Changes In Soil Erosion Rates Research Articles

Using radiotracers 137Cs and 210Pbex to document climate change in mountain areas through the estimate of soil erosion rates

Abstract. During the last few decades, a general increase in heavy rainfall events has been documented in many areas of the world. These events have caused changes in soil erosion rates and strongly affected the human activities in mountain areas by reducing the national income obtained from cultivated land. In this context, the use of fallout radiotracers can be an important tool for better understanding the consequences of climate change in these areas and proposing effective countermeasures in order to reduce soil loss. In this contribution, plot experiments carried out in southern Italy that involve the use of 137Cs and 210Pbex measurements were performed to estimate soil erosion rates during the last few decades. The overall results indicate an increase in soil erosion rates during the last 15–20 years and suggest the use of this technique to detect climate change in mountain areas.

Circulation weather types as a key factor on runoff initiation and sediment detachment in Mediterranean shrublands

In this research, the circulation weather types (CWTs) associated with individual surface pressure data at different atmospheric heights were used to correlate and quantify soil erosion events collecting soil loss (g m-2), runoff (l m-2) and sediment concentration (g L-1) using field plots and sediment collectors. Representative Mediterranean shrubland, located at Sierra de Enguera (Eastern Spain), was used as a case study where 213 rainfall episodes and related soil loss events were recorded for the 2010-2014 period. Average annual precipitation of 544 mm was registered, summarizing a total of 2,720.1 mm for the five years of the research period. A total of 34.4% of the registered precipitation events ranged from 10 to 29.9 mm, 23.5% from 30 to 49.9 mm, and 15.9% from 50 to 99.9 mm. The dynamic low-pressure with fronts (DLp+f) CWT was found to generate the highest precipitation amount reaching 60.6% of the total precipitation (105 of the 213 events). Over a third (35%) of the precipitation events occurred during Eastern CWT, which accounted for 48% of the total precipitation with average values of 17.6 mm per event. From the total runoff, 65.6% was related to the combined Eastern and cold drops (CD) CWT. The DLp+f CWT was found to produce 48.9% of sediment mobilization, of which 73.5% of this amount was generated by Eastern CWT. The highest sediment concentration event was found for the southern CWT under thermal low-pressure (TLp) reaching 51.65 g L-1, followed by A (anticyclones) with the Eastern CWT (42.23 g L-1). As a whole, the southern is the CWT generating the highest average sediment concentration (28.66 g L-1), followed by Easter CWT. Our findings suggest that CWTs contribute to foreseeing the periods with the highest soil losses and may help to prevent them. We discuss the need to analyse the changes in soil erosion rates due to CWT to better characterize the soil erosion process and assess the soil erosion rates, improve the current soil erosion models and investigate how climate change is changing the role CWT plays in runoff initiation and sediment delivery.

137Cs tracing of the spatial patterns in soil redistribution, organic carbon and total nitrogen in the southeastern Tibetan Plateau

The southeastern Tibetan Plateau, which profoundly affects East Asia by helping to maintain the stability of climate systems, biological diversity and clean water, is one of the regions most vulnerable to water erosion, wind erosion, tillage erosion, freeze–thaw erosion and overgrazing under global climate changes and intensive human activities. Spatial variations in soil erosion in terraced farmland (TL), sloping farmland (SL) and grassland (GL) were determined by the 137Cs tracing method and compared with spatial variations in soil organic carbon (SOC) and total nitrogen (total N). The 137Cs concentration in the GL was higher in the 0–0.03 m soil layer than in the other soil layers due to weak migration and diffusion under low precipitation and temperature conditions, while the 137Cs concentration in the soil layer of the SL was generally uniform in the 0–0.18 m soil layer due to tillage-induced mixing. Low 137Cs inventories appeared at the summit and toe slope positions in the SL due to soil loss by tillage erosion and water erosion, respectively, while the highest 137Cs inventories appeared at the middle slope positions due to soil accumulation under relatively flat landform conditions. In the GL, the 137Cs data showed that higher soil erosion rates appeared at the summit due to freeze–thaw erosion and steep slope gradients and at the toe slope position due to wind erosion, gully erosion, freeze–thaw erosion and overgrazing. The 137Cs inventory generally increased from upper to lower slope positions within each terrace (except the lowest terrace). The 137Cs data along the terrace toposequence showed abrupt changes in soil erosion rates between the lower part of the upper terrace and the upper part of the immediate terrace over a short distance and net deposition on the lower and toe terraces. Hence, tillage erosion played an important role in the soil loss at the summit slope positions of each terrace, while water erosion dominantly transported soil from the upper terrace to the lower terrace and resulted in net soil deposition on the flat lower terrace. The SOC inventories showed similar spatial patterns to the 137Cs inventories in the SL, TL and GL, and significant correlations were found between the SOC and 137Cs inventories in these slope landscapes. The total N inventories showed similar spatial patterns to the inventories of 137Cs and SOC, and significant correlations were also found between the total N and 137Cs inventories in the SL, TL and GL. Therefore, 137Cs can successfully be used for tracing soil, SOC and total N dynamics within slope landscapes in the southeastern Tibetan Plateau.

Impact of 2018 Kerala Floods on Soil Erosion: Need for Post-Disaster Soil Management

Extreme precipitation events lead to flash floods, which can trigger soil erosion and landslides. While damages to infrastructure and livelihoods are rapidly assessed on economic terms, damages to natural resources are not estimated due to limited observation record. This study conducted an analysis using remote sensing data to estimate changes in soil erosion rates before, during and after the Kerala 2018 floods, based on the Universal Soil Loss Equation (USLE). The USLE was driven by multiple data including: in situ rainfall data from Indian Meteorological Department (to estimate rainfall erosive factor), soil maps prepared by Food and Agriculture Organization (to estimate the soil erodibility factor from the properties of soil that consists of the percentage of clay, loam and silt), digital elevation model (to estimate topographic slope and length) from Shuttle Radar Topography Mission and multispectral imagery (to estimate cover management factor and conservation practice factor) from Landsat-8 satellite. Data from these sources were analysed using a Geographic Information System (GIS) platform. Results indicate a state-wise average increase of 80% (31–56 metric tons ha−1 year−1) in soil erosion rate during the floods. Of the districts, Idukki showed the highest increase, of 220% and more susceptibility to soil erosion, which is in comparison with government survey records. Results show that the floods and associated erosion were not only due to the rainfall event but also due to the rapid change in land use and land cover, from natural to human settlements. Therefore, government agencies need to protect land cover and reduce unsustainable development in ecologically sensitive environments, which if managed properly can act as a buffer for soil erosion extremes in Kerala.

Long‐term impact of land use changes on soil erosion in an agricultural catchment (in the Western Polish Carpathians)

AbstractThe change in land use and land cover (LULC) from natural vegetation to agricultural in mountain areas usually dramatically accelerates soil erosion rates if the land is used for crop production. The aim of research was to calculate soil erosion magnitude basing on the Revised Universal Soil Loss Equation (RUSLE) in response to long‐term changes in LULC in an agricultural Homerka catchment (19.3 km2) of the Polish Carpathians. The changes in LULC were derived from cadastral maps for 1846 and orthophotomaps for 2009. Three variants with different factors, rainfall–run‐off erosivity (R), practice support (P), and LULC, were analysed to investigate which has had the greatest impact on soil erosion changes over the last 160 years. An increase in forest area (by 67.81%) and decrease in cultivated land (by 91.94%) were observed, primarily due to the collapse of the communist system. The estimated soil erosion using the RUSLE model in the analysed catchment decreased by 77% (from 18.13 t ha−1 yr−1 in 1846 to 4.11 t ha−1 yr−1 in 2009). The long‐term changes in soil erosion rates and their spatial distribution are mainly associated with transformation from cultivated land to forest or grassland. The P factor was responsible for reduction of soil erosion rates by 8%, a minor impact. Over the last 160 years, the average and maximum annual precipitation changes were also statistically insignificant. Results reveal a dominant role of human impact, particularly with respect to LULC on soil erosion changes in mid‐mountain areas.

137Cs tracing dynamics of soil erosion, organic carbon, and total nitrogen in terraced fields and forestland in the Middle Mountains of Nepal

The Middle Mountains is one of the regions of Nepal most vulnerable to water erosion, where fragile geology, steep topography, anomalous climatic conditions, and intensive human activity have resulted in serious soil erosion and enhanced land degradation. Based on the Cs-137 tracing method, spatial variations in soil erosion, organic carbon, and total nitrogen (TN) in terraced fields lacking field banks and forestland were determined. Soil samples were collected at approximately 5 m and 20 m intervals along terraced field series and forestland transects respectively. Mean 137Cs inventories of the four soil cores from the reference site was estimated at 574.33 +/- 126.22 Bq m(-2) (1 Bq (i.e., one Becquerel) is equal to 1 disintegration per second (1 dps)). For each terrace, the Cs-137 inventory generally increased from upper to lower slope positions, accompanied by a decrease in the soil erosion rate. Along the entire terraced toposequence, Cs-137 data showed that abrupt changes in soil erosion rates could occur between the lower part of the upper terrace and the upper part of the immediate terrace within a small distance. This result indicated that tillage erosion is also a dominant erosion type in the sloping farmland of this area. At the same time, we observed a fluctuant decrease in soil erosion rates for the whole terraced toposequence as well as a net deposition at the toe terrace. Although steep terraces (lacking banks and hedgerows) to some extent could act to limit soil sediment accumulation in catchments, soil erosion in the terraced field was determined to be serious. For forestland, with the exception of serious soil erosion that had taken place at the top of slopes due to concentrated flows from a country road situated above the forestland site, spatial variation in soil erosion was similar to the "standard" water erosion model. Soil organic carbon (SOC) and TN inventories showed similar spatial patterns to the Cs-137 inventory for both toposequences investigated. However, due to the different dominant erosion processes between the two, we found similar patterns between the < 0.002 mm soil particle size fraction (clay sized) and Cs-137 inventories in terraced fields, while different patterns could be found between Cs-137 inventories and the < 0.002 mm soil particle size fraction in the forestland site. Such results confirm that Cs-137 can successfully trace soil erosion, SOC and soil nitrogen dynamics in steep terraced fields and forestland in the Middle Mountains of Nepal.

Response of 210Pbex inventory to changes in soil erosion rates on uncultivated land

This analysis studies changes in the variation 210Pbex inventory in soil in response to soil erosion on uncultivated land. A model was created to fit the response of 210Pbex inventory to variations in soil erosion rates on uncultivated land using the principle of mass balance. By numerical simulation of the variation in the soil erosion rate in soil of uncultivated land, we prove: (1) past use of what has long been considered the best method of determining 210Pbex levels over the past 100 to 200 years is not scientifically accurate; (2) the model shows that variation in 210Pbex inventory as a function of time varies according to the index law after variation of soil erosion rates in uncultivated land is considered; and (3) the time needed for the variation in 210Pbex inventory to reach a steady-state is affected by changes in the rate of soil erosion and the quality and depth of relaxation in soil of uncultivated land. The results of this research can guide efforts to measure soil erosion rates.

Projected rainfall erosivity changes under climate change from multimodel and multiscenario projections in Northeast China

Summary Future changes in precipitation will induce changes in the erosive power of rainfall and hence changes in soil erosion rates. In this study we calculated downscaled mean annual precipitation and USLE rainfall erosivity (R) for time periods 2030 through 2059 and 2070 through 2099 in Northeast China using future precipitation predicted from six GCM models under three emissions scenarios. To accomplish this we created a new approach wherein we combined the well evaluated methods developed by Zhang, 2005 , Zhang, 2007 for downscaling monthly precipitation products at time scales meaningful for modeling erosion processes, and the validated method developed by Yu, 2002 , Yu, 2003 for using a weather generator (CLIGEN) to generate accurate RUSLE erosivity factors. Changes were compared to 1960 through 1999 conditions. A stochastic weather generator (CLIGEN) calibrated to precipitation for the period 1960 through 1999 was used to temporally downscale the GCM output, from which the future R values were calculated. Our results suggested a general increase in erosivity over the region by the mid-21st century. Changes in rainfall erosivity under the higher greenhouse gas emissions scenarios, A1B and A2, exhibited the greatest projected changes. The results also indicated that changes in total annual rainfall amounts were not uniformly correspondent spatially to changes in erosivity. Multimodel means showed a generally larger increase in the northern portion of the region than that in the southern part. Future rainfall erosivity changes will have important impacts on soil and water resources in Northeastern China.

Monitoring of soil erosion and assessment for contribution of sediments to rivers in a typical watershed of the Upper Yangtze River Basin

AbstractAn assessment of the effectiveness of soil conservation practices is very important for watershed management, but the measurement over a small area does not necessarily represent the truth over a large area. Monitoring of soil erosion and analysis of sediment delivery were carried out in the Lizixi watershed (which is typical of the Upper Yangtze Basin, China), using remote sensing and a geographic information system (GIS). Land‐use and land‐cover maps were prepared by an interpretation of 1986 and 1999 images from SPOT and Landsat TM. Slope‐gradient maps were created from digital elevation model (DEM), while merged images of SPOT and Landsat TM were used to obtain land‐use information. The area of soil erosion was classified by an integration of slope gradients, land‐use types and vegetation cover rates, and soil erosion rates and their changes were calculated in a grid‐based analysis using an Erdas GIS. The change in sediment delivery ratio was estimated based on the changes in soil erosion rates from both monitoring and the truth survey. There was a reduction in soil erosion rate of 4·22 per cent during a 13‐year period after soil conservation practices were adopted in the Lizixi watershed. The amount of sediments transported into rivers has decreased by 51·08 per cent during the same period due to an integrated application of biological and engineering measures. The comparison of soil erosion severity between pre‐conservation and post‐conservation revealed that soil loss has been obviously diminished and the measures were quite effective. Copyright © 2004 John Wiley &amp; Sons, Ltd.

Use of 137Cs measurements to estimate changes in soil erosion rates associated with changes in soil management practices on cultivated land

Intensification of agricultural production in south-central Chile since the 1970s has caused problems of increased soil erosion and associated soil degradation. These problems have prompted a shift from conventional tillage to no-till management practices. Faced with the need to establish the impact of this shift in soil management on rates of soil loss, the use of caesium-137 ( 137Cs) measurements has been explored. A novel procedure for using measurements of the 137Cs depth distribution to estimate rates of soil loss at a sampling point under the original conventional tillage and after the shift to no-till management has been developed. This procedure has been successfully applied to a study site at Buenos Aires farm near Carahue in the 9th region of Chile. The results obtained indicate that the shift from conventional tillage to no-till management has caused net rates of soil loss to decrease to about 40% of those existing under conventional tillage. This assessment of the impact of introducing no-till management at the study site must, however, be seen as provisional, since only a limited number of sampling points were used. A simplified procedure aimed at documenting the reduction in erosion rates at additional sampling points, based solely on measurements of the 137Cs inventory of bulk cores and the 137Cs activity in the upper part of the soil has been developed and successfully tested at the study site. Previous application of 137Cs measurements to estimate erosion rates has been limited to estimation of medium-term erosion rates during the period extending from the beginning of fallout receipt to the time of sampling. The procedures described in this paper, which permits estimation of the change in erosion rates associated with a shift in land management practices, must be seen as representing a novel application of 137Cs measurements in soil erosion investigations.

Assessing Changes in Soil Erosion Rates: A Markov Chain Analysis

AbstractMarkov chain analysis (one-step and long-run) is applied to the National Resources Inventory (NRI) database to evaluate changes in wind-based soil erosion rates over time. The research compares changes in soil erosion rates between NRI sample sites with and without applied conservation practices for a random sample of Great Plains counties. No significant differences between sites are found for half of the counties evaluated. The effectiveness and efficiency of conservation policies are thus questioned in light of these research results.

A Technique for Local Soil Erosion Survey

Abstract A procedure for erosion assessment representation by symbols, using aerial photography, is required for use at the local scale. This scheme (employing 1:10 000 scale orthophotomaps as a base) was developed within the Bethlehem Runoff Augmentation Research (BRAR) project as a preliminary to hydrological modelling for investigating changes in soil erosion rates. A full legend of the symbols, as well as a description of their relevance to erosion assessment is discussed. As overlays onto the orthophoto base-map, the graphic erosion data and a simple slope classification were found to be of use in defining erosion sensitive areas. Present soil erosion activity and localities that may be prone to a high erosion potential could be identified with a view to selecting experimental and monitoring sites. The suggested sequence of survey procedure is outlined and a list of potential uses for the map is proposed besides that for which it was initially designed. These range from detailed specific collection of data through regional land capability assessments to forming a part of a nationwide survey, such as that proposed by SARCCUS.