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1.
Rill and gully development during an extreme winter runoff event in Norway   总被引：1，自引：0，他引：1  
Lillian ygarden 《CATENA》2003,50(2-4):217-242
Erosion on agricultural fields in Norway has earlier been reported to be mainly sheet and minor rill erosion. Exceptional rainfall events during January and February (230% of 30 years monthly mean) in 1990 led to extreme runoff and widespread erosion also on areas normally not considered to have a high erosion risk. This study presents the results of a field survey in three counties where rills and ephemeral gullies were measured after this event. Shifting weather conditions with freezing and thawing had given frozen subsoil. Topsoil conditions varied from ice- and snow-covered surface to thawed surface with frozen subsoil. In one of the areas with a high clay content, only the upper topsoil layer was unfrozen during this event. Extended sheet erosion and smaller rills occurred. In the southernmost locations, more of the topsoil profile was unfrozen. Combined with a high silt/sand content, more severe rilling and ephemeral gullies developed. Gullies developed down to the depth of the drainpipes in all locations. This erosion equals soil losses of more than 100 tons ha−1 or 8–9 mm soil lost from the entire field area. Different mechanisms for gully development were registered. Gullies developed as enlarged rills with headward migration and sidewall sloughing. Knickpoints in the slope could also lead to gully development. Concentrated water flow entering the field from farmyards, roads, neighbouring fields and woods could be the starting point for uncontrolled rilling and ephemeral gullying. The combination of frozen subsoil, saturated soil with low strength and intense rainfall led to gully development also on areas with gentle slopes, especially sandy soils. Management practices like crop cover, tillage and lack of surface water control highly influenced the development of gullies.  相似文献   

2.
Gully erosion reduces agricultural productivity by destroying valuable land resources, increases sediment concentrations, reduces water quality, and fills up reservoirs. Gully rehabilitation has proven to be challenging especially in the high‐rainfall areas of the Ethiopian Highlands and has therefore had limited success. This paper describes a successful low‐cost gully rehabilitation effort with community participation in the Birr watershed in the Blue Nile basin that begun in early 2013. Initially, farmers were reluctant to participate for religious reasons, but with the aid of local priests and respected elders, community discussions, and a visit to a rehabilitated gully, a consensus was reached to rehabilitate a 0·71‐ha upland gully. The rehabilitation measures consisted of regrading the gully head at a 45° slope, constructing low‐cost check dams from locally available materials, and planting Pennisetum purpureum grass and Sesbania sesban. At the end of the first post‐implementation rainy season, 2,200 tons of soil was conserved by the constructed check dams and newly planted vegetation, compared with soil losses of 680 and 560 tons in two untreated, nearby gullies. In 2014, an additional 3,100 tons of soil was conserved. In 2013, the marginal rate of return (MRR) on the gully rehabilitation investment was 2·6 based on the value of increased forage production alone. When we include trapped soil nutrient values, the rehabilitation MRR was increased to 10. Although these numbers are impressive, the best proof of the success was that farmers on their own initiative rehabilitated an additional five gullies in 2014. Copyright © 2015 John Wiley & Sons, Ltd.  相似文献   

3.
元谋干热河谷冲沟形态特征及其成因   总被引：8，自引：0，他引：8  
元谋干热河谷冲沟极为发育,发达的冲沟网络不但蚕食耕地,还产生大量泥沙,并加剧面蚀的发育发展,加速土地退化进程.在干热河谷开展冲沟侵蚀研究对于该区经济的可持续发展及江河泥沙的控制意义深远.采用野外实地调查、文献资料综合分析的方法,对元谋干热河谷冲沟形态特征及其成因进行了研究.结果表明:1)元谋干热河谷冲沟具有“沟壁陡立、沟谷深壑、活跃沟头常呈上凸下凹状”等形态特征;2)岩层结构、气候降雨、土壤属性是导致该区冲沟发育的主要原因.在此基础上指出,未来干热河谷冲沟侵蚀研究重点应集中于冲沟形态监测方法、冲沟发育过程及机制、冲沟产沙效应及人类活动对冲沟发育的影响等方面.  相似文献   

4.
Ephemeral gully erosion in northwestern Spain   总被引：2，自引：0，他引：2  
This study aimed to describe types of ephemeral gullies and to determine their origin, evolution and importance as sediment sources in A Coruña province (northwest Spain). Ephemeral gullies and/or rills have been measured in a representative sample of medium-textured soils, most prone to crusting, developed over basic schist. This sample consisted of 11 small sites, ranging from 0.63 to 7.34 ha. A case study of concentrated (rill+gully) erosion in a 0.47-ha catchment with coarse-textured soils developed over granite was also reported. The mean slope of the sites studied ranged from 6.1% to 16.8%. Main periods when soil surface was poorly covered were late spring (maize seedbeds) and late autumn–early winter (grassland and winter cereal seedbeds). Case studies where fields were left bare in winter were also investigated. Soil incision and channel formation were observed even with relatively low rainfall intensities when the soil surface was sealed, but also after a single short intense rainfall event on recently tilled surfaces. Concentrated erosion took place mainly on seedbeds and newly tilled soils in late spring and by autumn or early winter, but gullies also appeared in other seasons when the soil surface was left bare. In most of the cases studied, ephemeral gully erosion caused significant soil losses, ranging between 2 and 5 m3/ha for a single season to locally, over 25 m3/ha. Gully development was significantly affected by agricultural operations, such as lineal elements often acting as initial axes of concentrated erosion. Main gullies tended to reappear at the same position.  相似文献   

5.
Gully erosion and environmental change: importance and research needs   总被引：29，自引：0，他引：29  
Assessing the impacts of climatic and, in particular, land use changes on rates of soil erosion by water is the objective of many national and international research projects. However, over the last decades, most research dealing with soil erosion by water has concentrated on sheet (interrill) and rill erosion processes operating at the (runoff) plot scale. Relatively few studies have been conducted on gully erosion operating at larger spatial scales.Recent studies indicate that (1) gully erosion represents an important sediment source in a range of environments and (2) gullies are effective links for transferring runoff and sediment from uplands to valley bottoms and permanent channels where they aggravate off site effects of water erosion. In other words, once gullies develop, they increase the connectivity in the landscape. Many cases of damage (sediment and chemical) to watercourses and properties by runoff from agricultural land relate to (ephemeral) gullying. Consequently, there is a need for monitoring, experimental and modelling studies of gully erosion as a basis for predicting the effects of environmental change (climatic and land use changes) on gully erosion rates.In this respect, various research questions can be identified. The most important ones are:
What is the contribution of gully erosion to overall soil loss and sediment production at various temporal and spatial scales and under different climatic and land use conditions?
What are appropriate measuring techniques for monitoring and experimental studies of the initiation and development of various gully types at various temporal and spatial scales?
Can we identify critical thresholds for the initiation, development and infilling of gullies in different environments in terms of flow hydraulics, rain, topography, soils and land use?
How does gully erosion interact with hydrological processes as well as with other soil degradation processes?
What are appropriate models of gully erosion, capable of predicting (a) erosion rates at various temporal and spatial scales and (b) the impact of gully development on hydrology, sediment yield and landscape evolution?
What are efficient gully prevention and gully control measures? What can be learned from failures and successes of gully erosion control programmes?
These questions need to be answered first if we want to improve our insights into the impacts of environmental change on gully erosion. This paper highlights some of these issues by reviewing recent examples taken from various environments.  相似文献   

6.
基于Google Earth影像的横断山区沟蚀及侵蚀沟类型调查研究   总被引：2，自引：0，他引：2  
[目的]探讨横断山区侵蚀沟的类型、分布特征及影响因素,为研究沟蚀对横断山区土壤侵蚀及土地退化的影响提供依据。[方法]基于Google Earth高清影像结合GIS的方法,基于可见性的基本原则,对横断山区开展侵蚀沟的抽样调查。共布设调查单元2 242个,每个单元尺寸1km×1km。[结果]共有571个调查单元发现有侵蚀沟分布,占调查单元总数的25.5%,平均沟壑密度为2.20km/km2。沟蚀在海拔低于1 500m的区域发育显著,沟壑密度随坡度增加而增长,与年降雨相关性较弱。草地是沟蚀发育的主要土地利用类型,燥红土的沟蚀分布率及平均沟壑密度显著高于其他土壤类型。通过总结国内外现有的侵蚀沟分类体系及其异同,结合调查结果,判定该次调查的横断山区侵蚀沟类型主要为切沟和冲沟(包括有泥石流事件的冲沟)。[结论]横断山区切沟和冲沟分布广泛,发育强烈,其分布受海拔、坡度、土地利用及土壤类型等因素的影响较为显著。  相似文献   

7.
As most mountains in tropical and subtropical zones, the Western Sierra Madre suffers active present erosion, which may create some constraints to the social and economic development in the area.The objectives of this study of soil degradation in the Western Sierra Madre, are to determine the respective roles of gully and sheet erosion. This research is based on field observations, field measurements of runoff and, soil losses at the plot, as well as the watershed scales as an analysis of an exhaustive census of the few gullies located in an experimental area.Measured soil losses in the Western Sierra Madre are high although there are few gullies. Most of the sediment yield seems to originate in widespread degraded areas where stoniness is the main evidence of a previous stage of erosion. Previously overgrazing and deforestation were determined as the factors of the appearance of new soil surface characteristics which explain the high runoff and sediment productions. The soil compacted by cattle trampling reduces infiltration. The decrease of the vegetation cover triggers a rise in the splash effect and thus, a soil sealing.These processes induce an increase in runoff and soil losses. The main erosion type has been described as sheet erosion: it is characterised by the removal of fine soil particles and the remains of gravels, pebbles and blocks, which constitute a pavement on the soil. Gullies generally appear on the bottom of wide valleys and depressions, where soils are thick. It is shown that sheet erosion is two orders of magnitude higher than gully erosion at the hillslope scale.Due to the spatial distribution of land use and the geological context such as the heavily degraded areas close to the main rivers, the reduction of runoff and soil loss rates within the extension of a considered area, commonly observed in hydrology, only applies up to the elementary catchments scale (1 to 50 km2). Above this area, runoff coefficient and soil loss rates increase.  相似文献   

8.
切沟侵蚀是黄土高原丘陵沟壑区水土流失的重要形式之一，然而极端暴雨条件下不同土地利用类型坡面切沟侵蚀研究还鲜见报道。该研究以陕北2017年"7·26"特大暴雨为例，研究了岔巴沟流域3种土地利用类型（农地、休闲地和撂荒地）坡面切沟发育形态特征及体积估算模型。结果表明：1）农地、休闲地和撂荒地切沟长度分布在20 m内的占比分别为55.6%、34.8%和44.8%；农地切沟平均深度为110 cm，分别比休闲地和撂荒地高18.3%、19.2%；农地和休闲地切沟平均宽深比分别为0.87和0.84，横断面呈"宽-浅型"，而撂荒地切沟呈"方型"（宽深比1.01）。2）撂荒地切沟侵蚀体积分别比农地和休闲地减少47.8%和28.3%，表明植被恢复有效地削弱了极端暴雨作用下的切沟侵蚀。3）农地切沟不同坡段侵蚀体积由高到低为下坡、上坡、中坡，而休闲地和撂荒地切沟侵蚀体积沿坡长方向呈递增趋势；3种土地利用类型切沟在上坡段的沟岸拓宽速率大于下切速率，中下坡则相反。4）农地、休闲地和撂荒地切沟侵蚀体积均与切沟长度、横断面面积呈极显著幂函数关系（P<0.001），横断面面积是切沟体积估算更为有效的参数。研究结果可为黄土高原丘陵沟壑区不同土地利用类型坡面切沟侵蚀体积估算及其防治提供重要依据。  相似文献   

9.
Y. Avni   《CATENA》2005,63(2-3):185
Gully incision has been eroding the alluvial sediments and loess soils deposited and developed along the valleys in the arid and semiarid regions of Israel. This phenomenon is critical in the arid regions of the Negev Highlands where the agricultural fields, the main floral biomass and the areas which have the highest grazing value, are limited to narrow valleys filled with redeposited loessial sediments. The headcut migration and gully development in the region were studied between 1990 and 2001 in three representative drainage basins (Zipporim, Revivim and Sekher). During flood events, the runoff penetrates the alluvial cover of the valleys, forming vertical headcuts, which gradually retreat up the valley. The runoff is channeled into narrow gullies, preventing the floodwater from spreading over the whole width of the valley. The change in irrigation efficiency along the valleys is reflected in a sharp estimated drop of 70–90% in the floral biomass, causing the reduction of the range value by 83–99%. During the monitoring time interval (1990–2001), the linear gully retreat in the study area ranged between 12.3 and 250 m an average rate of 1.12–22.7 m year− 1 for each gully head. The process is accompanied by erosion of soil, which has high agricultural and range value. The total soil losses in these sites ranged between 800 and 9000 m3 at an average rate of 81–818 m3 year− 1 for each gully head, which is equivalent to 121–1227 Mg year− 1. During the monitoring period, approximately 0.11–0.87 ha of land lost its agricultural and range value in each basin under study, at an average rate of 0.01–0.079 ha year− 1. Since the Byzantine period (1400 BP), approximately 6.5 ha, which is 10% of the land that had high agricultural and range value in the Zipporim valley, lost its value due to gully erosion. No recovery effects of the gully channels were found in the nearby region. The soil erosion is generated by a long-term natural dynamic change in the soil / rock ratio evolving within the drainage basins through time since the termination of the last glacial phase. The loessic sediments, originally deposited within the drainage basins during the late Pleistocene glacial stage, are being removed under the present Holocene climate in several erosion stages. This ongoing phenomenon is causing degradation of soil and biomass and is severely reducing the agricultural and range potential of the region. These parameters indicate that an ongoing process of desertification is active in the arid environment of the Negev Highlands, and is advancing in proportion to the headcut retreat rates in the region. The soil erosion and headcut retreat have been active in the Negev Highlands for the last few millennia. If these processes continue in the future, the Negev Highlands region will lose its agricultural potential within a few millennia. However, the fact that the ancient inhabitants of the region implemented successful long-term land conservation techniques already 3000 years ago, implies that a sustainable land management policy can be adapted to the Negev Highlands, as well as to other semi-arid regions in the Middle East.  相似文献   

10.
Gully erosion often indicates extreme land degradation. In the highlands of Ethiopia, wide and deep gullies are common features, significantly affecting land used for agriculture. However, little action is being taken to address the problem. Where rehabilitation actions in Ethiopia are taking place, they are rarely studied by financially quantifying their costs and benefits. Therefore, this study developed methods of quantifying gully erosion costs and rehabilitation costs and benefits by considering the soil components of four model rehabilitated gullies in Ethiopia. Data were obtained from a physical survey supported by secondary information from relevant agricultural offices. Quantification was achieved by monetizing gully erosion cost through yield loss and gully rehabilitation calculations according to expenditure, while rehabilitation benefits were obtained by monetizing estimated deposited soil nutrients using fertilizer prices. Cost‐benefit values show that investment in gully rehabilitation can be an economically viable proposition in some instances. Stakeholders involved in gully rehabilitation should continue to invest in appropriate techniques of gully rehabilitation and management to ensure continued benefits from rehabilitated gullies and use of surrounding farmlands. Copyright © 2010 John Wiley & Sons, Ltd.  相似文献   

11.
According to the United Nations Convention to Combat Desertification (UNCCD), soil erosion is one of the main causes of desertification in the Northern Mediterranean. Recently, the role of channelled erosion in sediment delivery has been underlined by several studies. The aim of this paper is to describe a simplified experimental methodology settled up for studying the relationships between gully erosion and land use.The experimental site, which is wide about 720 ha, is located in a hilly area threatened by desertification in Central Eastern Sardinia (Italy). This area is characterised by irregular morphology with steep slopes, where agropastoral activities, particularly tillage with heavy machinery and overgrazing, are causing severe soil erosion and compromising agricultural productivity. Previous studies carried out in the same area highlighted the need to quantify and monitor soil erosion in order to outline management guidelines for farmers. In this study, an integrated methodology that uses aerial photographs and field surveys was applied to inventory the gullies of the area. The degree of activity and morphological characteristics of gullies were assessed in the field by measuring the position and shape of gully heads, and their width and depth. Total gully volume was also estimated. Relationships among distribution, density and morphological characteristics of gullies, and geomorphological features, land use and land use historical dynamics of the area have been studied. The results show the very significant impact of agricultural activities on gully activity and density.  相似文献   

12.
土壤理化及力学性质对干热河谷台地边坡沟蚀发育的影响   总被引：4，自引：2，他引：2  
金沙江干热河谷土地整理台地边坡沟蚀发育严重,水土流失强烈,高投入的土地整理工程效益难以发挥,严重威胁着该区的生态安全和社会经济发展。为查明干热河谷土地整理台地边坡沟蚀发育关键影响因子、防治台地边坡沟蚀发育,该研究采用野外实地测量法和实验室测定的方法,研究了干热河谷土地整理台地边坡的沟蚀发育形态特征,系统分析了土壤理化性质和力学性质对台地边坡沟蚀发育形态特征的影响。结果表明:1)非毛管孔隙度是影响台地边坡沟蚀发育形态特征的主要指标,但非毛管孔隙度对台地边坡沟蚀发育宽度、深度、截面积、密度以及割裂度的影响形式和影响程度有较大差异。2)抗剪强度仅对台地边坡沟道深度和截面积影响显著,而对沟道宽度、密度和割裂度的影响甚微。3)分散率对台地边坡沟道宽度和割裂度的影响较为明显,对沟道深度、截面积和密度无显著影响。4)沟道宽度和密度均主要受非毛管孔隙度控制,割裂度受分散率的影响最大,但沟道深度和沟道截面积受土壤性质的影响相对较弱。  相似文献   

13.
基于GPS与GIS 技术的长江上游山地冲沟的分布特征研究   总被引：5，自引：2，他引：5  
长江上游山地生态环境十分脆弱，冲沟系统广泛分布，但对该区冲沟的发生演变一直缺乏定量研究数据。以西昌长山岭地区为对象，应用RTK-GPS对该区冲沟系统进行测量，建立数字高程模型（DEM）；同时基于GIS技术，探讨了从DEM上提取冲沟系统的方法，并以实测冲沟系统为依据，对所提取的冲沟系统的精度进行了对比分析。结果表明，利用DEM提取冲沟系统是一种快速、有效的方法。与此同时，分析了长江上游地区山地冲沟系统的分布特征，结果表明，小流域的沟壑密度为46．7m／hm^2，冲沟侵蚀速率高达191．9t／（hm^2．a），小流域内的土壤侵蚀为极强度土壤侵蚀，以控制冲沟侵蚀为主的水土保持措施，是该地区生态环境建设中值得重视的关键问题。  相似文献   

14.
Gully development in the Moldavian Plateau of Romania   总被引：1，自引：0，他引：1  
Ion Ionita   《CATENA》2006,68(2-3):133
Gully erosion has been recognized as an important environmental threat in the Moldavian Plateau of Eastern Romania. The main objective of this study was to define the process-based gully development by providing quantitative information from long-term field measurements in small catchments.Three main areas of monitoring gullies were explored: aerial photographs of flights in 1960 and 1970, classical leveling and repeated survey through a particular close stakes grid after 1980. The Caesium-137 technique has been used effectively in the areas of deposition of gully sediments to obtain reliable information on dating specific levels of sediments and to provide chronological measures of gully development.Most of the discontinuous gullies exhibit both proper gullying, mainly if not exclusively by gully head advance, and aggradation of the gully basin floor. Results indicated that the mean gully head retreat was 0.92 m year− 1 and the mean areal gully growth was 17.0 m2 year− 1. Both values indicate a slow erosion rate for this area. The average annual regime of gullying is pulsatory, one that is best described by great fluctuations. Conventional measurements on sedimentation over the period 1987–1997 indicate a higher rate of aggradation in the upper half of the gully floor. Information on the Caesium-137 depth profile was used to provide estimates of a mean sedimentation rate of 4.4 cm year− 1 over the period 1963–1996 and 2.5 cm year− 1 after 1986 for the short successive discontinuous gullies. A new classification of the discontinuous gullies based on two criteria, respectively, the field patterns and the rate of aggradation within the gully basin floor was established.For continuous gullies, linear gully head retreat, areal gully growth and eroded material rates were quantified for three periods (1961–1970, 1971–1980 and 1981–1990). Results indicate that gully erosion has decreased since 1960. This gullying decline is due to the rainfall distribution, and the increased influence of soil conservation practices. The mean gully head retreat of 12.5 m year− 1 between 1961–1990 was accompanied by a mean areal gully growth of 366.8 m2 year− 1 and a mean erosion rate of 4168 t year− 1. As with discontinuous gullies, continuous gullies showed pulsatory development.The critical period for gullying over 1981–1996 covers 4 months from Mid March to Mid July in an area with mean annual precipitation around 500 mm. Another main finding of this 16-year stationary monitoring was that 57% of the total gullying occurred during the cold season, with the remainder during the warm season. Of the total gully growth, 66% results from only four years (1981, 1988, 1991 and 1996), when a greater amount of precipitation fell.  相似文献   

15.
Ex-post evaluation of erosion control measures in southern Mali   总被引：3，自引：0，他引：3  
As part of an impact study of a soil and water conservation (SWC) project in southern Mali, the effect of erosion control measures on soil erosion was evaluated. In one village, a baseline situation from 1988 was compared with the situation in 2003, after farmers had installed stone rows, live fences and grass strips, and had started cultivating across to the slope. This comparison showed a spectacular decrease in gully volume in cultivated fields of 87%, from 58 to 8 m3 ha−1. Estimated annual soil loss decreased with 77% from 42 to 10 t ha−1 year−1. However, baseline data on erosion gullies were not available for other villages. In the absence of baseline data, a simple ‘with–without’ comparison does not allow a correct evaluation because farmers install erosion control measures especially in fields with more erosion. Two alternative methods were used: a reconstructed baseline and a virtual time series. Using the reconstructed baseline, looking not only at active gullies but also at (partly) reclaimed gullies, we concluded that line interventions, gully interventions, and a combination of both, reduced the proportion of active gullies by 48%, 47% and 70%, respectively. Using a virtual time series, comparing erosion in fields with erosion control measures installed in different years, we concluded that erosion gradually decreased by 50% during the 3 years after installation of erosion control measures. In a separate study, we found a positive effect of gully interventions and sowing across to the slope in reducing sheet erosion. A reduction of the slope of the sowing direction by 1% reduced the cover of runoff deposit of coarse sand with 8%. Although a documented baseline is preferred, both a reconstructed baseline and a virtual time series are useful tools and make ex-post evaluations more relevant than a simple with–without comparison.  相似文献   

16.
The European Commission's Thematic Strategy for Soil Protection (COM(2012)46) identified soil erosion as an important threat to European Union's (EU) soil resources. Gully erosion is an important but hitherto poorly understood component of this threat. Here we present the results of an unprecedented attempt to monitor the occurrence of gully erosion across the EU and UK. We integrate a soil erosion module into the 2018 LUCAS Topsoil Survey, which was conducted to monitor the soil health status across the EU and to support actions to prevent soil degradation. We discuss and explore opportunities to further improve this method. The 2018 LUCAS Topsoil Survey consisted of soil sampling (0–20 cm depth) and erosion observations conducted in ca. 10% (n = 24,759) of the 238,077 Land Use/Cover Area frame Survey (LUCAS) 2018 in-field survey sites. Gully erosion channels were detected for ca. 1% (211 sites) of the visited LUCAS Topsoil sites. Commission (false positives, 2.5%) and omission errors (false negatives, 5.6%) were found to be low and at a level that could not compromise the representativeness of the gully erosion survey. Overall, the findings indicate that the tested 2018 LUCAS Topsoil in-field gully erosion monitoring system is effective for detecting the incidence of gully erosion. The morphogenesis of the mapped gullies suggests that the approach is an effective tool to map permanent gullies, whereas it appears less effective to detect short-lived forms like ephemeral gullies. Spatial patterns emerging from the LUCAS Topsoil field observations provide new insights on typical gully formation sites across the EU and UK. This can help to design further targeted research activities. An extension of this approach to all LUCAS sites of 2022 would significantly enhance our understanding of the geographical distribution of gully erosion processes across the EU. Repeated every three years, LUCAS soil erosion surveys would contribute to assess the state of gully erosion in the EU over time. It will also enable monitoring and eventually predicting the dynamics of gully erosion. Data collected were part of the publicly available Gully Erosion LUCAS visual assessment (GE-LUCAS v1.0) inventory.  相似文献   

17.
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   

18.
半干旱黄土丘陵沟壑区沟道侵蚀特征研究   总被引：6，自引：0，他引：6  
利用遥感、地理信息技术和数理统计方法,选择山西省吕梁市王家沟流域为典型区域,系统分析了半干旱黄土丘陵沟壑区沟道侵蚀特征。研究结果表明:在王家沟流域内共有沟道718条,其中冲沟109条,切沟286条,干沟302条及河沟21条。这4类沟道的发育特征和空间分布特征存在巨大差异;沟道侵蚀是王家沟流域内土壤侵蚀的主要形式,沟道侵蚀面积占总侵蚀面积的56.19%;流域内不同坡度范围内土壤侵蚀强度与沟道类型存在紧密联系。同时,人为因素也对黄土丘陵沟壑区的沟道侵蚀具有重要的影响。  相似文献   

19.
东北黑土区沟道侵蚀现状及其防治对策   总被引：2，自引：1，他引：2       下载免费PDF全文
沟道侵蚀是土地退化最严重的表现形式,东北黑土区是中国除黄土高原外沟道侵蚀最为严重的区域,沟道侵蚀严重威胁东北区域农业生产和生态环境。该研究基于多年的研究积累,结合国家侵蚀沟治理专项调查和国家重点研发计划项目研究成果以及已有文献,系统总结归纳了东北黑土区沟道侵蚀特征、发展演变趋势及其危害;梳理出现有侵蚀沟治理措施的成功经验及失败教训,凝练提出区域侵蚀沟防治目标及4种主要侵蚀沟治理模式,并给出了适用范围及条件;同时提出了新时代东北黑土区侵蚀沟防治对策建议。该研究为区域现代农业发展和生态文明建设决策以及沟道侵蚀治理工程的实施提供了科技支撑。  相似文献   

20.
Milo Stankoviansky 《CATENA》2003,51(3-4):223-239
The Myjava Hill Land is part of the area with the highest density of permanent gullies in Slovakia (up to 11 km km−2). Gullies are often 10–15 m deep, and occasionally extend >20 m. The pattern and density of gullies have been controlled primarily by the original land use from the pre-collectivization era. Old maps and historical sources indicate two to three periods of gully formation. The central part of the area, settled between the second half of the 16th and the beginning of the 19th centuries, was affected by gully formation in two periods, the first between the end of the 16th century and the 1730s and the second roughly between the 1780s and 1840s. Marginal parts of the study area to the west and south–west, which were settled earlier, may have been affected by disastrous gullying as early as the 14th century. Gullies were formed during periods of extensive forest clearance and expansion of farmland, but the triggering mechanism of gullying was extreme rainfalls during the Little Ice Age. However, periods of gully formation in the Myjava Hill Land were not fully synchronous with the well-known phases of gullying in other central European countries.  相似文献   

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