Soil Erosion Studies Research Articles

Laboratory Testing of Magnetic Tracers for Soil Erosion Measurement

Soil erosion, which includes soil detachment, transport, and deposition, is one of the important dynamic land surface processes. The magnetic tracer method is a useful method for studying soil erosion processes. In this study, five types of magnetic tracers were made with fine soil, fly ash, cement, bentonite, and magnetic powder (reduced iron powder) using the method of disk granulation. The tracers were uniformly mixed with soil and tested in the laboratory using simulated rainfall and inflow experiments to simulate the interrill and rill components of soil erosion, in order to select one or more tracers which could be used to study detachment and deposition by the erosive forces of raindrops and surface flow of water on a slope. The results showed that the five types of magnetic tracers with high magnetic susceptibility and a wide range of sizes had a range of 0.99-1.29 g cm −3 in bulk density. In the interrill and rill experiments, the tracers FC1 and FC2 which consisted of fly ash and cement at ratios of 1:1 and 2:1, respectively, were transported in phase with soil particles since the magnetic susceptibility of sediment approximated that of the soil which was uneroded and the slopes of the regression equations between the detachment of sediment and magnetic tracers FC1 and FC2 were very close to the expected value of 20, which was the original soil/tracer ratio. The detachment and deposition on slopes could be accurately reflected by the magnetic susceptibility differences. The change in magnetic susceptibility depended on whether deposition or detachment occurred. However, the tracer FS which consisted of fine soil and the tracers FB1 and FB2 which consisted of fly ash and bentonite at ratios of 1:1 and 2:1, respectively, were all unsuitable for soil erosion study since there was no consistent relationship between sediment and tracer detachment for increasing amounts of runoff. Therefore, the tracers FC1 and FC2 could be used to study soil erosion by water.

Using plot soil loss distribution for soil conservation design

Soil conservation design is generally based on the estimation of average annual soil loss but it should be developed taking into account storms of a given return period. However, use of frequency analysis in soil erosion studies is relatively limited. In this paper, an investigation on statistical distribution of soil loss measurements was firstly carried out using a relatively high number of simultaneously operating plots of different lengths, λ (11, 22, 33 and 44 m) at the experimental station of Sparacia (southern Italy). Using a simple normalization technique, the analysis showed that the probability distribution of the normalized soil loss is independent of both the scale length λ and the temporal scale, which are completely represented by the mean soil loss calculated for a given event using all replicated data collected in plots having the same length. Then, a comparison between the frequency distribution of soil loss and rainfall erosivity index of the USLE was carried out. An estimating criterion of the annual soil loss of a given return period was also developed. By this criterion, the frequency distribution of the rainfall erosivity factor can be used to design soil conservation practices.

A portable wind and rainfall simulator for in situ soil erosion measurements

Abstract Laboratory research in wind tunnels with the capability of simulating rainfall highlighted the importance of considering the complex interactions between wind and rainfall in the analysis of soil erosion processes. In order to overcome the inherent limitations of laboratory research and to further investigate these interactions under comparable conditions in the field, a Portable Wind and Rainfall Simulator (PWRS) has been developed. The aim of this study was to specify the wind and rainfall characteristics of the PWRS and to evaluate if its simulation quality and reproducibility is adequate for comparative soil erosion studies in the field. Wind velocity measurements show that a pre-shaped logarithmic boundary layer with a thickness of about 0.2 m exists. The uniformity of airflow across the tunnel is acceptable within the lower 0.3 m of the tunnel with maximum standard deviations below 0.7 ms − 1 . Maximum variability of wind velocities between three consecutive repetitions of the measurements is lower than 15%. The spatial rainfall distribution for windless rain show rather poor uniformity (Christiansen Uniformity (CU) coefficient = 60%), but very good reproducibility in-between five consecutive replications. About 90% of the test plot experiences a variability of rainfall below 5%. Simulated drop size distributions correspond very well with calculated Marshal–Palmer Distributions (MPD) of equal rainfall intensities (mean deviation of 2.1%). For wind-driven rain both above mentioned parameters clearly improve (CU = 76%, mean deviation = 1.7%). The mean rainfall intensities show also very low variability between the five replications with standard deviations of 0.31 mm h − 1 for windless rain (mean intensity 96 mm h − 1 ) and 0.69 mm h − 1 for wind-driven rain (mean intensity 88 mm h − 1 ). In conclusion, test results of the PWRS are very satisfactory, especially considering the physical constraints, which have to be taken into account to reach desired portability. The analysis presented in this study suggests in particular very good reproducibility of wind and rain conditions. The PWRS should therefore be a useful device for comparative in situ soil erosion measurements in the field and support the gathering of quantitative data on the relative importance of soil detachment rates between wind and water erosion, as well as windless and wind-driven rainfall.

Interpolação espacial da precipitação no Estado do Espírito Santo

The knowledge of spatial variability of rainfall is important in many agricultural and environmental sciences applications, such as crop production, water resources management, environmental management, and soil erosion studies. The purpose of this study was to evaluated two spatial interpolation methods applied to monthly rainfall in the State Espirito Santo, Brazil. Thirty years of monthly rainfall data (1997-2006) from 110 rain gauge stations, 94 stations in the State of Esprito Santo and 16 stations in the neighboring states, were used. The spatial interpolation methods ‘Inverse Distance to a Power’ (IPD), considering power from 2 to 6, and ‘Kriging’ (KR), exponential, spherical and linear models, were evaluated through the use of cross validation. The evaluation and selection of the best spatial interpolation methods was done by analyzing the statistical indexes (trusty index, adjusted efficiency coefficient and mean percent error). Results showed that KR method had better performance than IPD method concerning spatial interpolation of monthly rainfall in the State of Espirito Santo, presenting mean percent errors varying from 7.9 to 14.6%.

Response of Anatomical Features of Broadlesf Tree Root in Karst Area to Soil Erosion

Karst rocky desertification occurred in the southwest part of China was a seriously environmental problem, it is very important that expressing, dating, and reconstructing karst soil erosion process and history for understanding geomorphology of karst rocky desertification. Whereas accurately understanding karst soil erosion met a great obstacle of measuring problem for karst soil erosion from underground due to the dualistic systems of overground and underground. This was first time using exposed root anatomical features to imply karst soil erosion in China. Exposed and unexposed root samples in Puding, Guizhou, China were collected, and anatomical features were compared, parameters were measured, so as to obtain indicated information of soil erosion. Annual ring width could be appropriately applied to study the relationship of tree growth with environmental factors for the average sensitivity was larger than 0.2 for annual ring responding to soil layer. Tree root anatomical features were compared between exposed and unexposed root. The annual ring of unexposed root was smoothly increased from pith and decreased slowly when closed to bark, vessel size was the same and evenly distributed in each ring. Annual ring, pattern of vessel, and vessel size of exposed root was the same as unexposed root in prophase but an obviously mutation followed, annual ring narrowed, vessel lumen area reduced, vessel number decreased. After this mutation, a regular trend was shown but annual ring was narrower than unexposed root. From the anatomical changes of exposed root, the exact time of root exposure can be identified and the beginning of soil erosion happening. The response of anatomical features of tree root to soil erosion can offered a new method for the study of karst soil erosion and soil erosion historical record.

Assessment of Soil Erodibility in Taleghan Drainage Basin, Iran, Using Multivariate Statistics

Soil erosion has been recognized as one of the major forms of human-induced soil degradation. Due to land use changes in Iran, erosion has increased 800% between 1951 and 2002, calling for urgent action. But erosion research and policy development are hampered by a lack of information on the underlying factors controlling erosion. Soil types vary in their inherent susceptibility to erosion; but, like most countries, Iran lacks a network of field plots where erodibility is measured. A proxy for erodibility based on existing data and supplemented by an easily measured minimum data set is therefore needed. In this study, we use geological mapping and cluster, principal component, and factor analysis to group soils in the Taleghan Drainage Basin in Iran and subsequently determine their erodibility. First, a geological map of the area was prepared by photogeological methods and on-the-ground verification. Then, three soil profiles were investigated within similar landform units of each geological formation, and soil samples were taken. Physical and chemical properties that might impact soil erodibility (soil texture, pH, electrical conductivity, CaCO3, and soil organic matter) were used to create a matrix of soil properties and parent material. Application of cluster analysis and factor analysis to the data allowed identification of three geological (parent material) clusters. To investigate the mutual effect of land use and parent material on soil erodibility, a soil erodibility factor was obtained for three land use types in each cluster: rangeland, cropland (irrigated), and dry-land farming (nonirrigated). Geological cluster 1, consisting of marl, gypsum, and gypsiferous mudstone, was the most erodible; geological cluster 2, consisting of recent alluvium, alluvial fan, and landslip deposits, was of intermediate erodibility; and geological cluster 3, consisting of igneous rocks, dolomite, and conglomerate, was the least erodible. Within each geological cluster, dry-land farming was the most erodible, cropland was medium erodible, and rangeland was least erodible. The study suggests that geological and land use maps provide a useful framework for assessing soil erodibility. This work can guide future soil erosion studies and direct soil conservation policy to areas most susceptible to erosion.

Applying close range digital photogrammetry in soil erosion studies

Abstract Soil erosion due to rainfall and overland flow is a significant environmental problem. Studying the phenomenon requires accurate high‐resolution measurements of soil surface topography and morphology. Close range digital photogrammetry with an oblique convergent configuration is proposed in this paper as a useful technique for such measurements, in the context of a flume‐scale experimental study. The precision of the technique is assessed by comparing triangulation solutions and the resulting DEMs with varying tie point distributions and control point measurements, as well as by comparing DEMs extracted from different images of the same surface. Independent measurements were acquired using a terrestrial laser scanner for comparison with a DEM derived from photogrammetry. The results point to the need for a stronger geometric configuration to improve precision. They also suggest that the camera lens models were not fully adequate for the large object depths in this study. Nevertheless, the photogrammetric output can provide useful topographical information for soil erosion studies, provided limitations of the technique are duly considered.

Erosion Relevant Topographical Parameters Derived from Different DEMs—A Comparative Study from the Indian Lesser Himalayas

Topography is a crucial surface characteristic in soil erosion modeling. Soil erosion studies use a digital elevation model (DEM) to derive the topographical characteristics of a study area. Majority of the times, a DEM is incorporated into erosion models as a given parameter and it is not tested as extensively as are the parameters related to soil, land-use and climate. This study compares erosion relevant topographical parameters—elevation, slope, aspect, LS factor—derived from 3 DEMs at original and 20 m interpolated resolution with field measurements for a 13 km2 watershed located in the Indian Lesser Himalaya. The DEMs are: a TOPO DEM generated from digitized contour lines on a 1:50,000 topographical map; a Shuttle Radar Topography Mission (SRTM) DEM at 90-m resolution; and an Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) DEM at 15-m resolution. Significant differences across the DEMs were observed for all the parameters. The highest resolution ASTER DEM was found to be the poorest of all the tested DEMs as the topographical parameters derived from it differed significantly from those derived from other DEMs and field measurements. TOPO DEM, which is, theoretically more detailed, produced similar results to the coarser SRTM DEM, but failed to produce an improved representation of the watershed topography. Comparison with field measurements and mixed regression modeling proved SRTM DEM to be the most reliable among the tested DEMs for the studied watershed.

A Review of REE Tracer Method Used in Soil Erosion Studies

Rare earth elements (REEs) have been proved ideal tracers for soil erosion and aggregation. REE tracer method (REETM) used to study soil erosion, as a new technique, has been developed in recent 20 yr. It is able to quantitatively monitor the temporal and spatial variation of erosion intensity, compared with traditional approaches. The applications of REETM in studying of sediment differentiation law, erosion process evolution, determination of sediment sources and sedimentation investigations, and determination of prediction parameters, were reviewed. Some application limitations were summarized.

Correction factor to dye-measured flow velocity under varying water and sediment discharges

Summary Dye-tracing technique was a widely used method to determine the velocity of overland flow in soil erosion studies under both laboratory and field conditions. Few studies were performed to quantify the effects of sediment load on correction factor on steep slopes. This study was conducted to investigate the potential effects of sediment load on correction factor of overland flow to determine mean velocity in a glued hydraulic flume under a wide range of hydraulic conditions and sediment load. Slope gradient (S) varied from 8.7% to 34.2%, unit flow rate (q) from 0.66 to 5.26 × 10−3 m2 s−1, and sediment load (Qs) from 0 to 6.95 kg m−1 s−1. The Reynolds number (Re) ranged from 350 to 5899. Mean velocity was calculated from the volumetric relation using measured flow depth by a digital level probe and flow discharge. The results showed that correction factor decreased as S increased and increased as Re increased for sediment-free flow with a mean value of 0.659. Correction factor could be estimated with a logarithmic function of S and Re (R2 = 0.883). For the sediment-laden flow, correction factor varied from 0.233 to 0.682 with a mean value of 0.466. The correction factor decreased as sediment load (Qs) increased and increased as Re increased. It could be estimated with a logarithmic function of Re, and Qs (R2 = 0.796). For the combination of sediment-free and sediment-laden flows, the correction factor varied from 0.233 to 0.783 with a mean of 0.505. The correction factor was inversely related to slope gradient and sediment load, and directly to Reynolds number (R2 = 0.854). The overall results indicated that caution must be exercised and proper correction be made when using the dye tracer method to measure flow velocity in surface hydrology and erosion studies. Further studies with systematic advanced set up for sediment feeding are needed to quantify the potential effects of sediment load on correction factor under varying conditions of roughness element.

Development of new R, C and SDR modules for the SATEEC GIS system

Soil erosion is a natural phenomenon, but accelerated soil erosion is occurring with increased construction activities and intensive agricultural cultivation within many watersheds in recent years. To develop efficient soil erosion control best management practices, the soil erosion status in the target areas first needs to be understood spatially and temporally. The SATEEC system has been widely used for soil erosion studies because of its ease-of-use and limited input data requirement. However, SATEEC cannot be used for spatiotemporal analysis of soil erosion studies. Thus, the time-variant R, C, and GA-SDR modules were developed and integrated with the SATEEC system. The enhanced SATEEC 2.0 system estimated sediment yield values were compared with measured data for the Imha watershed. The R 2 value and the Nash–Sutcliffe coefficient were 0.72 and 0.72, respectively for calibration and 0.91 and 0.88, respectively for validation with the time-variant R, C and GA-SDR modules. The statistics indicate the enhanced SATEEC 2.0 system with these modules can be used for spatial and temporal analysis of soil erosion and sediment yield with higher accuracy and a limited input dataset, which is the primary philosophy of the SATEEC ArcView GIS system. Since the daily USLE C database was obtained from SWAT runs using the climate data and agricultural management data in Korea, the daily USLE C database should be adjusted depending on the climate condition and agricultural management when the SATEEC is applied to other watersheds having different climate and agricultural management systems.

A Rainfall Simulator for the in situ Study of Superficial Runoff and Soil Erosion

A rainfall simulator is an important tool for the study of runoff generation and soil loss because it can be used either under laboratory conditions, or in disturbed or natural soil. The objective of this study was to describe the design and operation of a rainfall simulator to evaluate soil loss in situ. The rainfall simulator has four full-cone spray nozzles with a Unijet system mounted in a straight line pipe configuration, and easily transported and assembled. Simulated rainfall uniformity was evaluated in the laboratory, whereas the applicability of the simulator in natural soil erosion plot conditions in an experimental field with different slopes was tested by quantifying runoff and evaluating soil erosion. Twenty simulations were carried out in the laboratory and sixteen in the field with slopes of 11, 21, and 39%. Four water-sprinklers in a straight line generated rainfall with uniformity close to 90%. The constructed simulator was easy to use and low cost, facilitating the necessary experimental replicates to achieve a suitable spatial representation of superficial runoff and soil loss on hillsides.

Selecting and Applying Cesium‐137 Conversion Models to Estimate Soil Erosion Rates in Cultivated Fields

The fallout radionuclide cesium-137 ((137)Cs) has been successfully used in soil erosion studies worldwide. However, discrepancies often exist between the erosion rates estimated using various conversion models. As a result, there is often confusion in the use of the various models and in the interpretation of the data. Therefore, the objective of this study was to test the structural and parametrical uncertainties associated with four conversion models typically used in cultivated agricultural landscapes. For the structural uncertainties, the Soil Constituent Redistribution by Erosion Model (SCREM) was developed and used to simulate the redistribution of fallout (137)Cs due to tillage and water erosion along a simple two-dimensional (horizontal and vertical) transect. The SCREM-predicted (137)Cs inventories were then imported into the conversion models to estimate the erosion rates. The structural uncertainties of the conversion models were assessed based on the comparisons between the conversion-model-estimated erosion rates and the erosion rates determined or used in the SCREM. For the parametrical uncertainties, test runs were conducted by varying the values of the parameters used in the model, and the parametrical uncertainties were assessed based on the responsive changes of the estimated erosion rates. Our results suggest that: (i) the performance/accuracy of the conversion models was largely dependent on the relative contributions of water vs. tillage erosion; and (ii) the estimated erosion rates were highly sensitive to the input values of the reference (137)Cs level, particle size correction factors and tillage depth. Guidelines were proposed to aid researchers in selecting and applying the conversion models under various situations common to agricultural landscapes.

Plutonium as a tracer of soil and sediment movement in the Herbert River, Australia

Plutonium fallout from atmospheric nuclear-weapons testing in the 1950s and 1960s constitutes an artificial tracer suitable for the study of recent soil erosion and sediment accumulation rates. Traditionally 137Cs has been the fallout isotope of choice for such studies, but the plutonium isotopes confer a number of advantages, which can be realised using the ultra-sensitive detection technique of Accelerator Mass Spectrometry (AMS). As a first application of plutonium to a whole-of-basin study, Pu has been measured in both soil and sediment across the catchment of the Herbert River, which is one of the major rivers draining into Australia’s Great Barrier Reef Lagoon. Its catchment includes undisturbed areas as well as regions of pasture and sugar cultivation. The Pu measurements allow the relative contributions of surface and gully erosion from the different land use areas to be determined, and permit the discharged material to be apportioned between the relevant sources.

10Be application to soil development on Marion Island, southern Indian Ocean

Marion Island, located in the southern Indian Ocean, constitutes the summit of an active shield volcano. It is a small terrestrial environment where glacially abraded bedrock became exposed c × 10 kyr ago. These conditions provide an interesting possibility for the assessment of 10Be accumulation rates and their application to soil erosion studies on the island. 10Be concentrations were measured in precipitation, soil profiles and an Azorella selago cushion plant. The data reveal a 10Be precipitation flux several times higher than model prediction. Estimation of the 10Be accumulation based on the soil inventory suggests a span between 2000 and 7000 yr. This time span is not in accordance with the accepted notion that the island was covered with ice about 10,000 yr ago and suggests either removal of 10Be from the soil profile, an overestimated Holocene 10Be-flux or a delayed soil development history. Our results provide new data on 10Be concentrations from the sub-Antarctic islands and contribute towards enlarging the southern-hemisphere 10Be database.

Calibration of simulated rainfall characteristics for the study of soil erosion on agricultural land

Rainfall simulation is a widely used method for soil erosion studies on agricultural land. Major problem of this experimental research method is the comparability between different simulators due to differences in simulated rainfall. Therefore the purpose of this study is to characterize the rainfall produced by a rainfall simulator which was widely used during the last decades. Four different calibration methods were used to assess the drop size distribution: (1) Indication Paper, (2) Plaster Micro Plot, (3) Joss–Waldvogel Disdrometer and (4) Laser Distrometer (Thies). Additionally, the latter one was used to measure drop fall velocity in combination with drop diameter. The spatial rainfall distribution pattern on the plot was measured with 100 rainfall gauges. The spatial rainfall distribution pattern clearly shows a heterogeneity, which is caused by the used nozzle configuration. Considerable differences in drop-size distribution can be observed depending on the used measurement technique. Laser Disdrometer and Plaster Micro Plot cover the whole produced drop size spectrum ranging from <0.5 mm to >3.0 mm, whereas Indication Paper as well as the Joss–Waldvogel Disdrometer primarily show drops smaller than 2.0 mm. Characterisation of rainfall is therefore strongly dependent on the used method and if different methods are used, may lead to contradictory results. The volume drop size distribution reflected by the Laser Distrometer is very similar to that one produced by rain with an intensity of 40 mm h −1. Nevertheless, with maximum velocities above 10 m s −1 small drops are by far too fast and large drops with velocities dominantly below 5 m s −1 are too slow compared to natural rainfall. As an overall result, the simulator can be characterised as suitable for runoff and infiltration measurements, but with constraints due to the low reproducibility of the spatial rain distribution. As a consequence of the produced drop spectrum and fall velocity the erosion quantities may be underestimated systematically. For this, methodological development has to be focussed on homogeneous spatial rainfall distributions and on increasing the amount of large drops with higher fall velocities.

Development and Application of SATEEC L Module for Slope Length Adjustment Based on Topography Change

Severe sediment-laden problem has been the hot issue in Korea. It was assumed that agricultural activities and landslides were the primary causes of these problems in watersheds. The USLE-based systems have been widely used in soil erosion studies. However the GIS-based USLE modeling system has limitation in USLE L factors. In this study, the SATEEC L module was developed to reflect the slope length segmentations in the fields. The SATEEC L module was applied to the study watershed to analyze the effects of using the SATEEC L module on estimated sediment. As shown in the comparisons between SATEEC estimated sediment with SWAT values, the SATEEC GA-SDR module derives the SDR with reasonably acceptable accuracies. However, it is worthy to note that the soil erosion using the SATEEC L module for the study watershed was lower than that without using the SATEEC L module by 25%, although the SATEEC estimated sediment values with and without using L module match the SWAT sediment values with similar accuracies. This is because the SATEEC GA-SDR module estimates lower SDR in case of greater soil erosion estimation without the L module and greater SDR in case of lower soil erosion estimation with the L module. This indicates that the SATEEC input parameters, especially L factor, need to be prepared with care for accurate estimation of SDR at a watershed scale and for accurate evaluation of BMPs in the watershed.

Pumped rainfall simulators: the impact of rain pulses on sediment concentration and size

AbstractMany pumped rainfall simulators used in soil erosion studies use pulsed rain to control the rainfall intensity. We examined the effect of the rain pulsing on sediment concentration and size using three different pulse cycles with the same rainfall intensity. There was considerable variation in sediment concentration through the pulse cycle: the highest concentration was up to four times that of the lowest concentration. Furthermore, the particle size distribution also varied: the peak median particle size was double the lowest median particle size. The magnitude of differences in sediment concentration and particle size were greater the longer the pulse cycle and these dynamics will vary between rainfall simulators and studies. We suggest the impact of the pulsing on sediment is significant and should be investigated prior to experimentation so that sampling periods are designed to avoid bias introduced by fine temporal scale sediment dynamics. Copyright © 2009 John Wiley &amp; Sons, Ltd.

Suitability of different erosivity models used in RUSLE2 for the South West Indian region

RUSLE2 is the most used soil erosion model in practice. The rainfall-erosivity factor (R) is one of the six factors that is taken into consideration while estimating soil loss at a hill slope profile. R is determined using rainfall data collected from any region making use of basic rainstorm kinetic energy versus rainfall intensity relationships, which are variable for different geographic regions. Indian researchers used a specific erosivity model for building an iso-erosivity map for India. Many other erosivity models around the world are now available. However, it is not clear whether one can replace RUSLE2 recommended model by the ones derived in other geographic regions for using in Indian soil erosion studies. This has been examined here on south-western Indian data. Various models derived in diverse places were analyzed and compared with the RUSLE2 recommended relationship; and found that, a few could very well replace the usual RUSLE2 recommended expression.

Preliminary studies of soil erosion in a valley bottom in Ibadan under some tillage practices

Preliminary studies of soil erosion in a valley bottom in Ibadan under some tillage practices