植被种群相似性具有一定差异,主要是由于受到一些伴生种和罕见种的影响。此研究对掌握该地形植被演替方向,明确植被恢复任务和目标具有一定意义。  相似文献   

黄土丘陵沟壑区坡向对产流产沙影响的研究   总被引：1，自引：0，他引：1  

方海燕  蔡强国  李秋艳 《中国水土保持》2011,(5):39-42

坡向是坡面产流产沙的重要影响因素。以黄土高原岔巴沟流域新庄径流试验场阴坡和阳坡2个径流小区为研究对象,根据发生在阳坡农地和阴坡荒坡地上的11场降雨事件,对阳坡和阴坡上的产流产沙状况进行了对比分析。结果表明:2个径流小区的产流产沙差异显著。阳坡农地由于太阳辐射量和温度高于阴坡,土壤含水量较低,同时表层土壤扰动较阴坡荒坡地大,土壤孔隙度高,使其产流能力小于阴坡;阳坡土质疏松,沙量来源充沛,径流含沙量和侵蚀模数大于阴坡的概率分别在88%和85%以上。降雨强度对阴坡、阳坡产流产沙差异的影响显著,阴坡和阳坡的产流产沙均在0.05的概率水平上受平均降雨强度的显著影响,表现出平均降雨强度越大阴坡、阳坡产流产沙差异越明显的特征,而降雨量对阴坡、阳坡产流产沙差异的影响并不明显,这是黄土高原超渗产流的特征之一。  相似文献   

Using LiDAR data to map gullies and headwater streams under forest canopy: South Carolina,USA   总被引：1，自引：0，他引：1  

L. Allan James  Darrell Glen Watson  William F. Hansen 《CATENA》2007

The southeastern Piedmont of the USA was severely gullied during the early 20th century. A thick canopy established by reforestation in many areas now inhibits the identification or mapping of gullies by aerial photography or other conventional remote sensing methods. An Airborne Laser-Scanning (ALS or LiDAR) mapping mission flown for the U.S. Forest Service in April, 2004 acquired bare-Earth topographic data. This paper tests the ability of the ALS topographic data to identify headwater channels and gullies for two branching gully systems in forested areas and to extract gully morphologic information. Comparisons are made with field traverses using differential GPS and reference cross sections measured by leveling surveys. At the gully network scale, LiDAR data provide accurate maps – the best available – with robust detection of small gullies except where they are narrow or parallel and closely spaced. Errors in mapping channel location and network topological connectivity under forest canopy increase with attempts to identify smaller features such as large rills. The ability of LiDAR data to map gullies and channels in a forested landscape should improve channel-network maps and topological models. At the gully reach scale, attempts to use LiDAR data to extract gully cross-section morphologic information under forest canopy were less successful due to systematic underestimation of gully depths and overestimation of gully top widths. Limited morphologic accuracy of the data set at this scale may be due to low bare-Earth point densities, shadowing of gully bottoms, and filtering of topographic discontinuities during post-processing. The ALS data used in this study are not suitable for detailed morphometric analysis or subtle change detection to monitor gullies or develop sediment budgets. Data collection may be improved by orienting flights over gullies and with increased point densities through improved scanner technology or better filtering and software capabilities to differentiate between vegetation and ground surfaces.  相似文献