Average Soil Erosion Rate Research Articles

GIS estimation of annual average soil loss rate from Hangar River watershed using RUSLE

Abstract Currently, soil erosion is the major environmental problem in the Blue Nile, Hangar watershed in particular. This study aimed to estimate the spatially distributed mean annual soil erosion and map the most vulnerable areas in Hangar watershed using the revised universal soil loss equation. In this model, rainfall erosivity (R-factor), soil erodibility (K-factor), slope steepness and slope length (LS-factor), vegetative cover (C-factor), and conservation practice (P-factor) were considered as the influencing factors. Maps of these factors were generated and integrated in ArcGIS and then the annual average soil erosion rate was determined. The result of the analysis showed that the amount of soil loss from the study area ranges from 1 to 500 tha−1 yr−1 with an average annual soil loss rate of 32 tha−1 yr−1. Considering contour ploughing with terracing as a fully developed watershed management, the resulting soil loss rate was reduced from 32 to 19.2 tha−1 yr−1. Hence, applying contour ploughing with terracing effectively reduces the vulnerability of the watershed by 40%. Based on the spatial vulnerability of the watershed, most critical soil erosion areas were situated in the steepest part of the watershed. The result of the study finding is helpful for stakeholders to take appropriate mitigation measures.

Response of the Meltwater Erosion to Runoff Energy Consumption on Loessal Slopes

Soil properties are influenced by freeze-thaw, which in turn influences soil erosion. Despite this, only a few studies have investigated the impacts on soil hydrodynamic processes. The objective of this study was to evaluate the impact of soil freezing conditions on runoff, its energy consumption, and soil erosion. A total of 27 laboratory-concentrated meltwater flow experiments were performed to investigate the soil erosion rate, the runoff energy consumption, and the relationship between the soil erosion rate and runoff energy consumption by concentrated flow under combinations of three flow rates (1, 2, and 4 L/min) and three soil conditions (unfrozen, shallow-thawed, and frozen). The individual and combined effects of soil condition, flow rate, and runoff energy consumption on the soil erosion rate were analyzed. For the same flow rate, the shallow-thawed and frozen slope produced mean values of 3.08 and 4.53 times the average soil erosion rates compared to the unfrozen slope, respectively. The number of rills in the unfrozen soil slope were 4, 3, and 2 under the flow rate of 1, 2, and 4 L/min, respectively. The number of rills in the thawed-shallow and frozen soil slope were all 1 under the flow rate of 1, 2, and 4 L/min. The rill displayed disconnected distribution patterns on the unfrozen slope, but a connected rill occurred on the shallow-thawed and frozen slopes. The average rill width on unfrozen, thawed-shallow, and frozen soil slopes increased by 1.87 cm, 4.38 cm, and 1.68 cm as the flow rate increased from 1 L/min to 4 L/min. There was no significant difference in the rill length on the frozen slope under different flow rates (p > 0.05). The runoff energy consumption ranged from unfrozen > shallow-thawed > frozen slopes at the same flow rate. The soil erosion rate had a linear relationship with runoff energy consumption. The spatial distribution of the runoff energy implied that soil erosion was mainly sourced from the unfrozen down slope, shallow-thawed upper slope, and frozen full slope.

Quantifying the effectiveness of mountain terraces on soil erosion protection with sediment traps and dry-stone wall laser scans

Mountain depopulation in the Mediterranean region over the past decades has led to a decline in the use and maintenance of agricultural terraces and consequently the collapsing of dry-stone walls, which can increase soil erosion rates and downstream sedimentation. A field experiment has been set up on a degrading terraced hillslope in the Troodos Mountains of Cyprus, to quantify the effectiveness of terrace maintenance on protecting cultivated land against soil erosion. The monitored site is cultivated with grapes. The terrace riser (22 m long) that forms the linear outlet of the hillslope has 11.4 m of standing dry-stone wall and 10.6 m of collapsed wall. It has been instrumented with seven 1 m wide sediment traps, three on standing sections of the wall and four on collapsed sections. When dry, sediment was collected from the traps after rainfall events, from December 2015 to November 2017. Uncertainties in the drainage areas of the 31.5-m long slope were quantified both for the terrace wall and for the individual traps through hydrologic delineations based on a detailed topographic survey. The sediment data were complemented by laser scanner surveys that were conducted in November 2015, May 2016 and April 2017, on a dry-stone terrace wall upslope from the outlet section. Wall degradation was assessed from the consecutive 3D model reconstructions. Rainfall was 469 mm in the first year and 515 mm in the second year and the average erosivity was 1148 MJ mm ha−1 h−1 y−1. The average soil erosion rate was 2.4 Mg ha−1 y−1, when linear drainage areas are considered (693 m2), 3.2 Mg ha−1 y−1 when the borders are delineated with the topographic data (520 m2). Nearly half of the soil erosion (43%) occurred during two very intense rainfall events (maximum 30-min intensity exceeding 35 mm h−1), out of the 34 monitored events. Erosion from standing terrace sections was 3.8 less than the erosion from the collapsed sections. For the scanned terrace wall, soil erosion from the standing sections was 2.2 lower than from the degraded sections. The laser scanner surveys identified some preferential erosion paths, but failed to recognize single stone collapses, whereas possible wall displacement was masked by scanning artifacts. The sediment traps were found to be an effective method for understanding and quantifying soil erosion in terraced mountain environments, while further research is needed to develop a more rigorous acquisition procedure for laser scanner surveys to derive useful information on wall degradation.

Connectivity assessment in Mediterranean vineyards using improved stock unearthing method, LiDAR and soil erosion field surveys

AbstractThe interaction between processes and landforms is accelerated in vineyards due to bare tilled soils that enhance splash, runoff, and erosion. Traditionally, in order to assess these processes, the stock unearthing method (SUM) is considered a useful methodology that uses the graft union of the vine plant as passive bio‐indicator of the topsoil level changes. However, SUM assumes that the topography between the rows is planar when development of a model of the current micro‐topography is performed. Thus, we consider that there is a need to develop a new methodology (ISUM: improved SUM) that, by adding new measurements in the inter‐row areas (at least 3), allows inclusion of the absent micro‐topographical information of SUM. In this way, the main aim of this research was to estimate the micro‐topographical changes and soil transport at three different slope positions (upper, middle and lower parts) in a 25‐years‐old vineyard in eastern Spain. LiDAR data were used to compare the connectivity processes at the catchment with the pedon scale. We obtained maps that showed topsoil level changes and detected soil depletion and accumulation signals. We estimated soil displacement rates of –1.6 Mg ha yr‐1 (depletion), +2.8 Mg ha yr‐1 and +13.3 Mg ha yr‐1 (accumulation) at upper, middle and lower slope positions, respectively. The total average soil erosion rates in the inter‐rows were –5.7 Mg ha‐1 yr‐1. In the row areas, deposition of +10.5 Mg ha yr‐1 was measured. Field erosion marks surveyed after each rainfall event gave insights to the connectivity at the inter‐row and the slope scale. It was found that at the row scale there were sinks of sediments underneath the vines and sources in the inter‐row parts, although they are the highest and lowest local topographical terrain, respectively. This is due to tillage erosion that redistributed the sediments. At the slope scale, the lower part of the slope collected sediments from the upper slope positions, which were transported along the middle part of the slope, as the measurement of ISUM and the field survey after intense rainfall events demonstrated. Connectivity of the flows along the whole slope were rare (twice), and along individual slope parts connectivity was found eight times, and 19 at the inter‐row scale after 8 years of field observations. Copyright © 2018 John Wiley & Sons, Ltd.

Estimation of sediment delivery ratio at sub-watershed level using revised and modified USLE

The success of planning for watershed developmental activities depends on the quality and quantity of information available of natural resources. The process of assessing soil erosion using conventional methods is cumbersome, time-consuming and costly therefore, in the present study, an attempt has been made to estimate sediment delivery ratio at sub-watershed level using RUSLE and SWAT Model. The raster layers of K, L, S, C, P factors and computed R factor value was used to derive gross soil erosion map of study area using raster calculator of spatial analyst tools in ArcGIS interface. The MUSLE was used to route and estimate the sediment yield at watershed outlet using SWAT model. Highest area covered by agricultural land (i. e. 41.54) of study area having 33.28 tons/ha/yr gross soil erosion needs immediate treatment of soil conservation in order to reduce water erosion. The average gross soil erosion rate for study area was estimated as 39.25 tons/ha/yr whereas, the sediment yield by SWAT was estimated to be 22.78 tons/ha./year. The estimated sediment delivery ratio indicates that 58 per cent of eroded soils go out of the watershed which reduces the soil depth and fertility of land on site and reaches Karjan reservoir thus reducing the water storage capacity of reservoir each year.

Appraisal of Soil Conservation Capacity Using NDVI Model-Based C Factor of RUSLE Model for a Semi Arid Ungauged Watershed: a Case Study

Revised Universal Soil Loss Equation (RUSLE) model and Geographic Information System (GIS) have been used to map and quantify vulnerability of soil erosion in a semi arid ungauged Jhagrabaria watershed of Allahabad district of state Uttar Pradesh, India. The spatial pattern of average annual soil erosion rate was estimated by integrating different thematic layers at GIS platform. GIS vector layers including, rainfall erosivity (Ro), slope length and steepness (LS) factor, soil erodibility (K), conservation practices (P), and cover management factor (C) have been estimated using satellite data and Normalized Difference Vegetation Index (NDVI), respectively. The resultant map of average annual soil erosion shows a maximum soil loss in range of 0.3 to 0.6 t ha−1 year−1 (82.41 km2 and 54.92% of watershed area). While maximum soil loss ranges from > 9.0 t ha−1 year−1 (0.67 km2 and 0.45% of watershed) was reported under hillocks (lower part) of the study area. The work outlines that the vegetation cover arrests the soil erosion in the region. The study provides spatial erosion risk maps of 30 m. These maps will be useful in developing better strategies for land planning and management in the environmentally sensitive small hillocks areas.

The effects of rainfall regimes and terracing on runoff and erosion in the Three Gorges area, China.

Changes in natural rainfall regimes have taken place and are expected to become more pronounced in future decades. These changes are also likely to be accompanied by changes in crop management practices. The main purpose of this study was to analyze runoff and soil loss in relation to rainfall regimes and terracing in the Three Gorges area, China. Based on 10years of field observation and k-mean clusters, 101 rainfall events were grouped into three rainfall regimes. Rainfall regime I was the group of events with strong rainfall intensity, high frequency, and short duration. Rainfall regime III consisted of events with low intensity, long duration, and high rainfall amount. Rainfall regime II was the aggregation of events of high intensity and amount, and less frequent occurrence. The results showed that event runoff coefficients were not significantly different among rainfall regimes. However, the average soil erosion rates in rainfall regimes I and II were significantly higher than that in regime III. The average erosion rates under rainfall regimes I, II, and III were 21.6, 39.7, and 9.8gm-2, respectively. The effect of rainfall regime on soil erosion also was changed by terracing. On unterraced cropland, soil erosion rate in rainfall regime I is significantly higher than that in regime III. However, the situation did not exist in unterraced orchard. Terracing significantly reduced runoff and soil erosion, and compensated the effects of rainfall regime on soil erosion, which indicated that runoff and erosion in terraced system may be little influenced by climate change. Based on these results, it was suggested more attention should be paid to the timing of rainfall events in relation to crop development and the high erosion on unterraced citrus orchard to control soil erosion in this area.

Estimation of potential soil erosion rate using RUSLE and E30 model

This research established an empirical methodology to estimate potential soil erosion rate based on revised universal soil loss equation (RUSLE) and E30 model. The study was conducted on a highly precipitated, rugged, tropical forested with steep slope watershed during 1992 to 2009. The fourth (4th) largest river of Papua New Guinea, and its catchment area was considered for this research. Lots of commercial mining and logging activities are the ongoing processes in the upper catchment area without proper conservation measures. Digital elevation model (DEM), landsat satellite images, average annual rainfall, soil texture data base were used to derived mandatory input factors into the RUSLE and E30 model. Raster calculator of ArcGIS spatial analyst was used to generate all input factors and final pixel-by-pixel based computation of soil loss pattern. The average potential soil erosion rate were calculated in the range of 20.34 mm/year to 23.70 mm/year through RSULE model and in the other hand the rate varies from 21.07 mm/year to 26.78 mm/year through E30 model during 1992 to 2009 respectively. The erosion rate through both model indicates extremely severe rate of erosion in the upper catchment area are required immediate attention of soil conservation practices.

Estimation of Soil Erosion Using RUSLE Model and GIS Techniques for Conservation Planning from Kulekhani Reservoir Catchment, Nepal

This study intended to spatially estimate the soil erosion rate of Kulekhani reservoir catchment area, Nepal applying Revised Universal Soil Loss Equation (RUSLE), adopting remote sensing data and geographic information system (GIS) techniques. Average soil erosion rate of watershed was found to be 195.11Mg ha -1 year -1 which is quite high as compared to threshold rate of erosion 15Mg ha -1 year -1 applicable for Himalayan region. It is concluded that soil erosion rate of comparatively 41% area was tolerable but has no distinct zone and approximately 58% area of catchment was on the verge of high to very severe intensity classes. Higher severity of soil erosion was scattered all over the watershed hence conservation measures should be implemented over whole catchment area. The research demonstrates that the use of remote sensing data and GIS has an abundant advantage in predicting soil erosion rate for the sustainable land use and ecological management planning of Himalayan region of Nepal.

Identification of soil erosion vulnerable areas in Chandrabhaga river basin: a multi-criteria decision approach

In this present paper on delineation of soil erosion prone areas in a plateau fringe sub basin river Chandrabhaga (length: 26 km and area: 119 sq km), a tributary of Mayurakshi river, drains over lateritic tract of western Birbhum district of West Bengal. Raster based weighted linear combination (WLC) method considering six soil erosion driving parameters have been done in Arc Gis and ERDAS environments. RUSLE is used to quantify the raster based qualitative spatial erosion vulnerable model produced through WLC. This model is also tallied with pegging operation based measurement of surface lowering rates in different soil erosion vulnerable areas for validating the same. Raster based spatial model reveals that out of total basin area, 19.87 % area is extremely prone to soil erosion with a rate of 21.78 Mg/ha/year and total of 51513.86 Mg/year as derived from RUSLE based estimation of soil loss. Estimated weighted average soil erosion rate of this present basin is 9.12 Mg/ha/year. Pegging operation based measurement of surface lowering rate as well as soil loss validates the spatial scaling of soil erosion. Surface lowering rate is 2.5 mm/year in the extremely vulnerable areas followed by and highly vulnerable areas (1.1 mm/year).

Soil erosion rates in two karst peak-cluster depression basins of northwest Guangxi, China: Comparison of the RUSLE model with 137Cs measurements

Reliable estimation of erosion in karst areas is difficult because of the heterogeneous nature of infiltration and sub-surface drainage. Understanding the processes involved is a key requirement for managing against karst rock desertification. This study used the revised Universal Soil Loss Equation (RUSLE) to estimate the annual soil erosion rates on hillslopes and compared them with 137Cs budget in the depressions at two typical karst peak-cluster depression basins in northwest Guangxi, southwestern China. Runoff plots data were used to calibrate the slope length factor (L) of the RUSLE model by adjusting the accumulated area threshold. The RUSLE model was sensitive to the value of the threshold and required DEMs with 1m resolution, due to the discontinuous nature of the overland flow. The average annual soil erosion rates on hillslopes simulated by the RUSLE were 0.22 and 0.10Mgha−1y−1 during 2006 through 2011 in the partially cultivated GZ1 and the undisturbed GZ2 basins, respectively. The corresponding deposition rates in the depressions agreed well with the 137Cs records when recent changes in precipitation and land use were taken into consideration. The study suggests that attention should be given to the RUSLE-L factor when applying the RUSLE on karst hillslopes because of the discontinuous nature of runoff and significant underground seepage during storm events that effectively reduces the effects of slope length.

Improving the global applicability of the RUSLE model – adjustment of the topographical and rainfall erosivity factors

Abstract. Large uncertainties exist in estimated rates and the extent of soil erosion by surface runoff on a global scale. This limits our understanding of the global impact that soil erosion might have on agriculture and climate. The Revised Universal Soil Loss Equation (RUSLE) model is, due to its simple structure and empirical basis, a frequently used tool in estimating average annual soil erosion rates at regional to global scales. However, large spatial-scale applications often rely on coarse data input, which is not compatible with the local scale on which the model is parameterized. Our study aims at providing the first steps in improving the global applicability of the RUSLE model in order to derive more accurate global soil erosion rates. We adjusted the topographical and rainfall erosivity factors of the RUSLE model and compared the resulting erosion rates to extensive empirical databases from the USA and Europe. By scaling the slope according to the fractal method to adjust the topographical factor, we managed to improve the topographical detail in a coarse resolution global digital elevation model. Applying the linear multiple regression method to adjust rainfall erosivity for various climate zones resulted in values that compared well to high resolution erosivity data for different regions. However, this method needs to be extended to tropical climates, for which erosivity is biased due to the lack of high resolution erosivity data. After applying the adjusted and the unadjusted versions of the RUSLE model on a global scale we find that the adjusted version shows a global higher mean erosion rate and more variability in the erosion rates. Comparison to empirical data sets of the USA and Europe shows that the adjusted RUSLE model is able to decrease the very high erosion rates in hilly regions that are observed in the unadjusted RUSLE model results. Although there are still some regional differences with the empirical databases, the results indicate that the methods used here seem to be a promising tool in improving the applicability of the RUSLE model at coarse resolution on a global scale.

National assessment of soil erosion and its spatial patterns in china

The spatial patterns of soil erosion (SE) are an important part of ecological security patterns and critical to erosion control. We assessed the SE and its spatial distribution in China based on geographic information system (GIS) and spatial data sets using the Universal Soil Loss Equation (USLE). The soil erosion area (SEA) and soil erosion amount (SEM) totaled 173.06 million ha and 8.87 billion Mg, respectively, with an average soil erosion rate (SER) of 9.39 Mg·ha−1·yr−1. Slight erosion dominated from the aspect of SEA, whereas extreme erosion contributed the most in terms of SEM. Spatial heterogeneity in soil erosion was obvious in China, with heavily eroded areas mainly concentrated in the Loess Plateau, the Three Gorges reservoir area, and the hot, dry valley of the Jinsha River. Regionally, the provinces of Tibet, Sichuan, Yunnan, Xinjiang, Inner Mongolia, Gansu, Shaanxi, Shanxi, Guizhou, and Guangxi, and the basins of the Yangtze River, Yellow River, and southwestern rivers made a large contribution to the SEA and SEM. Geographically, soil erosion increased, then decreased with increasing slope and elevation. Slopes of 15–25° and 8–15° and elevations of 1000–2000 m were the most seriously eroded. Cropland and grassland ecosystems were major sources of SE, with their SEA and SEM accounting for 64.44% and 77.96% of the total. This study revealed the current situation and spatial characteristics of SE in China on the national scale, which can serve as a scientific basis for regional SE control and decision‐making policy.

SPH Modeling of Hydraulics and Erosion of HPTRM Levee

Post-Katrina investigations revealed that most earthen levee damage occurred on the levee crest and landward-side slope as a result of either wave overtopping, storm surge overflow, or a combination of both. In this paper, combined wave overtopping and storm surge overflow of a levee embankment strengthened with high performance turf reinforcement mat (HPTRM) system was studied in a purely Lagrangian and meshless approach, two-dimensional smoothed particle hydrodynamics (SPH) model. After the SPH model is calibrated with full-scale overtopping test results, the overtopping discharge, flow thickness, flow velocity, average overtopping velocity, shear stress, and soil erosion rate are calculated. New equations are developed for average overtopping discharge. The shear stresses on landward-side slope are calculated and the characteristics of soil loss are given. Equations are also provided to estimate soil loss rate. The range of the application of these equations is discussed.

Sediment delivery from interfluve slopes into river valley

A complex approach for estimating sediment delivery from drainage basin slopes into river valley is proposed. The method includes morphometric analysis of drainage basin, mathematical modelling and radioactive isotope tracers application. The approach effectiveness is demonstrated by analysis of the River Lokna drainage basin slopes (Central Part of the European Russia). Total area of the drainage basin is 174.8 km 2 . Morphometric characteristics of 1293 elementary slopes (facets) were collected from the 1:100 000 scale topographic map and analysed. Average soil erosion rate from facet under conditions of bare fallow is 46.2±31.9 t/ha/year. For a range of locally typical crop rotations this value varies from 17.2±13.0 to 33.3±19.1 t/ha/year. Mapping of drainage basin slopes allowed distinguishing areas with highest potential erosion rates. About 33% of elementary slopes of the studied drainage basin are characterized by the LS -factor value exceeding 1.5. In hypothetical case of cultivation of all basin slopes under bare fallow, 77% of elementary slopes will be characterized by very high and catastrophic potential erosion rates (>20 t/ha/year). For a range of locally typical crop rotations this percentage is reduced to 44%. Application of radioactive isotopic tracer allowed us to obtain an independent evaluation of the model validity. Comparison of soil loss rates obtained independently by the model and the 137 Cs radioactive tracer for the morphologically simple short runoff-dissipating slope has shown high degree of coincidence. However for the more complex long convex slope the model produced higher values of soil loss rates (sometimes more than twice) than the 137 Cs-based estimates. It can be explained by the fact that the model takes no account of within-slope sediment redeposition which cannot be estimated by its current version.

基于GIS重庆土壤侵蚀及土壤保持分析

PDF HTML阅读 XML下载 导出引用 引用提醒 基于GIS重庆土壤侵蚀及土壤保持分析 DOI: 10.5846/stxb201309152278 作者: 作者单位: 中国科学院生态环境研究中心 城市与区域生态国家重点实验室,中国科学院生态环境研究中心 城市与区域生态国家重点实验室,中国科学院生态环境研究中心 城市与区域生态国家重点实验室,中国科学院生态环境研究中心 城市与区域生态国家重点实验室,中国科学院生态环境研究中心 城市与区域生态国家重点实验室 作者简介: 通讯作者: 中图分类号: 基金项目: 国家自然科学基金重点项目(40901289);国家科技支撑计划课题(2011BAC09B08-02) GIS-based spatial analysis of soil erosion and soil conservation in Chongqing, China Author: Affiliation: Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences,Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences,,, Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:土壤侵蚀作为一个重大的全球环境问题,严重地威胁着区域生态环境质量和社会经济。在考虑植被覆盖度与土壤侵蚀关系的前提下,通过查表法,构建不同土地覆盖类型和不同植被覆盖度下的C值图层,并基于地理信息技术(GIS)和通用土壤侵蚀方程(USLE)估算了重庆地区土壤侵蚀量,土壤保持量和土壤保持价值。结果表明:重庆地区2010年土壤侵蚀量约为2.23 亿t/a;土壤保持量约为14.69 亿t/a。利用市场价值法,机会成本法和影子工程法评价了各类生态系统土壤保持的生态价值。研究区2010年土壤保持价值相对于2006年有所提升,2010年生态系统因防止土壤侵蚀而产生的土壤保持总价值约为6.18×105 万元,其中保持土壤养分的价值为5.44×105 万元;减少废弃地的价值为2.65×104 万元;减轻泥沙淤积灾害的价值为4.78×104 万元。各生态系统类型中,森林生态系统土壤保持价值量最大,单位面积价值最高。 Abstract:Soil erosion is an important global environmental problem that signicantly impacts regional environmental quality and the social economy. Ecosystems protect soil from water and wind erosion and thereby provide "soil erosion control services," which is one of the most fundamental ecosystem services that safeguard human welfare. Chongqing Region is one of the most important ecological zones in China, and is located on the upper reaches of the Three Gorges Reservoir Area (TGRA), which is the largest dam project worldwide. The status of the ecosystem functions in Chongqing Region directly affects the TGRA. Recently, the ecological environment of this region has rapidly changed because of extensive change in land cover, due to rapid population growth and economic development. In addition to climate change mitigation and adaption, global changes in climate have highlighted the role of ecosystems in soil conservation. Owing to a combination of natural factors and recent human activities, soil erosion in certain parts of the Chongqing Region is becoming increasingly serious. However, few studies have focused on the quantitative estimates of the soil conservation service and its ecological value in the Chongqing Region.This study aimed to construct the C value layer of different land cover types and different vegetation coverage based on the table lookup method. In addition, soil loss and soil conservation services in Chongqing Region were evaluated by geographic information system (GIS) technology and the universal soil loss equation (USLE) with localized parameters. The spatial patterns of the soil conservation service and its ecological value were revealed. The results of the study indicate that, compared to the single land cover assignment method, the improved C value layer containing more spatial information enhances the accuracy of soil erosion results. To verify that this model may be reliability applied, we validated the model results based on observed data and statistical data based on average annual estimates between 2006 and 2010. Simulations of average annual soil erosion rates agreed well with the observation-based data (R2=0.85, P=0.000), which indicated that the simulated models may be used to infer soil erosion levels in this study. The results of the models showed that the total amount of soil loss and soil conservation services in Chongqing Region are 2.23×108 t/a and 14.69×108 t/a, respectively. Furthermore, we found that the soil conservation service improved from 2006 to 2010 as a result of vegetation restoration. Moreover, market valuation, opportunity cost, and shadow engineering methods were used to evaluate the ecological value of the soil conservation service. The total value of the soil conservation service in 2010 was about 6.18×109 yuan (RMB) /a, of which, about 5.44×109 yuan was of holding nutrients for N, P and K, about 2.65×108 yuan was of decreasing soil loss, and about 4.78×108 yuan was reducing reservoir silt. In addition, ecosystems located in the counties of Wuxi, Chengkou, and Fengjie (i.e., the east mountain areas), had much better erosion control than ecosystems in the west, and generally displayed much higher ecological value than the west with a capacity of >2×108 yuan/a. Among all ecosystem types, forests were superior in the total amount and capacity of soil conservation service value. These results provide specific information that is necessary for strengthening public awareness about protecting and restoring ecosystems. 参考文献 相似文献 引证文献

Identification of critical soil erosion prone areas and annual average soil loss in an upland agricultural watershed of Western Ghats, using analytical hierarchy process (AHP) and RUSLE techniques

The present work integrates analytical hierarchy process (AHP) with Revised Universal Soil Loss Equation (RUSLE) model to determine the critical soil erosion prone areas along with the spatial pattern of annual average soil erosion rates of an upland agricultural sub-watershed in the Western Ghats of Kerala, India. The critical soil erosion prone areas were identified by integrating geo-environmental variables such as land use/land cover, geomorphology, drainage density, drainage frequency, lineament frequency, slope, and relative relief after determining its relative contribution in conditioning the terrain susceptible to soil erosion by AHP technique, in a raster-based Geographic Information Systems environment. The spatial pattern of average annual soil erosion rates was obtained by RUSLE model that consider five factors, viz., rainfall erosivity (R), soil erodability (K), slope length and steepness (LS), cover management (C) and conservation practice (P) factors. The soil erosion probability map prepared by the AHP method was reclassified into soil erosion severity map showing regions of different erosion probability. Among this, the critical erosion zone occupies 4.23 % of the total area followed by high erosion severity zone occupies 18.39 % of the study area. Nil and low zones together constitute 44.15 % of the total area. The assessed annual average soil loss from the watershed shows an increased value of 4,227 t−1 h−1 year−1 as the maximum loss. The cross-comparison of potential soil erosion severity map with annual average soil loss in the area validates the finding of the study by a high spatial correlation. More erosion proneness and annual loss were observed in areas where the side slope plateau, denudational slope, and valley fills comes with high slope and relative relief. The intense terrain modification in this area with improper soil conservation measures makes the watershed more vulnerable to soil erosion.

Estimation of soil erosion and crop suitability for a watershed through remote sensing and GIS approach

Present study is in Patani micro-watershed situated in Satna District of Madhya Pradesh where soil erosion and crop suitability were estimated with Remote Sensing and GIS. The annual soil erosion potential was estimated using Universal Soil Loss Equation and suitable crops for particular watershed was suggested. The average rainfall erosivity factor (R), erodibility factor (K), highest and lowest value of slope length factor (LS), highest and lowest values of crop management factor (C), highest and lowest values of conservation factor (P) have been calculated. Average soil erosion rate of the watershed was estimated to be 8 tonnes/ha/yr. About 13.95% of the watershed area was found to be under slight erosion, 82.21% under the moderate erosion, high and severe erosion found in only 0.01% and remaining area was under very high erosion. Analysis shows that Patani micro-watershed is suitable for crops like maize, mustard, and greengram with minor limitations of soil and land characteristics.

Establishing reference inventories of 137Cs for soil erosion studies: Methodological aspects

The radiocaesium technique has become an attractive methodology for quantifying long-term average soil erosion and accumulation rates. It is based on comparing the 137Cs inventory in soils of a site which is suspected to be affected by soil redistribution to that of an adjacent undisturbed reference site. A major complication arises from the spatial variability of 137Cs generally present even at small areas of <1ha. In this paper we present statistically based procedures that efficiently allow to discriminate between soil erosion and pure spatial variation of 137Cs. We systematically explore the effect of study design and spatial variability of 137Cs on the sensitivity of the radiocaesium technique for soil erosion studies. The procedures and simulation results presented assist (i) in checking whether the sensitivity of the 137Cs technique is adequate for an intended study, and (ii) in developing an optimal study design.In addition it is shown that some of the statistical criteria proposed in the literature for discriminating soil redistribution from 137Cs variability show high error risks and should be avoided.

Responses of Runoff and Soil Erosion to Vegetation Removal and Tillage on Steep Lands

Land use and land cover change is a key driver of environmental change. To investigate the runoff and erosion responses to frequent land use change on the steep lands in the Three Gorges area, China, a rainfall simulation experiment was conducted in plots randomly selected at a Sloping Land Conversion Program site with three soil surface conditions: existing vegetation cover, vegetation removal, and freshly hoed. Simulated rainfall was applied at intensities of 60 (low), 90 (medium), and 120 mm h−1 (high) in each plot. The results indicated that vegetation removal and hoeing significantly changed runoff generation. The proportion of subsurface runoff in the total runoff decreased from 30.3% to 6.2% after vegetation removal. In the hoed plots, the subsurface runoff comprised 29.1% of the total runoff under low-intensity rainfall simulation and the proportion rapidly decreased with increasing rainfall intensity. Vegetation removal and tillage also significantly increased soil erosion. The average soil erosion rates from the vegetation removal and hoed plots were 3.0 and 10.2 times larger than that in the existing vegetation cover plots, respectively. These identified that both the runoff generation mechanism and soil erosion changed as a consequence of altering land use on steep lands. Thus, conservation practices with maximum vegetation cover and minimum tillage should be used to reduce surface runoff and soil erosion on steep lands.