首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献，搜索用时 78 毫秒
1.
Monitoring of runoff and erosion in farmers' fields and their impacts gives a better understanding of erosion. However, it is rare that monitoring at frequent intervals is done over a prolonged period. A part of the upper Wissey catchment in central Norfolk, eastern England was monitored for 10 years to assess the extent and frequency of erosion and runoff, their causes and impacts. Surface wash occurred more widely and more frequently than expected. Runoff and erosion took place a number of times in a year in a range of autumn‐ and spring‐sown crops, and occurred dominantly down tractor wheelings or ruts left after harvesting potatoes or sugar beet under wet conditions. Over 10 years erosion affected about half the 105 fields monitored, often more than once. Erosion was more extensive in autumn‐sown cereal fields, but often more severe and with greater off‐field effects, for example muddy flooding of roads from spring‐sown late harvested crops such as potatoes and sugar beet. Runoff from outdoor pig fields also flooded roads and houses. This study confirms other studies of the extent, frequency and severity of erosion in Britain, that rill erosion does not occur in every field in the landscape, that in the main, fields do not erode frequently and rates of erosion are generally small. Runoff and erosion within a field took place more frequently than had been suspected. Compaction and destruction of topsoil structure by machinery especially at harvest, or by outdoor pigs, is important in initiating runoff. Rates of erosion were generally very low and will not affect soil productivity adversely over the short‐term. However, flooding of roads and property, and especially pollution of water courses by sediment, nutrients and pesticides are important off‐field impacts and are the primary reason, over the short‐term, for mitigating runoff and erosion. Monitoring such as this sheds light on the problems of modelling to predict risk of erosion based on erosion rates. Copyright © 2017 John Wiley & Sons, Ltd.  相似文献   

2.
I. INTRODUCTIONThe Yellow River is a heavily sediment--laden river. The sediment load of the Yellow River ranks the first in the world while its annual runoff is only of medium size. Toharness the river, it is necessary to build reservoirs for regulating runoff to meet the demands of economic development. Since the founding of PRC in 1949, I S4 large and medium--sized reservoirs have been constructed on the main stem and the tributaries with atotal storage capacity of 84.5 billion m3.…  相似文献   

3.
The impact of vegetated filter strips (VFS) on sediment removal from runoff has been studied extensively in recent years. Vegetation is believed to increase water infiltration and decrease water turbulence thus enhancing sediment deposition within filter media. In the study reported here, field experiments have been conducted to examine the efficiency of vegetated filter strips for sediment removal from cropland runoff. Twenty filters with varying length, slope and vegetated cover were used under simulated runoff conditions with an average sediment concentration of 2700 mg/L. The filters were 2, 5, 10 and 15 m long with a slope of 2·3 and 5% and three types of vegetation. Three other strips with bare soil were used as a control. The experimental results showed that the average sediment trapping efficiency of all filters was 84% and ranging from 68% in a 2‐m filter to as high as 98% in a 15‐m long filter compared with only 25% for the control. The length of filter has been found to be the predominant factor affecting sediment deposition in VFS up to 10 m. Increasing filter length to 15 m did not improve sediment trapping efficiency under the present experimental conditions. The rate of incoming flow and vegetation cover percentage has a secondary effect on sediment deposition in VFS. Copyright © 2004 John Wiley & Sons, Ltd.  相似文献   

4.
Changxing Shi 《水文研究》2016,30(2):232-244
Using hydrological and sediment data, this study investigated decadal trends in sediment erosion/deposition in the Inner Mongolia reach of the upper Yellow River. The calculated yearly sediment erosion/deposition show that the reach was dominated by aggradation, degradation, and aggradation successively in three periods with the years around 1961 and 1987 as break‐points. By constructing relations between water discharge and sediment load, the contributions of key factors to the changes in sediment erosion/deposition in the reach were quantified. Results show that the sediment retention behind the main stem dams, the increase of natural runoff, and the decrease of sediment inputs from tributaries and upstream watershed were the main factors causing the transition from aggradation during 1955–1961 to degradation during 1962–1987. The reduction of natural runoff, the decrease of sediment retention behind dams, and the rise of sediment supply from tributaries were the key causes of the reversal from degradation in 1962–1987 to aggradation in 1988–2003. Water diversion has played an important role in the long‐term aggradation of the Inner Mongolia reach. The main stem dams had functioned to alleviate siltation after 1961, but their effects on siltation reduction had been gradually diminishing since the 1990s. Copyright © 2015 John Wiley & Sons, Ltd.  相似文献   

5.
In arid and semi‐arid rangeland environments, an accurate understanding of runoff generation and sediment transport processes is key to developing effective management actions and addressing ecosystem response to changes. Yet, many primary processes (namely sheet and splash and concentrated flow erosion, as well as deposition) are still poorly understood due to a historic lack of measurement techniques capable of parsing total soil loss into these primary processes. Current knowledge gaps can be addressed by combining traditional erosion and runoff measurement techniques with image‐based three‐dimensional (3D) soil surface reconstructions. In this study, data (hydrology, erosion and high‐resolution surface microtopography changes) from rainfall simulation experiments on 24 plots in saline rangelands communities of the Upper Colorado River Basin were used to improve understanding on various sediment transport processes. A series of surface change metrics were developed to quantify and characterize various erosion and transport processes (e.g. plot‐wide versus concentrated flow detachment and deposition) and were related to hydrology and biotic and abiotic land surface characteristics. In general, erosivity controlled detachment and transport processes while factors modulating surface roughness such as vegetation controlled deposition. The extent of the channel network was a positive function of slope, discharge and vegetation. Vegetation may deflect runoff in many flow paths but promoted deposition. From a management perspective, this study suggests that effective runoff soil and salt load reduction strategies should aim to promote deposition of transported sediments rather than reducing detachment which might not be feasible in these resource‐limited environments. Copyright © 2016 John Wiley & Sons, Ltd.  相似文献   

6.
In this study we analyzed runoff and sediment yield from land under various traditional and current land uses in Mediterranean mountain areas, using long‐term data from an experimental station in the Aísa Valley, Central Spanish Pyrenees. Monitoring at this station has provided 20 years of data that can help explain the hydrological and geomorphological changes that have been observed at larger spatial scales, and also the changes that have occurred to some of the most characteristic landscapes of the Mediterranean middle mountains. In spite of the problems associated with the use of small experimental plots, the results obtained are consistent with other studies in the Mediterranean region, and confirm the strong influence of land use changes on runoff generation and sediment yield. The results indicate that: (i) cereal cultivation on steep slopes (both alternating cereal cultivation and fallow on sloping fields and shifting agriculture on the steepest slopes) represents a major problem for soil conservation. This explains the occurrence throughout the Mediterranean mountains of many degraded hillslopes, which show evidence of sheet wash erosion, rilling, gullying and shallow landsliding; (ii) farmland abandonment has led to a marked reduction in runoff and sediment yield as a consequence of rapid plant recolonization, particularly by dense shrubs; (iii) the natural transformation of abandoned fields into grazing meadows has reduced runoff and sediment yield. Land use trends in the Mediterranean mountains are mainly characterized by generalized farmland abandonment and a decrease in livestock pressure. From a hydrological and geomorphological point of view the main consequences have been a reduction in overland flow from the hillslopes, and a reduction in sediment sources, with differences up to one order of magnitude in sediment yield from dense shrub cover and grazing meadow areas compared with areas under shifting agriculture. Copyright © 2012 John Wiley & Sons, Ltd.  相似文献   

7.
The European Soil Erosion Model (EUROSEM) is a dynamic distributed model, able to simulate sediment transport, erosion and deposition over the land surface by rill and interill processes in single storms for both individual fields and small catchments. Model output includes total runoff, total soil loss, the storm hydrograph and storm sediment graph. Compared with other erosion models, EUROSEM has explicit simulation of interill and rill flow; plant cover effects on interception and rainfall energy; rock fragment (stoniness) effects on infiltration, flow velocity and splash erosion; and changes in the shape and size of rill channels as a result of erosion and deposition. The transport capacity of runoff is modelled using relationships based on over 500 experimental observations of shallow surface flows. EUROSEM can be applied to smooth slope planes without rills, rilled surfaces and surfaces with furrows. Examples are given of model output and of the unique capabilities of dynamic erosion modelling in general. © 1998 John Wiley & Sons, Ltd.  相似文献   

8.
The Ganges-Brahmaputra-Meghna (GBM) delta plain within Bangladesh is one of the most vulnerable to relative sea level rise (RSLR) in the world especially under current anthropogenically modified (i.e., embanked) conditions. Tidal river management (TRM) as practiced in coastal regions of Bangladesh may provide an opportunity to combat RSLR by raising the land level through controlled sedimentation inside beels (depression within embanked polders) with re-opening of polders. To date, TRM has been applied to tide-dominated coastal regions, but the potential applicability of TRM for the beels within the polders of river-dominated and mixed flow (MF) regimes remains to be assessed. We apply a calibrated 2D numerical hydromorphodynamic model to quantify sediment deposition in a beel flooded through breaching of the polder dike under conditions of river-dominated, tide-dominated and MF regimes for different seasons and applying different regulation schemes for the flow into the beel. Simulation results show considerable seasonality in sediment deposition with largest deposition during the monsoon season. The potential of controlled flooding is highest in the tide-dominated region, where sediment accumulation can be up to 28 times higher than in the river-dominated region. Regulating flow into a beel increases trapping efficiency, but results in slightly lower total deposition than without regulation. We conclude that re-establishing flooding of the beel within the polder without regulating the flow into the beel through breaching of the polder dike is a promising strategy for the mixed and tide-dominated flow regions in the delta as the sediment accumulation can raise the land surface at a higher rate than RSLR and effective SLR (ESLR). In the more upstream river-dominated section of the delta, accumulation rates would be much lower, but the pressure of sea level rise on these areas is lower as well. Owing to the abundant availability of sediment, application of controlled flooding like TRM therefore provides an opportunity to counteract the impact of RSLR and ESLR by means of land raising, particularly along the tidal river reaches in the GBM delta.  相似文献   

9.
Observed rainfall and flow data from the Dongjiang River basin in humid southern China were used to investigate runoff changes during low‐flow and flooding periods and in annual flows over the past 45 years. We first applied the non‐parametric Mann–Kendall rank statistic method to analyze the change trend in precipitation, surface runoff and pan evaporation in those three periods. Findings showed that only the surface runoff in the low‐flow period increased significantly, which was due to a combination of increased precipitation and decreased pan evaporation. The Pettitt–Mann–Whitney statistical test results showed that 1973 and 1978 were the change points for the low‐flow period runoff in the Boluo sub‐catchment and in the Qilinzui sub‐catchment, respectively. Most importantly, we have developed a framework to separate the effects of climate change and human activities on the changes in surface runoff based on the back‐propagation artificial neural network (BP‐ANN) method from this research. Analyses from this study indicated that climate variabilities such as changes in precipitation and evaporation, and human activities such as reservoir operations, each accounted for about 50% of the runoff change in the low‐flow period in the study basin. Copyright © 2010 John Wiley & Sons, Ltd.  相似文献   

10.
The annual changes of sediment deposition-scour on the riverbed in the Sanhuhekou-Toudaoguai Reach of the upper Yellow River during the years 1952-2010 were investigated based on runoff and sediment transport observations from the Sanhuhekou and Toudaoguai hydrological stations. Multiple influencing factors such as reservoir operations, tributary inflows, as well as runoff and sediment loads from the Shidakongdui area were analyzed. The results show that even though the sediment loads from the major sources, the Shidakongdui area as well as the upstream tributaries such as the Qingshui River and the Zuli River have reduced especially since the 2000 s as a result of enhanced water-soil conservation measures and improvement of vegetation cover, the study reach was still generally in a status of cumulative aggradation. This is mainly due to the joint operations of the Liujiaxia Reservoir and the Longyangxia Reservoir, which significantly reduced the annual runoff and sediment loads at the Sanhuhekou Crosssection. The reservoirs also remarkably altered the summer flood characteristics of the study reach, inducing the shape of the annual flow curve changing from a 'single-peak' into a 'doublepeak'. These alternations sharply decreased the sediment transport capacity of flooding in the summer flood season which yields more than 90% of the sediment loads, leading to an unbalanced relation between the water and sediment. In addition, the estimated incoming sediment coefficient of the Sanhuhekou Crosssection ranged from 0.003 to 0.014 kg s/m~6, of which 0.004 kg s/m~6 was suggested as a rough critical value to determine the scour or deposition status of the study reach.  相似文献   

11.
Sediment load reduction in Chinese rivers   总被引：18，自引：9，他引：9  
In this paper, the changes in the annual runoff and sediment transport have been assessed by using the long term observation data from 10 gauging stations on 10 large rivers across China from far north to far south. It is found that the annual sediment yield has generally had a decreasing trend in the past half century. According to the changes in annual runoff and the sediment yield per area, rivers in China can be classified into the following three groups： 1） rivers with decreasing annual sediment transport and stable runoff; 2） rivers with both decreasing annual sediment transport and runoff and 3） rivers with greatly reduced annual sediment transport and decreasing annual runoff. The results indicate that, in all southern rivers （to the south of the Huaihe River including the Huaihe River）, there has been little change in average annual runoff but a dramatic decrease in annual sediment transport. In the northern rivers, however, both the annual sediment yield and the runoff show significant evidence of reduction. To further investigate the recent changes in annual runoff and sediment transport, the short-term observation data from these 10 gauging stations in the recent 10 years have been assessed. Results show that both the annual sediment transport and the runoff have decreased＂ significantly in the northern rivers in the past 10 years. Using the Yellow River at the Lijin Station as an example, the average annual runoff for the last 10 years is only 1/3 of the long term average value and the average annual sediment yield of the last 10 years is only 1/4 of the long term average value. More unusually, in the Yongding River the annual sediment yield has approached zero and the runoff has decreased significantly. In addition, the impacts of human activities on the changes in both runoff and sediment transport have been discussed.  相似文献   

12.
In recent years, high‐molecular‐weight anionic polyacrylamides (PAMs) have been tested on a variety of soils, primarily in temperate climates. However, little information is available regarding the effectiveness of PAM for preventing soil loss through runoff in tropical settings. Screening tests were performed using three negatively charged PAMs and one positively charged PAM on five Hawaii soils (two Oxisols, one Vertisol, and two Aridisols) to determine erosion loss, sediment settling, and aggregate stability. A laboratory‐scale rainfall simulator was used to apply erosive rainfall at intensities from 5 to 8·5 cm h?1 at various PAM doses applied in both dry and solution forms. Soil detachment due to splash and runoff, as well as the runoff and percolate water volumes, were measured for initial and successive storms. The impact of PAM on particle settling and aggregate stability was also evaluated for selected soil‐treatment combinations. Among the PAMs, Superfloc A‐836 was most effective, and significantly reduced runoff and splash sediment loss for the Wahiawa Oxisol and Pakini Andisol at rates varying between 10 and 50 kg ha?1. Reduced runoff and splash sediment loss were also noted for PAM Aerotil‐D when applied in solution form to the Wahiawa Oxisol. Significant reductions in soil loss were not noted for either the Lualualei Vertisol or the Holomua Oxisol. It is believed that the high montmorillonite content of the Lualualei Vertisol and the low cation‐exchange capacity of the Holomua Oxisol diminished the effectiveness of the various PAMs tested. The polymers were also found to enhance sediment settling of all soils and helped improve their aggregate stability. This screening study shows the potential use of PAM for tropical soils for applications such as infiltration enhancement, runoff reduction, and enhanced sedimentation of detention ponds. Copyright © 2005 John Wiley & Sons, Ltd.  相似文献   

13.
Water is a major limiting factor in arid and semi‐arid agriculture. In the Sahelian zone of Africa, it is not always the limited amount of annual rainfall that constrains crop production, but rather the proportion of rainfall that enters the root zone and becomes plant‐available soil moisture. Maximizing the rain‐use efficiency and therefore limiting overland flow is an important issue for farmers. The objectives of this research were to model the processes of infiltration, runoff and subsequent erosion in a Sahelian environment and to study the spatial distribution of overland flow and soil erosion. The wide variety of existing water erosion models are not developed for the Sahel and so do not include the unique Sahelian processes. The topography of the Sahelian agricultural lands in northern Burkina Faso is such that field slopes are generally low (0–5°) and overland flow mostly occurs in the form of sheet flow, which may transport large amounts of fine, nutrient‐rich particles despite its low sediment transport capacity. Furthermore, pool formation in a field limits overland flow and causes resettlement of sediment resulting in the development of a surface crust. The EUROSEM model was rewritten in the dynamic modelling code of PCRaster and extended to account for the pool formation and crust development. The modelling results were calibrated with field data from the 2001 rainy season in the Katacheri catchment in northern Burkina Faso. It is concluded that the modified version of EUROSEM for the Sahel is a fully dynamic erosion model, able to simulate infiltration, runoff routing, pool formation, sediment transport, and erosion and deposition by inter‐rill processes over the land surface in individual storms at the scale of both runoff plots and fields. A good agreement is obtained between simulated and measured amounts of runoff and sediment discharge. Incorporating crust development during the event may enhance model performance, since the process has a large influence on infiltration capacity and sediment detachment in the Sahel. Copyright © 2005 John Wiley & Sons, Ltd.  相似文献   

14.
This paper examines a variety of recirculation flow patterns that develop in the groyne fields on rivers. A comprehensive data set was obtained from flume experiments at Delft University of Technology and field measurements performed on the Elbe River in Germany. The analysis focuses on patterns of velocity, scour and deposition, and corresponding change of riverbed morphology. The results show that velocity patterns in the groyne fields depend mainly on the aspect ratio between groyne length and length of groyne field. When the aspect ratio is greater than 0·5, a one‐gyre pattern of recirculation develops, while at groyne fields with aspect ratios less than 0·5 a two‐gyre recirculation pattern emerges. The spatial distribution of fine‐sediment deposition between the groynes coincides with the locations of gyres. Moreover, the thickness of the fine‐sediment layer decreases toward the gyre margins where recirculation velocities are greatest. Although the total concentration of suspended sediment in the river does not change considerably as the flow moves through the groyne field, the biological and gravimetrical composition of the suspended material changes substantially within the groyne field. These changes are due to preferential deposition of coarse mineral particles and the replacement of those minerals with finer organic material. Copyright © 2002 John Wiley & Sons, Ltd.  相似文献   

15.
Jiongxin Xu 《水文研究》2013,27(18):2623-2636
Fenwei Graben is a famous sediment sink. The Longmen‐Sanmexia sediment sink of middle Yellow River is located in the middle part. Using the sediment budget based on annual data from the period 1920–2006 and flood‐event data from 154 flood events from the period 1950–1985, the variations in sediment storage, release and transport have been analysed. Data from different methods and sources indicate that, during an 1800‐year period, the variation of sedimentation rate in this sink has undergone a cycle from increase to decline; the cause for this can be found in the changes in the manner and intensity of human activities. Over 87 years, sediment storage in this sink can be separated into four stages which showed different trends, depending on changing human activities, such as reservoir construction, soil and water conservation and water diversion. Stepwise multiple regression shows that the runoff and sediment yield from three major source areas have differing influences on sediment storage in the sink. Copyright © 2012 John Wiley & Sons, Ltd.  相似文献   

16.
Experimental research in the Ethiopian highlands found that saturation excess induced runoff and erosion are common in the sub‐humid conditions. Because most erosion simulation models applied in the highlands are based on infiltration excess, we, as an alternative, developed the Parameter Efficient Distributed (PED) model, which can simulate water and sediment fluxes in landscapes with saturation excess runoff. The PED model has previously only been tested at the outlet of a watershed and not for distributed runoff and sediment concentration within the watershed. In this study, we compare the distributed storm runoff and sediment concentration of the PED model against collected data in the 95‐ha Debre Mawi watershed and three of its nested sub‐watersheds for the 2010 and 2011 rainy seasons. In the PED model framework, the hydrology of the watershed is divided between infiltrating and runoff zones, with erosion only taking place from two surface runoff zones. Daily storm runoff and sediment concentration values, ranging from 0.5 to over 30 mm and from 0.1 to 35 g l?1, respectively, were well simulated. The Nash Sutcliffe efficiency values for the daily storm runoff for outlet and sub‐watersheds ranged from 0.66 to 0.82, and the Nash–Sutcliffe efficiency for daily sediment concentrations were greater than 0.78. Furthermore, the model uses realistic fractional areas for surface and subsurface flow contributions, for example between saturated areas (15%), degraded areas (30%) and permeable areas (55%) at the main outlet, while close similarity was found for the remaining hydrology and erosion parameter values. One exception occurred for the distinctly greater transport limited parameter at the actively gullying lower part of the watershed. The results suggest that the model based on saturation excess provides a good representation of the observed spatially distributed runoff and sediment concentrations within a watershed by modelling the bottom lands (as opposed to the uplands) as the dominant contributor of the runoff and sediment load. Copyright © 2014 John Wiley & Sons, Ltd.  相似文献   

17.
There has been limited success in determining critical thresholds of ground cover or soil characteristics that relate to significant changes in runoff or sediment production at the microscale (<1 m2), particularly in semi‐arid systems where management of ground cover is critical. Despite this lack of quantified thresholds, there is an increasing research focus on the two‐phase mosaic of vegetation patches and inter‐patches in semi‐arid systems. In order to quantify ground cover and soil related thresholds for runoff and sediment production, we used a data mining technique known as conditional inference tree analysis to determine statistically significant values of a range of measured variables that predicted average runoff, peak runoff, sediment concentration and sediment production at the microscale. On Chromic Luvisols across a range of vegetation states in semi‐arid south‐eastern Australia, large changes in runoff and sediment production were related to a hierarchy of different variables and thresholds, but the percentage of bare soil played a primary role in predicting runoff and sediment production in most instances. The identified thresholds match well with previous thresholds found in semi‐arid and temperate regions (including the approximate values of 30%, 50% and 70% total ground cover). The analysis presented here identified the critical role of soil surface roughness, particularly where total ground cover is sparse. The analysis also provided evidence that a two‐phase mosaic of patches and inter‐patches identified via rapid visual assessment could be further delineated into distinct groups of hydrological response, or a multi‐phase rather than a two‐phase system. The approach used here may aid in assessing scale‐dependent responses and address data non‐linearity in studies of semi‐arid hydrology. Copyright © 2012 John Wiley & Sons, Ltd.  相似文献   

18.
This paper examines present and future resource utilization in the tidal section of the Georges River in the southern part of Sydney. Over the last 30 years, the physical characteristics of the river have changed as a result of urbanization, changed hydrologic regime and sand dredging. Urbanization has resulted in an increase in population from 190,000 in 1947 to 550,000. This has resulted in an increase in runoff, sediment input to the river and waste disposal. The change in hydrologic regime has resulted in a substantial increase in the magnitude and frequency of flooding which has increased erosion. Sand dredging has increased the channel capacity, enlarged the tidal prism and increased water turbidity. It has also resulted in extensive bank erosion in the upper part of the river and extensive deposition lower down as tailings are deposited. Although most of these changes have resulted in the deterioration of environmental quality, use of the river for recreation and as an urban amenity has increased.  相似文献   

19.
Longshan Zhao  Rui Hou  Faqi Wu 《水文研究》2019,33(22):2918-2925
Reservoir tillage (RT) improves the soil rainwater harvesting capacity and reduces soil erosion on cropland, but there is some debate regarding its effectiveness. The objective of this study was to further verify the effect of RT on soil erosion and explore the reasons for this effect by analysing microrelief changes during rainfall. Rainfall intensities of 60, 90, and 120 mm/hr and three slope degrees (5, 15, and 25°, representing gentle, medium, and steep slopes) were considered. A smooth surface (SS) served as the control. The microrelief changes were determined based on digital elevation models, which were measured using a laser scanner with a 2‐cm grid before and after rainfall events. The results showed that compared with the values for the SS, RT reduced both the runoff and sediment by approximately 10‐20% on the gentle slope; on the medium slope, although RT also reduced the runoff in the 90‐ and 120‐mm/hr intensity rainfall events, the sediment increased by 158.90% and 246.08%; on the steep slope, the sediment increased by 92.33 to 296.47%. Overall, when the runoff control benefit of RT was lower than 5%, there was no sediment control benefit. RT was effective at controlling soil loss on the gentle slopes but was not effective on the medium and steep slopes. This is because the surface depressions created by RT were filled in with sediment that eroded from the upslopes, and the surface microrelief became smoother, which then caused greater soil and water loss than that on an SS at the later rainfall stage.  相似文献   

20.
The response of runoff and erosion to soil crusts has been extensively investigated in recent decades. However, there have been few attempts to look at the effects of spatial configuration of different soil crusts on erosion processes. Here we investigated the effects of different spatial distributions of physical soil crusts on runoff and erosion in the semi‐arid Loess Plateau region. Soil boxes (1.5 m long × 0.2 m wide) were set to a slope of 17.6% (10°) and simulated rainfall of 120 mm h?1 (60 minutes). The runoff generation and erosion rates were determined for three crust area ratios (depositional crust for 20%, 33%, and 50% of the total slope) and five spatial distribution patterns (depositional crust on the lower, lower‐middle, middle, mid‐upper, and upper slope) of soil crusts. The reduction in sediment loss (‘sediment reduction’) was calculated to evaluate the effects of different spatial distributions of soil crusts on erosion. Sediment yield was influenced by the area ratio and spatial position of different soil crusts. The runoff rate reached a steady state after an initial trend of unsteadily increasing with increasing rainfall duration. Sediment yield was controlled by detachment limitation and then transport limitation under rainfall. The shifting time of erosion from a transport to detachment‐limiting regime decreased with increasing area of depositional crust. No significant differences were observed in the total runoff among treatments, while the total sediment yield varied under different spatial distributions. At the same area ratio, total sediment yield was the largest when the depositional crust was on the upper slope, and it was smallest when the crust was deposited on the lower slope. The sediment reduction of structural crust (42.5–66.5%) was greater than that of depositional crust (16.7–34.3%). These results provide a mechanistic understanding of how different spatial distributions of soil crusts affect runoff and sediment production. Copyright © 2017 John Wiley & Sons, Ltd.  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号