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Water erosion, a notorious major threat to food security and ecosystem sustainability, is strongly conditioned by spatial and temporal scale effects. This paper systematically reviews the scale issues in runoff and sediment delivery (SIRSD) as a research field by integrating the traditional review approach and bibliometric analysis. This review summarises SIRSD's roots and the scale effect on runoff and sediment delivery. Then, we provide quantitative insights into the SIRSD domain's development history, thematic structure, geographic distribution, international cooperation, and methodologies. Findings show that: i) SIRSD arises from the gap between the non-linearity of runoff and sediment delivery across scales and our ability to measure it. Point-based and short-term measurements cannot capture the non-linearities from the spatio-temporal heterogeneities and cross-scale interactions of factors or processes. ii) Previous literature provides evidence that the spatial scaling of specific runoff (r), soil erosion (SE), sediment yield (SSY), or sediment delivery ratio (SDR) with drainage area (A) or slope length (L) exhibits contrasting patterns due to distinct mechanisms. Infiltration-excess and saturation-excess processes account for inverse and positive r - A relations, respectively. Interrill-erosion and rill-erosion cause inverse and positive SE-L relations. Hillslope-erosion and channel/bank-erosion explain inverse and positive SSY-A relations. Downstream increasing deposition and additional sediment inputs drive inverse and positive SDR-A relations. These scaling relationships can be nonlinear or complex due to spatial heterogeneities in land use, vegetation, topography, climate, lithology, and soil characteristics. Hence, applying an empirical scaling equation developed from the region with distinct environmental contexts is not recommended. Furthermore, the existing scaling patterns or equations may require updating given global climate and land use change. iii) SIRSD is a complex and multidisciplinary issue investigated by scientists from 93 countries since 1928. International research has substantially facilitated the understanding of SIRSD; still, more collaboration should focus on less-developed countries with high soil and water loss risks and urgent conservation needs, such as those in Africa and South America under cropland expansion. iv) Scale mismatch and scale break have discredited large-scale erosion and sediment assessments. Incorporating gully and bank erosion into modelling, extending the scale range of the L factor, and expanding the sediment scaling scope from watershed to slope may make a difference. Therefore, more research with nested design incorporating multiple scales is necessary for cross-scale analysis and scalable modelling. Addressing global climate change requires improving real-time urban flood forecasting and integrating downscaled climate models with hydrology, erosion, and sediment transport models. • A bibliometric review of the global SIRSD research for the first time. • SIRSD is rooted in the gap between natural nonlinearity and our measuring ability. • Scaling of specific runoff, erosion, sediment yield, and SDR has diverse patterns. • Scale mismatch and scale break discredit large-scale modelling and assessments. [ABSTRACT FROM AUTHOR]

• The runoff, sediment load and runoff erosion power decreased significantly. • Compared with runoff, runoff erosion power-sediment relationship is better. • The power function of runoff erosion power and sediment is better than linear. • Erosion in particular geographic locations responds strongly to runoff erosion power. In recent years, the acceleration of urbanization in the Yangtze River Economic Belt (YREB) has brought about problems such as soil erosion, ecosystem degradation and decline in ecological service functions. Therefore, this paper selects the Fujiang River Basin (FRB) in Upper Yangtze River (UYR), and analyzes the relationship between runoff erosion power (REP) and sediment transport (ST) on the basis of analyzing the variation characteristics of hydrological elements. Based on SWAT model, a variety of scenarios are set up to quantitatively analyze the impact of different land use changes on runoff and ST and REP in the basin. The results indicated that: (1) The annual precipitation in FRB from 1960 to 2018 did not change significantly, while the annual runoff, annual ST and annual REP decreased significantly. Compared with runoff and runoff depth, the relationship between sediment transport modulus (STM) and REP is the best, especially the power function between them is better than the linear function. (2) The results of the evaluation indexes of the simulation results of the SWAT model based on the measured runoff and sediment data from 2008 to 2018 are pass and above, that is, the simulation results are considered reliable. (3) Under the five scenarios of conversion of sloping farmland to forest, conversion of dry land to paddy field and conversion of grassland to bushland and forest land, the runoff and ST in the basin decreased but the overall range was small. The simulation results of SWAT model show that the erosion of specific areas in the basin shows the greatest degree of weakening with the decrease of REP. [ABSTRACT FROM AUTHOR]

• Mass movement is an important erosion mode and sediment source in gully network. • Mass movement increased sediment concentration and led to peak sediment concentration. • Mass movement was prone to be triggered by rainfall with a medium-duration and moderate-intensity. • Rainfall amount and slope gradiet determined the trigger and total volume of mass movement. Mass movement erosion on the gully sidewalls is recognized as an important erosion mode and sediment source in hilly and gully watersheds. However, the trigger of mass movement erosion and transport of gravity-detached material remain poorly understood. A series of rainfall simulation experiments were conducted on six loess gully sidewall models, with a height (1 m), three rainfall (60 mm, 48 mm and 24 mm) and two slope gradients (70° and 80°), to quantitatively explore the sensitivity factor and transport mechanisms of mass movement. Results revealed that the accumulation volume and initiation of the mass failure were significantly influenced by rainfall amount. The accumulative volume of failure events was observed to increase in a linear pattern with increasing rainfall amount. The minimum cumulative rainfalls for the initiation of mass failure on the loess gully sidewalls were approximately 43.6, 28.2 and 65.6 mm for short-duration and high-intensity, medium-duration and moderate-intensity and short-duration and moderate-intensity rainfalls, respectively. This implied that the initiation of mass failure was more prone to rainfall events with a medium-duration and moderate-intensity than those with a high intensity and short duration. Rainfall amount and initial slope gradient were the most sensitive elements driving the number and volume of the mass movement erosion. Mass movement erosion raised sediment concentration, but the eroded material was unable to be transported by runoff in a timely manner. Average sediment concentrations at the model outlet increased by 1.9–11.9 times following the occurrence of mass failures compared to those before. A low instantaneous sediment delivery ratio of 0.032 for the mass movement erosion. The experimental findings help comprehend the influence of mass movement erosion on sediment supply on the gully sidewall in the hilly and gully network, i.e. the Loess Plateau. [ABSTRACT FROM AUTHOR]

Prescribed fire is a common management practice in Mediterranean region to reduce the amount of fuel and to decrease the wildfire risk. The objective of this study is to assess the effect of a prescribed fire on some soil properties, hydrological response and vegetation recovery in experimental plots 5 years after. The results showed that: i) with the exception of electrical conductivity, the prescribed fire did not affect the analyzed soil properties, and ii) overland flow and sediment transport were increased during the first two years, returning to levels pre-fire, 5 years post-fire. The rainfall threshold for overland flow generation was lower during the following months after the prescribed fire owing to the depletion of the vegetation cover. Immediately after the fire, the vegetation cover was of 1.9%, being the three main soil surface components that dominated the hydrological response: charcoal and decayed wood; blackish and greyish ash, and bare soil. However, these areas decreased very rapidly during the second year following the fire, principally, owing to the regrowth of herbaceous plants and shrubs. In addition, the vegetation cover in burned plots was 16.1% higher than that measured in the unburned ones. Overall, the prescribed fire only had an impact on runoff and sediment transport in the two years post-fire, as consequence of vegetation removal. [ABSTRACT FROM AUTHOR]

• Physically based 2D hydrodynamic and sediment transport model, CCHE2D. • High resolution mesh, topography photogrammetry, experimental landform evolution. • Watershed hydrology, raindrop soil detachment, displacement, erosion and transport. • Distributed solution, tilled watershed, cornfield tillage ridge and furrow morphology. • Simulated runoff, sediment transport, landform evolution; channel network analysis. Soil and gully erosion is a critical threat to sustainable agricultural land management and productivity. Soil erosion by rain splash, sheet runoff, and concentrated flow are complex problems conditioned by the combined interactions of soil physical properties, hydrology, human activity, landscape topography, and climate. Effective management of erosion processes driven by rainfall and surface runoff requires a combined effort of field observation, physical experimentation, and numerical simulation. A physically-based hydrodynamic numerical model, CCHE2D with updated raindrop erosion effects, is applied to simulate landscape evolution processes as a result of raindrop impact and overland flow. The numerical model simulates a thin layer of runoff and concentrated flow over complex terrains, and predicts sediment transport due to raindrop splash detachment, transport and soil surface erosions. Soil erosion and landform evolution simulations due to rainfall are presented for an experimental landscape and a tilled large scale agricultural field. Photogrammetric field data were collected using an unmanned aerial system (UAS) following planting and subsequent rainstorms. Numerical simulation results agreed well with the observed experimental soil surface topography, sediment yield, and drainage network developments. The simulated soil and gully erosion in the tilled field also agreed well with observations. This research successfully demonstrates how high resolution spatial and temporal topographic measurements in experimental and field landscapes can be simulated and interrogated by 2D physically-based hydrodynamic and morphodynamic models. The accurate predictions of tillage field and gully erosion process in agriculture watersheds with complex tillage conditions also indicated the usefulness of the model for studying soil and landscape degradation. [ABSTRACT FROM AUTHOR]

Silver nanoparticles (AgNPs) are being used in many products as they have unique antimicrobial-biocidal properties. After disposal of these products AgNPs can reach the soil environment possibly affecting soil organisms and disrupting plants. This work aimed to study the transport of AgNPs by water and sediment during overland flow and soil erosion. This was done in a laboratory setting, using a flume and rainfall simulator. A low concentration of AgNPs (50 μg·kg − 1 ) was applied to two soil-flumes with slope percentages of 20% and 10%. The rainfall was applied in four events of 15 min each with a total amount of rainfall of 15 mm during each event. After applying the rainfall, samples of the non-transported background soil (BS) and the transported sediment (Sf) were collected from the flume surface. Runoff sediment (RS) and water (RW) were collected from the outlet. AgNPs were detected in all samples collected. However, concentration varied according to sample type (soil or water), time of collection (for runoff water and sediment) and the slope of the soil flume. Higher concentrations of AgNPs in soil were detected in the BS than in the Sf likely due to the BS having more fine particles (silt and clay). The AgNPs concentration in the runoff sediments increased with subsequent applied rain events. In addition, increasing the slope of the flume from 10% to 20% increased the total AgNPs transported with the runoff sediment by a factor 1.5. The study confirms that AgNPs can be transported by both overland flow and sediment due to erosion. [ABSTRACT FROM AUTHOR]

• Linkage between soil surface microrelief and overland flow was examined. • Differently oriented wheel tracks served as water flow paths or as sediment sinks. • Increase of surface connectivity after a rain was shown by functional connectivity. • Structural connectivity showed reorganization of the surface runoff pathways. Although wheel tracks cover only a small portion of the surface of agricultural fields, their effect on surface runoff and sediment transport is substantial. Wheel tracks change the microrelief of the soil surface, and influence how the surface is further altered by rainfall and runoff. This study presents a plot-scale microrelief analysis of a tilled surface with wheel tracks under simulated rainfall. Digital elevation models of the microrelief with 1 cm spatial resolution were obtained using the Structure from Motion method. The random roughness, the structural connectivity, and functional connectivity were calculated for before-rainfall and after-rainfall soil surface conditions. The experiments were carried out on inclined, freshly-tilled plots (8 m long, 2 m wide). The wheel tracks were created by four passages of machinery in the slope direction (SWT) and in the contour-line direction (CWT). The experiments were compared to reference plots without wheel tracks (NWT). The wheel tracks increase water and sediment connectivity if they are oriented in slope-wise direction. Microrelief analysis shows that SWT drains water from the surrounding soil. The soil surface adjacent to SWT can also become more connected with the wheel track, due to changes in microrelief introduced by rainfall and runoff. The calculated higher connectivity in the SWT plot corresponded to the measured increased sediment loads. This suggests faster overland flow and therefore shorter flow pathways on the soil surface microrelief. CWT leads to a decrease in the water and sediment connectivity compared to the NWT and SWT plots. Although the surface runoff can overflow the CWT, the network of flow paths results in decreased flow velocity and a slower sediment transport rate. However, the CWT effect is not permanent, and declines as the wheel tracks become silted with the deposited sediment. It is shown that detailed microrelief data provide relevant information for a study of the changes in flow routing in a tilled agricultural field with the presence of a wheel track. SWT accelerates the runoff and especially the sediment transport. During a rainfall event, the hydraulic connection between the wheel track and the surrounding soil increases dramatically. CWT reduces the surface runoff and also the sediment transport. In the long term, rainfall events and surface runoff alter the microrelief connectivity, causing the soil surface to be more hydraulically connected, irrespective of the wheel track orientation. This study demonstrates the effect of wheel tracks on water and sediment transport. The results draw attention to the importance of appropriate soil protection measures, as a bare unprotected surface microrelief exposed to rainfall leads to increased sediment connectivity. [ABSTRACT FROM AUTHOR]

• Under the action of concentrated flow, the change of surface runoff of karst gently sloping farmland is mainly controlled by the magnitude of concentrated flow. • Under the action of concentrated flow, the underground runoff of karst gentle slope farmland is significantly negatively correlated with the slope. • Concentrated flow can lead to severe soil erosion in karst gently sloping farmland. Exposed bedrock in karst areas considerably alters runoff paths causing partial runoff to converge into a concentrated flow, which is a potential source of soil erosion risk. However, research is lacking on how concentrated flow affects regional soil erosion. In this study, the surface and underground dual structure in karst areas was simulated in a steel tank. Combined with runoff plot monitoring, the runoff conversion process and erosion characteristics of gently sloping farmland in karst areas under different water discharge rates were examined through indoor concentrated flow discharge scouring tests, and the influence of concentrated flow changes on the runoff spatial distribution and sediment yield in gently sloping farmland was clarified. The results demonstrated the following: (i) there existed a significant positive correlation between surface runoff and the water discharge rate (p < 0.01); the partial correlation coefficient value reached 0.87. The higher the water discharge rate, the more surface runoff formation was facilitated. (ii) When the slope remained the same, the underground runoff was relatively high at 3 L/min. Given the same discharge, a significant negative correlation between underground runoff and slope was found (p < 0.05); the partial correlation coefficient value reached −0.71. (iii) In response to a water discharge rate of 5 L/min, surface soil erosion was serious, and the maximum sediment transport modulus was 174.088 g/min∙m2. A significant cubic function relationship existed between the scouring time and surface sediment yield. Overall, a critical flow rate occurred between 3 and 5 L/min, which controlled changes in surface runoff, subsurface runoff and surface sediment yield. Under highly concentrated flow, drastic soil erosion could occur. These results can provide a scientific basis for the control and prevention of concentrated flow-induced erosion in karst areas. [ABSTRACT FROM AUTHOR]

• SWAT hydrological model has high potential in the assessment of watershed changes. • Land use changes caused by forest fires affect hydrological response of watershed. • Significant increase in surface runoff and sediment load in the post-fire scenario. • Sediment yield increased by 6.5 times with the highest fire spatial distribution. • Forest fire scenarios help to limit hydrological impacts of fire on sediment load. Forest fires profoundly affect the nature of watershed responses to precipitation, increases in runoff rate and volume, and post-fire sediment discharge. A post-fire watershed assessment to identify potential trouble spots for soil erosion and flooding can help land managers for decision-making on deploy mitigation, remediation measures, and restoration action plans. Predicting the potential impact of fires on runoff and soil erosion requires distributed hydrological modeling methods. This study used the Soil and Water Assessment Tool (SWAT), a rainfall-runoff model, to investigate the hydrological consequences of forest fires and their impact on sediment load under different burnt scenarios. For the pre-fire (baseline) scenario, the watershed is calibrated by using the measured discharge and suspended sediment concentration data from the weather station during the time step to estimate post-fire changes at the sub-catchment scale. The total water and sediment yield for the selected sub-catchment in the post-fire scenario with the highest spatial distribution of forest fire, due to the excessive surface runoff (an increase of 14.5%) increased significantly, resulted in 6.5 times increase in sediment yield. The results obtained from the study indicate a significant increase in sediment transport into the stream in the post-fire scenario. A large volume of soil losses occurred during the time step. In contrast, due to removing trees and vegetation from the ground, less evapotranspiration and infiltration occurred in selected sub-catchment areas after forest fires. In terms of watershed management, understanding the consequences of forest fires on hydrological services will be an effective method for sediment budget control. Therefore, applying the rainfall-runoff and erosion models for the watershed with developing plausible forest fire scenarios can be a productive method to deal with the threats and hydrological risks such as soil erosion and sediment transfer to the downstream environment. [ABSTRACT FROM AUTHOR]

Earthworms are ecological engineers that play an important role in hydrological processes and soil erosion by their burrowing and casting activities. Little is known, however, about the ecological function of the activities of an anecic species (Metaphire guillelmi) from the Loess Plateau in China where the soil is severely eroded. We conducted rain-simulation experiments on artificial slopes (mesocosms) filled with soil from Loess Plateau. Two rain intensities (90 and 120 mm h−1) and slope gradients (5° and 15°) were used to investigate the influences of earthworm activity on runoff and soil loss under multiple conditions. Data from 15 d of earthworm activity and 1 h of rain indicated that earthworm activity significantly reduced runoff but aggravated soil erosion. Runoff initiation time increased 2.7–3.1-fold, contributing to the promotion of water infiltration, and the amounts and rates of runoff were 35.8–61.6% and 35.1–60.8% lower under earthworm activity than the controls, respectively. Earthworms greatly influenced the physical and chemical properties of the soil, and these properties were strongly correlated with runoff initiation time and cumulative runoff. The surface casts produced by the earthworms on the soil surface were completely dispersed, increasing the cumulative sediment by a maximum of 169%. Both rain intensity and slope gradient greatly influence runoff and soil detachment, but with earthworm activity, slope gradient was more influential due to its superior contribution to sediment transport. This study quantified the effects of M. guillelmi on runoff and soil erosion and provides basic data for developing a more integrated control of soil erosion on the Loess Plateau. • The increase in infiltration related to earthworm activities decreases runoff. • Soil erosion is aggravated by the low stability of surface cast under intense rainfall. • Earthworm impact on soil loss is larger at lower rain intensity and steeper slope. [ABSTRACT FROM AUTHOR]

Abstract: We quantified the sediment volume transported by a major debris flow event in the Halltal, Austrian Alps, using a combination of terrestrial (TLS) and airborne laser scanning (ALS) which has rarely been carried out before. A digital terrain model (DTM) derived from ALS data (pre-event surface) was combined with a DTM derived from TLS data (post-event surface). Both datasets were aligned and compared in a cut and fill analysis estimating differential volumes. The main focus lay on the evaluation and accuracy assessment of the applied method. Tie-point based registration of both datasets proved to be insufficient; additional alignment by Multi Station Adjustment was necessary to minimise the averaged height error between both datasets, amounting for a volumetric error of less than 10% which is comparable to pure ALS-campaigns. Larger errors were estimated for complex terrain with low scanning resolutions. A particular problem in data processing was the low and dense shrub vegetation in the study area which required a specifically adapted filter algorithm. An insufficient ground representation was observed for the ALS-data overestimating ground heights for averaged 70cm. Despite these limitations, the approach proved to be suitable for accurate extreme event quantification. The starting zones of the debris flows lie at the bedrock-debris interface where runoff is concentrated. Volumes of 5000 to 12,000m3 were assessed. Volume estimation worked better for the erosional than for the depositional features; this is because the erosional gullies are relatively deep and the calculation is not affected by pre-event vegetation. While erosion and sedimentation are balanced for one of the three catchments investigated, the deposited volumes are higher than the detected eroded volumes for the other two. The reasons are not fully understood. The magnitude of the flows was determined by catchment size, topographical characteristics and deforestation by a major wildfire in 1946. [Copyright &y& Elsevier]

Abstract: We examined runoff and sediment transport associated with large-scale construction projects in Fujian Province, China. Six experimental plots, comprised of four plot types, were designed to mimic typical conditions immediately following disturbance. It was found that natural vegetative cover reduces both runoff and erosion by approximately 36 and 7457 times over bare ground, and 16 and 1801 times over typically planted grasses, respectively. The increase in erosion associated with the replacement of native vegetation with bare ground or grasses due to large-scale infrastructure projects in Fujian from 1999 to 2004, amounted to an estimated loss of 1.76×107 tonnes of top soil and 3.04×108 m3 of surface runoff from the province during the bare soil construction phase, and an additional 4.25×106 tonnes of top soil and 1.35×108 m3 of surface runoff from the province associated with the first year of operation for each project. This has implications for frequency and occurrence of landslides and other geographic hazards, the transport of chemicals into waterways, the transport of goods through shipping passages, and the fertility of land in Fujian. [Copyright &y& Elsevier]

Abstract: The contributions and relationships of erosion by splash and overland flow over a steep slope in a Japanese beech forest in plots with different percentages of ground cover were examined. Three erosion plots (2m wide×5m long) with average understory coverage of 1%, 45%, and 94% were installed. Sediment transported by rain splash and by overland flow was sampled separately. For the plots with sparse, moderate, and high understory coverage, the average proportions of splash soil to total soil erosion during the monitoring period were 16%, 32%, and 18%, respectively. A significant correlation between the amount of splash soil and precipitation was found in the plots with 1% and 45% understory coverage, whereas no statistical relationship was identified for the plot with high understory coverage. At the sparse ground cover plot showing the largest sediment movement, the contribution of splash transport decreased with increasing precipitation. The amount of sheetwash erosion was significantly correlated with the amount of splash soil under the condition of sparse ground cover. This relationship was more pronounced during high precipitation events and the rainy season. Splash contribution to the sediment transport was in the range of 0.8%–76.7%, 2.8%–81% and 2.1%–60.8% for plot with high, moderate and low ground cover, respectively. The sparse ground cover showed the largest variation of splash and sheetwash contribution in soil erosion. This variability was due to variation in ground cover and soil surface wetness condition which led to a variation of detachment and non-linear relationship of sheetwash splash. [Copyright &y& Elsevier]

Abstract: Through the alteration of the physical characteristics of a landscape, such as the destruction of vegetation and the formation of a hydrophobic layer, a fire can dramatically amplify erosion rates. On the basis of field observations, it has been proposed that the deposition of a layer of ash on the ground surface can enhance the erosion of mountainous terrain by surface runoff and might even be a necessary condition for the generation of progressively bulked debris flows. In this study, a flume was constructed to investigate the role of ash in increasing both the volume and the transport capacity of runoff. The experiments demonstrated that the presence of ash on the soil surface reduces the ability of flowing water to infiltrate; this effect is even greater when the ash has been pre-wetted. In addition, the ability of ash slurries to infiltrate decreases with increasing ash concentration. The results also indicate that the transport capacity of runoff is enhanced by the incorporation of ash into the flow because of the increased fluid density. However, the addition of ash reduces the boundary Reynolds number such that, at high ash concentrations and with fine-grained sediment, sediment transport declines as the flow becomes hydraulically smooth. The experimental results were also used to evaluate the ability of steep flow fronts, a common characteristic of debris flows and flash floods, to increase sediment transport rates. Finally, it is proposed that ash slurries may evolve into progressively bulked debris flows through a positive feedback between fluid density, transport capacity, and erosivity. [Copyright &y& Elsevier]

[Display omitted] • Erosion and hydrology were studied in small eucalyptus (EC) and grassland (GC) catchments. • Two-fold higher surface runoff and sediment yield in GC compared with EC. • In El Niño year, annual sediment yield was 4.2 times greater in GC than in EC. • Hysteresis patterns showed faster sediment delivery in GC than in EC. • Well-managed commercial forests produce less runoff and erosion. Land use change in the Southern Grasslands biome with the introduction of exotic, fast-growing forest species is a controversial topic, because of the potential effect on water and soil resources. The aim of this study was to assess the effects of afforesting degraded grassland on streamflow and sedimentation in subtropical headwater catchments. Two small, headwater catchments were studied, one planted with Eucalyptus saligna (EC: 0.83 km2) and another with grasslands and extensive livestock (GC: 1.10 km2). Rainfall, runoff, and sediment discharge were monitored from September 2013 to March 2017. The results show two-fold greater surface runoff and sediment yield occurred in GC than in EC. Maximum and mean runoff coefficients were, respectively, 45.5 and 10.2% in GC, and 12.4 and 2.2% in EC; suspended sediment yield was, respectively, 67.9 and 22.4 Mg km−2 in GC and EC; and bed load sediment yield was only 0.053 and 0.006 Mg km−2. El Niño year with high rainfall produced the greatest annual sediment yield, with values 4.2 times greater in GC (167.7 Mg km−2) than in EC (39.9 Mg km−2). Hydrographs/sedimentographs synchronization and hysteresis patterns suggest faster sediment delivery in GC than in EC, but further studies are needed to conciliate sediment sources results with sediment fingerprinting. Staggered forest harvest (21% of the planted eucalyptus) led to sediment yield comparable to the observed during the pre-harvest period, and lower than in grassland catchment. In conclusion, well‐managed forest plantations, including staggered forest harvesting and preservation of riparian forest, are less prone to sedimentation than degraded grassland under intensive grazing. Well-managed afforestation of degraded lands contributes to soil conservation in the studied region, whereas low ecological performance of degraded grassland calls for soil and pasture management practices to increase forage offer to grazing animals, while conserving soil and water resources in the catchments. [ABSTRACT FROM AUTHOR]

A concept for the continuous modelling of erosion, solute and sediment transport at the catchment scale is presented. The simulation is based on the application of the OPUS model designed for single slopes. In order to apply the model at the catchment scale, the study area (54 km2) is discretized into numerous slopes. The simulation results are compared with measurements at different spatial and temporal scales of a mesoscale catchment used for drinking water supply. Three small sub-catchments, ranging between 21 and 29 ha, are used to validate the model at the local scale. Process observations at this scale are used to modify the OPUS model. While for the validation of the long-term water and solute transport daily measurements at the catchment outlet were available and used, the long-term simulation of the sediment transport is validated by analysing the sediments trapped in the drinking water reservoir.The results suggest that the model concept is applicable to a large range of scales from single events to decades and from single slopes to mesoscale catchments. However, the quality of the simulation depends on the kind of process considered. Best model results are achieved with the simulation of runoff and nitrate discharge, whereas the simulation of sediment transport is less satisfying. [Copyright &y& Elsevier]

The understanding of soil erosion processes and the development of accurate erosion prediction models require understanding of detachment, deposition, and sediment transport in rills. The objectives of this study were to determine whether sediment transport capacity is a unique value for given soil, flow rate, and slope, and to determine if equilibrium sediment concentration in the rill obtained by detachment was different from that observed under depositional conditions. Experiments on a Carmi loam (fine, mixed, mesic Typic Hapludalf) simulated rill erosion under net detachment and net deposition conditions. Two discharge rates of 6 and 9 l min−1 and two sediment input regimes of 0 and excess of transport capacity were tested on soil beds with lengths of 2, 4, 6, 7, and 8 m at 7% slope. Sediment load reached steady state conditions within the 8-m distance on the rill. At 9 l min−1 discharge, 8 m length, and excess sediment added to the flow, sediment delivery was 71 g l−1 versus 31 g l−1 for the corresponding case with no sediment added. Overall, for the conditions tested, rill flow transported two times more sediment than it could detach. The flow did not reach its maximum potential transported load through detachment of soil due in part to changes in the sediment size distribution under deposition and possibly to the protective action of bedload particles moving along the rill bottom and/or changes in flow turbulence associated with sediment laden flow. [Copyright &y& Elsevier]

• Prescribed fire promoted herbaceous growth in bare interspaces. • Litter enhanced infiltration and provided protection against erosion. • Increased vegetation cover altered flow paths and reduced runoff and soil loss. • Reduced soil surface connectivity post-fire improved hydrologic function. • Hydrologic function continues to improve 9 yr after fire. Woody species encroachment into herbaceous and shrub-dominated vegetations is a concern in many rangeland ecosystems of the world. Arrival of woody species into affected rangelands leads to changes in the spatial structure of vegetation and alterations of biophysical processes. In the western USA, encroachment of pinyon (Pinus spp.) and juniper (Juniperus spp.) tree species into sagebrush steppes poses a threat to the proper ecohydrological functioning of these ecosystems. Prescribed fire has been proposed and used as one rangeland improvement practice to restore sagebrush steppe from pinyon-juniper encroachment. Short-term effects of burning on the ecohydrologic response of these systems have been well documented and often include a period of increased hydrologic and erosion vulnerability immediately after burning. Long-term ecohydrologic response of sagebrush steppe ecosystems to fire is poorly understood due to lack of cross-scale studies on treated sites. The aim of this study is to evaluate long-term vegetation, hydrologic, and erosion responses at two pinyon-juniper-encroached sagebrush sites 9 years after prescribed fire was applied as a restoration treatment. Thirty-six rainfall simulation experiments on 6 m × 2 m plots were conducted for 45 min under two conditions: a dry run (70 mm h−1; dry antecedent soils) and a wet run (111 mm h−1; wet antecedent soils). Runoff and erosion responses were compared between burned and unburned plots. Overall, increases in herbaceous cover in the shrub-interspace areas (intercanopy area between trees) at both sites 9 years post-burn resulted in runoff- and erosion-reduction benefits, especially under the wet runs. While the initially more degraded site characterized by 80% bare ground pre-burn, registered a higher overall increase (40% increase) in canopy cover, greater post-fire reductions in runoff and erosion were observed at the less degraded site (57% bare ground pre-burn). Runoff and erosion for the wet runs decreased respectively by 6.5-fold and 76-fold at the latter site on the burned plots relative to control plots, whereas these decreases were more muted at the more degraded site (2.5 and 3-fold respectively). Significant fragmentation of flow paths observed at the more-degraded site 9 years post-fire, suggests a decreased hydrologic connectivity as a mechanism of runoff and erosion reduction during post-fire recovery. [ABSTRACT FROM AUTHOR]