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A meta-analysis of soil erosion rates across the world
... On this background, an amazing record of sediment observation data exists for the Shirasaka Experimental Watershed of the Ecohydrology Research Institute of The University of Tokyo that goes back to 1929. We are aware of the value of this record being the longest direct sediment discharge measurement worldwide as far as we know (e.g., García-Ruiz et al., 2015) and thought it is important to describe how people have monitored sediment output. The site was established in an area where many denudated slopes existed. ...
... More than 11 years of hillslope plot-scale measurements have shown that bare slopes yield 5,000 to 10,000 m 3 /km 2 /y of sediment, and those values fluctuate by about an order of magnitude from year to year (Fujita & Nakagawa, 1964;Suzuki & Fukushima, 1989). Those are the highest erosion rates reported worldwide (García-Ruiz et al., 2015). Suzuki & Fukushima (1989) also reported that sediment yield was immediately reduced by 2-3 orders of magnitude when terraces were cut and planted on bare slopes for erosion control works. ...
... Assuming that the floodplain and weir pond capture 89.5% of the annual sediment (Karki & Shibano, 2007) and that the source of sediment has not changed over time, then the 10-year average total sediment yield from the catchment likely amounted to 1730 ± 743 t/ km 2 /y in the beginning (1929)(1930)(1931)(1932)(1933)(1934)(1935)(1936)(1937)(1938) and dropped to 253 ± 175 t/ km 2 /y in recent years (2013)(2014)(2015)(2016)(2017)(2018)(2019)(2020)(2021)(2022). That means, in the 1930s, the catchment discharged the highest levels of sediment yield among erosion rates reported from catchments across the world, but sediment yields decreased to almost the median of worldwide yields in recent years (111 t/km 2 /y, García-Ruiz et al., 2015). ...
Mountainous areas are a source of sediment supply to downstream plains and coasts; thus, it is essential to understand the changes in sediment discharge that follow land cover change. In Japan, many mountain areas near populated lands that were degraded by overutilization before the beginning of the 20th century are now forested. However, little is known about how the sediment dynamics have changed during this period. The Shirasaka Experimental Watershed (88.5 ha) of the Ecohydrology Research Institute of the University of Tokyo was established in an area with bare hillslopes on granite bedrock, and sediment discharge has been monitored there since 1929. This study describes the details of the amazing long‐term sediment monitoring program and demonstrates changes in sediment discharge. The catchment has a gauging weir where deposited sediment has been regularly removed to maintain water discharge measurements. This record of dredging and/or deposited volumes provides the sediment discharge data. Erosion control work started in the 1910s. Bare land covered 8.6% of the watershed area in 1930 but decreased to less than a few percent in the 1980s. In the 1930s, sediment yield was about 1,000 m ³ /km ² /y, gradually declined over time, and became close to 100 m ³ /km ² /y in the 1990s. Annual sediment yield was, for the most part, larger than the sediment production predicted for surface erosion at hillslopes between 1930s and 1990s. It took more than 60 years for the catchment's sediment yield to become close to the amount of sediment production at the hillslope of that time. The time lag between forest recovery and the decline in the catchment's sediment discharge demonstrates the lasting effect of anthropogenic disturbance and is attributable to channel storage. The long‐term data also demonstrated that the effects of record‐breaking rainfall events are smaller than those of past anthropogenic disturbances on catchment scale sediment dynamics.
... During the last century, field plots have been used to estimate soil erosion rates in many countries, in the effort to better understand soil erosion processes under different land use types and how to mitigate its effect. The extent of plot experiments can for example, be seen from compilations of available plot data which were collated for Europe (Cerdan et al. 2010;, China (Guo et al. 2015), Brazil (Anache et al. 2017) and worldwide (García-Ruiz et al. 2015), who all collected several thousand plot-years of data. The data show that soil erosion rates are higher on land used for (conventional) agricultural activities than on land under (semi-)natural vegetation. ...
... It is commonly seen that a few large events are responsible for the majority of soil loss over time (García-Ruiz et al. 2015;Strohmeier et al. 2016). The importance of extreme events highlights the need for the measurement equipment to be able to handle such events regarding both high runoff Total soil erosion 8.2 t ha −1 7.1 t ha −1 FIGURE 7 | Period of natural soil erosion events for which the calibration functions were applied. ...
... intensities, sediment loads and storage capacity of the subsamples. Furthermore, field measurements should be carried out over long study periods of 20-25 years to capture extreme events reliably (García-Ruiz et al. 2015) and to derive statistically sound average soil erosion rates (Auerswald et al. 2009). Our results show that the computation of uncalibrated soil erosion from measurement plots might have large deviations from the actual soil loss, particularly for periods with intense erosion events. ...
In situ soil erosion monitoring is essential to investigate the effects of soil erosion control measures and to provide effective management strategies to maintain soil health and for future climate change adaptation. However, reliable soil erosion monitoring in the field depends on the accuracy of the installed measurement equipment under a range of environmental conditions. This study evaluated how slot position in a multislot divisor, runoff intensity and soil type affect runoff and sediment measurements of tipping bucket measurement boxes for soil erosion monitoring. A controlled experimental setup simulated runoff events using two different soil types to analyse potential differences in collected runoff, sediment and its textural composition among slot positions. Based on the results, we present a calibration strategy for tipping bucket measurement boxes to adjust for deviations in collected runoff and sediment. The results reveal that tipping stability declines at frequencies over 40 tips per minute, with the central slot collecting up to 4% of water volume, exceeding other slots. Water and sediment collection at the central slot maintained a consistent pattern under 40 tips per minute, while deviations in sand content between collected and parent soils were observed but did not impact overall sediment mass significantly. Calibration functions applied to a measurement plot during a period of natural runoff events under field conditions exhibited underrepresentation of runoff and sediment levels in uncali-brated records. Runoff calibration results in more accurate total erosion estimates, especially crucial for high-frequency runoff events where uncalibrated results overestimated soil loss by up to 13%.
... Land use and land cover changes have frequently led to catastrophic episodes of soil erosion across many areas of the world (Bork, Lang 2003). Therefore, within the anthropocene context, land use and land cover changes are recognized as the primary drivers increasing soil erosion rates worldwide (García-ruiz et al. 2015). ...
... The impacts of humans on soil erosion are profound and complex, especially in areas with frequent human activities. Soil erosion studies confirm that agricultural activities are associated with the highest erosion rates, despite high variability depending on agricultural uses (Verheijen et al. 2009;García-ruiz et al. 2013García-ruiz et al. , 2015. The greatest erosion rates have been measured in vineyards (i.e., Kosmas et al. 1997;ramos, Martínez-Casasnovas 2006;Cerdan et al. 2010), mainly due to the low level of plant cover and the steepness of vineyard slopes , making vineyards particularly susceptible to heavy rainfall and soil erosion processes. ...
... One of the most critical issues in soil erosion studies is the scarcity of long-term datasets. García-ruiz et al. (2015) identified that most soil erosion studies are short--term, typically around two years, with few extending beyond ten years. They suggested that an optimum study period is 20-25 years to reduce variability in erosion rates and incorporate the occurrence of extreme events. ...
Soils provide the substrate for 95% of human food and essential ecosystem services, such as water regulation and biodiversity, while also serving as the most efficient CO₂ sink on the Earth’s surface. However, soil degradation poses a major threat, with significant changes in most of the Earth’s soil attributed to human activities. Common soil hazards in the Anthropocene include: (i) soil compaction, (ii) salinization, (iii) soil contamination, (iv) landslides, (v) decline in soil organic matter, and (vi) soil erosion. Anthropogenic activities greatly impact soil organic carbon (SOC) through land use and land cover changes, agricultural practices, and land management. Indirect effects, such as wildfires, also influence SOC dynamics. Most studies indicate that land use and land cover changes, along with land management, have a greater impact on SOC than the direct effects of climate change. Soil erosion, though a natural process, is significantly exacerbated by anthropogenic factors, leading to a drastic increase in global erosion rates in the Anthropocene. Numerous challenges, opportunities and knowledge gaps have been identified. However, a deeper understanding of both natural and human-induced soil hazards and challenges is necessary. This short review, highlights that a significant amount of work is still needed to fully comprehend the impacts of human activities on soil. Continued research, exploring new questions, is crucial.
... Although soil erosion shows extreme variability worldwide, some general trends can be identified when analyzing soil erosion rates from multiple sources. The results obtained from a meta-analysis of more than 4000 sites worldwide (García-Ruiz et al. 2015) demonstrate the effects of steep slopes, precipitation, and land uses, with agricultural lands being particularly active as sediment source areas (Lal 1988;Cerdan et al. 2010;Cerdà et al. 2012;Dotterweich 2013;García-Ruiz et al. 2015;Panagos et al. 2015;Salvati et al. 2015;Quinton and Fiener 2023). In the Mediterranean region, the combination of steep slopes, heavy rainfall, and a long history of cultivation, fire, and grazing has led to some of the highest erosion rates in the world (Kosmas et al. 1997;García-Ruiz et al. 2013). ...
... Although soil erosion shows extreme variability worldwide, some general trends can be identified when analyzing soil erosion rates from multiple sources. The results obtained from a meta-analysis of more than 4000 sites worldwide (García-Ruiz et al. 2015) demonstrate the effects of steep slopes, precipitation, and land uses, with agricultural lands being particularly active as sediment source areas (Lal 1988;Cerdan et al. 2010;Cerdà et al. 2012;Dotterweich 2013;García-Ruiz et al. 2015;Panagos et al. 2015;Salvati et al. 2015;Quinton and Fiener 2023). In the Mediterranean region, the combination of steep slopes, heavy rainfall, and a long history of cultivation, fire, and grazing has led to some of the highest erosion rates in the world (Kosmas et al. 1997;García-Ruiz et al. 2013). ...
... This conclusion has been reached through experiments with simulated rainfall and with experimental plots of several square meters in area. It is well known that neither simulated rainfall nor plots provide real erosion rates (e.g., Boix-Fayos et al. 2006;García-Ruiz et al. 2015). Moreover, the size of the experimental plots is very variable, and their results are hardly comparable (see Table 2). ...
The expansion of international markets for some agricultural products explains the growth in marginal areas of the surface occupied by subtropical crops (especially avocado and mango) and the rapid penetration of pistachio plantations in the Mediterranean regions of the world. The traditional Mediterranean crops (vineyards, and olive and almond orchards) have also experienced remarkable locational changes. In most cases, this expansion has taken place towards marginal slopes, generally very steep, many of them cultivated decades ago and already abandoned. The consequence is an increased risk of erosion, which can only be counteracted by planting herbaceous plants or native shrubs between the rows of trees. Thus, changes in international markets for agricultural products can have important environmental consequences in terms of runoff generation and sediment yield, as well as disturbances in the spatial organization of rural landscapes.
... Zhang et al., 2014;El Kateb et al., 2013;Zhou and Shangguan, 2007). Cultivated agricultural land areas are particularly prone to erosion (García-Ruiz et al., 2015) which has consequences on agricultural soils and on the locations where the eroded sediment is transported. The sediments can degrade downstream water quality and block drainage infrastructure (e.g. ...
... The processes leading to erosion are spatiotemporally variable due to local soil properties, topography, and weather conditions (e.g. Remund et al., 2021;Ulén et al., 2012) and challenging to accurately estimate in different locations (García-Ruiz et al., 2015). Several erosion mitigation measures have been developed and their impacts have been demonstrated in different agricultural land areas (e.g. ...
... Furthermore, also empirical measurement campaigns have uncertainties (e.g. García-Ruiz et al., 2015) which highlights the value of combining data with models. While our study focused particularly on spatially analyzing erosion control at long-term erosion hotspot areas, considerations on erosion dynamics could also be useful in terms of exploring the potential of temporal targeting. ...
Spatial patterns of land-cover and agricultural operations have clear impacts on soil erosion. Allocating a portion of cultivated area for grass is a widely applied strategy to control erosion. However, it is still unclear how much and where grassed area should be spatially targeted in different landscapes to control erosion efficiently. To address this challenge, we estimate the potential of high-resolution RUSLE-based spatial targeting of grassed areas to improve erosion mitigation in two topographically different catchments in southern Finland. Erosion reductions of 1) policy-based targeting (buffer strips along main streams according to current CAP strategy) were compared with 2) RUSLE-targeted grassed areas (based on the highest computed erosion values within field parcels and sub-catchments). Furthermore, we computationally explored 3) how different rates of optimally located grass areas affected erosion and 4) how the areas could be computationally processed to continuous entities. The erosion reductions were estimated with 2×2 m2 resolution RUSLE computations in all the scenarios. The RUSLE-targeted grassed areas demonstrated greater erosion reductions compared to the policy-based siting of grass areas along riparian fields. With optimal targeting, erosion risks could potentially be reduced up to 24 percentage points (up to 46% erosion reduction), compared to the buffer strips. Increasing optimally targeted grassed area gradually from 0 to 100% decreased erosion non-linearly. The largest share of erosion was generated in disproportionally small land areas (~20% of the land area). The location of the hotspots in relation to the streams varied between the sub-catchments and field parcels. These quantifications demonstrate the potential value of models for targeted landscape scale spatial erosion management. A more comprehensive assessment of erosion mitigation could benefit of improved empirical validation and consideration of other aspects of erosion and sediment transport, such as local drainage efficiency and reduction of erosion during flooding of rivers.
... Areas with undulating landscapes, agricultural land, sub-humid regions, semi-arid land, and dry land are particularly erosion-sensitive. [7] Given the challenging geographical and topographic conditions in the higher Himalayan regions, field-based surveys and investigations have their limitations. Consequently, RS and GIS techniques play a pivot role in offering viable solutions and enhancing our comprehension of hydrological processes on a regional scale in the Himalayas. ...
To implement effective conservation plans, it is crucial for policymakers first to evaluate the extent of soil deterioration within the designated region to develop more targeted and impactful measures. The soil erosion model (RUSLE) incorporated with geospatial techniques was used to examine soil loss in high altitude Alaknanda River basin, situated in the Uttarakhand, Chamoli district in the Western Himalayas for a fifteen-year period (2004–2018). The estimated soil depletion was categorized into six distinct levels of erosion vulnerability, spanning from minimal to extremely high-risk classes. The study highlights the significant vulnerability of the Alaknanda River basin to soil loss, having an anticipated average loss of 28.45 t ha−1 yr−1, surpassing the permissible limit of 25 t ha−1 yr−1 in young mountain environments. The majority of the eroded portion is categorized within the slight erosion class at 43.67%, and the minority of the eroded region falls under the medium erosion class at 3.78%. The overall temporal variation in mean soil loss shows a rising pattern from 2004 to 2010, followed by a decrease from 2010 to 2018, following a pattern like that of the Ŗ-factor temporal trend, which also increases from 2004 to 2010 and decreases thereafter, underscoring the significant influence of rainfall on soil loss in Alaknanda. This geospatial evaluation of soil degradation in the Alaknanda basin offers valuable perspectives on the underlying factors resulting in erosion and pinpoints key areas that warrant priority interventions.
... Experiences from these regions suggest that check dams or other similar engineering measures have a wide potential for application on a global scale. However, significant differences in precipitation characteristics, topographic conditions and soil properties in different regions may lead to different hydrological and erosion control effects of check dams [38,39]. Therefore, a systematic study of the effects of check dams on runoff and erosion dynamics under different precipitation characteristics is of great significance for optimizing soil and water conservation measures and achieving sustainable regional development. ...
As one of the most important soil and water conservation engineering measures, the check dam plays an important role in the process of soil erosion control on the Loess Plateau of China. Combined with the hydrodynamic model, the regulation effects of runoff and erosion hydrodynamics on check dams was studied under different precipitation types in the Xiliugou watershed of Loess Plateau. The Xiliugou watershed is dominated by the four precipitation types, short duration and small total amounts (P1), long duration and small total amounts (small total amounts), short duration and larger total amounts (P3) and short duration and largest total amounts (P4). The results show that the peak flow time may lag behind in the upper and middle reaches, while it may be advanced in the downstream in the parallel layout of the dam system watershed. The check dam system plays a significant role in reducing runoff and erosion hydrodynamics. The construction of check dams results in a significant reduction in the peak flow under the P2 precipitation type, reaching 39.41%. For the average maximum velocity, runoff shear stress and runoff power along the main channel, the P2 precipitation type results in a significant reduction in hydrodynamics in the dam system watershed, reaching 16.72%, 21.44% and 33.10%, respectively. However, for peak velocity, runoff shear stress and runoff power along the main channel, the P3 precipitation type results in a significant reduction in hydrodynamics in the dam system watershed, reaching 14.34%, 19.99% and 31.42%, respectively. The regulation effect of the check dam system on erosion hydrodynamics is stronger in the middle reaches and gradually weakened in the lower reaches of the watershed.
... Approximately 42% of the studies in our dataset originate from Canada and the United States. Similar biases have been observed in soil science research, as highlighted by [51,52], which reported a heavy reliance on North American data for soil erosion rate estimates. Expanding datasets to include more studies from regions such as South Asia, Western Africa, and South America-along with standardized field measurement protocols-will improve model reliability and enhance our understanding of SOC sequestration potential. ...
Regenerative agriculture is pivotal for mitigating climate change, with no-tillage practices on cropland being generally effective at raising soil organic carbon (SOC). Yet, our understanding of the compound impact of soil and environmental factors on SOC gain potential after transitioning to no-till practices is still developing. Using imbalanced machine learning classification, here we quantify key thresholds to hierarchically classify SOC gain potential by switching from conventional tillage to long-term no-tillage with residue retention. Our findings reveal that antecedent SOC level exerts the primary influence, with a reduced gain potential for antecedent SOC exceeding 50 tonnes per hectare. Wet climate (Dryness Index < 1.5) and low productivity (net annual primary productivity < 5.5 tonnes per hectare) could further lessen the effectiveness of SOC sequestration. These key thresholds identify vast areas across Africa, Australia, South Asia, Southern Europe, and parts of North and South America as high-potential croplands for carbon sequestration and offer guidelines for assessing the reliability of regenerative agriculture in local and regional contexts.
... These studies have shown that forests, more than any other vegetation, reduce annual runoff and peak flows and support low flows (Robinson and Whitehead, 1993;Ice and Stednick, 2004). Similarly, several studies have demonstrated the critical role of land use and forest cover in reducing soil erosion (e.g., García-Ruiz et al., 2015). ...
... Land degradation [85][86][87] Data were retrieved from the National Soil Erosion Inventory (INES) (spatial resolution of 1 km) in the Autonomous Community of Asturias Biodiversity Ecosystem diversity [88][89][90] Data derived from calculations using the Shannon index (spatial resolution of 1 km), a tool for quantifying biodiversity. It provides a comprehensive measure of community diversity, considering both the number of species present and their relative abundance. ...
The Mediterranean Diet is a highly sustainable diet, and legumes are among the products that best characterize this concept. This study evaluates the environmental sustainability of the Protected Geographical Indication (PGI) legume Phaseolus vulgaris L. cultivated in the Asturias region, Spain. Employing a multi-indicator approach, the study aims to define and measure certain biodiversity indicators useful for assessing the ecological quality and sustainability of the agroecosystems under consideration. Spatial analyses were conducted with GIS-based methodologies, integrating the Analytic Hierarchy Process (AHP) to generate a Sustainability Index (SI). The study found that a significant positive spatial autocorrelation was observed using Moran’s I test (Moran’s I = 0.74555, p < 0.01), indicating that the SI values were not equally distributed but clustered around particular regions. Furthermore, the Getis-Ord Gi* analysis determined statistically significant hotspots, mainly distributed in the western and southwestern areas, including regions near Cangas del Narcea and Tineo. This paper highlights the importance of integrating spatial analysis for environmental assessments to develop sustainability approaches. Soil quality, water use, biodiversity, and land management are some of the factors that affect sustainability outcomes in the region. The results underscore the role of PGI in promoting sustainable agricultural practices by meeting geographical and quality requirements for local production.
... The higher soil loss rate is reported in South America, Africa, and Asia, and it varies from 28 to 40 ton/hectare/year (Seutloali, Dube, and Sibanda 2018). Following population growth, soil erosion is considered to be a second most significant environmental challenge globally (García-Ruiz et al. 2015). Since the World War II, around 85% of land degradation can be attributed worldwide to soil erosion, contributing to a 17% decrease in productivity of crop (Angima et al. 2003). ...
Assessing soil and sediment loss are the main aims of the paper using the Revised Universal Soil Loss Equation (RUSLE) and the InVEST SDR models in the Ken River Basin (KRB). The annual soil loss varied from few-ton/hectare/year to 1630.5. The high erosion susceptibility was prevalent in the elevated area and low soil erosion severity was seen in the low-lying plains of the middle and lower reaches. The maximum sediment export (430.16-ton/hectare/year) was noticed in the hills of the Vindhyans, Bundelkhand, and Deccan traps. Contrary to this the low sediment transport was observed in the flat alluvium plains. The conservation practices are slightly more effective in the KRB. Its crop cover reduces the impact of rain's kinetic energy, increase recharge, and mitigates soil erosion. These research output may be helpful to planners in minimizing soil and sediment loss and in enhancing the soil conservation and agricultural productivity.
... Depending on the local environmental and topographic settings, specific forms of soil redistribution can prevail, showing typical patterns across topographic soil gradients that are more affected or less affected by soil redistribution. For example, natural soil loss through erosion is most evident in regions with limited soil cover, such as arid zones, high-altitude areas, or locations exposed to high winds or torrential rain combined with steep terrain 76 . In these regions, soils are much shallower and, in most cases, less weathered than in regions where dense vegetation cover protects soils from erosion and allows soil formation to continue without major soil disturbance. ...
... This land use effect is clearly observed in the small streams within the PRB (Figures 2b-2d and, 2f, and 2h). Together, geomorphologic, hydroclimatic, and land use conditions can also alter soil characteristics, such as soil erosion rate and R h (García-Ruiz et al., 2015;Hursh et al., 2017). R h affects the decomposition of soil organic carbon (SOC), which represents a significant portion of soil respiration and serves as a notable source of soil CO 2 (Schindlbacher et al., 2009). ...
Anthropogenic perturbations have substantially altered riverine carbon cycling worldwide, exerting influences on dissolved carbon dioxide (CO2) and methane (CH4) dynamics at multiple levels. However, the magnitude and role of anthropogenic activities in modulating carbon emissions across entire river networks, as well as the influence of climatic controls, remain largely unresolved. Here, we explore the controlling factors of riverine CO2 and CH4 dynamics across 62 subtropical, monsoon‐influenced streams and rivers through basin‐wide seasonal measurements. We found that land use and aquatic metabolism played significant roles in regulating the spatial and temporal patterns of both gases. Increased nutrient levels and organic matter contributed to higher partial pressure of CO2 (pCO2) and CH4 (pCH4). Dissolved oxygen, stable carbon isotope of dissolved inorganic carbon, the proportion of impervious surface, catchment slope, and river width were the major predictors for pCO2. For pCH4, the major predictors were Chlorophyll a and water temperature, which influence organic matter availability and methanogenesis. Seasonal variations in pCO2 and pCH4 were strongly modulated by hydroclimatic conditions, with temperature markedly regulating river ecosystem metabolism. These findings highlight the likelihood of significant changes in riverine carbon emissions as climate changes and land use patterns evolve, thereby profoundly affecting the global carbon cycle.
... The observed and expected decrease in mean precipitation (WD1) due to climate change is accompanied by an increase of extreme precipitation (WD2), flooding (WD3) and, subsequently, increased erosivity [44]. In tropical and sub-tropical regions, the on-site impacts of soil erosion dominate and are manifested in very high rates of soil loss, in some cases exceeding 100 t ha -1 yr -1 [45,46], while in temperate regions, the off-site costs of soil erosion are often a greater concern; for example, siltation of dams and ponds and downslope damage to property, roads and other infrastructure [47]. 6. ...
Water Infrastructure (WI), incorporating water supply, wastewater, and stormwater systems, is vulnerable to climate change impacts that can disrupt their functionality; thus, WI needs to be adapted to climate change. In 2021, the European Commission (EC) released the technical guidelines on “Climate-proofing Infrastructure” that include mitigation and adaptation strategies; these guidelines, and the relevant guides that followed, focus mainly on climate change aspects without examining sufficiently the engineering features of WI that are described mainly in the relevant hydro-environmental research; this research is vast and includes various terminologies and methods for all aspects of climate change adaptation. The adaptation procedure of WI to climate change is improved when this research is known to guidelines’ developers. In the present work, to facilitate this knowledge transfer, we typologize the hydro-environmental research via its classification into five categories that are based on the EC guidelines and then perform a literature review that we present as follows: firstly, we introduce and typologize the climate hazards for WI systems and identify the most common of them in the Mediterranean region that we classify into seven groups; then, we classify the hydro-environmental research into five categories based on the EC guidelines, present the main aspects for each of these categories, discuss the future research; and finally, we summarize the conclusions.
... Soil erosion is one of the primary causes of land degradation, and disturbance of natural ecosystems, which reduces the productivity and fertility of the soil, and hinders the development of sustainable agriculture and natural resources (García-Ruiz et al., 2015;Wuepper et al., 2020). Several reviews and studies have extensively covered the mechanisms and drivers of soil erosion, focusing on factors such as climate change, land use, slope, rainfall intensity, soil characteristics, and soil management (García-Ruiz 2010; Hossini et al., 2022;Li & Fang, 2016;Nearing et al., 2004;Vanwalleghem et al., 2017) as well as the economic and environmental impacts of soil erosion and land degradation (Den Biggelaar et al., 2001;Girona-García et al., 2023;Issaka & Ashraf, 2017;Majoro et al., 2020;Jiao et al., 2009). ...
Soil erosion is a major concern for both agricultural and natural resources. Soil water repellency (SWR) is known to hinder wetting of soils, decreasing infiltration of water and thus increasing overland flow—the driving force for erosion. These hydrological impacts of SWR on erosion, are quite well established. In contrast, the mechanical impacts of SWR, namely on the resistance to erosion, are poorly understood. Here, we provide a critical review of the current understanding of both the hydrological and mechanical impacts of SWR on erosion. Analysis of compiled experimental data provides contradictory evidence: an increase in erosion with increasing SWR in some cases, versus a decrease in others, with a strong dependency on the mechanism (weather, fire, or pollution-induced SWR). We offer a plausible explanation for this contradiction—that the net erosional impacts of SWR depend on the balance between its hydrological and mechanical effects on erosion, and exemplify this in a simple 1D slope model. Our simulations illustrate the dual nature of SWR's influence on soil erosion, and explain the diversity of published data. Finally, we identify research gaps and suggest ways to address them.
... Эрозия почв является серьезным препятствием в обеспечении экологического равновесия ландшафтов. В мировой литературе накоплен обширный экспериментальный материал по изучению эродированных почв и поиска путей их рационального использования [1][2][3]. В Российской Федерации проблема остается недостаточно изученной в связи с масштабами территории и разнообразием почвенно-климатических условий. В Западной Сибири распашка крутых склонов без применения почвозащитных приемов привела к увеличению площади эрозионно опасных земель. ...
Предложена оценка состояния залежных почв в постэрозионной стадии самовосстановления с использованием почвенно-растительной диагностики и показателей активности сапротрофного микробного сообщества (СМС) почвы. Объекты исследования - смыто-намытые почвы и растительность на разновозрастных (15 и 30 лет) залежах эрозионного склона. Ботанический состав растительного сообщества на залежных участках соответствовал дерновинной стадии и частично вторичной целины. В верхней части профиля (дерновый горизонт) эродированных почв залежей содержание общих и подвижных элементов питания растений было повышенным, в нижней части - варьировало и зависело от мощности намытого слоя. При помощи методики мультисубстратного тестирования (МСТ) сравнили метаболический профиль СМС почв целинного и залежных участков. На целине интенсивность потребления всех групп субстратов СМС почвы резко снижалась с глубиной. На залежных участках в почвенном слое 0-10 см активность СМС не уступала показателям целины, ниже по профилю - зависела от мощности намытого слоя. В целом СМС эродированных почв залежей оказалось более активным в сравнении с целинной почвой, что очевидно связано с наличием доступного к потреблению органического вещества. Показатели функционального спектра СМС тесно коррелировали с почвенно-агрохимическими параметрами. Уровень плодородия почв в пост эрозионной стадии самовосстановления не уступал показателям целины.
An assessment of the state of fallow soils in the post-erosion stage of self-healing is proposed using soil-vegetation diagnostics and indicators of the activity of the saprotrophic microbial community (SMC) of the soil. The objects of study were eroded-and-drift soils and vegetation on fallows of different ages (15 and 30 years) on the eroded slope. The botanical composition of the plant community in fallow areas corresponded to the sod stage and partly secondary virgin lands. In the upper part of the profile (sod horizon) of the eroded soils of fallows, the content of total and mobile plant nutrients was increased; in the lower part, it varied and depended on the thickness of the eroded layer. Using the technique of multisubstrate testing (CLPP), we compared the metabolic profile of SMC in soils from virgin and fallow plots. In the virgin plot, the intensity of utilization of all substrate groups of soil SMC substrates sharply decreased with depth. In fallows in the soil layer of 0-10 cm, the activity of SMC was not inferior to virgin, lower along the profile it depended on the thickness of the eroded layer. In general, the SMC of eroded fallow soils turned out to be more active in comparison with virgin soil, which is obviously associated with the presence of organic matter available for consumption. Indicators of the functional spectrum of SMC closely correlated with soil parameters. The level of soil fertility in the post-erosion stage of self-restoration was not inferior to virgin plot.
... Watershed management has emerged as a key strategy for achieving a sustainable environment [4]. Soil, one of our most important resources, to produce food, fiber, and other agricultural goods necessary for human survival [5], is under threat of degradation [7]. Each year, approximately 10 million hectares of cropland are lost due to soil erosion, leading to a reduction in the available cropland for global food production [8]. ...
Soil erosion, primarily driven by natural and human-induced factors, is a significant contributor to soil degradation and natural disasters. Effective watershed management practices can mitigate these issues. This study aimed to create a soil erosion susceptibility map for the sub-watersheds of the Teesta River using the Weighted Aggregated Sum Product Assessment (WASPAS) model. Ten morphometric parameters were considered to assess susceptibility, including Bifurcation Ratio, Circulatory Ratio, Basin Length, Stream Frequency, Drainage Density, Basin Perimeter, Basin Width, Shape Factor, Drainage Texture, and Elongation Ratio. The relative weights of these parameters were determined using the AHP-ENTROPY method. The integrated weights were then applied in the WASPAS model to rank the sub-watersheds. Results indicate that sub-watersheds Rangit (SW5), Chel (SW14), Rangyong Chhu (SW4), Lhonak Chhu (SW1), Chakung Chhu (SW6), and Lish (SW13) are highly susceptible to soil erosion. These sub-watersheds should be prioritized for conservation efforts. The originality of this study lies in its application of the WASPAS method in the context of soil erosion, providing a more comprehensive and accurate assessment compared to traditional methods.
... The spatial distribution of LS values suggests that northern regions with steep gradients are particularly vulnerable. This is corroborated by recent studies that have shown the amplification of soil erosion risks in areas having steep and rugged terrain (García-Ruiz et al. 2015). ...
Soil erosion is a significant environmental issue that requires a thorough investigation of soil properties and behaviors to effectively mitigate its effects. Current study aims to spatially examine soil erosion in the Panjkora Basin by integrating the “Revised Universal Soil Loss Equation” (RUSLE) models with geospatial techniques. The RUSLE factors, including soil erodibility (K) and topographic (LS) factors, were computed using secondary data sources. Soil survey data was utilized to estimate the K factor, while “digital elevation model” (DEM) was employed to estimate LS factor. The support practice (P) and cover management (C) factor were obtained from literature as secondary data. Rainfall erosivity (R) was computed with daily rainfall data and Hurni’s equation. In Geographic Information System (GIS), overlay analysis was conducted to spatially combine the K factor, rainfall-runoff erosivity, slope steepness, slope length, support and conservation practices, and cover and management factor. This integrated approach facilitated the estimation of annual soil loss within Panjkora Basin, which was determined to be 57 tons/ha/year. The analysis revealed that the LS and K factors, as well as drainage density, were strongly linked with soil loss in the upstream areas. The R factor exhibited spatial variation, ranging from 57 to 89 MJ/ha/year, with high values observed in the southern parts and low values in the northern parts of the basin. The findings of the current study hold potential for researchers, relevant departments, and decision-makers involved in land use planning and management strategies, particularly in environmentally sensitive mountainous regions. The results can assist in making informed decisions and developing measures to reduce soil erosion risks and promote sustainable land to use practices in the Panjkora Basin.
... Climate changes, especially the changes evident during the last 30 years, have a considerable effect on the development of water erosion in different regions of the world [44,51,60]. A large part of the land resources used in agriculture are found in the temperate climate zone, in which all climate changes display a uniform trend determined by a gradual increase in the winter air temperatures and an increase in the frequency of extreme rainfalls in the warm season [38,40]. ...
First time comprehensive studies of soil erosion were carried out in a 42-hectare catchment area (near the Lomovets, Orel region) in the zone of Luvic Phaeozems with erosion resistance is significantly lower than that of Chernozems. Analysis of archival and historical cartographic materials showed that the duration of plowing of the catchment is 200 ± 10 years. The rates of soil erosion and accumulation over the entire plowing period, post Chernobyl period, last 50 ± 25 years and single erosion event (which occurred on May 31, 2022) were determined based on the use of field methods (soil-morphological, radiocesium, rain rills method, detailed survey using drone) and WaTEM/SEDEM erosion model calculation. The estimates of soil losses and accumulation indicate significant fluctuations in the rates of erosion-accumulative processes over the past 200 years, which are mainly due to the conditions of the formation of melt runoff, the repeatability and distribution of runoff-forming heavy rain within the warm season, the set of crops sown, the frequency and methods of tillage, changes in field boundaries. The average annual estimates of soil erosion for the agricultural period are higher than those for the post-Chernobyl period, since the rates of soil erosion have decreased in the last three decades. Estimates of soil losses using the WaTEM/SEDEM model are generally comparable with the results of determining soil losses based on the soil-morphological method, provided that the redistribution of sediment to the lower boundaries of arable land is taken into account. The spatial structure of a single erosive event turned out to be largely close to the spatial structure of the location of the areas of eroded and aggradational soils formed during the entire agricultural period.
... The observed and expected decrease in mean precipitation (WD1) due to CC is accompanied by an increase of extreme precipitation (WD2), flooding (WD3) and subsequently increased erosivity [43]. In tropical and sub-tropical regions, the on-site impacts of soil erosion dominate, and are manifested in very high rates of soil loss, in some cases exceeding 100 t ha -1 yr -1 [44,45], while in temperate regions, the off-site costs of soil erosion are often a greater concern; for example, siltation of dams and ponds, downslope damage to property, roads and other infrastructure [46]. 13. ...
Water Infrastructure (WI) incorporating water supply, wastewater, and stormwater systems is vulnerable to Climate Change (CC) impacts that can disrupt their functionality; thus, WI needs to be adapted to CC. In 2021 the European Commission (EC) released the technical guidelines on “Climate-proofing Infrastructure” that include mitigation and adaptation strategies; these guidelines and the relevant guides that followed, focus mainly on CC aspects without examining sufficiently the engineering features of WI that are described mainly in the relevant hydro-environment research; this research is vast and includes various terminologies and methods for all aspects of CC adaptation. The adaptation procedure of WI to CC can be significantly improved when this research is known to guidelines’ developers. To facilitate this knowledge transfer, we performed a review on the hydro-environmental research that we present in this paper as follows: firstly, we introduce and typologize the climate hazards for WI systems and identify the most important of them in the Mediterranean Region that we classify into seven groups; then, we classify the hydro-environmental research into five categories that is based on the EC guidelines, present the main aspects for each of these categories, discuss the future research, and finally we summarize the conclusions.
... Erosion is a natural process in land forming that, by itself, is beneficial as it creates natural spaces like deltas, coasts, and river valleys (Strahler and Strahler, 2002;Tricart, 1962). However, human activities have led to accelerated soil erosion being recognized as a major problem for society, especially in cultivated areas with fertile soils, causing the degradation of an important resource, and at the same time, causing substantial damages off site, by destruction and degradation of infrastructure, causing significant economic and human losses (García-Ruiz et al., 2015;Panagos et al., 2015). Since the last century, thousands of researchers have used validated methods to quantify soil loss, runoff (both surface and subsurface one), and the concentration of sediments, nutrients, and contaminants. ...
The global scientific community, particularly soil erosion researchers, is increasingly recognizing the urgent need to address plastic pollution and the accumulation of microplastics in soil. Human activities such as urban expansion, food packaging, and the use of agricultural materials have driven a significant rise in microplastic contamination. The problem is compounded by the difficulty, expense, and time-intensive nature of analyzing soil erosion samples to accurately identify microplastic types, sources, and their effects. Soil erosion, while naturally shaping landscapes like hillslopes, deltas or river valleys, has evolved into a critical issue due to human-induced changes, threatening fertile agricultural zones and areas prone to landslides, with serious economic and human consequences. While validated methods exist to quantify soil erosion, runoff, and pollutant concentrations, these techniques inadvertently introduce microplastics into the environment by plastic materials during sampling, transport, and lab analysis. This not only skews historical and current data on microplastic levels in soils but also alters natural soil conditions around research plots. To address these challenges, this paper advocates for the refinement of measurement techniques to minimize contamination, a reassessment of current methodologies, and a concerted effort to reduce human impact on soil health, thereby safeguarding a critical natural resource.
... The measurements better consider the heterogeneity in soil and management conditions, while the RUSLE/IC/ SDR simulations consider the accumulation of connectivity effects over larger areas than the experimental fields or plots. The reduction effect is known to be scale-dependent (García-Ruiz et al., 2015;Leys et al., 2010). Buffer strips, in turn, had average simulated reductions of 39-55 % and 23-34 % (P1-P3) at Aura and Mustio River catchments, respectively. ...
Models play a crucial role in guiding agricultural erosion management, though their incorporation of sediment connectivity and management strategies varies. This study evaluated the RUSLE/IC/SDR model's potential for simulating agricultural erosion management at both the field scale and across two catchments. We tested the model's ability to simulate erosion management measures at a high spatial resolution (2 m × 2 m) across diverse topographies, assessed whether incorporating sediment connectivity improves RUSLE-based erosion management planning within catchments, and explored its capacity to tailor measures based on local connectivity characteristics. Our findings showed significant variability in sediment sources and connectivity. The simulation of no-till and buffer strip measures effectively demonstrated their varying effectiveness across fields and catchments. At the catchment scale, erosion management planning that incorporates sediment connectivity through the RUSLE/IC/SDR approach did not contribute to significant additional sediment delivery reduction compared to using RUSLE alone. However, at the field scale, RUSLE/IC/SDR offered improved opportunities for tailoring erosion management measures to local sediment connectivity characteristics. These simulations highlight both the potential and limitations of RUSLE/IC/SDR, advancing our understanding of its application for erosion management. In conclusion, while RUSLE/IC/SDR represents a valuable extension of RUSLE, further research is needed to fully realize its practical applications. Nonetheless, it shows promise for high-resolution simulation of sediment connectivity and erosion management at the field scale, across large catchments and regions.
... The most susceptible and critical soil erosion issues are found in arid, semi-arid, and sub-humid climates, as well as in cultivated lands and hilly or mountainous areas (García-Ruiz et al. 2015). In the tropical hilly and mountainous region of the Himalayas, soil erosion is a grave concern. ...
Land degradation is accelerating in the Himalayan ecosystem, resulting in the loss of soil nutrients due to severe erosion. Soil erosion presents a significant environmental challenge, resulting in both on-site and off-site consequences, such as reduced soil productivity and siltation in reservoirs. Soil erodibility (K factor), an inherent soil property, determines the susceptibility of soils to erosion. Sampling across hilly and mountainous terrain pose challenges due to its complex landscape. Despite these challenges, it is essential to study K factor variations in different land use/land cover types to comprehend the threat of erosion. Digital soil mapping offers an opportunity to overcome this limitation by providing spatial predictions of soil properties. The objective of our study is to map the spatial distribution of soil erodibility using the Random Forest (RF) model, a machine learning method based on sampled in situ soil data and environmental covariates. We collected 556 surface soil samples from the mountainous catchment (Tehri dam catchment) using the stratified random sampling approach. The model performed satisfactorily in both training (r² = 0.91; RMSE = 0.00185) and testing (r² = 0.45; RMSE = 0.00318) phases. Subsequently, we generated a digital map with a resolution of 12.5 m to depict the distribution of the K factor. Our analysis revealed that key environmental variables influencing the prediction of the K factor included geology, mean NDVI, and climatic factors. The average K factor value was estimated at 0.0304 and ranging from 0.0251 to 0.0400 t ha h ha⁻¹ MJ⁻¹ mm⁻¹. A higher K factor was observed in the barren land (0.0344) primarily located in the higher and trans-Himalayan region of seasonally snow-covered areas. These areas typically feature young soils with weak soil formation and unstable soil aggregates. Subsequently cropland/cultivated soils (0.0307) exhibited higher K factor values due to the breakdown of soil aggregates by ploughing activities and exposing carbon to decomposition. The average K factor value of evergreen (0.0294) and deciduous (0.0295) forests were the lowest compared to other land use/land cover types indicating the role of forests in resisting soil erosion. By assessing and predicting soil erodibility, land planners and farmers can implement erosion control measures to protect soil health, prevent sedimentation in water bodies, and sustain agricultural productivity in the Himalayas.
... . Current levels of annual global soil loss rates are expected to increase due to changes in precipitation patterns and sustained adoption of highly intensive growing practices in response to increasing food demand (García-Ruiz et al. 2015;Eekhout and de Vente 2022). ...
... Erosion: Erosion is the loss of soil due to physical factors such as water, wind, or farming practices such as tillage [47]. Global estimates [39] of soil erosion range from roughly 20 Gt yr -1 to more than 200 Gt yr -1 depending on scale, study period, and method used [45]. Climate change has the potential to exacerbate waterinduced soil erosion, particularly in areas where precipitation volumes and intensity are expected to rise [97]. ...
At roughly 2500 Peta gram (Pg) C, soil organic carbon (SOC) is the biggest carbon store in terrestrial ecosystems and is a crucial contributor to vital soil functions and ecosystem services, such as agricultural soil productivity. SOC stocks are in a dynamic equilibrium between C inputs, primarily from crop residues and organic manures, and C loss owing to decomposition and mineralization of soil organic matter (SOM) under long-term constant land management and environmental circumstances. In addition, the rate of C addition in native ecosystems is governed by the nature and productivity of the local flora, which is mostly influenced by climatic conditions. However, being a complex system, various factors, such as soil management and land-use change influence the soil C pool. Along with temperature gradients from temperate to tropical regions, SOC supplies were shown to be shrinking on a global and regional basis. This reflects the rates of SOM decomposition as a function of temperature, which fluctuates more rapidly than net primary production (NPP). SOM decomposition rates are also influenced by several parameters, including soil temperature and moisture, soil respiration and pH, and soil physical properties including texture and clay mineralogy. Nonetheless, increased temperatures as a result of climate change are thought to be the primary driver of accelerated decomposition, which results in considerable reductions in SOC supplies and sequestration. Furthermore, climatic change contributes to soil deterioration by increasing the mineralization of the SOC pool and causing desertification (irreversible expansion of desert landforms). Similarly, erosion is a degrading process that affects C dynamics and leads to terrestrial carbon loss through the breakdown of structural aggregates, as well as lower productivity in eroding areas due to a lack of soil nutrients. Thus, for an in-depth understanding of worldwide soil C dynamics and to provide support to C management and decision support systems to policymakers and land managers in the face of changing climates, comprehensive research on the influence of multiple climate-induced drivers on soil C is required.
... The RUSLE is a simple and one of the most widely used models for assessing soil erosion [2,4,26,35]. However, its applications in Nigeria are still very low [2,7,18,19,25] and in Anambra, there are very few studies that employed the RUSLE [1,20,14,50]. Yet, of all the studies that employed the RUSLE model, none attempted to validate the result except Egbueri et al. [14] albeit using a multicriteria decision system which did not validate soil loss but rather soil erosion susceptibility levels. ...
Soil erosion is a severe environmental problem in Anambra State but insufficient data hampers effective conservation and planning. Hence, in-situ measurements were done during the 2022 rainy season to assess erosion responses to changes in vegetation cover, slopes, scale, and soil characteristics. Runoff plots were set up in Isu-Aniocha, Aguleri, and Oko. Soil loss was 0.74 kg m-2 mon-1 in Oko, 0.36 kg m-2 mon-1 in Aguleri, and 0.09 kg m-2 mon-1 in Isu-Aniocha. Soil loss per unit of rainfall was 0.37 kg mm-1 (Oko), 0.08 kg mm-1 (Aguleri), and 0.04 kg mm-1 (Isu-Aniocha). The erosion rate was 6 times higher on bare plots than on vegetated plots. The RUSLE model performed relatively well in the area. The soil erosion rate from the RUSLE model has a percentage bias of 9.04% indicating a little underestimation of soil erosion in the area. Soil loss rate is higher on small plots, but the reverse is the case when the gross soil loss is considered. Time is critical to erosion occurrence in the State as the worst erosion scenarios occurred in the last month of the season. Therefore, effective soil conservation measures should be prioritized toward the end of the season. Also, soils should be protected with vegetation and other covers.
The task of soil erosion estimation received a significant push by integrating remote sensing and geographical information systems (GIS) with the Revised Universal Soil Loss Equation (RUSLE) in the early 1990s due to its ease of applicability. The Topographic (LS) factor played a quintessential role in soil loss determination, especially for undulating regions. In most worldwide soil erosion studies, the topographic factor extracted from the Digital Elevation Model (DEM) using “LS equations” failed to account for the varying slopes before the material joins a stream or a river. In this study, the slope length (L) and slope steepness factor (S) derived without and with the slope cutoff factor are compared and analyzed for a hilltop mine. The results reflect that the LS factor and, ultimately, soil erosion are over‐estimated owing to the absence of any limits on the slope length (L) factor in undulating terrains when used conventionally in a GIS environment. The mean soil erosion estimated with slope cutoff factor is 252.26 ton ha ⁻¹ year ⁻¹ , whereas 332.81 ton ha ⁻¹ year ⁻¹ in the conventional application of the same LS equation. The overestimation of soil erosion was reduced by 35% as per the volume‐based validation study. Thus, the study proves the usefulness of the slope cutoff factor, which, to date, has mostly been neglected in soil loss research and soil erosion studies for undulating terrains. The pattern of soil erosion also highlights the negating impact of vegetation on steep slopes, cementing their role as Nature based Solution (NbS) for soil erosion by dynamic landscapes like Mines.
Quantifying soil denudation, sediment transport, and deposition processes in watersheds over millennial timescales is crucial for a comprehensive understanding of soil erosion dynamics. However, most current studies on soil erosion over such timescales primarily rely on the qualitative interpretation of field-based sedimentary records. Southwest China underwent substantial environmental changes during the Holocene, with soil erosion being notably influenced by long-term human activities. In this study, we selected a crater lake catchment with a straightforward sediment source as the case study area. The Landlab landscape evolution model was employed to simulate and reconstruct temporal and spatial soil erosion processes. Higher erosion rates were observed during 10.9–10.3 ka, 8.8–7.9 ka, 3.9–3.2 ka, and after 1.0 ka, with the lowest level recorded between 7.7 and 4.2 ka. During the Holocene, approximately 64% of the catchment area underwent denudation in gullies and mountains, while 36% of the area, including flatlands and lakes, was deposited. Our findings indicate that vegetation exerted a significantly greater impact on soil erosion compared than precipitation. The simulated erosion rate increased rapidly after ~1.0 ka with an average increase of 1.2 times, driven by human activities. This study highlights the need for additional field geological evidence to validate the model.
Geomorphic change detection (GCD), geotechnical engineering, and hazard mapping are analyses that require the lowest possible absolute total error in digital elevation models (DEMs). One of the most common GCD analyses is the quantification of soil erosion. NRTK (Network Real-Time Kinematic) is one of the three primary modes within the broader method of direct georeferencing (DG). NRTK uses a network of multiple GNSS reference stations to provide real-time correction data to a UAV, enabling centimeter-level positioning accuracy. This approach eliminates the need for ground control points (GCPs), reducing both costs and survey time. However, its application in multi-temporal soil erosion analysis remains insufficiently researched. In this paper the NRTK approach in GCD analysis is evaluated using Matrice 210 RTK V2 at two case studies. In addition, the absolute accuracy of the NRTK was tested on three other sites. Although achieved results can be regarded as promising, especially at lower altitudes, this research highlights drawbacks when employing the NRTK in analysing soil erosion measurement. Namely, the use of the DG-based models in GCD analysis generated unreliable results when compared with the reference model derived using the SfM photogrammetry with GCP. In both study sites, the NRTK approach significantly overestimated the amount of accumulated sediment, affected the total net sediment difference, and eliminated a substantial amount of change. Although the NRTK approach shows limitations in reliably quantifying volumetric changes in soil erosion measurements, results indicate that NRTK can be applied for analyzing linear gully headcut retreat rates. For applications where achieving the lowest absolute total error is not a priority, NRTK can be a relatively reliable solution. However, researchers should exercise caution when using it to analyze soil erosion over different time scales, particularly if the rate of morphological change is low.
This study developed a rainfall-runoff-sediment yield integrated modelling using KINEROS2 (K2) and the inverse problem (IP) method to evaluate sediment yield in a small Amazonian catchment. This contribution aims to explore the challenges associated with quantifying sediment yield in small catchments, where data availability is limited and uncertainties in both measurements and parameters are prevalent. Additionally, the region is experiencing significant deforestation, agricultural expansion, and forest fires, which contribute to erosion, degradation of productive land, and increased sediment yield. The inverse problem (IP) method was considered for modelling-prediction of hydrosedimentological data in watershed, as it offers an analytical approach that integrates measured data with mathematical models simultaneously. This method is particularly valuable in contexts of data scarcity and parameter calibration, enabling simulations to align with observed data. This process is challenging due to the complexity and variability of hydrosedimentological data. The IP approach uses KINEROS2, incorporating all available information on sediment yield and model parameters to improve prediction accuracy. However, the model showed good agreement with the correlation coefficient (R²) equal to 0.75 in calibration and 0.78 in validation, respectively. In this case, Nash–Sutcliffe coefficients were above 0.70 and RMSE values between 0.27 and 1.99, indicating a 95% reliability in sediment yield simulations.
The factors influencing soil erosion are diverse and complex. However, a comprehensive comparative analysis of the various factors remains insufficient. By collecting, selecting and summarizing related studies across China, this study established a comprehensive dataset that includes runoff depth (R) and soil loss (SL) under various soil erosion factors (soil order, land use, vegetation coverage, slope length, slope gradient, and precipitation), to identify erosion pattern in different runoff plots based on rainfall events. Results showed that the average runoff depth (WR) and weighted average soil loss (WSL) of observed water erosion events in China are 20.10 mm and 331.92 t/km2, respectively. Semi-alfisols, amorphic soils, and pedocals reveal significantly higher R and SL. Forests prove most effective in mitigating soil and water loss, whereas grasslands and bare land exhibit similar runoff levels. Vegetation coverage of 40–60 % notably reduces both R and SL. R and SL fluctuate with the increase in slope length and slope gradient, but increase with growing precipitation. When the slope length exceeds 15 m and the gradient surpasses 25°, R and SL decrease significantly. Precipitation is the most significant factor impacting both R (contributing 58.70 %) and SL (contributing 30.25 %). This study underscores interactions among erosion factors and proposes multivariate linear regression models to predict R and SL based on these variables. It also contributes to clarifying the effects of erosion factors on slopes, providing a scientific basis for soil erosion modeling and control.
Quantitative analysis and prediction of gully head erosion hold paramount importance for terrain evolution studies and risk mitigation effort. However, previous findings could not reconcile high temporal resolution with long time series coverage, particularly at the watershed scale. In this study, a calculation method for the active gully head erosion rate (AGHER) was proposed on the basis of interferometric synthetic aperture radar (InSAR) technology, thereby combining the historical climate data to estimate the annual AGHER. Additionally, we investigated the relative importance of extreme rainfall events on erosion rates. The results indicated that the long‐term annual AGHER in the study area ranged from 51.83 to 89.50 mm year ⁻¹ from 1980 to 2023 on the Dongzhi Plateau (DZP). Extreme rainfall events (rainfall amount ≥ 150 mm) emerged as the foremost erosion‐causing factor, accounting for a contribution rate ranging from 69.8% to 75.0%. Furthermore, through field surveys, we identified 21 gully heads that represent potential hazards to high‐speed railways (HSRs). Although the proportion of gullies affecting rail infrastructure may be relatively modest in century‐long projections, it notably increases against the background of worldwide escalation due to the occurrence of extreme precipitation events. This study establishes a robust foundation for gully erosion management and risk assessment on the Loess Plateau.
Soil erosion on bare slopes in coastal reclamation areas reduces the efficiency of water conservation projects and poses a threat to the water environment in saline tidal flats. Slope shape and soil hydrological conditions are affected by severe soil detachment and rapid sedimentation processes during rainfall, which in turn influence soil erosion processes. In this study, the influences of slope gradient, slope length, initial soil water content and groundwater depth on slope erosion processes of saline sodic soils were investigated through simulated rainfall experiments. We found that the effect of slope gradient on soil loss varied with slope length. For the long‐slope treatments with the same total length of initially air‐dried soil (AD), the unit width sediment yield rate ( Rs ) significantly ( p = 0.05) increased with increasing slope gradient from 30° to 60°. For the short‐slope treatments with different total lengths, opposite trends were observed for the runoff rate and Rs variation with increasing gradient. The Rs values of the slopes with initially saturated surface soil (SS) and a groundwater depth of 0.8 m (GW) were significantly ( p = 0.05) greater than that under the AD treatment. On the 60° SS treatment slopes and 45° and 60° GW treatment slopes, soil erosion induced distinct collapse failure and altered the original slope shape, yielding lower gradients and larger lengths, which significantly ( p = 0.05) increased Rs in turn. Canonical correlation analysis (CCA) revealed that 71.6% of the variance in the set of dependent variables (sediment yield and runoff) could be explained by the first pair of canonical variables, which mainly represented slope topography factors, and 12.1% of the variance could be explained by the second pair, which mainly represented soil hydrological conditions. The conclusions of this study could provide a theoretical foundation for slope protection in coastal reclamation areas.
Cattle farming is one of the main agricultural activities in Colombia, but its mainly extensive nature generates significant social and environmental impacts, such as land grabbing, agricultural frontier expansion, increased greenhouse gas emissions, and deforestation. To transform cattle systems towards sustainability, the Policy Guidelines for Sustainable Cattle 2022–2050 (LPGBS) were launched in 2022, resulting from conversations between sector institutions and the national government. Although the LPGBS are proposed as the roadmap for cattle farming in the coming decades, their implementation has faced delays and raised doubts among the involved institutions. This research analyzes the current state of the LPGBS to identify difficulties and determine strategies that promote sustainability in cattle systems by building capacities. The research is based on a mixed-methods approach and contains a literature review on the evaluation of public policies in the cattle sector, complemented by 26 key-informant interviews with experts from public and private institutions involved in developing the LPGBS. These interviews provided key perspectives and practical experiences to understand current difficulties in the implementation of the LPGBS and identify the capacities needed to achieve the planned transition to sustainable cattle farming. Results reveal several difficulties in the LPGBS design stage, including institutional weakness, low governmental participation, and lack of trust among stakeholders. However, important progress was made, such as the construction of social, environmental, and productive sustainability criteria, the consolidation of the sustainability approach at the cattle landscape level, and regional participation. The capacities necessary to drive the implementation of the LPGBS include strengthening rural extension programs, access to financing, and the implementation of a traceability system for monitoring and evaluation. These findings highlight the importance of evaluating policies at early stages to provide crucial information for decision-makers and public policy formulators to correct and improve implementation processes.
Agriculture continues to be one of the most important sources of nonpoint source pollution to surface water bodies. Consequently, it is critical to identify and prioritize high‐contributing agricultural fields and sub‐field areas for reducing soil erosion and sediment delivery by implementing best management practices (BMPs). Current erosion risk assessment tools are either complex modelling approaches or rely on a simplified reality and generalized assumption. The Daily Erosion Project (DEP) is a daily estimator of precipitation, hillslope runoff, detachment and soil loss covering ~630 000 km ² across the Midwest United States. These estimations are reported daily and publicly at the hydrologic unit code 12 watershed resolution (approximately 100 km ² ). The main objective of this study was to develop a new tool (named Overland Flow Element tool [OFEtool]) that downscales the watershed scale of DEP to estimate average runoff and soil displacement within a field, helping to locate erosive hotspots at multiple scales. We also demonstrated the applicability of OFEtool in Bennet Creek‐Sugar Creek in East Central Iowa (the United States) and compared its results with other erosion vulnerability tools such as the Soil Vulnerability Index for Cultivated Cropland (SVI‐cc) and a GIS‐based Revised Universal Soil Loss Equation (RUSLE). The same erosion risk classes and ranges (low, moderate, moderately high and high) were implemented for all indexes. The advantages of the OFEtool compared to the SVI‐cc and RUSLE models are related to the use of an event‐based modelling approach, such as DEP, with updated soil loss estimates based on temporal changes in climate inputs and land use and management. The OFEtool uses a 6‐year time frame and a more up‐to‐date field inputs, while RUSLE provides a long‐term average and SVI‐cc only considers soil and topographical factors for risk assessment. Results indicated that the spatial distribution of vulnerable fields (and parts of the fields) followed a similar trend as other tested indices. However, the risk level associated with each tool differed (SVI‐cc > RUSLE > OFEtool). These differences could arise from intrinsic disparities within the tools (inputs, timing, processes considered, assumptions). While currently limited to the DEP domain and relying on the DEP random sampling scheme, further research is warranted to validate the tool at other Midwest locations and ensure it captures the watershed's landscape variability (combination of terrain, soil, land use and management) required to identifying critical erosion hotspots.
Soil erosion inventory of a river basin is vital for effective soil conservation and sustainable development considering the ongoing Global change. In the current study, gross soil erosion rates (A) are estimated for a mountainous river in a tropical climate, the Karamana River Basin (KRB), southern India by utilizing the Revised Universal Soil Loss Equation (RUSLE). The RUSLE model computes ‘A’, as a product function of five variables; rainfall erosivity (R), soil erodibility (K), topographic factor (LS), crop management factor (C), and erosion control practice factor (P). To compute these five parameters, the digital elevation model, slope, normalized vegetation index (NDVI), rainfall and land use/land cover (LULC) are used along with the texture data of soil samples collected from KRB. The estimated A values range between 0 to 738.44 t ha−1 year−1, with an average of 10.22 t ha−1 year−1 whereas the sediment yield (SY) estimated by utilizing the sediment delivery ratio (SDR) model ranges between 0 to 246.68 t ha−1 year−1 with an average of 1.58 t ha−1 year−1 for KRB. For further validation, a soil erosion potential index (SEPI) map is developed to identify the soil erosion-prone zones of KRB using the geo-environmental thematic maps following the analytic hierarchy process (AHP). Finally, rainfall impacts on soil erosion are evaluated and quantified for KRB, considering the recent marked variations in rainfall that are induced by the extreme climatic events (cyclones/high rainfall/floods) along the West coast of India. The outcome of this study suggests that increasing rainfall by one standard deviation of the long-term average causes a significant increase in low and medium soil erosion regions.
Soil erosion and subsequent sedimentation pose significant challenges in the Sikkim Himalayas. In this study, we conducted an assessment of the impact of rainfall-induced soil erosion and sediment loss in South Sikkim, which falls within the Teesta Basin, employing Revised Universal Soil Loss Equation (RUSLE) and Sediment Yield Index (SYI) models. Leveraging mean annual precipitation data, a detailed soil map, geomorphological landforms, Digital Elevation Models (DEMs), and LANDSAT 8 OLI data were used to prepare the factorial maps of South Sikkim. The results of the RUSLE and SYI models revealed annual soil loss >200 t ha−1 yr−1, whereas mean values were estimated to be 93.42 t ha−1 yr−1 and 70.3 t ha−1 yr−1, respectively. Interestingly, both models displayed similar degrees of soil loss in corresponding regions under the various severity classes. Notably, low-severity erosion <50 t ha−1 yr−1 was predominantly observed in the valley sides in low-elevation zones, while areas with severe erosion rates >200 t ha−1 yr−1were concentrated in the upper reaches, characterized by steep slopes. These findings underscore the strong correlation between erosion rates and topography, which makes the region highly vulnerable to erosion. The prioritization of such regions and potential conservation methods need to be adopted to protect such precious natural resources in mountainous regions.
The variations in soil erosion significantly impact regional ecological security. Under rapid urbanisation, extensive ecological restoration and climate change, soil erosion development in the red soil region of southern China is ambiguous. Therefore, this study investigated the current (1980s–2020) and future (2050) erosion characteristics in a typical soil erosion control catchment (Changting section catchment) in this region by using the Cellular Automata Markov model and CMIP6 data to predict future scenarios and the Revised Universal Soil Loss Equation to estimate soil erosion. The results showed significant changes in the vegetation coverage of major land uses from 1980s to 2020, which was mainly caused by continuous soil and water conservation (SWC). The land use subtypes that were obtained by reclassifying land use based on the threshold of vegetation cover on soil erosion control, reflect a continuous transformation from those with poor SWC effectiveness to those with great SWC effectiveness. Therefore, the estimated soil erosion intensity continued to decrease from 1980s to 2020, and the contribution of land use/land cover (LULC) impacts ranged from 74%–195%. However, predictions of land use subtypes indicated that LULC may be stable after 2020; thus, soil erosion changed little when the climate was almost unchanged in 2050. Under climate change scenarios, soil erosion may increase by 111%–121%, and the contribution of precipitation impacts was 63%–66%. The major driving factor of soil erosion changes may shift from LULC to precipitation after 2020. Therefore, in the future, the potential for reducing soil erosion by vegetation restoration may be limited, and more engineering measures should be applied to address the erosion risk caused by climate changes. This study provides prospects for land use/land cover and soil erosion in the red soil region of southern China.
India, a subtropical country, also has relatively more environmental problems because of intense rainfall that occurs quickly, as well as other natural and man-made causes of soil degradation. The use of predictive models in GIS is observed beneficial for computing the virgin net soil erosion as well as deposition. Thus, the study aims to evaluate the spatial long-term average annual soil erosion (gross soil erosion rate), net soil erosion as well as a deposition for the east-flowing Cauvery River Basin (CRB) using RUSLE integrated with the TLA-SDR model in Geographic Information System (GIS) at recent (2020 to 2022) periods. The estimation of gross soil erosion rates (A) ranges between 0 and 94,194.4 t h⁻¹ year⁻¹, mean of ~ 223 t h⁻¹ year⁻¹. The sediment yield (SY) of CRB varies from 0 to 10,895.4 t h⁻¹ year⁻¹ with a mean of 26 t h⁻¹ year⁻¹. Moreover, the transport capacity (TC) of CRB varies between 0 and 5,339,136 t h⁻¹ year⁻¹, with a mean of 16 t h⁻¹ year⁻¹. Further, net erosion is estimated with TC and deposition which has an average value of ~ 4.5 t ha⁻¹ year⁻¹ (i.e., ~ 2% of the gross erosion), of which 1.15% of CRB shows very severe erosion while 56.68% shows high deposition. The study also addresses the effect of various LULC types on soil loss and reveals that barren rocks have the highest soil loss, followed by forest, build-up, barren land, agricultural land, and plantation. Likewise, the study assesses whether rapid climate change may exacerbate erosion rates and concludes that greater erosion rates are recorded with rising rainfall. Additionally, when comparing the total erosion to total sediment yield rate of CRB with major basins like Ganga (GBA) and Kosi (KB), signifying the topographical, climatic as well as tectonic setup of the region. The study’s findings will be an important tool for decision-makers as they execute management plans over the CRB, and this technique will used broadly to identify management methods in river catchments worldwide.
The paper presents experimental field data on water erosion of loess soil in Lublin Upland. The results confirm the relationships accepted in widely used Universal Soil Loss Equation (USLE) and explain the differences between experimental and predicted data. Although this equation has been worked out on the basis of about 10,000 "plot-years" data, it should be used very carefully in conditions of loess soils in Poland.
The interplay between rainfall, runoff and soil loss is not simple. Responses of hydrological and erosional systems to a given runoff event are always modified by the land's surface. However, knowledge of the frequency-magnitude distributions of erosion events is essential both from the practical perspective of land management, and for an understanding of the role of small and large erosion events in landscape evolution. This study analyses frequency-magnitude distributions of rainfall, runoff and erosion from sites in the UK, Belgium, Canada and the USA. Frequency-magnitude distributions of rainfall appear to be a poor predictor of distributions of runoff or soil loss. Site-specific influences appear to affect distributions of erosion to a greater extent than distributions of runoff: there is a greater change in the spread of absolute values between rainfall and erosion distributions than there is between rainfall and runoff distributions. For the small- to medium-sized events, soil loss frequency-magnitude distributions show a tendency toward linearity when plotted on a log-log scale. The distribution of the small- to medium-sized erosion events can be approximated by a cumulative power law function. The under-representation of larger events relative to such a distribution may be due to shifts in the balance between erosive processes, and to 'finite-size effects' which constrain the maximum size of erosion event which can occur on a given area. If the frequency-magnitude distributions of erosion events can be approximated by a power-law, then the contribution of small events to total erosion is likely to be underestimated in measured datasets. These results suggest links with recent, but controversial, theoretical work on 'self-organised criticality'. It is important for geomorphologists to look beyond disciplinary confines and be aware of such links.
This paper examines the patterns of sediment transport in rivers in terms of the sources of sediment and its transport and deposition through the river network. The analysis is in the context of dramatic human influences on river sediment transport and how they might influence freshwater ecosystems. The review of Australian work shows that erosion of hillslopes and stream banks has greatly increased in historical times, supplying vast quantities of sediment to rivers, much of which is still stored within the river system. The stored sediment will continue to effect in-stream and estuarine ecosystems for many decades. In most Australian catchments the dominant source of sediment is streambank erosion. An analysis of historical channel widening suggests that a conceptual framework of relative stream power can explain the diversity of behaviour observed in the numerous case studies. Sediment delivery through catchments is considered first in a generic whole network sense, which emphasizes the crucial role played by riverine deposition in determining catchment sediment budgets. A method is then presented for analysing the diverse spatial patterns of sediment storage in any river network. Finally, the paper considers the temporal changes to channel morphology in response to a human-induced pulse of sediment.
Time compression was studied at the Aísa Valley Experimental Station to assess the effect of large rainfall events on suspended sediment load. The study was focused on the response of land under traditional and current land uses/land covers in Mediterranean mountain areas, including dense shrub cover, grazing meadow, abandoned field, cereal cultivation, fallow land and both active and abandoned shifting agriculture. The results confirm the importance of the largest rainfall events in explaining the geomorphological effects that occur during a small number of such events. Three groups of land uses were distinguished: (i) dense shrub cover and grazing meadow, which showed relatively little time compression; (ii) cereal cultivation, fallow land, and both active and abandoned shifting agriculture, which were characterized by a high degree of time compression and a major impact of the largest events; and (iii) the abandoned field, which was intermediate in response between the other two groups. The greater geomorpho-logical effects of the largest events in the plots at the Aísa Valley Experimental Station relative to those reported in studies in the USA, is a consequence of the Mediterranean climate charac-teristics, and in part because of scale effects. The contribution of the three largest events to total accumulated suspended sediment load ranged from 25.4 to 71.2% whereas for the five largest events it ranged from 35.4 to 76.9%. For each of the land uses the 25 largest events represented more than 80% (in some cases more than 90%) of the total suspended sediment load recorded since 1991.
Recent studies in small experimental catchments under Mediterranean-type climate revealed a complex hydrological catchment response, presenting saturation excess runoff generation and, to a minor degree, infiltration excess flow. Many of these catchments, however, belong to areas with sub-humid or humid Mediterranean climate. Catchment studies were carried out since 1991 in savannah-like grazed land (dehesas), which are widespread in south-western Spain, and also elsewhere in the Mediterranean. Albeit knowledge gained by previous studies, no thorough analysis has been carried out on the temporal variation of discharge production using the complete dataset. The objectives include i) an analysis of the temporal variation of discharge and rainfall at different temporal scales, ii) exploration of the role of antecedent soil moisture conditions in runoff production, iii) empirical modeling of rainfallrunoff relationships at the event scale and iv) definition of the importance of interannual rainfall variation on discharge production. The analysis were based on rainfall and runoff which were monitored at a time resolution of 5 minutes and periodically measured soil moisture from various depth in the valley bottom. Regression analysis as well as the comparison of hydrographs illustrate on the importance of antecedent rainfall conditions. Soil moisture in the valley bottom was crucial to understand the hydrological behaviour of the catchment. A soil moisture threshold of 0.37 m3 m-3 was defined above which runoff coefficients increase sharply. This situation is reached with 170 mm of antecedent rain falling in a continuous way. The results indicate that saturation excess flow and preferential subsurface flow processes are responsible of most of the runoff generated. Hortonian type overland flow dominates under dry soil conditions and is produced by high intensity rainfall.
Non-linear regression analysis with data grouped according to antecedent catchment conditions produced highly significant regression models, explaining event discharge with three variables: Maximum 60-minute rainfall intensity (I60), event rainfall minus I60 and mean antecedent daily rainfall. Variability of monthly runoff is best explained by interannual rainfall variation rather than by mean seasonal distribution. During droughts, which are a common feature in the Mediterranean, discharge was very low. Runoff is highly concentrated in time with 10% of the months accounting for 85% of total discharge.
The dynamics of the torrential upper reach of the Ijuez River, Central Spanish Pyrenees, was analyzed in relation to the spatial organization of grain size. The reach is located in the Eocene flysch, which usually acts as a high sediment production area, particularly during periods of intense human activity. The Ijuez Valley was cultivated and densely populated until the middle of the 20th century, resulting in general deforestation and the development of debris flows, shallow landslides, sheet wash erosion and deep gullies. As a consequence, the alluvial plain became characterized by the presence of large quantities of coarse sediment. The spatial organization of sediment showed a progressive downstream decline in the cobble and boulder size, especially in the channel, whereas the remainder of the alluvial plain showed large variability. No trend in the occurrence of the largest boulders was evident throughout the reach, confirming the importance of debris and hyperconcentrated flows in sediment transport. The torrential reach did not have a negative exponential longitudinal profile, in contrast to that usually observed for mountain rivers. This was attributed to the large quantity of heterometric sediment derived from the hillslopes, which resulted in no marked decline in sediment size and consequent change in the longitudinal profile. A recent trend of scouring was detected, reflecting the reduction in sediment supply following farmland abandonment and reforestation, which have reduced connectivity between the hillslopes and the channel.
An analysis of morphological changes during the last six decades is presented for the Rambla de Cervera, a Mediterranean ephemeral stream located in the eastern sector of the Iberian Mountain Range. The studied channel (16.5 km) has two contrasted sectors: a horst confined sector (5.5 km) and a graben sector (11 km). Channel changes were analysed through the analysis of aerial photographs, with geographical information systems (GIS) and comparison of topographic surveys made with a GPS-RTK. Between 1946 and 2006 the Rambla de Cervera, underwent channel adjustments comparable to those observed in other Mediterranean rivers. The gravel channel markedly narrowed, losing width (68.5%) and channel surface area (45.7%), and incision processes occurred along the entire study reach at an average depth of 3.5 m. The progressive reduction of discharge and sediment supply due to land use changes, gravel mining and hydroclimatic variability has been considered responsible for these changes. However, these morphological changes exhibit an interesting temporal variability, with a maximum decrease of the gravel channel in the period 1946-1956 and another clear narrowing stage between 1977 and 1991, whereas incision mainly progressed after 1977. In addition, a contrasted behavior between the graben and horst sectors has been observed and analyzed. The horst sector underwent a constant and continuous trend, whereas the graben sector had more intense changes and two stages with significant reverse trajectories. The differential behavior of the graben and horst sectors was caused by the different responses generated by the overlapping of the lack of sediment supply, the timing and intensity of flood events and the particular hydraulic conditions of both sectors. The hydraulic geometry of the different river sections conditioned the effectiveness of flood events, influencing on the existence or absence of floodplain destructive trajectories and on the stability of fluvial forms.
The SHETRAN model for simulating the sediment yield arising from shallow landslides at the scale of a river catchment was applied to the 45-km(2) Ijuez catchment in the central Spanish Pyrenees, to investigate the effect of loss of forest cover on landslide and debris flow incidence and on catchment sediment yield. The application demonstrated how such a model, with a large number of parameters to be evaluated, can be used even when directly measured data are not available: rainfall and discharge time series were generated by reference to other local records and data providing the basis for a soil map were obtained by a short field campaign. Uncertainty bounds for the outputs were determined as a function of the uncertainty in the values of key model parameters. For a four-year period and for the existing forested state of the catchment, a good ability to simulate the observed long term spatial distribution of debris flows (represented by a 45-year inventory) and to determine catchment sediment yield within the range of regional observations was demonstrated. The lower uncertainty bound on simulated landslide occurrence approximated the observed annual rate of landsliding and suggests that landslides provide a relatively minor proportion of the total sediment yield, at least in drier years. A scenario simulation in which the forest cover was replaced by grassland indicated an increase in landsliding but a decrease in the number of landslides which evolve into debris flows and, at least for drier years, a reduction in sediment delivery to the channel network.
Predicting the sediment yield at a catchment scale is one of the main challenges regarding fluvial geomorphology, however, it involves some difficulties. In this study, we have taken advantage of the construction of a new hydraulic infrastructure to study the sediment yield in its drainage basin between 2007 and 2010. This infrastructure is a small dam constructed in the riverine zone of the Entrepeñas Reservoir (upper Tagus catchment, central Spain), which generates a small water body, the Pareja Limno-reservoir (0.94 hm3), with a drainage area of 88 km2. It was built to mitigate the environmental and socioeconomic impacts of the construction and use of the Entrepeñas Reservoir, including the “arid band” phenomenon.
Sediment yield was studied taking three sediment cores in the shallowest section, the central part and the deepest zone of the limno-reservoir. The layer of surface sediment was analized and a decreasing thickness of sediment towards the deepest zone of the limno-reservoir was observed. After assigning an area of the limno-reservoir to each core record, estimated annual sedimentation rate was 2032 Mg year-1, which supposes an annual storage capacity loss around 0.3% and a specific sediment yield in the drainage basin around 0.23 Mg ha-1 year-1. Comparing this value with previous soil loss studies performed in the basin, sediment delivery ratio in the basin varies from 2.2% to 3.8%.
Both sediment yield and sediment delivery ratio showed low values for the Mediterranean context. The characteristics of the basin (small area, elongated shape with one main river channel, abundant vegetation), the absence of other erosive processes than rill and interrill erosion and the lower aggressiveness of rainfall in the center of the Iberian Peninsula may explain these results. The presence of the National Road N-204 surrounding the limno-reservoir may play a role in the low sediment delivery, especially from the adjoining hillslopes.
Soil erosion and sediment yield are strongly affected by land use/land
cover (LULC). Spatially distributed erosion models are of great interest
to assess the expected effect of LULC changes on soil erosion and
sediment yield. However, they can only be applied if spatially
distributed data is available for their calibration. In this study the
soil erosion and sediment delivery model WATEM/SEDEM was applied to a
small (2.84 km2) experimental catchment in the Central
Spanish Pyrenees. Model calibration was performed based on a dataset of
soil redistribution rates derived from point 137Cs
inventories, allowing capture differences per land use in the main model
parameters. Model calibration showed a good convergence to a global
optimum in the parameter space, which was not possible to attain if only
external (not spatially distributed) sediment yield data were available.
Validation of the model results against seven years of recorded sediment
yield at the catchment outlet was satisfactory. Two LULC scenarios were
then modeled to reproduce land use at the beginning of the twentieth
century and a hypothetic future scenario, and to compare the simulation
results to the current LULC situation. The results show a reduction of
about one order of magnitude in gross erosion (3180 to 350 Mg
yr-1) and sediment delivery (11.2 to 1.2 Mg yr-1
ha-1) during the last decades as a result of the abandonment
of traditional land uses (mostly agriculture) and subsequent vegetation
recolonization. The simulation also allowed assessing differences in the
sediment sources and sinks within the catchment.
Soil erosion processes are closely related to climate characteristics
and land uses together with certain soil properties. Changes in any of
these factors will result in changes in the intensity of soil erosion
and in the processes involved, with immediate consequences on water
quality, fluvial channel dynamics and reservoir silting, at short term,
and on ecosystems productivity at long term, thus affecting some key
environmental, welfare and livelihood aspects. In the case of the
Mediterranean region, future environmental scenarios forecast an
increase in temperature and a decrease in precipitation (most probably
accompanied by an increase in intensity). At the same time, an opposite
trend in the spatial organization of human activities is foreseen for
the highlands and the lowlands, named respectively deintensification (or
land abandonment) and intensification. Effective land management
strategies should focus particularly on the factors which are rapidly
influenced by human activities, that is, land cover and land uses;
moreover, they should deal with the complexity derived by such dual
spatial scenario/organization. The increasing information on the
consequences of different land cover/land uses on soil erosion under
different environmental conditions must be the basis for new land
management strategies, which look at the territory with a global
perspective, considering both the in-situ and ex-situ consequences of
any decision. A deep reflection is needed for discussing what we know
and what we have to know in the next future for being increasingly
effective and for coping against the immediate challenges we must face.
This paper presents a global synopsis about the geomorphic evidence of soil erosion in humid and semihumid areas since the beginning of agriculture. Historical documents, starting from ancient records to data from the mid-twentieth century and numerous literature reviews form an extensive assortment of examples that show how soil erosion has been perceived previously by scholars, land surveyors, farmers, land owners, researchers, and policy makers. Examples have been selected from ancient Greek and Roman Times and from central Europe, southern Africa, North America, the Chinese Loess Plateau, Australia, New Zealand, and Easter Island. Furthermore, a comprehensive collection on the development of soil erosion research and soil conservation has been provided, with a particular focus on Germany and the USA.
Assessments of the implications of soil erosion require quantification of soil erosion rates (SE) and sediment yield (SSY) at regional scales under present and future climate and land use scenarios. A range of models is available to predict SE and SSY, but a critical evaluation of these models is lacking. Here, we evaluate 14 models based on 32 published studies and over 700 selected catchments. Evaluation criteria include: (1) prediction accuracy, (2) knowledge gain on dominant soil erosion processes, (3) data and calibration requirements, and (4) applica-bility in global change scenario studies. Results indicate that modelling of SE and SSY strongly depends on the spatial and temporal scales considered. In large catchments (N10,000 km 2), most accurate predictions of suspended sediment yield are obtained by nonlinear regression models like BQART, WBMsed, or Pelletier's model. For medium-sized catchments, best results are obtained by factorial scoring models like PSIAC, FSM and SSY Index, which also support identification of dominant erosion processes. Most other models (e.g., WATEM–SEDEM, AGNPS, LISEM, PESERA, and SWAT) represent only a selection of erosion and sediment transport processes. Consequently, these models only provide reliable results where the considered processes are indeed dominant. Identification of sediment sources and sinks requires spatially distributed models, which, on average, have lower model accuracy and require more input data and calibration efforts than spatially lumped models. Of these models, most accurate predictions with least data requirements were provided by SPADS and WATEM–SEDEM. Priorities for model development in-clude: (1) simulation of point sources of sediment, (2) balancing model complexity and the quality of input data, (3) simulation of the impact of soil and water conservation measures, and (4) incorporation of dynamic land use and climate scenarios. Prediction of the impact of global change on SE and SSY in medium sized catchments is one of the main challenges in future model development. No single model fulfils all modelling objectives; a further integration of field observations and different model concepts is needed to obtain better contemporary and future predictions of SE and SSY.
The classic approach defines an extreme event as a rare event identified by magnitude–frequency analysis and quantified by its deviation from a central value. They are key to understand geomorphological dynamics, since they are responsible for a considerable amount of work and “time compression”. Time compression means that most of the geomorphic work (particularly sediment transport) is produced in very short temporal intervals (i.e. in few events). Moreover, it is well known from magnitude–frequency analyses that events not necessarily extreme by magnitude could be responsible for a large amount of geomorphic work. To analyse the time compression of geomorphological processes, a new approach has recently been suggested, based on the effects of “largest events”, defined by rank, whatever the magnitude. In this paper, we analyse the relation between the relative contribution of the largest daily event to the total suspended sediment load in relation to catchment size at the continental scale. For this purpose, we used two massive datasets of daily suspended sediment load facilitated by the United States Geological Survey (i.e. USGS Ancillary database), and the Hydrological Service of Canada (i.e. HYDAT dataset). The whole study area covers most of the temperate and sub-polar latitudinal climate conditions. Original data include information from more than 1800 catchments comprising appr. 3×106 daily events. The data show that the contribution of few events represents a high proportion of the total basin suspended sediment load. For instance, the mean contribution of the 25-largest daily events varies between 63% and 46% of the total load depending on the basin area, while the mean contribution of just the 5-largest events varies between 39% and 23%. The analysis suggests that the relative contribution of different n-largest aggregated daily events on total suspended sediment load decreases as catchment size increases. This is a general pattern and means that, for instance, time compression of suspended load is exacerbated in small catchments; hence, relatively few events are the key to explain the catchment sediment export. In addition, the relative contribution of the n-largest daily event to the suspended sediment load seems to be independent of climate conditions in small catchments, particularly in those
Farmland abandonment is a major problem in parts of Europe, particularly in mountain areas and semiarid environments. In such places, farmland abandonment represents a significant land use change from cropping to a complex of plant successions. The present study assesses the hydromorphological effects of land abandonment in Europe, and the consequences thereof with respect to water resource availability and soil erosion. The evolution of abandoned fields depends on (i) the time of abandonment; (ii) climatic conditions in the abandoned area; (iii) particular characteristics of the fields; (iv) the land management regimen following abandonment; and, (v) the role played by government policy. Throughout most of Europe, vegetation on abandoned farmland has evolved into dense forest or shrub. The expansion of vegetation explains, in part, the perceived decline in water resources, reductions in soil loss and sediment delivery, and the progressive improvement of soil characteristics. Such evolution has resulted in changing stream morphology, featuring narrowing and incision, and a decline in sedimentation level in Mediterranean reservoirs. The abandonment of bench terrace fields coincided with an increase in the occurrence of small landslides in the steps between terraces, as well as changes in the spatial organization of saturated areas. Plant colonization is slower in semiarid areas, increasing the development of soil crusts that reduce infiltration and increase overland flow. Land policies with detailed capability are necessary to remediate the consequences of farmland abandonment in various European environments.
For the past 25 years the Basel Soil Erosion Research Group (BSERG) has carried out long-term soil erosion measurements in catchments of north-western Switzerland (Jura Plateau and High Rhine Valley) and southern Baden-Wurttemberg. The very diverse cultural landscape had affected the application of research methods, modelling, and practical soil conservation measures. Soil erosion is not just perceived as being a geomorphic process only, but as an important component within the landscape geoecosystem. Hence, the BSERG developed a soil erosion research concept which is based on a geoecological approach and follows a multiple-step method focusing on the topic dimension. Long-term measurements are required to overcome the problems caused by the high temporal and spatial variability of the geoecological model parameters, and to provide a solid data base for soil conservation measures and realistic soil erosion modelling. The validity of existing soil erosion models was thoroughly tested. Not only the modification of such models for Swiss geoecological and agricultural conditions but also their practical application were found to pose major problems. The BSERG started to build their own GIS-based models following a statistical-empirical concept, which, of course, is still based on the landscape-ecological system and the topic to choric dimension as a methodical foundation. The first model developed by the BSERG was the GVEM BS ("GIS-based Method on Erosion Modelling BaSel"), which is well able to identify areas of potential erosion hazard, but is still a rather static model. In a second phase of modelling, process dynamics within the catchments were included into the calculations. Run-off processes, sediment sources, flow paths and the sediment and matter fluxes in the transition zone between flow paths on arable fields and the recipient streams could now be modelled. This was accomplished by the statistical-empirical, rainfall-event based model ESSEM ("Empirical Swiss SEdiment Yield Model"), which in a three-step approach describes the sediment displacement within small subcatchments. Besides the processes within the crucial zone along recipients, the occurrence and density of typical man-made elements in the Swiss cultural landscape, such as roads, barriers, filter strips, drainage systems etc. play an important role in controlling soil erosion processes. Future BSERG research activities will focus on both the enhancement of the data base and the validity and practical applicability of the soil erosion models as a tool for soil conservation purposes.
While much attention has been given to erosion processes in badlands, an integrated analysis of sediment production and export rates in badland areas at various spatial scales is currently lacking. This study reviews area-specific sediment yield (SY) from badlands in the Mediterranean measured at different spatial scales, using various measuring techniques, in order to investigate the relationship between size of study area (A) and SY. A database representing 16 571 plot-year and catchment-year data on SY at 87 Mediterranean study sites was compiled. The most commonly reported lithologies associated with badlands are marls, clay rocks and mudstones, and to a lesser extent shales. A high variability of SY from badlands in the Mediterranean region is observed. The relation between A and SY for Mediterranean environments with badlands is significantly different from that reported for Mediterranean environments without badlands. A complex A-SY relationship is identified: for areas < 10 ha, SY is very high (mean SY=475 t ha–1 y–1), whereas for areas > 10 ha, SY decreases non-linearly (power law) with increasing A (mean SY=75 t ha–1 y–1 and drops from 164.5 t ha–1 y–1 for 10 ha <A<200 ha to 9.3 t ha–1 y–1 for A>100 000 ha). This difference is explained by several factors. For A < 10 ha there is little or no sediment storage within badland areas, while for A > 10 ha progressively more sediment can be trapped in different sinks. Further, for A > 10 ha, area-specific erosion rates do not increase (or even decrease) due to decreasing average hillslope gradients and a decreasing fraction of erosion-prone (bare/badland) area. No significant relationships between SY, lithology, and mean air temperature nor mean annual precipitation were observed.
The authors regret that the paper published by Nadal-Romero et al. (2011) contains an error related to 19 Spanish Sediment yield (SY) data reported by Cantón et al. (2001b, 2003) and by Lázaro et al. (2008). Table 1 indicates the correct SY data. Re-plotting these data results in some changes in Figures 7 to 16 of the paper by Nadal-Romero et al. (2011). Most changes in the re-drawn figures occur for SY measured on very small areas (i.e. < 0.0001 ha) (Figures 7 to 11). Here we briefly discuss each of these figures focusing on the changes due to the use of the correct SY data.
Intense erosion processes are widespread in the Mediterranean region, and include sheet wash erosion, rilling, gullying, shallow landsliding, and the development of large and active badlands in both subhumid and semi-arid areas. This review analyses the main environmental and human features related to soil erosion processes, and the main factors that explain the extreme variability of factors influencing soil erosion, particularly recent land use changes. The importance of erosion in the Mediterranean is related to the long history of human activity in a region characterized by low levels of annual precipitation, the occurrence of intense rainstorms and long-lasting droughts, high evapotranspiration, the presence of steep slopes and the occurrence of recent tectonic activity, together with the recurrent use of fire, overgrazing and farming. These factors have resulted in a complex landscape in which intensification and abandonment, wealth and poverty can co-exist. The changing conditions of national and international markets and the evolution of population pressure are now the main drivers explaining land use changes, including farmland abandonment in mountain areas, the expansion of some subsidized crops to marginal lands, and the development of new terraces affected by landslides and intense soil erosion during extreme rainstorm events. The occurrence of human-related forest fires affecting thousands of hectares each year is a significant problem in both the northern and southern areas of the Mediterranean basin. Here, we highlight the rise of new scientific challenges in controlling the negative consequences of soil erosion in the Mediterranean region: 1) to reduce the effects and extent of forest fires, and restructure the spatial organization of abandoned landscapes; 2) to provide guidance for making the EU agricultural policy more adapted to the complexity and fragility of Mediterranean environments; 3) to develop field methods and models to improve the identification of runoff and sediment contributing areas; 4) to contribute to the conservation of landscapes (i.e. bench-terraced fields) having high cultural and productivity values; 5) to improve knowledge of the hydrological and geomorphological functioning of badlands, with the aim of reducing sediment yield and accessibility; 6) to better understand the effect of climate change on soil erosion in the Mediterranean region; and 7) to improve quantitative information on long-term soil erosion.
As the criterion for judging whether a soil has potential risks of erosion, productivity loss and whether a river has downstream over-sedimentation as well as the ultimate criterion for erosion control for the preservation of soil productivity and environmental security in the long term, the level of soil loss tolerance (T value) must be determined in a scientific manner. This overview summarized the development of T value. The factors influencing T value were then discussed, and the calculation methods for T value were also presented and evaluated. Finally, it was proposed that the evaluation of T value should be based on three criteria (referred to as T1, T2 and T3, respectively) with respective definitions and research fields involved. Two key issues, which can prevent the damage by soil erosion, i.e. tolerance for agrochemicals and self-restoration capacity of ecological environments should be addressed in the near future.
Analyses undertaken in this paper show that the Universal Soil Loss Equation (USLE) tends to overestimate low values of soil loss when the soil surface has a high capacity to infiltrate rainfall, but the degree of overestimation falls as the capacity of the soil to produce runoff increases. The USLE-M, a version of the USLE that uses the product of the runoff ratio and the EI30 as the event erosivity index, is more efficient in estimating soil loss because runoff is considered explicitly in the event erosivity index, whereas it is not in the USLE. The results show clearly that the problem of the USLE and the RUSLE overpredicting observed erosion losses, when erosion losses are low, is related to a large degree to model formula. In addition, the removal of restrictions to what constitutes a valid EI30 value increases the capacity of the RUSLE to overpredict low soil losses. As the USLE is an empirical model, values of USLE K, C, and P can only be used when the event erosivity parameter is EI30. Models like EPIC ignore this fact.
Rates of erosion on cultivated land in the UK are frequently 10-500 times greater than those on non-cultivated land. Eroded material may be stored within fields, and most measurements probably underestimate actual erosion rates. The initiation of erosion is influenced by physical factors and farming practices; however, many of the physical factors such as slope length are the result of decisions taken by man. Little is known of farmers' attitudes to erosion and conservation. Off-farm costs of erosion may be far higher than on-farm costs and need to be investigated. -from Author
A preliminary assessment of the spatial scale dependency of sediment yield from the Eden basin in northwest England is made on the basis of: suspended and bed load yield estimates at scales from 1 to 1370 km2, spot samples of suspended sediment concentration, and a dual resolution mapping exercise in which a generalized soil erosion risk map for the upper Eden (322 km 2) is complemented by a high resolution (2 m) map of erosion features and sediment transport pathways in a 5.4-ha farm field. Overall, annual specific total sediment yield decreases as basin area increases: specific bed load yield decreases rapidly but specific suspended load yield may even show a small downstream increase. The spot sampling campaign and the dual resolution mapping exercise suggest that this could reflect the impact of livestock farming in the more lowland areas. The results demonstrate the importance of sediment source and transport path-ways in explaining scale dependency in sediment yield.
Land abandonment throughout the twentieth century led to an intense landscape transformation in the mountain areas of the Iberian Peninsula. In some cases, and after 50 years of abandonment, agriculture returned with the development of commercial farms and the intensification of the agrarian activities. In the Easter Iberian Peninsula, following the abandonment of olive groves, vineyards and cereals during the 50's, has been in the past two decades the expansion of intensive citrus production on sloping terrain. Geomorphological transects and simulated rainfall experiments have quantified the impact of traditional rainfed cultivation of the 50's, abandonment, and the intensification of farming on the processes and landforms of erosion on the northern slopes of the Serra Grossa, south of the province of Valencia. It was found that the citrus groves have the highest number of rills and gullies. These erosive morphologies were not in the traditional crop tillage, and when they formed in the abandoned fields were soon controlled by the growth of vegetation. The abandonment of the crops reduced the soil losses, but the intensification of the agriculture with the citrus production has accelerated the soil erosion rates that exceed by several orders of magnitude (x4) the soil erosion rates measured during the abandonment and multiply by 17 the quantified traditional rainfed agriculture soil losses. Tillage of traditional rainfed orchards reduced runoff, but increased the concentration of sediments of the surface wash.
Catchment sediment budgeting is an attempt to identify the sources, sinks and pathways of eroded material within catchments. However, the identification of these quantities is not straightforward, and the conceptual underpinnings of sediment budgets make unwarranted and untested assumptions about process stability. Many sediment budgets leave one or more quantities unmeasured and obtain estimates of them by subtraction (assuming budget closure). Consequently, errors in sediment budgets are often hidden and are not quantified. There has been an emphasis on suspended sediment, which, for management purposes, may not be useful. Sediment budgeting can act as a framework for a research agenda on catchment processes. What has been lacking from this agenda has been an adequate consideration of the time taken for sediment to travel via the various pathways to the catchment outlet. The storage term in such budgets has been used as a poor substitute for a thorough understanding of sediment velocity through catchments.
The rainfall properties of drop size and spatial distribution are important factors in infiltration rate and splash detachment. Interception by plant canopy can transform rainfall properties. In this paper, interception processes are dimensionally analyzed. Relationships between properties of rainfall measured under plant canopy and dimensionless rainfall and canopy descriptors are reported. Significance of transformations to soil erosion processes is discussed.
Water erosion is one of the most active processes in soil genesis and dynamics. It is also at the origin of significant environmental problems. Soil surface state is one of the most important factors for erosion risk assessment. However, it is Ž not easy to determine the effect of this factor at a large scale. A field experiment was held in Pays de Caux Normandy,. France in order to study and quantify crusting, runoff and sheet erosion at the cultivated field and catchment scales. We measured crust formation, runoff and erosion during two seasons on 1-m 2 , 20-m 2 and 500-m 2 experimental plots and on a small catchment. Results allow a ranking of the most important factors influencing crusting and erosion at the different scales. They also enable the development of relationships for upscaling from small plot results to the cultivated field and catchment for specific conditions. However, upscaling from plots to catchments is generally difficult and needs to take catchment spatial structures into account. We distinguish between runoff and erosion scale transfer, the latter being at the origin of specific problems that need further research to be solved.
Channel changes are the consequence of changes in sediment yield from the slopes and in the connectivity between slopes and channels because of distinct land use and climate impacts. In this study we investigated the characteristics and evolution of a short reach in the headwater of the Ijuez River, central–southern Pyrenees. Assessment of a series of sedimentary and geomorphic structures confirmed major changes to the valley bottom, mainly related to changes in the intensity of human activity. The oldest sedimentary structure is a terrace level located 3–4 m above the current alluvial plain. General deforestation, overgrazing and recurring fires in the montane belt (1100–1600 m a.s.l.) have led to increased soil erosion and connectivity, and to the triggering of debris flows that have been deposited on the fluvial terrace. Woody fragments from within the debris flows were dated using AMS 14C radiocarbon techniques, yielding ages between 100 and 115 cal yr BP, which coincides with the period of maximum deforestation and human density in the Pyrenees. Depopulation and farmland abandonment since the beginning of the 20th century has resulted in generalized natural and artificial reforestation, a shrinkage of the eroded areas, and a decline in connectivity between slopes and the channel. The most important consequence has been channel incision and narrowing, and the development of a sediment armour layer. Active sediment transport is continuing, although there has been a decrease in sediment yield from the slopes. This article is protected by copyright. All rights reserved.
Caesium-137 derived from nuclear testing in the past century has been
widely used as a sediment tracer of soil redistribution, providing
information on medium term (40-50 years) erosion rates. To date, most
studies have focused on individual fields of limited extent, but
estimated rates and patterns of soil redistribution require upscaling to
catchment level. An attempt to assess soil redistribution processes with
strong geomorphic control on complex terrain, such as an internally
drained karst catchment, is presented in this work. A comprehensive
geomorphological survey of the Estanya Lake catchment (Spanish Pyrenees)
enabled the main geomorphic elements to be identified with a grid
resolution of 5 × 5 m, which was the basis for the terrain
analyses. A detailed DEM was constructed and improved after field
identification of the drainage system and point measures on gentle
slopes with Total Topographic Station. A 100 × 100 m sampling grid
was established to derive point data of 137Cs inventories
across the catchment. Geostatistical interpolation of point samples of
137Cs inventories in soil was carried out to identify and
assess the areas of sediment gain and loss by comparing with
137Cs reference inventories. Profile activity models were
used to calibrate 137Cs data and to derive estimates of soil
redistribution. GIS was used to provide spatially distributed erosion
and deposition rates in the landscape for the whole catchment. The
median values of soil erosion and deposition of 4.7 and 3.1 Mg ha-
1 year- 1, respectively, showed a large variability and
reveal coupling between erosional and depositional forms in the
catchment. The highest erosion and deposition rates were found in
cultivated fields at the southern sector of the catchment. The spatial
analysis of the results supports the importance of taking into account
geomorphological features in karst catchments as relevant controlling
factors in soil redistribution processes.
In this study we analyzed runoff and sediment yield from land under various traditional and current land uses in Mediterranean mountain areas, using long-term data from an experimental station in the Aísa Valley, Central Spanish Pyrenees. Monitoring at this station has provided 20years of data that can help explain the hydrological and geomorphological changes that have been observed at larger spatial scales, and also the changes that have occurred to some of the most characteristic landscapes of the Mediterranean middle mountains. In spite of the problems associated with the use of small experimental plots, the results obtained are consistent with other studies in the Mediterranean region, and confirm the strong influence of land use changes on runoff generation and sediment yield. The results indicate that: (i) cereal cultivation on steep slopes (both alternating cereal cultivation and fallow on sloping fields and shifting agriculture on the steepest slopes) represents a major problem for soil conservation. This explains the occurrence throughout the Mediterranean mountains of many degraded hillslopes, which show evidence of sheet wash erosion, rilling, gullying and shallow landsliding; (ii) farmland abandonment has led to a marked reduction in runoff and sediment yield as a consequence of rapid plant recolonization, particularly by dense shrubs; (iii) the natural transformation of abandoned fields into grazing meadows has reduced runoff and sediment yield. Land use trends in the Mediterranean mountains are mainly characterized by generalized farmland abandonment and a decrease in livestock pressure. From a hydrological and geomorphological point of view the main consequences have been a reduction in overland flow from the hillslopes, and a reduction in sediment sources, with differences up to one order of magnitude in sediment yield from dense shrub cover and grazing meadow areas compared with areas under shifting agriculture.
The concept of the sediment delivery problem was introduced into the literature in 1983 by Des Walling. This concept describes how only a fraction of sediment eroded within a catchment will reach the basin outlet and be represented as sediment yield, and that sediment storage mechanisms operating within a catchment explain this discrepancy. Since this paper was published, geomorphologists have been examining in great detail the fate of sediment eroded from the landsurface, and the pathways and timeframes of sediment transport and storage in catchments. However, to fully understand the internal dynamics of sediment flux requires a ‘fresh look at the sediment delivery problem’. A framework is required that can incorporate the various processes involved in sediment movement from source areas through a basin to its outlet, and can take account of the spatial distribution of, and timeframes over which, these processes operate.
This paper presents a conceptual framework for analysis of catchment (dis)connectivity that incorporates both spatial and temporal variability in the operation of the sediment cascade. This approach examines where blockages occur to disrupt these longitudinal, lateral and vertical linkages in catchments. Depending on the position of blockages (termed buffers, barriers and blankets), and their sediment residence time, various parts of a catchment may be actively contributing sediment to the sediment cascade and be switched on, or inactive and switched off. This paper discusses how such a framework can be used to model response times to disturbance and explain the manifestation of geomorphic change in catchments. The paper then highlights challenges geomorphologists face in applying such a framework to understand the internal dynamics of the catchment sediment cascades, and forecast how environmental change might affect the operation of sediment fluxes into the future. Copyright
This report describes the need for monitoring the effects of climatic change on soil erosion. The importance of monitoring not only runoff, but monitoring and experimental studies at the larger scale of hillslope and catchments is stressed.
Land degradation and soil erosion are perceived as important problems in the dryland zones of the Mediterranean. Three-year measurements of hydrological and soil erosion data from a series of nested experimental watersheds in a semi-arid area of SE Spain are discussed. The aim was to study the role and effects of thresholds on the spatial connections between different system compartments, such as response units and sub-catchments that act at different levels of scale (plot to watershed scale). It was also the aim to quantify runoff and erosion at these different scales. Several types of thresholds are described and these are related to vegetation type and pattern, soil surface roughness, distance to the main channel, land use and tillage effects (intrinsic properties of the landscape) as well as rainfall intensity, duration and depth (external influence). The expansion of runoff generating areas under Hortonian overland flow is discussed in relation to vegetation structure and rainfall. Results showed that runoff and sediment yield results highly depend on the vegetation structure. The relation between rainfall intensity and rainfall depth and the hydrological response were established at five levels of scale. Three spatio-temporal process domains were analysed: the spot- and plot-processes at the finest scale, the hillslope, micro- and sub-catchment processes at the intermediate scale and catchment scale and main channel network processes at the broadest scale. An event with a 5-year recurrence period is discussed to illustrate the importance of scale related thresholds, explaining the relative importance of high intensity rainfalls. Soil erosion was found to be a magnitude larger on terraced valley bottoms (2500–3000 gm−2) when compared to the semi-natural hillslopes, where erosion figures were less than 10 gm−2. This indicated that the contribution of sediment from terraced cultivated lands is important and are an underestimated part of the sediment budget of semi-arid catchments.
The mean size of particles mantling quartz monzonite debris slopes in the Mojave Desert is found to be correlated with slope gradient, but the relation is shown to vary from one debris slope to another as a result of differences in joint spacing and mode of weathering of the underlying quartz monzonite. -from Authors
The role of erosion by water in the UK is considered. A summary of available data describing water erosion is presented providing insights into rates of erosion from the hillslope scale to the large catchment scale. Evidence suggests that soil erosion rates in excess of acceptable thresholds occur on a wide range of soils and under a wide range of land uses throughout the country. Given the recent shift towards erosion modelling and away from erosion monitoring, discussion of the quality of existing available observed data in the context of model evaluation is made. Much quality data exist in the UK to describe erosion by water, but it is argued here that few datasets provide the necessary detail with which to evaluate model performance accurately, especially when the description of the spatial heterogeneity of soil loss is a goal. Furthermore, the paradox between data collection (to improve models) and erosion modelling (to replace data collection) is highlighted as an issue that must be addressed within the discipline if full use of datasets and improvement of models is to be made.
Soil erosion by water is one of the most important land degradation processes in Mediterranean environments. This process is strongly linked to problems of flooding and channel management. This article reviews existing knowledge on these topics and defines research gaps. In the framework of environmental change studies it is important to consider soil erosion at various spatial and temporal scales. Most field measurements and modelling efforts have hitherto concentrated on water erosion processes operating at the runoff plot scale. Soil erosion processes operating at other spatial scales have received much less attention in the literature. Yet, there are indications that gully and channel erosion are probably the dominant sediment sources in a variety of Mediterranean environments. Beside water erosion, other erosion processes operating within catchments, such as tillage erosion, land reshaping for land preparation (e.g., terracing) or soil quarrying can have significant impacts on soil profile truncation. Land use changes strongly affect the intensity of these processes.
The conditions, position and connectivity of the runoff and sediment generating areas within catchments have a profound effect on flood characteristics within the main channels but the dynamics are not well understood. Some research has taken place into meteorological conditions producing catastrophic flooding and into development of hydrological models using catchment variables. Much less is known of the properties and effects of flood waves within channels, partly because of lack of records of these infrequent events. It is not only water but also sediment which causes destruction in floods, yet sediment is frequently ignored in channel management. The extreme conditions associated with floods in the region, the variability of flows and of flood zones, the mobility of the channels and the high sediment loads create particular challenges for channel management. Trends in land use and channel management are tending to exacerbate these problems.
From this review it can be concluded that there is still an important need for process-based understanding and modelling of key soil erosion processes operating at a range of scales: i.e., from plots over hillslopes, catchments to regions. In particular, more research is needed on the linkages between upland areas which produce large volumes of runoff and sediment and channels on the other hand. Such linkages are through gullies and sedimentation zones. Monitoring and experi mental data on key soil erosion and channel processes operating within Mediterranean landscapes are crucial for the improvement of soil erosion and channel models for a range of scales. In particular, long-term monitoring of soil erosion processes and stream channel changes seems to be essential to observe the effects of infrequent torrential rain events on severe erosion, flooding and stream channel changes as well as on the transient response of Mediterranean landscapes to changes in land use and climate. Systematic collation of historical evidence of changes would be valuable. Implications of land and water use need to be examined in detail. A wide range of alternative strategies and techniques of channel and basin management must be explored and modelled. A holistic approach to management of the fluvial system is recommended.
The purpose of this paper is to explore the role that drainage basins and networks play in filtering and modulating the effects of environmental change. The record of this change is often inferred from the properties of alluvial stratigraphy in river valleys. However, the variable time lags and smoothing effects caused during the flux of sediment through a drainage basin are very poorly understood, and need to be clarified before the depositional record can be linked to the causes of change. Interactions amongst drainage network elements - main valleys and tributaries - result in complex patterns of storage and delivery in time and space, and these interactions are reviewed in this paper. While the combination of cosmogenic isotopic dating of erosional records. and the use of shallow seismic and ground penetrating radar methods may provide data on the empirical linkages between sediment sources and sinks, a significant research need is for a modelling framework to enable cut-and-fill records to be simulated, and to provide a rigorous connection between the valley-fill depositional record and the environmentally-driven variations in sediment production. This will require a return to the long-neglected analysis of drainage network structure, and an improved understanding of the within-catchment variations in the sediment delivery ratio. Until this is achieved, it will be premature to assume direct connections between environmental change and the record of alluviation in many valleys.
This paper investigates the signature of climate and landscape spatial variabilities on flash-floods events. Through the case of the catastrophic 8-9 September 2002 Cévennes-Vivarais event, the impact of the space-time structure of the rainfall on the distributed hydrological response is evaluated. Comparisons are made with other spatial variabilities that may also contribute to the flash-flood generation such as initial soil moisture condition, topography, landscape characteristics, hydraulic processes. A model-based approach is suggested and was applied on 19 catchments. It is shown that the spatial variability of rainfall and of the initial soil moisture conditions were both of first order in the flash-floods generation and that the spatial variability of landscape properties were of second order. This methodology will be applied on other extreme hydro-meteorological events surveyed by the OHM-CV (Cévennes-Vivarais Mediterranean Hydrometeorological Observatory), with the aim of providing clues on processes that should be particularly focused when measuring and simulating such intense mesoscale meteorological events.
Soil erosion measurements on small upland watersheds totaling 229 watershed-years show that most of the total erosion occurring over a long-term period of record comes from a few large storms. Nine 1ha (2.5 acre) watersheds containing residual soils with silt loam surfaces on B and C slopes were farmed under a corn-wheat-meadow-meadow rotation. Four of the watersheds were farmed in straight rows across the slope; five were contoured. More than 92% of the erosion came in the corn years; the rest came in the wheat years. Erosion from the contoured watersheds averaged 30% of that from the straight-row treatment. With >4000 rainfall events during the study period, the five biggest erosion-producing events on each watershed occounted for 66% of the total erosion over 28yr. On one watershed, one storm caused >1/2 the long-term measured erosion. -from Authors
An exceptional rainfall and hydrological event occurred on 19–21 October 2012 in the central western Pyrenees and was particularly significant in the Upper Aragón River basin and its tributaries, mainly the Irati River. Analysis of historical records showed that, considered separately, the event of 19 and 20 October ranked between the second and fifth highest most extreme daily precipitation events. For the two days combined (with a total between 200 and 260 mm), the precipitation event was the most extreme 2-day event among all observation stations but one. The consequent flood destroyed part of an urban area, and a long stretch of a national road triggered landslides, enlarged the alluvial plain and caused generalised soil erosion in cultivated fields cropped with winter cereals. Badlands in the marls of the Inner Depression yielded high volumes of sediment. The floods in the tributaries were relatively moderate (return periods of 14–42 years), whereas in the Upper Aragón River, the flood corresponded to a return period of approximately 400–500 years and to 142 years at the end of the Yesa reservoir, although difficulties in estimating the discharge increased the uncertainty of these values. The Yesa and Itoiz reservoirs considerably reduced the intensity of the flood in the middle and lower Aragón River and confirmed the importance of the water level in the reservoirs when such rainfall events occur. The water storage in the Yesa reservoir increased from 16% to 53% as a consequence of the event. More integrated studies are necessary to decrease the risks associated with flood hazards. This is particularly the case in mountain areas, where the steep slopes and longitudinal gradients of the rivers shorten the concentration time of floods and increase the energy that erodes channels and riverbanks.
Effective mean annual precipitation is related to sediment yield from drainage basins throughout the climatic regions of the United States. Sediment yield is a maximum at about 10 to 14 inches of precipitation, decreasing sharply on both sides of this maximum in one case owing to a deficiency of runoff and in the other to increased density of vegetation. Data are presented illustrating the increase in bulk density of vegetation with increased annual precipitation and the relation of relative erosion to vegetative density.
It is suggested that the effect of a climatic change on sediment yield depends not only upon direction of climate change, but also on the climate before the change. Sediment concentration in runoff is shown to increase with decreased annual precipitation, suggesting further that a decrease in precipitation will cause stream channel aggradation.
We analyzed the empirical relationship between plant coverage and sediment ratio curves (SR) at two semi-arid Mediterranean sites (inland Spain). Comparison of b values in the fitted equation (SR = a * e−b*x), with x as % cover) shows a significant difference (P < 0.05) between Rosmarinus officinalis, and an association of lichen and Lygeum spartum. We hypothesize that both the architecture of individual plants and the association of plants, could play a key role in partitioning rainfall between stemflow and throughfall. This, in turn, affects soil erosion by water.