Home About us Contact
|
Home About us Contact | ||
|
|
||
Soil Loss (soil + loss)
Kinds of Soil Loss Terms modified by Soil Loss Selected AbstractsThe effect of single vegetation elements on wind speed and sediment transport in the Sahelian zone of Burkina FasoEARTH SURFACE PROCESSES AND LANDFORMS, Issue 10 2007J. K. Leenders Abstract Soil loss caused by wind erosion is a widespread phenomenon in the Sahelian zone of West Africa. According to Sahelian farmers, scattered vegetation standing in amongst the crop has the potential for a wind erosion control strategy. This study was conducted to study the effect of single vegetation elements on the pattern of average wind speed and sediment transport. This was done by two experiments that were carried out during the rainy seasons of 2002 and 2003 in north Burkina Faso, West Africa. Wind speeds were measured using three sonic anemometers, at a sampling frequency of 16 Hz. Sediment transport was determined by calculating the mass fluxes from 17 MWAC catchers. In this study, a shrub was defined as a vegetation element with branches until ground and a tree as a vegetation element with a distinctive trunk below a canopy. Behind shrubs wind speed near the soil surface was reduced up to approximately seven times the height of the shrub. The observed reduction in wind speed in the area where wind speed was reduced was 15 per cent on average. At the sides of the shrub, wind speed was increased, by on average 6 per cent. As the area of increase in wind speed is one-third of the area of decrease in wind speed, the net effect of a shrub is a reduction in wind speed. A similar pattern was visible for the pattern of sediment transport around a shrub. Downwind of a shrub, sediment transport was diminished up to seven times the height of the shrub. Probably most of this material was trapped by the shrub. Trees showed a local increase of wind around the trunk, which is expected to relate to an increase in sediment transport around the trunk. Mass flux measurements of sediment transport were not made, but visual observations in the field substantiate this. Behind the canopy of a tree, a tree acts similarly to a shrub regarding its effects on average wind speed, but as a tree is generally a larger obstacle than a shrub the extent of this effect is larger than for shrubs. Thus, whereas shrubs are more effective than trees regarding their direct effect on soil loss by trapping sand particles near the soil surface, trees are more effective in affecting soil loss indirectly by reducing the wind speed downwind more effectively than shrubs. Therefore, to reduce soil loss in an area, the presence of both trees and shrubs is crucial. Copyright © 2007 John Wiley & Sons, Ltd. [source] Erosion and Nutrient Loss on Sloping Land under Intense Cultivation in Southern VietnamGEOGRAPHICAL RESEARCH, Issue 1 2008NGUYEN VAN DE Abstract To help improve the well-being of the local people, a joint Vietnamese-UK team set out to establish a way of estimating soil and nutrient losses under different land management scenarios, using field data extrapolated through remote sensing and GIS, to obtain catchment-wide estimates of the impact of land cover change. Immigration from remote provinces to the Dong Phu District of Binh Phuóc Province, about 120 km north of Ho Chi Minh City, has led to disruption of soil surface stability on easily eroded clayey sandstones, creating rapid nutrient depletion that affects crop yields and siltation in the channel of the Rach Rat river downstream. The poor farmers of the areas see crop yields drop dramatically after two or three years of cultivation due to the fertility decline. Soil loss varies dramatically between wet season and dry season and with ground cover. Erosion bridge measurements showed a mean loss of 85.2 t ha,1 y,1 under cassava saplings with cashew nuts, 43.3 t ha,1 y,1 on uncultivated land and 41.7 t ha,1 y,1 under mature cassava. The rates of erosion were higher than those reported in many other parts of Vietnam, reflecting the high erodibility of the friable sandy soils on the steep side-slopes of the Rach Rat catchment. However, although the actual measurements provide better soil loss data than estimates based on the parameters of soil loss equations, a large number of measurement sites is needed to provide adequate coverage of the crop and slope combinations in this dissected terrain for good prediction using GIS and remote sensing. [source] Measurements of rain splash on bench terraces in a humid tropical steepland environmentHYDROLOGICAL PROCESSES, Issue 3 2003A. I. J. M. Van Dijk Abstract Soil loss continues to threaten Java's predominantly bench-terraced volcanic uplands. Sediment transport processes on back-sloping terraces with well-aggregated clay-rich oxisols in West Java were studied using two different techniques. Splash on bare, cropped, or mulched sub-horizontal (2,3°) terrace beds was studied using splash cups of different sizes, whereas transport of sediment on the predominantly bare and steep (30,40/deg ) terrace risers was measured using a novel device combining a Gerlach-type trough with a splash box to enable the separate measurement of transport by wash and splash processes. Measurements were made during two consecutive rainy seasons. The results were interpreted using a recently developed splash distribution theory and related to effective rainfall erosive energy. Splash transportability (i.e. transport per unit contour length and unit erosive energy) on the terrace risers was more than an order of magnitude greater than on bare terrace beds (0·39,0·57 versus 0·013,0·016 g m J,1). This was caused primarily by a greater average splash distance on the short, steep risers (>11 cm versus c. 1 cm on the beds). Splashed amounts were reduced by the gradual formation of a protective ,pavement' of coarser aggregates, in particular on the terrace beds. Soil aggregate size exhibited an inverse relationship with detachability (i.e. detachment per unit area and unit erosive energy) and average splash length, and therefore also with transportability, as did the degree of canopy and mulch cover. On the terrace risers, splash-creep and gravitational processes transported an additional 6,50% of measured rain splash, whereas transport by wash played a marginal role. Copyright © 2002 John Wiley & Sons, Ltd. [source] Studying the effects of Mahonia aquifolium populations on small-scale mountain agro-ecosystems in Hungary with the view to minimise land degradationLAND DEGRADATION AND DEVELOPMENT, Issue 3 2009C. Hudek Abstract After the political changeover in Hungary in 1989, many farm owners faced problems typical of a small sized farm (<1,ha) as well as a lack of various resources. This led to many farms with great horticultural backgrounds being abandoned, especially in mountainous areas where erosion control is essential for soil conservation. Severe changes can occur on soil through property abandonment. The local socio-economic aspects must be taken into consideration as well as the problem of soil degradation as this will be a motivating factor in preservation initiatives. Under horticultural management, Mahonia aquifolium was tested to determine its efficiency in water erosion control in mountainous conditions in Hungary. Soil loss and water runoff were measured after every rainfall event at six different plots: four cultivated M. aquifolium populations with different ages (4, 12, 20 and 25 years old) and two control plots. A bare soil field and a grass field represented the control plots. The results show that as the age of the M. aquifolium populations increase, the cumulative runoff and sediment values decrease. It also showed that 2 years after setting up a new M. aquifolium plantation, the cumulative runoff decreased by 69 per cent and the cumulative soil loss decreased by 74 per cent. This indicates that a M. aquifolium population could play a significant role in erosion control within a short period of time. Copyright © 2009 John Wiley & Sons, Ltd. [source] Throughfall, runoff and soil erosion after prescribed burning in gorse shrubland in Galicia (NW Spain)LAND DEGRADATION AND DEVELOPMENT, Issue 1 2005J. A. Vega Abstract The first-year effect of two different prescribed burning treatments on throughfall, runoff and soil erosion was evaluated in gorse shrubland (Ulex europaeus L.) in Galicia (NW Spain). The treatments compared were: intense burn, light burn and control (no burn). Accumulated annual throughfall represented between the 81 and 87,per,cent of total rainfall in intensely burned and lightly burned areas, respectively, whereas in the unburnt areas it was 60,per,cent. No significant differences between burning treatments were found for the annual throughfall. However, runoff was significantly greater in intensely burned plots (1·5-times) than in lightly burned plots. Burning also resulted in a significant increase in runoff (between 2·5 and 1·7-times, respectively) compared with controls. Total soil losses were small in all treatments, but the intense burn caused significantly greater soil erosion (5·8-times) compared with the unburned areas. Soil losses after the light burn did not significantly differ from the control although they were higher (2·3-times). The relationships obtained between erosion and several rainfall parameters were significantly different in burned areas compared to the control. The same response was observed for runoff. Annual erosion losses showed a strong dependence on percentage of bare soil even for small values of this variable. Litter thickness was also a very important variable influencing on erosion rates. This study indicated that by combining ignition techniques and high litter moisture content to maintain the percentage of bare soil below 85,per,cent, soil erosion was low. Nevertheless, this result was constrained by the low rainfall that occurred during the study. Copyright © 2005 John Wiley & Sons, Ltd. [source] Effectiveness of grass strips in trapping suspended sediments from runoffEARTH SURFACE PROCESSES AND LANDFORMS, Issue 9 2010Chengzhong Pan Abstract Little information is available concerning the performance of grass strips for erosion control from steep cropland. An experiment was conducted on 5-m-long grass strips with slopes of 3°,15° that were subjected to silt laden runoff and simulated rainfall, to investigate the sediment trapping processes. The grass strips had three treatments including intact grass control (C), no litter (dead grass material covering the soil surface was removed) (NL), and no litter or leaves (only 2,3,cm grass stems and roots were reserved) (NLL). Generally the grass strips had a high effectiveness in trapping sediment from steep cropland runoff. Sediment trapping efficiency (STE) decreased with increasing slope gradient, and even for a 15° slope, STE was still more than 40%. Most sediment deposited in the backwater region before each grass strips. The removal of grass litter or/and leaves had no significant influence on STE. The sediment median size (D50) in inflow was greater than that in outflow, and the difference (,D50) decreased with increasing slope. A positive power relationship between STE and ,D50 can be obtained. Grass strips were more effective in trapping sediments coarser than 10 or 25,µm, but sediments finer than 1,µm were more readily removed from runoff than particles in the range of 2 to approximately 10,µm. Grass litter had less influence on flow velocity than leaves because the deposited sediment partially covered the litter layer. Mean flow velocity and its standard deviation were negatively correlated with STE, and they can help make good estimation of STE. Results from this study should be useful in planting and managing forage grass to effectively conserve soil loss by runoff from steep slopes on the Loess Plateau of China. Copyright © 2010 John Wiley & Sons, Ltd. [source] Rainfall variability and hydrological and erosive response of an olive tree microcatchment under no-tillage with a spontaneous grass cover in SpainEARTH SURFACE PROCESSES AND LANDFORMS, Issue 7 2010E. V. Taguas Abstract Most studies on runoff and soil loss from olive orchards were performed on plots, despite the fact that measurements that examine a range of erosive processes on different scales are essential to evaluate the suitability of the use and soil management of this type of land. The main environmental limitations of much of the land used for olive orchards in the Mediterranean are the steep slopes and the shallow soil depth , and this was the case in the study area. Soil erosion and runoff over two hydrological years (2005,2006 and 2006,2007) were monitored in an olive orchard microcatchment of 6·1,ha under no-tillage with spontaneous grass in order to evaluate its hydrological and erosive behaviour. Moreover, soil parameters such as organic matter (%OM), bulk density (BD) and hydraulic saturated conductivity (Ks) were also examined in the microcatchment to describe management effects on hydrological balance and on erosive processes. In the study period, the results showed runoff coefficients of 6·0% in the first year and 0·9% in the second. The differences respond to the impact of two or three yearly maximum events which were decisive in the annual balances. On the event scale, although maximum rainfall intensity values had a big influence on peak flows and runoff, its importance on mean sediment concentrations and sediment discharges was difficult to interpret due to the likely control of grass cover on volume runoff and on soil protection. In the case of annual soil erosion, they were measured as 1·0,Mg,ha,1,yr,1 and 0·3,Mg,ha,1,yr,1. Both are lower than the tolerance values evaluated in Andalusia (Spain). These results support the implementation of no-tillage with spontaneous grass cover for sloping land, although the reduced infiltration conditions determined by Ks in the first horizon suggest grass should be allowed to grow not only in spring but also in autumn. In addition, specific measurements to control gullies, which have formed in the terraced area in the catchment, should be included since it is expected that they could be the main sources of sediments. Copyright © 2010 John Wiley & Sons, Ltd. [source] Windblown dust influenced by conventional and undercutter tillage within the Columbia Plateau, USA,EARTH SURFACE PROCESSES AND LANDFORMS, Issue 10 2009B. S. Sharratt Abstract 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. [source] Modelling increased soil cohesion due to roots with EUROSEMEARTH SURFACE PROCESSES AND LANDFORMS, Issue 13 2008S. De Baets Abstract As organic root exudates cause soil particles to adhere firmly to root surfaces, roots significantly increase soil strength and therefore also increase the resistance of the topsoil to erosion by concentrated flow. This paper aims at contributing to a better prediction of the root effects on soil erosion rates in the EUROSEM model, as the input values accounting for roots, presented in the user manual, do not account for differences in root density or root architecture. Recent research indicates that small changes in root density or differences in root architecture considerably influence soil erosion rates during concentrated flow. The approach for incorporating the root effects into this model is based on a comparison of measured soil detachment rates for bare and for root-permeated topsoil samples with predicted erosion rates under the same flow conditions using the erosion equation of EUROSEM. Through backwards calculation, transport capacity efficiencies and corresponding soil cohesion values can be assessed for bare and root-permeated topsoils respectively. The results are promising and present soil cohesion values that are in accordance with reported values in the literature for the same soil type (silt loam). The results show that grass roots provide a larger increase in soil cohesion as compared with tap-rooted species and that the increase in soil cohesion is not significantly different under wet and dry soil conditions, either for fibrous root systems or for tap root systems. Power and exponential relationships are established between measured root density values and the corresponding calculated soil cohesion values, reflecting the effects of roots on the resistance of the topsoil to concentrated flow incision. These relationships enable one to incorporate the root effect into the soil erosion model EUROSEM, through adapting the soil cohesion input value. A scenario analysis shows that the contribution of roots to soil cohesion is very important for preventing soil loss and reducing runoff volume. The increase in soil shear strength due to the binding effect of roots on soil particles is two orders of magnitude lower as compared with soil reinforcement achieved when roots mobilize their tensile strength during soil shearing and root breakage. Copyright © 2008 John Wiley & Sons, Ltd. [source] Dynamics of soil erosion rates and controlling factors in the Northern Ethiopian Highlands , towards a sediment budgetEARTH SURFACE PROCESSES AND LANDFORMS, Issue 5 2008Jan Nyssen Abstract This paper analyses the factors that control rates and extent of soil erosion processes in the 199 ha May Zegzeg catchment near Hagere Selam in the Tigray Highlands (Northern Ethiopia). This catchment, characterized by high elevations (2100,2650 m a.s.l.) and a subhorizontal structural relief, is typical for the Northern Ethiopian Highlands. Soil loss rates due to various erosion processes, as well as sediment yield rates and rates of sediment deposition within the catchment (essentially induced by recent soil conservation activities), were measured using a range of geomorphological methods. The area-weighted average rate of soil erosion by water in the catchment, measured over four years (1998,2001), is 14·8 t ha,1 y,1, which accounts for 98% of the change in potential energy of the landscape. Considering these soil loss rates by water, 28% is due to gully erosion. Other geomorphic processes, such as tillage erosion and rock fragment displacement by gravity and livestock trampling, are also important, either within certain land units, or for their impact on agricultural productivity. Estimated mean sediment deposition rate within the catchment equals 9·2 t ha,1 y,1. Calculated sediment yield (5·6 t ha,1 y,1) is similar to sediment yield measured in nearby catchments. Seventy-four percent of total soil loss by sheet and rill erosion is trapped in exclosures and behind stone bunds. The anthropogenic factor is dominant in controlling present-day erosion processes in the Northern Ethiopian Highlands. Human activities have led to an overall increase in erosion process intensities, but, through targeted interventions, rural society is now well on the way to control and reverse the degradation processes, as can be demonstrated through the sediment budget. Copyright © 2007 John Wiley & Sons, Ltd. [source] The effect of single vegetation elements on wind speed and sediment transport in the Sahelian zone of Burkina FasoEARTH SURFACE PROCESSES AND LANDFORMS, Issue 10 2007J. K. Leenders Abstract Soil loss caused by wind erosion is a widespread phenomenon in the Sahelian zone of West Africa. According to Sahelian farmers, scattered vegetation standing in amongst the crop has the potential for a wind erosion control strategy. This study was conducted to study the effect of single vegetation elements on the pattern of average wind speed and sediment transport. This was done by two experiments that were carried out during the rainy seasons of 2002 and 2003 in north Burkina Faso, West Africa. Wind speeds were measured using three sonic anemometers, at a sampling frequency of 16 Hz. Sediment transport was determined by calculating the mass fluxes from 17 MWAC catchers. In this study, a shrub was defined as a vegetation element with branches until ground and a tree as a vegetation element with a distinctive trunk below a canopy. Behind shrubs wind speed near the soil surface was reduced up to approximately seven times the height of the shrub. The observed reduction in wind speed in the area where wind speed was reduced was 15 per cent on average. At the sides of the shrub, wind speed was increased, by on average 6 per cent. As the area of increase in wind speed is one-third of the area of decrease in wind speed, the net effect of a shrub is a reduction in wind speed. A similar pattern was visible for the pattern of sediment transport around a shrub. Downwind of a shrub, sediment transport was diminished up to seven times the height of the shrub. Probably most of this material was trapped by the shrub. Trees showed a local increase of wind around the trunk, which is expected to relate to an increase in sediment transport around the trunk. Mass flux measurements of sediment transport were not made, but visual observations in the field substantiate this. Behind the canopy of a tree, a tree acts similarly to a shrub regarding its effects on average wind speed, but as a tree is generally a larger obstacle than a shrub the extent of this effect is larger than for shrubs. Thus, whereas shrubs are more effective than trees regarding their direct effect on soil loss by trapping sand particles near the soil surface, trees are more effective in affecting soil loss indirectly by reducing the wind speed downwind more effectively than shrubs. Therefore, to reduce soil loss in an area, the presence of both trees and shrubs is crucial. Copyright © 2007 John Wiley & Sons, Ltd. [source] Experimental study of rill bank collapseEARTH SURFACE PROCESSES AND LANDFORMS, Issue 2 2007Jovan R. Stefanovic Abstract Rill bank collapse is an important component in the adjustment of channel morphology to changes in discharge and sediment flux. Sediment inputs from bank collapse cause abrupt changes in flow resistance, flow patterns and downstream sediment concentrations. Generally, bank retreat involves gradual lateral erosion, caused by flow shear stress, and sudden bank collapse, triggered by complex interactions between channel flow and bank and soil water conditions. Collapse occurs when bank height exceeds the critical height where gravitational forces overcome soil shear strength. An experimental study examined conditions for collapse in eroding rill channels. Experiments with and without a deep water table were carried out on a meandering rill channel in a loamy sand and sandy loam in a laboratory flume under simulated rainfall and controlled runon. Different discharges were used to initiate knickpoint and rill incision. Soil water dynamics were monitored using microstandpipes, tensiometers and time domain reflectometer probes (TDR probes). Bank collapse occurred with newly developed or rising pre-existing water tables near rill banks, associated with knickpoint migration. Knickpoint scour increased effective bank height, caused positive pore water pressure in the bank toe and reduced negative pore pressures in the unsaturated zone to near zero. Matric tension in unsaturated parts of the bank and a surface seal on the ,interrill' zone behind the bank enhanced stability, while increased effective bank height and positive pore water pressure at the bank toe caused instability. With soil water contents >35 per cent (sandy loam) and >23 per cent (loamy sand), critical bank heights were 0·11,0·12 m and 0·06,0·07 m, respectively. Bank toe undercutting at the outside of the rill bends also triggered instability. Bank displacement was quite different on the two soils. On the loamy sand, the failed block slid to the channel bed, revealing only the upper half of the failure plane, while on the sandy loam the failed block toppled forwards, exposing the failure plane for the complete bank height. This study has shown that it is possible to predict location, frequency and magnitude of the rill bank collapse, providing a basis for incorporation into predictive models for hillslope soil loss or rill network development. Copyright © 2006 John Wiley & Sons, Ltd. [source] Soil detachment and transport on field- and laboratory-scale interrill areas: erosion processes and the size-selectivity of eroded sedimentEARTH SURFACE PROCESSES AND LANDFORMS, Issue 8 2006O. Malam Issa Abstract Field- and laboratory-scale rainfall simulation experiments were carried out in an investigation of the temporal variability of erosion processes on interrill areas, and the effects of such variation upon sediment size characteristics. Poorly aggregated sandy soils from the semi-arid environment of Senegal, West Africa, were used on both a 40 m2 field plot and a 0·25 m2 laboratory plot; rainfall intensity for all experiments was 70 mm h,1 with a duration of 1 to 2 hours. Time-series measurements were made of the quantity and the size distribution of eroded material: these permitted an estimate of the changing temporal balance between the main erosion processes (splash and wash). Results from both spatial scales showed a similar temporal pattern of runoff generation and sediment concentration. For both spatial scales, the dominant erosional process was detachment by raindrops; this resulted in a dynamic evolution of the soil surface under raindrop impact, with the rapid formation of a sieving crust followed by an erosion crust. However, a clear difference was observed between the two scales regarding the size of particles detached by both splash and wash. While all measured values were lower than the mean weight diameter (MWD) value of the original soil (mean 0·32 mm), demonstrating the size-selective nature of wash and splash processes, the MWD values of washed and splashed particles at the field scale ranged from 0·08 to 0·16 mm and from 0·12 to 0·30 mm respectively, whereas the MWD values of washed and splashed particles at the laboratory scale ranged from 0·13 to 0·29 mm and from 0·21 to 0·32 mm respectively. Thus only at the field scale were the soil particles detached by splash notably coarser than those transported by wash. This suggests a transport-limited erosion process at the field scale. Differences were also observed between the dynamics of the soil loss by wash at the two scales, since results showed wider scatter in the field compared to the laboratory experiments. This scatter is probably related to the change in soil surface characteristics due to the size-selectivity of the erosion processes at this spatial scale. Copyright © 2006 John Wiley & Sons, Ltd. [source] Interrill erosion on cultivated Greek soils: modelling sediment deliveryEARTH SURFACE PROCESSES AND LANDFORMS, Issue 8 2006D. Dimoyiannis Abstract For interrill erosion, raindrop-induced detachment and transport of sediment by rainfall-disturbed sheet flow are the predominant processes, while detachment by sheet flow and transport by raindrop impact are negligible. In general, interrill subprocesses are inter-actively affected by rainfall, soil and surface properties. The objective of this work was to study the relationships among interrill runoff and sediment loss and some selected para-meters, for cultivated soils in central Greece, and also the development of a formula for predicting single storm sediment delivery. Runoff and soil loss measurement field experiments have been conducted for a 3·5-year period, under natural storms. The soils studied were developed on Tertiary calcareous materials and Quaternary alluvial deposits and were textured from sandy loam to clay. The second group of soils showed greater susceptibility to sealing and erosion than the first group. Single storm sediment loss was mainly affected by rain and runoff erosivity, being significantly correlated with rain kinetic energy (r = 0·64***), its maximum 30-minute intensity (r = 0·64***) and runoff amount (r = 0·56***). Runoff had the greatest correlation with rain kinetic energy (r = 0·64***). A complementary effect on soil loss was detected between rain kinetic energy and its maximum 30-minute intensity. The same was true for rain kinetic energy and topsoil aggregate instability, on surface seal formation and thus on infiltration characteristics and overland flow rate. Empirical analysis showed that the following formula can be used for the successful prediction of sediment delivery (Di): Di = 0·638,EI30tan(,) (R2 = 0·893***), where , is a topsoil aggregate instability index, E the rain kinetic energy, I30 the maximum 30-minute rain intensity and , the slope angle. It describes soil erodibility using a topsoil aggregate instability index, which can be determined easily by a simple laboratory technique, and runoff through the product of this index and rain kinetic energy. Copyright © 2006 John Wiley & Sons, Ltd. [source] Runoff and soil loss under individual plants of a semi-arid Mediterranean shrubland: influence of plant morphology and rainfall intensityEARTH SURFACE PROCESSES AND LANDFORMS, Issue 5 2006E. Bochet Abstract The influence of plant morphology and rainfall intensity on soil loss and runoff was determined at the plant scale for three representative species of a semi-arid patchy shrubland vegetation of east Spain, representing contrasting canopy structures and plant phenologies (Rosmarinus officinalis, Anthyllis cytisoides and Stipa tenacissima). Twenty-seven microplots of less than 1 m2, each containing one single plant, were built to quantify runoff volume and sediment yield under the canopies of the three species. Runoff and rates of soil loss measured in these plots under natural rainfall conditions were compared with control microplots built in the bare inter-plant areas. Precipitation was automatic-ally recorded and rainfall intensity calculated over a two-year period. Results indicated that individual plants played a relevant role in interrill erosion control at the microscale. Compared with a bare soil surface, rates of soil loss and runoff reduction varied strongly depending on the species. Cumulative soil loss was reduced by 94·3, 88·0 and 30·2 per cent, and cumulative runoff volume was reduced by 66·4, 50·8 and 18·4 per cent under the Rosmarinus, Stipa and Anthyllis canopies, respectively, compared with a bare surface. Anthyllis was significantly less efficient than the two other species in reducing runoff volume under its canopy. Differences between species could only be identified above a rainfall intensity threshold of 20 mm h,1. The different plant morphologies and plant compon-ents explained the different erosive responses of the three species. Canopy cover played a major role in runoff and soil loss reduction. The presence of a second layer of protection at the soil surface (litter cover) was fundamental for erosion control during intense rainfall. Rainfall intensity and soil water status prior to rainfall strongly influenced runoff and soil loss rates. The possible use of these species in restoration programmes of degraded areas is discussed. Copyright © 2006 John Wiley & Sons, Ltd. [source] Sediment production in large gullies of the Mediterranean area (NE Spain) from high-resolution digital elevation models and geographical information systems analysisEARTH SURFACE PROCESSES AND LANDFORMS, Issue 5 2003J. A. Martínez-Casasnovas Abstract Recent studies in the Mediterranean area have shown gully erosion to have a very significant contribution to total soil loss. In the Penedès vineyard region (NE Spain), between 15 and 27% of the land is affected by large gullies and gully-wall retreat seems to be an ongoing process. Multi-date digital elevation model (DEM) analysis has allowed computation of sediment production by gully erosion, showing that the sediment production rates are very high by the, up-to-date, usual global standards. Here, we present a study carried out using large-scale multi-date (1975 and 1995) aerial photographs (1 : 5000 and 1 : 7000) to monitor sediment yield caused by large gullies in the Penedès region (NE Spain). High-resolution DEMs (1 m grid) were derived and analysed by means of geographical information systems techniques to determine the gully erosion rates. Rainfall characteristics within the same study period were also analysed in order to correlate with the soil loss produced. Mass movement was the main process contributing to total sediment production. This process could have been favoured by rainfalls recorded during the period: 58% of the events were of an erosive character and showed high kinetic energy and erosivity. A sediment production rate of 846 ± 40 Mg ha,1 year,1, a sediment deposition rate of 270 ± 18 Mg ha,1 year,1 and a sediment delivery ratio of 68·1% were computed for a gully area of 0·10 km2. The average net erosion within the study period (1975,95) was 576 ± 58 Mg ha,1 year,1. In comparison with other methods, the proposed method also includes sediment produced by processes other than only overland flow, i.e. downcutting, headcutting, and mass movements and bank erosion. Copyright © 2003 John Wiley & Sons, Ltd. [source] Use of vegetative furrows to mitigate copper loads and soil loss in runoff from polyethylene (plastic) mulch vegetable production systemsENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 3 2004Pamela J. Rice Abstract The transport of runoff with high copper concentrations and sediment loads into adjacent surface waters can have adverse effects on nontarget organisms as a result of increased turbidity and degraded water quality. Runoff from vegetable production utilizing polyethylene mulch can contain up to 35% of applied copper, a widely used fungicide/bactericide that has adverse effects on aquatic organisms. Copper is primarily transported in runoff with suspended particulates; therefore, implementation of management practices that minimize soil erosion will reduce copper loads. Replacing bare-soil furrows with furrows planted in rye (Secale cereale) significantly improved the sustainability of vegetable production with polyethylene mulch and reduced the potential environmental impact of this management practice. Vegetative furrows decreased runoff volume by >40% and soil erosion by >80%. Copper loads with runoff were reduced by 72% in 2001, primarily as a result of reduced soil erosion since more than 88% of the total copper loads were transported in runoff with suspended soil particulates. Tomato yields in both years were similar between the polyethylene mulch plots containing either bare-soil or vegetative furrows. Replacing bare-soil furrows with vegetative furrows greatly reduces the effects of sediments and agrochemicals on sensitive ecosystems while maintaining crop yields. [source] Soil infiltration, runoff and sediment yield from a shallow soil with varied stone cover and intensity of rainEUROPEAN JOURNAL OF SOIL SCIENCE, Issue 4 2005Uttam Kumar Mandal Summary Stones on the surface of the soil enhance infiltration and protect the soil against erosion. They are often removed in modern mechanized agriculture, with unfortunate side-effects. We evaluated experimentally the influence of surface stones on infiltration, runoff and erosion under field conditions using a portable rainfall simulator on bare natural soil in semi-arid tropical India, because modernization and mechanization often lead to removal of these stones in this region. Four fields with varied cover of stones from 3 to 65% were exposed to three rainfall intensities (48.5, 89.2 and 136.8 mm hour,1). Surface stones retarded surface runoff, increased final infiltration rates, and diminished sediment concentration and soil loss. The final infiltration ranged from 26 to 83% of rainfall when the rainfall intensity was 136.8 mm hour,1. The reduction in runoff and soil erosion and increase in infiltration were more pronounced where stones rested on the soil surface than where they were buried in the surface layer. The sediment yield increased from 2 g l,1 for 64.7% stone cover with rainfall of 48.5 mm hour,1 to 70 g l,1 for 3.5% stone cover with rain falling at 136.8 mm hour,1. The soil loss rate was less than 2 t ha,1 hour,1 for the field with stone cover of 64.7% even when the rainfall intensity was increased to 136.8 mm hour,1. The effects of stones on soil loss under the varied rainfall intensities were expressed mathematically. The particles in the sediment that ran off were mostly of silt size. [source] Quantifying prehistoric soil erosion,A review of soil loss methods and their application to a Celtic square enclosure (Viereckschanze) in Southern GermanyGEOARCHAEOLOGY: AN INTERNATIONAL JOURNAL, Issue 8 2007Matthias Leopold This paper discusses the strengths and weaknesses of three different methods for quantifying prehistoric soil erosion. Method A estimates erosion by determining the amount of colluvium stored downhill. Method B involves reconstructing a former erosion surface using truncated soil horizons. Method C compares the elevation of a paleosol beneath an earthwork with the modern surface in the surrounding area. Each method was applied to a Celtic earthwork (Viereckschanze) at Poign (near Regensburg) in Southern Germany in order to cross-check the different results. For an erosion area of 3.6 ha and during 300 years of agricultural usage, Method A calculates a minimum erosion rate of 20.8 t/ha/a. Method B computes 10 t/ha/a of soil loss. Method C yields the highest rate of erosion with 24.2 t/ha/a. We have confidence in Method C, which implies an underassesment of soil loss in using methods A or B. © 2007 Wiley Periodicals, Inc. [source] RUNOFF PRODUCTION AND EROSION PROCESSES ON A DEHESA IN WESTERN SPAIN,GEOGRAPHICAL REVIEW, Issue 3 2002ANTONIO CEBALLOS ABSTRACT. Runoff generation and soil erosion were investigated at the Guadalperalón experimental watershed (western Spain), within the land-use system known as dehesa, or open, managed evergreen forests. Season and type of surface were found to control runoff and soil-loss rates. Five soil units were selected as representative of surface types found in the study area: hillslope grass, bottom grass, tree cover, sheep trails, and shrub cover. Measurements were made in various conditions with simulated rainfall to gain an idea of the annual variation in runoff and soil loss. Important seasonal differences were noted due to surface cover and moisture content of soil, but erosion rates were determined primarily by runoff. Surfaces covered with grass and shrubs always showed less erosion; surfaces covered with holm oaks showed higher runoff rates, due to the hydrophobic character of the soils. Concentrations of runoff sediment during the simulations confirmed that erosion rates at the study site depended directly on the sediment available on the soil surface. [source] Elevated carbon dioxide and irrigation effects on water stable aggregates in a Sorghum field: a possible role for arbuscular mycorrhizal fungiGLOBAL CHANGE BIOLOGY, Issue 3 2001Matthias C. Rillig Summary While soil biota and processes are becoming increasingly appreciated as important parameters for consideration in global change studies, the fundamental characteristic of soil structure is a neglected area of research. In a sorghum [Sorghum bicolor (L.) Moench] field experiment in which CO2[supplied using free-air CO2 enrichment (FACE) technology] was crossed factorially with an irrigation treatment, soil aggregate (1,2 mm) water stability increased in response to elevated CO2. Aggregate water stability was increased by 40% and 20% in response to CO2, at ample and limited water supply treatments, respectively. Soil hyphal lengths of arbuscular mycorrhizal fungi (AMF) increased strongly (with a threefold increase in the dry treatment) in response to CO2, and the concentrations of one fraction (easily extractable glomalin, EEG) of the AMF-produced protein glomalin were also increased. Two fractions of glomalin, and AMF hyphal lengths were all positively correlated with soil aggregate water stability. The present results further support the hypothesis that AMF can become important in global change scenarios. Although in this field study a causal relationship between hyphal length, glomalin and aggregate stability cannot be demonstrated, the present data do suggest that AMF could mediate changes in soil structure under elevated CO2. This could be of great importance in agricultural systems threatened by erosional soil loss. [source] The effect of soil type, meteorological forcing and slope gradient on the simulation of internal erosion processes at the local scaleHYDROLOGICAL PROCESSES, Issue 13 2010Guillaume Nord Abstract Numerical simulation experiments of water erosion at the local scale (20 × 5 m) using a process-based model [Plot Soil Erosion Model_2D (PSEM_2D)] were carried out to test the effects of various environmental factors (soil type, meteorological forcing and slope gradient) on the runoff and erosion response and to determine the dominant processes that control the sediment yield at various slope lengths. The selected environmental factors corresponded to conditions for which the model had been fully tested beforehand. The use of a Green and Ampt model for infiltration explained the dominant role played by rainfall intensity in the runoff response. Sediment yield at the outlet of the simulated area was correlated positively with rainfall intensity and slope gradient, but was less sensitive to soil type. The relationship between sediment yield (soil loss per unit area) and slope length was greatly influenced by all environmental factors, but there was a general tendency towards higher sediment yield when the slope was longer. Contribution of rainfall erosion to gross erosion was dominant for all surfaces with slope lengths ranging from 4 to 20 m. The highest sediment yields corresponded to cases where flow erosion was activated. An increase in slope gradient resulted in flow detachment starting upstream. Sediment exported at the outlet of the simulated area came predominantly from the zone located near the outlet. The microrelief helped in the development of a rill network that controlled both the ratio between rainfall and flow erosion and the relationship between sediment yield and slope length. Copyright © 2010 John Wiley & Sons, Ltd. [source] Predicting unit plot soil loss in Sicily, south ItalyHYDROLOGICAL PROCESSES, Issue 5 2008V. Bagarello Abstract Predicting soil loss is necessary to establish soil conservation measures. Variability of soil and hydrological parameters complicates mathematical simulation of soil erosion processes. Methods for predicting unit plot soil loss in Sicily were developed by using 5 years of data from replicated plots. At first, the variability of the soil water content, runoff, and unit plot soil loss values collected at fixed dates or after an erosive event was investigated. The applicability of the Universal Soil Loss Equation (USLE) was then tested. Finally, a method to predict event soil loss was developed. Measurement variability decreased as the mean increased above a threshold value but it was low also for low values of the measured variable. The mean soil loss predicted by the USLE was lower than the measured value by 48%. The annual values of the soil erodibility factor varied by seven times whereas the mean monthly values varied between 1% and 244% of the mean annual value. The event unit plot soil loss was directly proportional to an erosivity index equal to , being QRRe the runoff ratio times the single storm erosion index. It was concluded that a relatively low number of replicates of the variable of interest may be collected to estimate the mean for both high and particularly low values of the variable. The USLE with the mean annual soil erodibility factor may be applied to estimate the order of magnitude of the mean soil loss but it is not usable to estimate soil loss at shorter temporal scales. The relationship for estimating the event soil loss is a modified version of the USLE-M, given that it includes an exponent for the QRRe term. Copyright © 2007 John Wiley & Sons, Ltd. [source] Erosion models: quality of spatial predictionsHYDROLOGICAL PROCESSES, Issue 5 2003Victor Jetten Abstract An Erratum has been published for this article in Hydrological Processes 18(3) 2004, 595. An overview is given on the predictive quality of spatially distributed runoff and erosion models. A summary is given of the results of model comparison workshops organized by the Global Change and Terrestrial Ecosystems Focus 3 programme, as well as other results obtained by individual researchers. The results concur with the generally held viewpoint in the literature that the predictive quality of distributed models is moderately good for total discharge at the outlet, and not very good for net soil loss. This is only true if extensive calibration is done: uncalibrated results are generally bad. The more simple lumped models seem to perform equally well as the more complex distributed models, although the latter produce more detailed spatially distributed results that can aid the researcher. All these results are outlet based: models are tested on lumped discharge and soil loss or on hydrographs and sedigraphs. Surprisingly few tests have been done on the comparison of simulated and modelled erosion patterns, although this may arguably be just as important in the sense of designing anti-erosion measures and determining source and sink areas. Two studies are shown in which the spatial performance of the erosion model LISEM (Limburg soil erosion model) is analysed. It seems that: (i) the model is very sensitive to the resolution (grid cell size); (ii) the spatial pattern prediction is not very good; (iii) the performance becomes better when the results are resampled to a lower resolution and (iv) the results are improved when certain processes in the model (in this case gully incision) are restricted to so called ,critical areas', selected from the digital elevation model with simple rules. The difficulties associated with calibrating and validating spatially distributed soil erosion models are, to a large extent, due to the large spatial and temporal variability of soil erosion phenomena and the uncertainty associated with the input parameter values used in models to predict these processes. They will, therefore, not be solved by constructing even more complete, and therefore more complex, models. However, the situation may be improved by using more spatial information for model calibration and validation rather than output data only and by using ,optimal' models, describing only the dominant processes operating in a given landscape. Copyright © 2003 John Wiley & Sons, Ltd. [source] Hydrological and erosional response to natural rainfall in a semi-arid area of south-east SpainHYDROLOGICAL PROCESSES, Issue 4 2001M. Martinez-Mena Abstract A better knowledge of soil erosion by water is essential for planning effective soil and water conservation practices in semi-arid Mediterranean environments. The special climatic and hydrological characteristics of these areas, however, make accurate soil loss predictions difficult, particularly in the absence of minimal data. Two zero-order experimental microcatchments (328,759 m2), representative of an extensive semi-arid watershed with a high potential erosion risk in the south-east of Spain, were selected and monitored for 3 years (1991,93) in order to provide information on the hydrological and erosional response. A pluviogram and hydrograph recorded data at 1-min intervals during each storm, after which the soil loss was collected and the particle size of the sediment was analysed. Runoff coefficients of about 9% and soil losses of between 84·83 and 298·9 g m,2 year,1 were observed in the area. Rapid response times (geometric mean values lower than 2 h) and low runoff thresholds (mean values between 3·5 to 5·9 mm) were the norm in the experimental areas. A rain intensity of over 15 mm h,1 was considered as ,erosive rainfall' in these areas because of the total soil loss and the transport capacity of the overland flow. Differences in pore-size distribution explained the different hydrological responses observed between areas. The erosional response was more complex and basically seemed to be determined by soil aggregate stability and topographical properties. A greater proportion of finer particles in the eroded material than in the soil matrix indicated selective erosion and the transport of finer material. Copyright © 2001 John Wiley & Sons, Ltd. [source] SOIL EROSION AND SEDIMENT YIELD PREDICTION ACCURACY USING WEPP,JOURNAL OF THE AMERICAN WATER RESOURCES ASSOCIATION, Issue 2 2004John M. Laflen ABSTRACT: The objectives of this paper are to discuss expectations for the Water Erosion Prediction Project (WEPP) accuracy, to review published studies related to WEPP goodness of fit, and to evaluate these in the context of expectations for WEPP's goodness of fit. WEPP model erosion predictions have been compared in numerous studies to observed values for soil loss and sediment delivery from cropland plots, forest roads, irrigated lands and small watersheds. A number of different techniques for evaluating WEPP have been used, including one recently developed where the ability of WEPP to accurately predict soil erosion can be compared to the accuracy of replicated plots to predict soil erosion. In one study involving 1,594 years of data from runoff plots, WEPP performed similarly to the Universal Soil Loss Erosion (USLE) technology, indicating that WEPP has met the criteria of results being "at least as good with respect to observed data and known relationships as those from the USLE," particularly when the USLE technology was developed using relationships derived from that data set, and using soil erodibility values measured on those plots using data sets from the same period of record. In many cases, WEPP performed as well as could be expected, based on comparisons with the variability in replicate data sets. One major finding has been that soil erodibility values calculated using the technology in WEPP for rainfall conditions may not be suitable for furrow irrigated conditions. WEPP was found to represent the major storms that account for high percentages of soil loss quite well,a single storm application that the USLE technology is unsuitable for,and WEPP has performed well for disturbed forests and forest roads. WEPP has been able to reflect the extremes of soil loss, being quite responsive to the wide differences in cropping, tillage, and other forms of management, one of the requirements for WEPP validation. WEPP was also found to perform well on a wide range of small watersheds, an area where USLE technology cannot be used. [source] The impact of cotton geotextiles on soil and water losses from Mediterranean rainfed agricultural landLAND DEGRADATION AND DEVELOPMENT, Issue 2 2010A. Giménez-Morera Abstract High soil erosion risk of Mediterranean cultivated soils is due to steep slopes, high rainfall intensities and low vegetation cover. Traditional land management as ploughing and herbicides give rise to high soil erosion rates. This paper reports on the use of a cotton geotextiles to control soil and water losses on agricultural land under Mediterranean climatic conditions. Eight paired plots (1, 2, 4 and 16,m2) were studied during 1-year period under natural rainfall. Forty rainfall simulations under wet and dry climatic conditions, and water drop penetration time (WDPT) tests, were carried out in order to analyze the effect of a geotextile on soil and water losses on a typical rainfed orchard in Eastern Spain. Results showed that an 8,mm thick cotton geotextile reduced soil loss to negligible values (from 14 to 0·1,Mg,ha,1,y,1) due to the low sediment concentration as geotextile covered 100% of the soil. However, infiltration rates decreased and runoff increased due to the hydrophobic response of the cotton material. The runoff discharge increased from 8% to 16% for the 2004 period under natural rainfall and from 27% to 87% under simulated rainfall when summer dry conditions were reached. The cotton geotextile reduced local soil losses at plot-scale, but increased runoff. Copyright © 2010 John Wiley & Sons, Ltd. [source] Erosion modelling approach to simulate the effect of land management options on soil loss by considering catenary soil development and farmers perceptionLAND DEGRADATION AND DEVELOPMENT, Issue 6 2008A. C. Brunner Abstract The prevention of soil erosion is one of the most essential requirements for sustainable agriculture in developing countries. In recent years it is widely recognized that more site-specific approaches are needed to assess variations in erosion susceptibility in order to select the most suitable land management methods for individual hillslope sections. This study quantifies the influence of different land management methods on soil erosion by modelling soil loss for individual soil-landscape units on a hillslope in Southern Uganda. The research combines a soil erosion modelling approach using the physically based Water Erosion Prediction Project (WEPP)-model with catenary soil development along hillslopes. Additionally, farmers' perceptions of soil erosion and sedimentation are considered in a hillslope mapping approach. The detailed soil survey confirmed a well-developed catenary soil sequence along the hillslope and the participatory hillslope mapping exercise proved that farmers can distinguish natural soil property changes using their local knowledge. WEPP-model simulations show that differences in soil properties, related to the topography along the hillslope, have a significant impact on total soil loss. Shoulder and backslope positions with steeper slope gradients were most sensitive to changes in land management. Furthermore, soil conservation techniques such as residue management and contouring could reduce soil erosion by up to 70 percent on erosion-sensitive slope sections compared to that under tillage practices presently used at the study site. The calibrated model may be used as a tool to provide quantitative information to farmers regarding more site-specific land management options. Copyright © 2008 John Wiley & Sons, Ltd. [source] Nutrient losses from rain-fed bench terraced cultivation systems in high rainfall areas of the mid-hills of NepalLAND DEGRADATION AND DEVELOPMENT, Issue 5 2007G. P. Acharya Abstract Between the elevations of 1000 and 2000,m in the mid-hills of Nepal, over 12 million people subsist on land-holdings of less than 0·5,ha. These farmers have limited access to commercial inputs such as fertilisers and are reliant on organic manures for soil fertility maintenance. Participatory research was conducted with farmers on bari land (upper slope rain-fed crop terraces) in the hill community of Landruk (bench terraces 0,5° slope, 3000,3500,mm annual rainfall, which aimed to develop soil and water management interventions that controlled erosion without resulting in high leaching, and so were effective in minimising total nutrient losses. Interventions tested were the control of water movement through diversion of run-on and planting fodder grasses on terrace risers on bench terraces. The interventions were effective in reducing soil loss from the bari land in comparison with existing farmer practices, but no effect was observed on nutrient losses in solution form through runoff and leaching. Losses of NO3 -N in leachate ranged from 17·3 to 99·7,kg,ha,1,yr,1, but only 0·7 to 5·6,kg,ha,1,yr,1 in runoff. The overall nutrient balance suggests that the system is not sustainable. Fertility is heavily dependent on livestock inputs and if the current trends of declining livestock numbers due to labour constraints continue, further losses in productivity can be expected. However, farmers are interested in interventions that tie ecosystem services with productivity enhancement and farmers' priorities should be used as entry points for promoting interventions that are system compatible and harness niche opportunities. Copyright © 2007 John Wiley & Sons, Ltd. [source] A systems analysis of soil and forest degradation in a mid-hill watershed of Nepal using a bio-economic modelLAND DEGRADATION AND DEVELOPMENT, Issue 5 2005B. K. Sitaula Abstract Forest degradation, manifested through decline in forest cover, and the resulting soil erosion and organic carbon losses, is a serious problem caused by a complex coupling of bio-physical, socio-economic and technological factors in the Himalayan watersheds. Greater understanding of the linkages between these factors requires a systems approach. We have proposed such an approach using a bio-economic model to explore the system behaviour of forest degradation, soil erosion, and soil C losses in the forest areas. The outcome of the model simulation over a 20-year period indicates that soil erosion and C loss rates may increase more than four-fold by the year 2020 under the existing socio-economic and biophysical regime (the base scenario). Reductions in the population growth rate, introduction of improved agricultural technology and increase in the prices of major agricultural crops can help slow down the rates of forest decline, soil erosion and C loss or even stabilize or reverse them. The results suggest that economic incentives may be highly effective in the reduction of soil loss, as well as C release to the atmosphere. Copyright © 2005 John Wiley & Sons, Ltd. [source] | |||||||||||||||||||