Water Erosion Processes Research Articles

The Contribution of Astragalus adsurgens Roots and Canopy to Water Erosion Control in the Water–Wind Crisscrossed Erosion Region of the Loess Plateau, China

AbstractSimulated rainfall experiments were conducted to investigate the effect of Astragalus adsurgens roots and canopy on water erosion yield, erosion processes and soil resistance to erosion. Experiments were conducted on grass, root and bare slopes, with sandy soil from a water–wind crisscrossed erosion region of the Loess Plateau, China. A. adsurgens coverage on grass slopes was approximately 40%. There were three rainfall intensities of 30, 60 and 90 mm h–1 and four slope gradients of 3, 6, 9 and 12°. A. adsurgens had a significant effect on soil erosion control; soil loss was reduced by ~70% on slopes with the grass compared with bare slopes. The grass roots reduced soil loss more than its canopy, particularly in high‐intensity rainfall, which reduced soil loss by 82%. The presence of the grass and its roots changed the soil erosion process, reducing soil erodibility (Kr) and increasing the critical shear stress (τc). The soil erosion rate on the bare slope increased steadily over time; on the grass and root slopes, its rate initially increased, then decreased and then finally stabilized. Kr on the grass and root slopes was reduced by 96% and 89%, respectively, compared with the bare slope, while the corresponding τc increased by 92% and 195% respectively. These results provide insights into the mechanisms of grass on soil and water conservation and may help to improve vegetation construction in water–wind crisscrossed erosion regions of the Loess Plateau. Copyright © 2016 John Wiley & Sons, Ltd.

Water erosion susceptibility mapping by applying Stochastic Gradient Treeboost to the Imera Meridionale River Basin (Sicily, Italy)

Soil erosion by water constitutes a serious problem affecting various countries. In the last few years, a number of studies have adopted statistical approaches for erosion susceptibility zonation. In this study, the Stochastic Gradient Treeboost (SGT) was tested as a multivariate statistical tool for exploring, analyzing and predicting the spatial occurrence of rill–interrill erosion and gully erosion. This technique implements the stochastic gradient boosting algorithm with a tree-based method. The study area is a 9.5km2 river catchment located in central-northern Sicily (Italy), where water erosion processes are prevalent, and affect the agricultural productivity of local communities. In order to model soil erosion by water, the spatial distribution of landforms due to rill–interrill and gully erosion was mapped and 12 environmental variables were selected as predictors. Four calibration and four validation subsets were obtained by randomly extracting sets of negative cases, both for rill–interrill erosion and gully erosion models. The results of validation, based on receiving operating characteristic (ROC) curves, showed excellent to outstanding accuracies of the models, and thus a high prediction skill. Moreover, SGT allowed us to explore the relationships between erosion landforms and predictors. A different suite of predictor variables was found to be important for the two models. Elevation, aspect, landform classification and land-use are the main controlling factors for rill–interrill erosion, whilst the stream power index, plan curvature and the topographic wetness index were the most important independent variables for gullies. Finally, an ROC plot analysis made it possible to define a threshold value to classify cells according to the presence/absence of the two erosion processes. Hence, by heuristically combining the resulting rill–interrill erosion and gully erosion susceptibility maps, an integrated water erosion susceptibility map was created. The adopted method offers the advantages of an objective and repeatable procedure, whose result is useful for local administrators to identify the areas that are most susceptible to water erosion and best allocate resources for soil conservation strategies.

The Impact of Heavy Grazing on Soil Quality and Pasture Production in Rangelands of SW Spain

AbstractSoil degradation phenomena, including water erosion and physical and biological processes, have already been reported in rangelands of southwestern Spain. The increasing numbers of livestock since 1986 have been highlighted as one of the key causes. The main goal of this work is to analyse the effects of the excessive number of animals on soil quality and pasture production on privately owned farms dedicated to extensive ranching. Soil properties and surface cover, pasture production, rainfall and land management variables such as livestock density were analysed during a period of 3 years (2008–2011). The study was carried out in 22 livestock enclosures selected from ten farms distributed throughout the Spanish region of Extremadura. The occurrence of bare soil patches and water erosion processes, as well as an increase of mean bulk density in the soil layer from 5 to 10 cm in depth, was observed in the enclosures with animal stocking rates exceeding 1 AU ha−1. Indications that confirm the negative effects of increased bulk density on pasture production and quality were also found. Copyright © 2016 John Wiley & Sons, Ltd.

The monitoring of southern chernozem soil humus content with using multispectral satellite images Landsat: spatial and temporal aspects

For rational use of soils it is necessary to possess exact information on soil properties. The traditional methods of monitoring of soils and (or) their separate properties based on local, one-time supervision don’t give an adequate assessment of a current state of a soil cover it should be noted. Transition to spatio-temporal methods with use of modern geoinformation and space technologies is necessary. Remote satellite methods of soil monitoring gain fast distribution, owing to the efficiency, a certain objectivism and relative low cost now, and also because of unique opportunities of one-time coverage by the images received from big height, enough territories, big on the area. For the development of remote monitoring chernozems southern used materials of multispectral scanning multispectral camera ETM + ( «Enhanced Thematic Mapper Plus»), which is on board the satellite «Landsat-7» (data of 2006, 2010, 2012) and OLI («Operational Land Imager»), which is on board the satellite «Landsat-8»(data 2015). The information obtained from them is unified from the point of view of preservation of geometry, calibration, a covering, spectral characteristics, quality of the image and availability of data, despite various carriers of devices ETM+ and OLI. The composite image which has been received from three cloudless satellite images of spring of 2012 (three terms of shooting – 21.04, 30.04, 05.05) has allowed to make the correlation analysis of extent of influence of maintenance of organic matter in a layer of soil of 0–10 cm at a brightness with various spectral channels of the camera ETM+. Such analysis has shown that the closest connection exists between the content of soil organic matter and brightness of the second (green), the third (red) and the fourth (the neighbor infrared) spectral channels. From them three, the greatest value of correlation has dependence between the content of soil organic matter (humus) and brightness of the red spectral channel (r=-0,32). For the purpose of spatio-temporal interpretation of the equation of multiple regressions, 20 agro landscapes in different parts of the Right-bank steppe of Ukraine (The Mykolayiv district and Zhovtnevy district of the Mykolayiv oblast) have been selected. For each agro landscapes was defined content of soil organic matter in the soil using Landsat 7 satellite images taken in 2006 and in 2010 and Landsat images 8 for 2015. The made estimates of maintenance of soil organic matter have shown on processes of fast loss of humus in all layers of soil. Annual losses of soil organic matter in a layer of 0–10 cm from 2006 for 2015 have made 0,16 % in a year, in a layer of 0–50 cm of about 0,13 % in a year, and in a layer of 0–100 cm at 0,10 % in a year. The irrational structure of sown areas and distribution of wind and water erosion processes is the reason of this sad process.

Understanding the role of soil erosion on co2-c loss using 13c isotopic signatures in abandoned Mediterranean agricultural land

Understanding soil water erosion processes is essential to evaluate the redistribution of soil organic carbon (SOC) within a landscape and is fundamental to assess the role of soil erosion in the global carbon (C) budget. The main aim of this study was to estimate the C redistribution and losses using 13C natural abundance. Carbon losses in soil sediment, dissolved organic carbon (DOC) and CO2 emission were determined. Four bounded parallel plots were installed on a 10% slope. In the upper part of the plots, C3soil was replaced with C4soil. The SOC and δ13C were measured after 145.2mm rainfall in the upper (2m far from C4strip), middle (4m far from C4strip) lower (6m far from C4strip) trams of the plot and in the sediments collected in the Gerlach collector at the lower part of the plot. A laboratory incubation experiment was performed to evaluate the CO2 emission rate of soils in each area. OC was mainly lost in the sediments as 2.08g−2 of C was lost after 145.2mm rainfall. DOC losses were only 5.61% of off-site OC loss. Three months after the beginning of the experiment, 15.90% of SOC in the upper tram of the plot had a C4 origin. The C4-SOC content decreased along the 6m length of the plot, and in the sediments collected by the Gerlach collector. CO2 emission rate was high in the upper plot tram due to the high SOC content. The discrimination of CO2 in C3 and C4 portion permitted to increase our level of understanding on the stability of SOC and its resilience to decomposition. The transport of sediments along the plot increased SOC mineralization by 43%. Our study underlined the impact of rainfall in C losses in soil and water in abandoned Mediterranean agriculture fields and the consequent implications on the C balance.

National approaches to evaluation of the degree of soil degradation

Approaches to evaluation of the degree of soil degradation and the related normative documents applied by specialists from state institutes for land management of the former Soviet Union in the course of largeand medium-scale soil surveys in the 1960s–1990s are analyzed. It is shown that the types and rates of soil degradation were specified without proper consideration for the taxonomic position of particular soils. Reference (nondegraded) soils were not clearly defined, which made it difficult to judge the degree of soil degradation by means of a comparative analysis of degraded and nondegraded soils. Such reference soils are suggested for several types of soil degradation (dehumification, compaction, depletion of nutrients, etc.). Additional diagnostic criteria of the degree of soil degradation caused by wind and water erosion, waterlogging, swamping, and other adverse processes are specified. The study of qualitative and quantitative changes in the soil properties during the post-Soviet period is important for the development of land monitoring system and for the analysis of economic aspects of land degradation. To ensure reliability of data on changes in the soil properties and soil cover patterns, possible errors related to incorrect comparison of the data obtained by traditional and modern approaches should be taken into account.

Impact of climate changes on erosion processes in Republic of Bashkortostan

Climatic data for 1881–1980 and 2005–2014 obtained from the main meteorological stations in the Republic of Bashkortostan have been analyzed. It was shown that an increase in average monthly and annual air temperatures occurred in the Republic; in addition, warming is mostly expressed in the summer–autumn period. The amount of average annual precipitation declined, and the ratio changed as follows: the percentage of precipitation was higher in the winter–spring period of the year than in the summer. Climate change contributes to the overall reduction in the intensity of water-erosion processes and the enhancement of deflation on unprotected bare lands in the southern forest steppe area and in the mountain forest belt.

Can we manipulate root system architecture to control soil erosion?

Abstract. Soil erosion is a major threat to soil functioning. The use of vegetation to control erosion has long been a topic for research. Much of this research has focused on the above-ground properties of plants, demonstrating the important role that canopy structure and cover plays in the reduction of water erosion processes. Less attention has been paid to plant roots. Plant roots are a crucial yet under-researched factor for reducing water erosion through their ability to alter soil properties, such as aggregate stability, hydraulic function and shear strength. However, there have been few attempts to specifically manipulate plant root system properties to reduce soil erosion. Therefore, this review aims to explore the effects that plant roots have on soil erosion and hydrological processes, and how plant root architecture might be manipulated to enhance its erosion control properties. We demonstrate the importance of root system architecture for the control of soil erosion. We also show that some plant species respond to nutrient-enriched patches by increasing lateral root proliferation. The erosional response to root proliferation will depend upon its location: at the soil surface dense mats of roots may reduce soil erodibility but block soil pores thereby limiting infiltration, enhancing runoff. Additionally, in nutrient-deprived regions, root hair development may be stimulated and larger amounts of root exudates released, thereby improving aggregate stability and decreasing erodibility. Utilizing nutrient placement at specific depths may represent a potentially new, easily implemented, management strategy on nutrient-poor agricultural land or constructed slopes to control erosion, and further research in this area is needed.

An integrated assessment of soil erosion dynamics with special emphasis on gully erosion in the Mazayjan basin, southwestern Iran

Soil erosion by water is a significant problem in arid and semi-arid areas of large parts of Iran. Water erosion is one of the most effective phenomena that leads to decreasing soil productivity and pollution of water resources; especially, in the Mazayjan watershed in the southwest of Fars Province gully erosion contributes to the sediment dynamics in a significant way. Consequently, the intention of this research is to identify the different types of soil erosion processes acting in the area and to assess the process dynamics in an integrative way. Therefore, we applied GIS and satellite image analysis techniques to derive input information for the numeric models. For sheet and rill erosion the Unit Stream Power-based Erosion Deposition Model (USPED) was utilized. The spatial distribution of gully erosion was assessed using a statistical approach, which used three variables (stream power index, slope, and flow accumulation) to predict the spatial distribution of gullies in the study area. The eroded gully volumes were estimated for a 7-year period by fieldwork and Google Earth high-resolution images. Finally the gully retreat rates were integrated into the USPED model. The results show that the integration of the SPI approach to quantify gully erosion with the USPED model is a suitable method to qualitatively and quantitatively assess water erosion processes. The application of GIS and stochastic model approaches to spatialize the USPED model input yields valuable results for the prediction of soil erosion in the Mazayjan catchment. The results of this research help to develop an appropriate management of soil and water resources in the southwestern parts of Iran.

Sustainable management of natural resource potential of agriculture in Ukraine on the principles of the Rio Conventions

The actuality of integration of Rio Convention provisions including Convention to Combat Desertification and land degradation into agrarian policy of Ukraine is analyzed. The current state of land resources using and factors of degradation processes of soil cover are characterized. It is shown their influence on agroecosystems productivity, risks of drought phenomena increasing and desertification processes. In the process of climate changes the torrential precipitation pattern and wind regime will increase, that under the conditions of sharp increasing of clean-cultivated crops areas, including corn, sunflower and soybean, will significantly reduce agrolandscapes resistance to drought, increase the risks of catastrophic manifestation of water-erosion processes and dust storms. All of this requires the development and implementation of more effective methods of land resources management, directed to the soil fertility reproduction and nature protection structure formation of agrolandscapes and land management systems. For the purpose of implementation measures concerning combat desertification, monitoring of degradation processes and informative-consultative support of landowners and land users it is proposed to create authoritative «State Service for land protection and soil fertility». It is shown that the current legal provision of land desertification and degradation in the present conditions is not a limiting factor, therefore requires improvement and further development, in particular concerning the protection and sustainable land use and soil fertility reproduction.

Amorphous silica mobilization by inter‐rill erosion: insights from rainfall experiments

AbstractAmorphous silica (ASi) carried in suspension by rivers is an important component in the global Si budget. Water erosion processes in cultivated catchments are likely to drive ASi delivery to the river system. However, no studies have investigated the controls on ASi mobilization by erosional processes in croplands. Rainfall experiments were performed on split fields (i.e. a part conventionally ploughed and a part under reduced tillage) to simulate ASi mobilization by inter‐rill erosion in croplands, and identify its dependency on soil, field and rainfall characteristics. The ASi content of the soil and the inter‐rill erosion rate were determined as the major controls on ASi mobilization. Variables such as tillage technique and crop type did not have a consistent direct or indirect effect. Inter‐rill erosion is clearly selective with respect to ASi, indicating association of ASi with the fine soil fraction and with soil organic carbon. Our experiments demonstrate that erosion increases due to human perturbation will increase the delivery of reactive Si to aquatic systems. We estimate that globally, c. 7% of all reactive Si that enters aquatic systems is derived from erosion of agricultural soils. Copyright © 2015 John Wiley & Sons, Ltd.

Monitoring the effect of conservation practices on the erosion rates in some small watersheds in Eastern Romania

It is known that the successful implementation of control measures to preserve soil quality on slope agricultural lands depends largely on the designer’s ability to select a control strategy for a specific site, considerable simpler and less costly. The paper refers to several small watersheds with agricultural use, representative for Eastern hilly area ofRomania, where different types of soil conservation measures have been applied. The study included monitoring of some factors to highlight the role of soil conservation practices in reducing water erosion process. In this respect, it was studied the dynamics of the climatic, pedological, relief, vegetation, hydrology and erosion parameters. Runoff and erosion rates for individual storms were studied both at the plot and microbazin level by performing measurements on standard runoff plots, respectively in the network flow sections. Also, RUSLE model and Geographic Information System were used to simulate spatial distribution of erosion and sedimentation processes. Significant interactions and feedbacks were found to occur between soil characteristics and vegetation, which influenced both runoff and erosion responses. Monitoring allowed more direct linkages to be made between management practices and their impacts on runoff and soil erosion.

An experimental study of rill erosion and morphology

Rill erosion is recognized as an important process of water erosion on agricultural land. The objectives of this study are to examine the effects of rainfall intensity on rill network development and to present some indicators for a quantitative description of rill morphology. A soil pan (10m long, 3m wide and 0.5m deep and with an adjustable slope gradient from 0 to 30°) was subjected to three successive rains under rainfall intensities of 50 and 100mmh−1. The results showed that rainfall intensity significantly affected rill erosion, especially in the active period of rill network development. The magnitude of rill erosion was 28.5 and 33.1kgm−2 and contributed 78.6% and 76.2% to the soil loss under rainfall intensities of 50 and 100mmh−1, respectively. The formation of rill network under the 50mmh−1 intensity was more complex than that under the 100mmh−1 intensity; for the latter rill networks developed fast and then varied slightly. The mean rill inclination angle (δmean), rill density (ρ), degree of rill dissection (μ) and mean rill tortuosity complexity (cmean) increased with the increase of rains under the same rainfall intensity. The μ value was the optimal derivative morphological indicator to estimate rill erosion and morphology, which was followed in descending order by δmean, cmean and ρ.

Способы повышения почвозащитной эффективности лесных насаждений

This article discusses ways to improve soil protective efficiency, reclamation use and preservation of protective forest plantations. In addition to the hydrological and soil protection functions, these spaces contribute to a more even distribution of snow on the protected spaces and prevent them blowing away in his beams, improve the microclimate of surrounding fields and, ultimately, increase the productivity of crops. Afforestation system is the basis of territorial and environmental framework, that ensures the stability of agro-ecosystems. The major role in improving forest conditions and, as a consequence, an increase in the growth of trees, played an impoundment ability of trenches. They created additional moisture due to the detention of surface runoff from melted snow and rain water. The sharp decline in water-erosion processes, transfer a surface flow to intersoil, improves the water regime of the territory and has a beneficial effect on the growth of pendent white birch. Thus, the use of reclamation of forest belts in the variant with trenches is the highest (100%), this can be explained by regular flow of meltwater in the forest area, as subsurface flow. The trench with filler intercepts virtually the entire flow, that is absorbed in its melted bottom and filler, and during the active snowmelt in the way of overflow of trenches, flowing is held earth mound on the border of the forest belt. As a consequence, the gullies and ravines are not formed on young woodland belt, that was benefit on the growth and survival of seedlings of pendent white birch. 

Extreme water content as a factor of inadequate hydro-ecological safety in the Upper Don Basin

The article considers the high and low water content of rivers, water-erosion processes in the Upper Don basin in terms of undermined hydro-ecological safety. The underlying causes are the character of dangerous hydrologic phenomena and natural and socioeconomic consequences.

Assessing the impact of soil surface characteristics on vineyard erosion from very high spatial resolution aerial images (Côte de Beaune, Burgundy, France)

We describe a new method to map intra-plot soil surface heterogeneities at a 5cm spatial resolution. Our approach unites aerial image classification acquired at very high spatial resolution (VHSR) with local soil sampling. VHSR aerial image processing, based on image classification, allows precise mapping of the spatial distribution of soil surfaces; soil sampling defines soil typology by physical and chemical characteristics. This method has been applied to a plot area located on the hillslopes of Burgundy vineyards (Monthelie, France), where decennial erosion data were already available, in order to assess the effect of soil surface characteristics and slope angle on erosion intensity and localisation. From this method, four classes of radiance were distinguished and interpreted as four soil surface state classes (SSC), defining specific areas within the studied plot. These SSCs have been characterised by their grain-size distribution, their organic carbon, calcium carbonate, and total nitrogen contents.By allowing soil surface states to be mapped at five centimetre resolution, this approach provides novel insights into the characterisation of soil patterns and into erosion analysis on cultivated hillslopes. Our work shows that the spatial distribution of soil erosion is related to the local slope steepness but also to the spatial distribution of stoniness that results from water and tillage erosion processes.

Local Initiatives of Land Rehabilitation in the Sudano-Sahelian Region: Case of <i>Hardé</i> Soils in the Far North Region of Cameroon

Local initiatives of hardé soils rehabilitation in Maroua region have been analyzed. Fieldwork consisted of conducting observations and surveys beside farmers in two study sites, Mizileng and Zokok. Investigations on perception of land degradation signs by farmers show that appearance of encrusted surfaces and loss of vegetation cover are signs more expressed in both study sites. Causes expressed include acceleration of water and wind erosion processes, excessive falling of trees, inappropriate farming techniques and climatic hazards. The main consequences are declining of crop yields, lack of farming land and loss natural pastures. Rehabilitation actions undertaken by local communities surveyed include earth dikes, tillage including cart or hoe ploughing, application of organic matter, integrating farming techniques such as fallowing, association and rotation of crop, and lastly, parking of animals on plots to be rehabilitated. Populations assert in their majority perceive in six months to three years signs of real change on planning plots. Constraints to those rehabilitation actions include material requirements that are mostly not available or accessible to farmers in the study area and access to land. Globally, there is no integration of local knowledge in the implementation of projects and consequences are localized and ephemeral efficiency, but also not conclusive results. Implementation of an innovation in rural areas must take into account the factors of ownership and inscribe in a well-defined trajectory. This trajectory must be dynamic and reflexive where local knowledge will cope with expert knowledge to ensure impact and sustainability of innovation.

Ерозійна деградація дерново-підзолистих ґрунтів Надсянської рівнини

The effects of water erosion processes on the state of sod-weak pidzolic soils at Nadsiannia moraine-outwash plain have been outlined. The morphological description of the explored soils of various erodibility degrees and their comparison has been done. The degradation level has been defined according to the following criteria: power of humus horizon and humus reserves in the soil profile. Key words: degradation, sod-podzolic soils, erosion, morphological description, degree of erodibility.

Analysis of water erosion processes using terrestrial laser scanning

1) Institute of Environmental Development and Protection, Wroclaw University of Environmental and Life Science, Pl. Grunwaldzki 24a, 50-363 WROCŁAW 2) Institute of Geodesy and Geoinformatics, Wroclaw University of Environmental and Life Science, Ul. Grunwaldzka 53, 50-363 WROCŁAW 3) Department of Spatial Economy, Wroclaw University of Environmental and Life Science, Ul. Grunwaldzka 53, 50-363 WROCŁAW

Spatial distribution of water erosion risk in a watershed with eucalyptus and Atlantic Forest

The process of water erosion occurs in watersheds throughout the world and it is strongly affected by anthropogenic influences. Thus, the knowledge of these processes is extremely necessary for planning of conservation efforts. This study was performed in an experimental forested watershed in order to predict the average potential annual soil loss by water erosion using the Universal Soil Loss Equation (USLE) and a Geographic Information System (GIS), and then compared with soil loss tolerance. All the USLE factors were generated in a distributed approach employing a GIS tool. The layers were multiplied in the GIS framework in order to predict soil erosion rates. Results showed that the average soil loss was 6.2 Mg ha-1 yr-1. Relative to soil loss tolerance, 83% of the area had an erosion rate lesser than the tolerable value. According to soil loss classes, 49% of the watershed had erosion less than 2.5 Mg ha-1 yr-1. However, about 8.7% of the watershed had erosion rates greater than 15 Mg ha-1 yr-1, being mainly related to Plinthosol soil class and roads, thus requiring special attention for the improvement of sustainable management practices for such areas. Eucalyptus cultivation was found to have soil loss greater than Atlantic Forest. Thus, an effort should be made to bring the erosion rates closer to the native forest. Implementation of the USLE model in a GIS framework was found to be a simple and useful tool for predicting the spatial variation of soil erosion risk and identifying critical areas for conservation efforts.