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1.
A standalone version of the Wind Erosion Prediction System (WEPS) erosion submodel, the Single‐event Wind Erosion Evaluation Program (SWEEP), was released in 2007. A limited number of studies exist that have evaluated SWEEP in simulating soil loss subject to different tillage systems under high winds. The objective of this study was to test SWEEP under contrasting tillage systems employed during the summer fallow phase of a winter wheat–summer fallow rotation within eastern Washington. Soil and PM10 (particulate matter ≤10 µm in diameter) loss and soil and crop residue characteristics were measured in adjacent fields managed using conventional and undercutter tillage during summer fallow in 2005 and 2006. While differences in soil surface conditions resulted in measured differences in soil and PM10 loss between the tillage treatments, SWEEP failed to simulate any difference in soil or PM10 loss between conventional and undercutter tillage. In fact, the model simulated zero erosion for all high wind events observed over the two years. The reason for the lack of simulated erosion is complex owing to the number of parameters and interaction of these parameters on erosion processes. A possible reason might be overestimation of the threshold friction velocity in SWEEP since friction velocity must exceed the threshold to initiate erosion. Although many input parameters are involved in the estimation of threshold velocity, internal empirical coefficients and equations may affect the simulation. Calibration methods might be useful in adjusting the internal coefficients and empirical equations. Additionally, the lack of uncertainty analysis is an important gap in providing reliable output from this model. Published in 2009 by John Wiley & Sons, Ltd. 相似文献
2.
Winter wheat–summer fallow is the conventional cropping system employed on >1·5 million ha within the Columbia Plateau of eastern Washington and northern Oregon. Wind erosion contributes to poor air quality in the region, yet little is known concerning the magnitude of soil and PM10 (particulate matter of ≤10 µm in aerodynamic diameter) loss from agricultural lands. Therefore, loss of soil and PM10 was assessed from a silt loam in eastern Washington during 2003 and 2004. Field sites were maintained in fallow using conventional tillage practices in 2003 (9 ha field) and 2004 (16 ha field) and instrumented to assess horizontal soil flux and PM10 concentrations at the windward and leeward positions in the field during high‐wind events. Soil flux was measured using creep and airborne sediment collectors while PM10 concentrations were measured using high‐volume PM10 samplers. Aggregate size distribution of parent soil and eroded sediment was characterized by rotary and sonic sieving. Six high‐wind events occurred over the two year period, with soil loss ranging from 43 kg ha?1 for the 12–22 September 2003 event to 2320 kg ha?1 for the 27–29 October 2003 event. Suspension‐sized particulates (<100 µm in diameter) comprised ≥90 per cent of the eroded sediment, indicating that direct suspension may be an important process by which the silt loam eroded. The corresponding loss of PM10 for these two events ranged from 5 to 210 kg ha?1. Loss of PM10 comprised 9–12 per cent of the total soil loss for the six events. This study suggests that the relatively small loss of PM10 from eroding agricultural fields maintained in summer fallow can affect air quality in the Columbia Plateau. Therefore, alternative tillage practices or cropping systems are needed for minimizing PM10 emissions and improving air quality in the region. Copyright © 2006 John Wiley & Sons, Ltd. 相似文献
3.
Exceedance of the US Environmental Protection Agency national ambient air quality standard for PM10 (particulate matter ≤10 µm in aerodynamic diameter) within the Columbia Plateau region of the Pacific Northwest US is largely caused by wind erosion of agricultural lands managed in a winter wheat–summer fallow rotation. Land management practices, therefore, are sought that will reduce erosion and PM10 emissions during the summer fallow phase of the rotation. Horizontal soil flux and PM10 concentrations above adjacent field plots (>2 ha), with plots subject to conventional or undercutter tillage during summer fallow, were measured using creep and saltation/suspension collectors and PM10 samplers installed at various heights above the soil surface. After wheat harvest in 2004 and 2005, the plots were either disked (conventional) or undercut with wide sweeps (undercutter) the following spring and then periodically rodweeded prior to sowing wheat in late summer. Soil erosion from the fallow plots was measured during six sampling periods over two years; erosion or PM10 loss was not observed during two periods due to the presence of a crust on the soil surface. For the remaining sampling periods, total surface soil loss from conventional and undercutter tillage ranged from 3 to 40 g m–2 and 1 to 27 g m–2 while PM10 loss from conventional and undercutter tillage ranged from 0·2 to 5·0 g m–2 and 0·1 to 3·3 g m–2, respectively. Undercutter tillage resulted in a 15% to 65% reduction in soil loss and 30% to 70% reduction in PM10 loss as compared with conventional tillage at our field sites. Therefore, based on our results at two sites over two years, undercutter tillage appears to be an effective management practice to reduce dust emissions from agricultural land subject to a winter wheat–summer fallow rotation within the Columbia Plateau. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
4.
Wind erosion modelling efforts, both ?eld and wind tunnel studies, have traditionally focused on saltation‐based processes for estimating dust emissions from high wind events. This approach gives generally good results when saltation‐sized particles, 90 µm to 2 mm mean diameter, are prevalent on the exposed soil surface. The Columbia Plateau, located in north‐central Oregon and south‐central Washington, is a region with extensive loess deposits where up to 90 per cent of sieved particles (by mass) are less than 100 µm mean diameter. During high‐wind events, large amounts of soil and ?ne particulate matter are suspended. However, ?eld surfaces typically show little evidence of surface scouring or saltation, e.g. soil drifts or covered furrows. Velocity pro?le analysis of two high‐wind events and additional data from a third event show evidence of direct suspension process where saltation is not a major mechanism for eroding soil or generating dust emissions. Surface roughness heights are less than saltation roughness height estimates during peak wind speeds. Copyright © 2004 John Wiley & Sons, Ltd. 相似文献
5.
The Wind Erosion Prediction System (WEPS) and Revised Wind Erosion Equation (RWEQ) are widely used for estimating wind‐induced soil erosion at a field scale. Wind is the principal erosion driver in the two models. Wind erosivity, which describes the capacity of wind to cause soil erosion, is defined as erosive wind power density (WPD) in WEPS, and wind value (W) in RWEQ. In this study, the daily average WPD (AWPD) and the daily average W (Wf) were chosen to investigate the effect of averaging time on wind erosivity estimation based on observed wind data. We compare the daily AWPD and Wf calculated from 1, 5, 10, 15, 30, and 60 minute average wind speed data. The results of comparisons indicate that averaging wind speed can significantly influence estimates of wind erosivity. Compared with the daily AWPD and Wf calculated from one minute average wind speed data, all daily AWPD and Wf values calculated from 5, 10, 15, 30, and 60 minute averaged wind speeds tend to be significantly lower than values calculated from one minute values. In general, longer averaging times tend to produce smaller values of daily AWPD or Wf, which may lead to an under‐estimation of wind erosion. Further studies are needed to extend and apply the findings obtained in this study to actual wind erosion predictions. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
6.
Research to investigate relations between simultaneous processes of soil erosion by wind and PM10 emissions from dry land fields on the Columbia Plateau, Washington, has been initiated by the U.S. Department of Agriculture — Agricultural Research Service (ARS) and Washington State University. Dry land agriculture is the primary cropping system world-wide but is constantly threatened by erosive winds which reduce the soil resource and/or remove fines which are the most active soil portion for plant production. Soils on the Columbia Plateau are very fine-grained containing more than 4 per cent of freely occurring aggregates or particles less than 10 μm aerodynamic diameter. Analysis from eight wind events show that significant relations exist between total mass of soil in both horizontal (saltation) and vertical (suspension) transport. The data suggest that by limiting horizontal soil erosion, emitted dust can be simultaneously reduced. Aggressive conservation tillage can be an effective weapon in reducing soil erosion by maintaining surface residue and roughness. 相似文献
7.
The prediction of wind erosion and dust emissions is important for controlling erosion and identifying dust sources in arid and semiarid regions of the world. This study predicts quantitatively wind erosion and dust emissions in Xinjiang Province, central Asia. The wind erosion prediction system (WEPS) was used to simulate annual soil and PM10 (particulate matter ≤10 μm in aerodynamic diameter) loss at 64 meteorological stations across the province. Soil and PM10 loss were simulated from bare surfaces at all 64 stations and from cotton and wheat fields at 11 stations. Simulated annual bare soil and PM10 loss were lowest in the Junggar (soil and PM10 loss were, respectively, 121.7 and 7.6 kg m-2) and Tarim basins (soil loss was 78.2 kg ha-1 and PM10 loss was 6.5 kg m-2) and highest in the Tu-ha Basin (soil and PM10 loss were, respectively, 638.2 and 37.7 kg m-2). Stations with the highest annual soil loss in the Tarim and Tu-ha basins also had the highest number of days with wind speeds >8 m s-1. This indicated wind influenced erosion, but other factors such as soil type also affect wind erosion. The maximum monthly bare soil and PM10 loss occurred in May in the three basins, substantiating that dust storms occur most frequently during spring in the region. Simulated soil and PM10 loss were lower for cotton and wheat than bare soil, thus suggesting that maintaining vegetative cover during a portion of the year provided some protection to the soil surface from wind erosion. © 2018 John Wiley & Sons, Ltd. 相似文献
8.
V. Hrissanthou 《水文研究》2006,20(18):3939-3952
The Yermasoyia Reservoir is located northeast of the town of Limassol, Cyprus. The storage capacity of the reservoir is 13·6 × 106 m3. The basin area of the Yermasoyia River, which feeds the reservoir, totals 122·5 km2. This study aims to estimate the mean annual deposition amount in the reservoir, which originates from the corresponding basin. For the estimate of the mean annual sediment inflow into the reservoir, two mathematical models are used alternatively. Each model consists of three submodels: a rainfall‐runoff submodel, a soil erosion submodel and a sediment transport submodel for streams. In the first model, the potential evapotranspiration is estimated for the rainfall‐runoff submodel, and the soil erosion submodel of Schmidt and the sediment transport submodel of Yang are used. In the second model, the actual evapotranspiration is estimated for the rainfall‐runoff submodel, and the soil erosion submodel of Poesen and the sediment transport submodel of Van Rijn are used. The deposition amount in the reservoir is estimated by means of the diagram of Brune, which delivers the trap efficiency of the reservoir. Daily rainfall data from three rainfall stations, and daily values of air temperature, relative air humidity and sunlight hours from a meteorological station for four years (1986–89) were available. The computed annual runoff volumes and mean annual soil erosion rate are compared with the respective measurement data. Copyright © 2006 John Wiley & Sons, Ltd. 相似文献
9.
Severe soil erosion during a 3‐day exceptional rainfall event: combining modelling and field data for a fallow cereal field 
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下载免费PDF全文 Manuel López‐Vicente Laura Quijano Leticia Gaspar Leticia Palazón Ana Navas 《水文研究》2015,29(10):2358-2372
Exceptional rainfall events cause significant losses of soil, although few studies have addressed the validation of model predictions at field scale during severe erosive episodes. In this study, we evaluate the predictive ability of the enhanced Soil Erosion and Redistribution Tool (SERT‐2014) model for mapping and quantifying soil erosion during the exceptional rainfall event (~235 mm) that affected the Central Spanish Pyrenees in October 2012. The capacity of the simulation model is evaluated in a fallow cereal field (1.9 ha) at a high spatial scale (1 × 1 m). Validation was performed with field‐quantified rates of soil loss in the rills and ephemeral gullies and also with a detailed map of soil redistribution. The SERT‐2014 model was run for the six rainfall sub‐events that made up the exceptional event, simulating the different hydrological responses of soils with maximum runoff depths ranging between 40 and 1017 mm. Predicted average and maximum soil erosion was 11 and 117 Mg ha?1 event?1, respectively. Total soil loss and sediment yield to the La Reina gully amounted to 16.3 and 9.0 Mg event?1. These rates are in agreement with field estimations of soil loss of 20.0 Mg event?1. Most soil loss (86%) occurred during the first sub‐event. Although soil accumulation was overestimated in the first sub‐event because of the large amount of detached soil, the enhanced SERT‐2014 model successfully predicted the different spatial patterns and values of soil redistribution for each sub‐event. Further research should focus on stream transport capacity. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
10.
P. I. A. Kinnell 《地球表面变化过程与地形》2009,34(10):1393-1407
Simulations using a mechanistic model of raindrop driven erosion in rain‐impacted flow were performed with particles travelling by suspension, raindrop induced saltation and flow driven saltation. Results generated by both a high intensity storm, and a less intense one, indicate that, because of the effect of flow depth on the delivery of raindrop energy to the bed, there is a decline in sediment concentration, and hence soil loss per unit area, with slope length when particles are transported by raindrop induced saltation. However, that decline is reversed when the critical velocities that lead to flow driven saltation are episodically exceeded during an event. The simulations were performed on smooth surfaces and a single drop size but the general relationships are likely to apply for rain made up of a wide range of drop size. Although runoff is not always produced uniformly, as a general rule, flow velocities increase with slope length so that, typically, the distance particles travel before being discharged during an event increase with slope length. The effect of slope length on soil loss per unit area is often considered to vary with slope length to a power greater than zero and less that 1·0. The simulations show that effect of slope length on sediment discharge is highly dependent on the variations in runoff response resulting from variations in rainfall duration‐intensity‐infiltration conditions rather than plot length per se. Consequently, predicting soil loss per unit area using slope length with positive powers close to zero when sheet erosion occurs may not be as effective as commonly expected. Erosion by rain‐impacted flow is a complex process and that complexity needs to be considered when analysing the results of experiments associated with rain‐impacted flow under both natural and artificial conditions. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
11.
P. I. A. Kinnell 《水文研究》2012,26(10):1449-1456
Sheet and interrill erosion areas are sources of soil material rich in nutrients and pollutants. The loss of soil, nutrients and other chemicals from these areas is a matter of concern both in terms of maintaining soil productivity and the health of offsite environments. Many experiments on rainfall erosion have shown enrichment of fine material, nutrients and other chemicals in the sediment discharged for sheet and interrill erosion areas, but often these results were obtained over short periods of time. A qualitative mechanistic model of raindrop‐induced saltation is used to illustrate how this transport mechanism influences the composition of sediment discharged by rain‐impacted flow. Initially, fast moving particles are enriched in the sediment discharge but, over time, during a rainfall event, slower moving particles become more represented. Raindrop‐induced saltation promotes the storage of material on the soil surface with a coarser composition than the original soil. Winnowing of material from this storage by the development of flow‐driven saltation during high‐intensity events can modify the composition of the sediment discharged later by raindrop‐induced saltation. Given stable soil particles, the composition of the sediment discharged at the steady state is the same as the original soil. Enrichment is a non‐steady‐state phenomenon and failure to recognize the transient nature of enrichment may lead to inappropriate interpretation of the implications of the results from short‐term experiments. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
12.
Lumped surface and sub‐surface runoff for erosion modeling within a small hilly watershed in northern Vietnam 下载免费PDF全文
下载免费PDF全文 Yen Tan Bui D. Orange S. M. Visser Chu Thai Hoanh M. Laissus A. Poortinga Duc Toan Tran L. Stroosnijder 《水文研究》2014,28(6):2961-2974
Developing models to predict on‐site soil erosion and off‐site sediment transport at the agricultural watershed scale represent an on‐going challenge in research today. This study attempts to simulate the daily discharge and sediment loss using a distributed model that combines surface and sub‐surface runoffs in a small hilly watershed (< 1 km2). The semi‐quantitative model, Predict and Localize Erosion and Runoff (PLER), integrates the Manning–Strickler equation to simulate runoff and the Griffith University Erosion System Template equation to simulate soil detachment, sediment storage and soil loss based on a map resolution of 30 m × 30 m and over a daily time interval. By using a basic input data set and only two calibration coefficients based, respectively, on water velocity and soil detachment, the PLER model is easily applicable to different agricultural scenarios. The results indicate appropriate model performance and a high correlation between measured and predicted data with both Nash–Sutcliffe efficiency (Ef) and correlation coefficient (r2) having values > 0.9. With the simple input data needs, PLER model is a useful tool for daily runoff and soil erosion modeling in small hilly watersheds in humid tropical areas. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献
13.
Potential wind erosion rate response to climate and land‐use changes in the watershed of the Ningxia–Inner Mongolia reach of the Yellow River,China, 1986–2013 下载免费PDF全文
下载免费PDF全文 Climate and land‐use changes could strongly affect wind erosion and in turn cause a series of environmental problems. Thus, the objective of this study was to assess potential wind erosion rate (PWER) response to climate and land‐use changes in the watershed of the Ningxia–Inner Mongolia Reach of the Yellow River (NIMRYR), China. The watershed of NIMRYR suffers from serious wind erosion hazards, and over recent decades, wind erosion intensity and distribution has changed, following climate and land‐use changes. To understand these processes in the NIMRYR watershed, the Integrated Wind Erosion Modelling System (IWEMS) and the Revised Wind Erosion Equation (RWEQ) were used to calculate the PWER under different climate conditions and land‐use scenarios, and to assess the influences of climate and land‐use changes on the PWER. The results show the PWER in the whole watershed had a significant declining trend from 1986 to 2013. The results of the relationship among PWER, climate change, and land‐use changes showed that climate change was the dominant control on the PWER change in this watershed. Compared to the period 1986–1995, the average PWER decreased 23.32% and 64.98% as a result of climate change in the periods 1996–2005 and 2006–2013, respectively. In contrast with climate change, the effects of land‐use changes on the average PWER were much lower, and represented a change in PWER of less than 3.3% across the whole watershed. The study method we used could provide some valuable reference for wind erosion modelling, and the research results should help climate and land‐use researchers to develop strategies to reduce wind erosion. Copyright © 2017 John Wiley & Sons, Ltd. 相似文献
14.
Prompt location of areas exposed to high erosion is of the utmost importance for soil and water conservation planning. Erosion models can be useful tools to locate sources of sediment and areas of deposition within a catchment, but the reliability of model predictions of spatial patterns of erosion at catchment scale has seldom been validated against observations. This study aimed to evaluate the performance of a simple empirical model (Morgan, Morgan and Finney model, MMF) in predicting spatial patterns of erosion at two small catchments in the East African Highlands: Kwalei (Tanzania) and Gikuuri (Kenya). Erosion maps predicted by the MMF model were compared with erosion maps obtained by direct survey. In Kwalei, erosion features were especially frequent in fields of annual crops. In Gikuuri, slope was the critical erosion factor, with estimated erosion rates >10 kg m?2 a?1 on slopes >18 per cent. Predicted erosion rates were mainly transport‐limited and ranged from <0·01 to 13·50 kg m?2 a?1 in Kwalei and 9·29 kg m?2 a?1 in Gikuuri. The performance of the MMF model in predicting the spatial patterns of erosion was acceptable in Kwalei, but poor in Gikuuri. However, by excluding the elements at the valley bottoms in Gikuuri Catchment, the performance of the model improved dramatically. The spatial pattern of erosion predicted by the MMF model was driven by the accumulation of surface runoff, which did not consider the possibility of re‐infiltration along the slope. As a result, the MMF erosion patterns predicted by the model increased invariably from the ridges to the valley bottoms, hampering the model suitability for locating areas subjected to high and very high erosion. It is concluded that the model predictions could be substantially improved by introducing a more realistic hydrological component for the prediction of surface runoff along the hill‐slope. Copyright © 2005 John Wiley & Sons, Ltd. 相似文献
15.
Wind erosion on the north‐eastern Tibetan Plateau: constraints from OSL and U‐Th dating of playa salt crust in the Qaidam Basin 下载免费PDF全文
下载免费PDF全文 Wenxia Han Zhibang Ma Zhongping Lai Erwin Appel Xiaomin Fang Lupeng Yu 《地球表面变化过程与地形》2014,39(6):779-789
The arid Qaidam Basin is the largest (~3.88 × 104 km2) basin on the north‐eastern Tibetan Plateau. Wind erosion in the area has been regarded as an important trigger for intra‐basin tectonic balance upheaval, geomorphologic development and as a major supplier of dust to the Chinese Loess Plateau downwind. An initial estimate of the rate of wind erosion (Kapp et al., 2011) based on geological cross‐sections has suggested up to 3.2 × 104 km3 of sediments has been deflated over the past 2.8 Ma, lowering the landscape by an average of 0.29 mm/yr. In this paper we re‐evaluate this estimate by dating surface crusts present on three playas within the basin. Understanding the development of these playas is crucial to assessing the overall role of the wind in shaping the regional landscape because they are typically capped with a thick salt crust which effectively protects them from wind erosion. Optically stimulated luminescence (OSL) and U‐series dating from a pit section and from the top of a deep drill core, together with results from magnetostratigraphy and a climate proxy record correlated to the marine oxygen isotope record, are used here to determine the age of the playa plains and suggest that the salt crusts have an age of c. 0.1 Ma. This young age and the wide distribution of resistant thick salt crusts of the playa plains indicate a much lower degree of wind erosion than previously suggested. The crusts protect the surface from significant surface erosion (including sediment exhumation and unloading) and whilst some wind erosion does occur, it is unlikely to be sufficient to trigger tectonic uplift of the basin or to be a major dust source for the Loess Plateau as previously suggested. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献
16.
Deposition of suspended dust near eroding source fields can have detrimental effects on vegetation, as well as on soil and water quality. This study was undertaken to quantify dust deposition within 200 m of a source field during wind erosion events. Erosion was measured with BSNE samplers on a small field of Amarillo fine sandy loam at field at Big Spring, TX. Suspension‐sized dust discharge averaged 33 ± 5 per cent of the total sediment discharge and ranged from 18·0 to 147·4 kg m?1 during eight selected storm events. Within 200 m of the source field boundary, dust collected in deposition samplers placed above a vegetated surface averaged 34 per cent of initial dust discharge. Predicted deposition, according to a line source model, was 43 per cent. Actual deposition was likely near that predicted, because of lateral diffusion of the dust and some under‐sampling by the disk samplers. Thus, the line source model seems useful in estimating both the pattern and quantity of deposition. About 30 per cent of the suspended dust was deposited within the initial 50 m of vegetated surface, but only about 12–15 per cent was deposited in the initial 10 m. Published in 2006 by John Wiley & Sons, Ltd. 相似文献
17.
Wind erosion is an important soil erosion and hence a soil degradation problem in the Sahelian zone of West Africa. Potentially, the characteristic dryland vegetation with scattered trees and shrubs can provide for soil erosion protection from wind erosion, but so far adequate quantification of vegetation impacts is lacking. The aim of this study was to develop a model of wind‐blown soil erosion and sediment transport around a single shrub‐type vegetation element. Starting with the selection of a suitable transport equation from four possible sediment transport equations, the effects of a single vegetation element on wind speed were parameterized. The modified wind speed was then applied to a sediment transport equation to model the change in sediment mass flux around a shrub. The model was tested with field data on wind speed and sediment transport measured around isolated shrubs in a farmer's field in the north of Burkina Faso. The simple empirical equation of Radok (Journal of Glaciology 19 : 123–129, 1977) performed best in modelling soil erosion and sediment transport, both for the entire event duration and for each minute within an event. Universal values for the empirical constants in the sediment transport equation could not be obtained because of the large variability in soil and roughness characteristics. The pattern of wind speed, soil erosion and sediment transport behind a shrub and on either side of it was modelled. The wind speed changed in the lee of the vegetation element depending on its porosity, height and downwind position. Wind speed was recovered to the upstream speed at a downwind distance of 7·5 times the height of the shrub. The variability in wind direction created a ‘rotating’ area of influence around the shrub. Compared to field measurements the model predicted an 8% larger reduction in sediment transport in the lee of the vegetation element, and a 22% larger increase beside the vegetation element. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
18.
Crust strength: a wind tunnel study of the effect of impact by saltating particles on cohesive soil surfaces 总被引：1，自引：0，他引：1
A wind tunnel study examined the effect of distributions of saltating particles on sediment surfaces which were characterized by distributions of their tensile strength. The sediments consisted of varying proportions of large sand‐sized particles with a fine particle cement. The energies of the impacting particles and the surface strengths were compared with the mass of material lost from the surface. It is important to consider distributions of parameters rather than mean values only, since abrasion and erosion may occur from surfaces not predicted from average strength and saltation velocities. At the impact velocities used in this study (mean velocity 4·4 m s?1, with standard deviation of 0·51), surfaces containing less than 12 per cent fine material were easily eroded, but insignificant erosion occurred when the fine particle content exceeded 60 per cent. Small amounts of cementing material were easily ruptured, allowing the large sand grains to be moved (largely in creep) by the bombarding particles. A significant amount of energy was lost to the bed. As the percentage of fine material increased, the surface became more difficult to break up and less energy was lost to the bed. The probability that erosion will occur for known energy distributions of impacting particles and surface strength can be calculated and the mass loss increases exponentially with a decrease in the percentage of fine cementing particles. Copyright © 2001 John Wiley & Sons, Ltd. 相似文献
19.
Despite the wealth of soil erosion models available for the prediction of both runoff and soil loss at a variety of scales, little quantification is made of uncertainty and error associated with model output. This in part reflects the need to produce unequivocal or optimal results for the end user, which will often be an unrealistic goal. This paper presents a conceptually simple methodology, Generalized Likelihood Uncertainty Estimation (GLUE), for assessing the degree of uncertainty surrounding output from a physically based soil erosion model, the Water Erosion Prediction Project (WEPP). The ability not only to be explicit about model error but also to evaluate future improvements in parameter estimation, observed data or scientific understanding is demonstrated. This approach is applied to two sets of soil loss/runoff plot replicates, one in the UK and one in the USA. Although it is demonstrated that observations can be largely captured within uncertainty bounds, results indicate that these uncertainty bounds are often wide, reflecting the need to qualify results that derive from ‘optimum’ parameter sets, and to accept the concept of equifinality within soil erosion models. Attention is brought to the problem of under‐prediction of large events/over‐prediction of small events, as an area where model improvements could be made, specifically in the case of relatively dry years. Finally it is proposed that such a technique of model evaluation be employed more widely within the discipline so as to aid the interpretation and understanding of complex model output. Copyright © 2000 John Wiley & Sons, Ltd. 相似文献
20.
Nicholas P. Webb Craig L. Strong Adrian Chappell Samuel K. Marx Grant H. McTainsh 《地球表面变化过程与地形》2013,38(14):1662-1671
Soil erosion is an important component of the global carbon cycle. However, little attention has been given to the role of aeolian processes in influencing soil organic carbon (SOC) flux and the release of greenhouse gasses, such as carbon dioxide (CO2), to the atmosphere. Understanding the magnitude and mechanisms of SOC enrichment in dust emissions is necessary to evaluate the impact of wind erosion on the carbon cycle. This research examines the SOC content and enrichment of dust emissions measured using Big Spring Number Eight (BSNE) wind‐vane samplers across five land types in the rangelands of western Queensland, Australia. Our results show that sandy soils and finer particulate quartz‐rich soils are more efficient at SOC emission and have larger SOC dust enrichment than clay‐rich aggregated soils. The SOC enrichment ratios of dusts originating from sites with sand‐rich soil ranged from 2·1–41·9, while the mean enrichment ratio for dusts originating from the clay soil was 2·1. We hypothesize that stronger inter‐particle bonds and the low grain density of the aggregated clay soil explain its reduced capacity to release SOC during saltation, relative to the particulate sandy soils. We also show that size‐selective sorting of SOC during transport may lead to further enrichment of SOC dust emissions. Two dust samples from regional transport events were found to contain 15–20% SOC. These preliminary results provide impetus for additional research into dust SOC enrichment processes to elucidate the impact of wind erosion on SOC flux and reduce uncertainty about the role of soil erosion in the global carbon cycle. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献