•Raindrop impact increased the width and length of rills.•Rainfall plays a major role in increasing interrill erosion under high inflow rates.•Rainfall decreased the critical flow hydrodynamic ...parameters for soil loss.•Interaction between rainfall and inflow on soil loss was positive except for the lowest inflow rate.
Limited information has isolated the impacts of rainfall on rill formation and erosion on steep hillslopes where upslope inflow simultaneously exists. Field simulation experiments were conducted on steep hillslopes (26°) under rainfall (60mmh−1), inflow (6, 12, 18, 24, 30, 36Lmin−1m−1), and combination of rainfall and inflow to explore the impacts of rainfall on rill formation, and the interaction between rainfall and inflow on soil erosion. Rainfall decreased soil infiltration rate (10%–26%) mainly due to soil crust by raindrop impact. Rainfall strengthened rill formation, which behaved in the increment in rill width (5%–26%), length (4%–22%), and depth (3%–22%), but this increment decreased as inflow rates increased. Additionally, the contribution of rainfall on rill formation was most significant at the initial stage, followed by the final stage and active period of rill development. Rainfall increased rill erosion (8%–80%) and interrill erosion (36%–64%), but it played a dominant role in increasing interrill erosion under relatively high inflow rates. The most sensitive hydrodynamic parameter to soil erosion was shear stress and stream power under inflow and ‘inflow+rainfall’ conditions, respectively. For the lowest inflow rate, the reduction in soil loss by interaction between rainfall and inflow accounted for 20% of total soil loss, indicating a negative interaction. However, such interaction became positive with increasing inflow rates. The contribution rate to rill erosion by the interaction was greater than that of interrill erosion under relatively low inflow rates. Our results provide a better understanding of hillslope soil erosion mechanism.
Rill erosion processes on saturated soil slopes are important for understanding erosion hydrodynamics and determining the parameters of rill erosion models. Saturated soil slopes were innovatively ...created to investigate the rill erosion processes. Rill erosion processes on saturated soil slopes were modelled by using the sediment concentrations determined by sediment transport capacities (STCs) measurement and the sediment concentrations at different rill lengths. Laboratory experiments were performed under varying slope gradients (5°, 10°, 15°, and 20°) and unit‐width flow rates (0.33, 0.67, and 1.33 × 10−3 m3 s−1 m−1) to measure sediment concentrations at different rill lengths (1, 2, 4, and 8 m) on saturated soil slopes. The measured sediment concentrations along saturated rills ranged from 134.54 to 1,064.47 kg/m3, and also increased exponentially with rill length similar to non‐saturated rills. The model of the rill erosion process in non‐saturated soil rills was applicable to that in saturated soil rills. However, the sediment concentration of the rill flow increased much faster, with the increase in rill length, to considerably higher levels at STCs. The saturated soil rills produced 120–560% more sediments than the non‐saturated ones. Moreover, the former eroded remarkably faster in the beginning section of the rills, as compared with that on the non‐saturated soil slopes. This dataset serves as the basis for determining the erosion parameters in the process‐based erosion models on saturated soil slopes.
A series of laboratory experiments on saturated soil slope were performed under various hydraulic conditions involving four slopes and three unit‐width flow rates. The measurements of erosion process and the sediment concentrations at the STC level were used to model the rill erosion process as a function of rill length. We concluded that the saturation of rill bed enhanced erosion, and saturated soil rills were eroded remarkably faster within the beginning rill section than the non‐saturated ones.
This article focuses on the need to improve current knowledge of sedimentation and erosion processes in small reservoirs using the example of the Pocheň reservoir (Czech Republic). We combined data ...from sediment cores with unmanned aerial vehicle imaging and ground-penetrating radar survey data. The results show a distinct sediment distribution, grain-size gradient, petrophysical properties, and geochemistry. Sediment thickness increases in the proximal-to-distal direction (from the inflow to the dam) with frequent erosion near the inflow, especially during floods. This contributed to the sediment relocation towards distal sites with a tendency towards downstream accretion. After reservoir flushing, sedimentation processes were replaced by drawdown-enhanced erosion. Considerable erosion occurred along a temporary drawdown channel, resulting in headward erosion and channel incision. Lateral erosion resulted in drawdown-channel widening. The most extensive lateral erosion took place in the middle part of the reservoir, where the channel created a complex multichannel-branched system.
Controlling soil erosion, especially in its initial stages, is greatly important in natural resources management. Consequently, the present research aimed to control splash and interrill erosion in ...two soil types (marl at Marzan-Abad and loess at Maraveh-Tapeh sites in northern Iran) using biochar (BC) and polyacrylamide (PAM). We established 0.5 × 0.5-m plots and applied BC (800 g·m−2), PAM (2 g·m−2), and BC + PAM (800 g·m−2 + 2 g·m−2) with control plots and three replications on a slope of ~25%. We used a rainfall simulator to achieve rainfall intensity of 50 mm·h−1 with 30-min duration in the experiments. Analysis of the results obtained from the variables of splash and interrill erosion during the rainfall-runoff process showed that the PAM significantly (p ≤ 0.05) increased all study variables of splash erosion. For interrill erosion, it reduced the variables of soil loss and sediment concentration. However, the difference was not significant (p > 0.05) compared to the control plot and runoff from the two treatment sites increased relative to that from the control plots. The plot treated with BC showed decreased runoff volume, runoff coefficient, and soil loss compared to the control plot at the Marzan-Abad site, but the differences were not statistically significant (p > 0.05). However, the plot in which loess soil was treated with BC at the Maraveh-Tapeh site exhibited considerably (p ≤ 0.05) increased runoff and soil loss compared to the control plot. The entire results verified a wide range for benefit reduction of study treatments from +25.09 to −37.49% for runoff and from +38.59 to −231% for soil loss with more effectiveness for Maraveh-Tapeh Loess soil as well as combined application of BC and PAM. These findings contribute to improved understanding of proper application of soil amendments to control runoff and soil loss in loam and loess soils.
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•Hydrologic processes in biochar and/or polyacrylamide-treated soil were studied.•Effects of the treatments were studied on runoff/soil loss in semi-filed condition.•Polyacrylamide effectively reduced soil loss in marl and loess soils.•Biochar differently affected runoff and soil loss control in marl and loess soils.
A dynamic model of soil erosion along hillslopes considering soil detachment and sediment transport is still a major challenge in terms of its applicability to field conditions. Data availability for ...model calibration and validation is very limited for physically process models. An improved hillslope erosion dynamic model (HED) with a simple structure and strong application on field plots was established based on the sediment feedback mechanism in this study. Observed runoff and sediment data from field plots with slope gradients of 14.1 %-62.5 % and slope lengths of 7.9-64.7 m within runoff events for the Chagagou catchment on the Loess Plateau of China were used to evaluate the HED. We confirmed that the power function can reproduce the soil detachment capacity (Φ) and sediment transport capacity (T
) under varying field slope conditions (gradients and lengths). The two parameters associated with the power function of Φ or T
are consistent across the variable conditions. When the HED model simulates the process and event sediment discharge, the unified model parameters could be obtained. The simulation precision of above results ranged from 0.44 to 0.95 for Nash-Sutcliffe simulation efficiency (NSE), from 0.65 to 0.96 for R
and from -32.37 % to 31.61 % for relative error (RE). The feedback term of HED was close to one as the slope length approached zero. Decreasing of sediment yield as slope length increased was quite consistent with the measured data due to the reasonable sediment feedback term. The critical slope lengths were more easily reached, and the feedback term value along the slope decreased more rapidly at steeper slopes and higher runoff events. HED can be further integrated into distributed watershed models for predicting sediment discharge within runoff events.
Simulated rainfall experiments were performed on bare, undecomposed litter layer and semi‐decomposed litter layer slopes with litter biomasses of 0, 50, 100 and 150 g m−2, respectively, to evaluate ...the effect of the undecomposed layer and semi‐decomposed layer of Quercus variabilis litter on the soil erosion process and the particle size distribution of eroded sediment. The undecomposed layer and semi‐decomposed layer of litter reduced the runoff rate by 10.91–27.04% and 12.91–36.05%, respectively, and the erosion rate by 13.35–40.98% and 17.16–59.46%, respectively. The percentage of smaller particles (clay and fine silt particles) decreased and the percentage of larger particles (coarse silt and sand particles) increased with an increased rainfall duration on all treated slopes, while the extent of the eroded sediment particle content varied among the treated slopes with the rainfall duration, with bare slopes exhibiting the largest variability, followed by undecomposed litter layer slopes and finally semi‐decomposed litter layer slopes. The clay and sand particles were transported as aggregates, and fine silt and coarse silt particles were transported as primary particles. Compared with the original soil, sediment eroded from all treated slopes was mainly enriched in smaller particles. Furthermore, the loss of the smaller particles from the undecomposed litter layer slopes was lower than that from the semi‐decomposed litter layer slopes, indicating that the undecomposed litter layer alleviated soil coarsening to some extent. The findings from this study improve our understanding of how litter regulates slope erosion and provide a reference for effectively controlling soil erosion.
The runoff and erosion reduction rates provided by the semi‐decomposed litter layer slopes were greater than those with the undecomposed litter layer slopes, respectively.
The percentage of smaller particles decreased and the percentage of larger particles increased as rainfall duration increased on all treated slopes.
The less loss of the smaller particles from the undecomposed litter layer slopes was observed than from the semi‐decomposed litter layer slopes.
► Transport processes of soil particles under simulated rainfall were investigated. ► There were at least two different mechanisms affecting particle transport. ► Relative importance of the two ...mechanisms was related to flow stream power. ► Bed-load transport was an important mechanism during rill erosion processes.
Sediment size distribution greatly affects sediment transport and deposition. A better understanding of sediment sorting will improve understanding of erosion and sedimentation processes, which in turn will improve erosion modeling. To address this issue, a total of 12 rainfall simulation experiments were conducted in a 1m by 5m box with varying steep slopes (10°, 15°, 20° and 25°), and the simulated rainfall lasted for 1h at a rate of 90mmh−1. For each simulated event, runoff and sediment were sampled at 3-min intervals, which were performed to study in detail the temporal change in size distribution of the eroded materials. These data were used to interpret the real-time sequence of transport mechanisms acting in response to the simulated rainfall. Total soil loss is the sum of suspended, saltating and contact loads. The proportion of sediment<0.002mm showed little temporal fluctuation (generally 12–14%), although it was highly correlated to instantaneous rain power (R2=0.452, P<0.01, n=120). Suspension–saltation transports the finer than 0.054mm size sediment was the most important erosion mechanism during interrill erosion processes. However, after rill development on hillslopes, bed-load transport by rolling of medium to large-sized sediment particles (coarser than 0.152mm) became an increasingly important transport mechanism, and it were also enhanced by increased slope. Overall, the study supports a strong relationship between the sediment transport of contact (rolling) load and stream power. The partition of soil loss into these more meaningful components appears to be essential both for initial data interpretation and for subsequent use of such data for soil loss prediction.
•Sediment size distribution was crucial for SOC and SIC transport.•SIC content was largely determined by coarse particles.•Selective transport processes varied the proportion of SOC and SIC in ...eroding sites.
The soil carbon (C) reservoir involves soil organic and inorganic carbon stocks. The influence of soil erosion processes on soil organic carbon (SOC) migration has been investigated in the literature, but the influence on soil inorganic carbon (SIC) remains uncertain. Variations in the proportion of SOC and SIC in eroded sediment can influence C cycling, so we conducted a detailed laboratory study to investigate the selective transport of SOC and SIC in eroded sediment in treatments with different raindrop sizes and inflow rates. We used the boosted regression trees (BRT) models to estimate the SOC and SIC contents according to the ratio of flow depth and raindrop diameter (h/D), the maximum shear stress (τ*max), the runoff rate, the stream power (ω), the sediment concentration (SC), the soil loss rate (SLR), and various particle-related factors, including D50, D4,3, D3,2, clay content, silt content and sand content of non-dispersed sediment. The BRT model explained 42.1% and 56.1% of the variation in the SOC and SIC contents in the sediment, respectively. The relative importance of particle-related factors was approximately 50%, demonstrating that the particle size distribution (PSD) of sediment was a crucial factor for both SOC and SIC transport. The SOC content was sensitive to the presence of fine particles, while the SIC content was largely determined by coarse particles because smaller particles with a higher specific surface area tended to adsorb more SOC whereas coarser particles contained more carbonates in the form of binding agents. In sediment under intensive rainfall on steep slopes, the SOC tended to be depleted, while the SIC was slightly enriched. Our study demonstrates that both SIC and SOC were selectively transported by water erosion and fills gaps in this field of research. Moreover, this work implies that the PSD of the sediment provides important information about the variation in SOC and SIC and should be considered when modelling the global C cycle.
Achieving change through gully erosion research Wilkinson, Scott N.; Rutherfurd, Ian D.; Brooks, Andrew P. ...
Earth surface processes and landforms,
January 2024, 2024-01-00, 20240101, Volume:
49, Issue:
1
Journal Article
Peer reviewed
Open access
This is an introduction to a special issue arising from the 8th International Conference on Gully Erosion, held in Townsville, Australia in 2019. Research has improved understanding of gully erosion ...processes and increasingly emphasizes sophisticated near‐and‐remotely sensed methods to characterize and measure gullies. These data can then be analysed using equally sophisticated models and scenarios can be simulated. These advances improve the capacity to predict gully initiation and development over time and space. It is often assumed that better prediction translates into greater impact and uptake of research to solve real world gully erosion problems. Examples of impressive associations between research programmes and major gully management programmes are evident. However, there has been little assessment of the impact of gully research. We argue for a greater focus on achieving impact including interventions that better manage and prevent gully erosion. Opportunities to deliver research impact are assessed using three indicators of progression towards impact; the practical usability of research, whether it is in use by non‐researchers, and whether it is useful in guiding improvements in management. Like other natural hazards, gully erosion is a phenomenon of the social, economic and environmental context in which it occurs. Defining the contexts and consequences of gully erosion and using these to frame further research is therefore a means to increase research impact. Enhancing collaboration between research disciplines and with practitioners who act on the research, and a greater focus on the translation of results into practice, is another avenue. Expanding the monitoring and evaluation of gully management can better demonstrate the impact of past research and enable further useful investigations. We urge gully erosion researchers to consider the potential impact of their research, including how it can more effectively inform better and more cost‐effective management and political decisions.
Following the 8th International Symposium on Gully Erosion we propose an increased focus on research impact on gully management and prevention, by defining the consequences of gully erosion, enhancing collaboration, focusing on use by practitioners, and expanding monitoring and evaluation.
