Artificial Rainfall Experiments Research Articles

The effects of herbs on the runoff and sediment-producing mechanism in Jinyang Ancient City

Abstract To study the effects of herbs on the runoff and sediment producing mechanism of Jinyang Ancient City, this study used the method of field artificial rainfall experiments to compare the earthen sites slope effects on the runoff producing, sediment producing, and soil infiltration of the plant slope surface in different periods. The conclusions are as follows. The phenomenon of petrichor was related to the withered herb coverage on the surface of the slope. The fluctuation amplitude of the soil volume moisture content was related to its distance to the surface. The runoff producing effects of different slopes were in descending order of Bare Soil slope, Fresh Herbs slope, and Withered Herbs slope. The sediment producing effects were in descending order of Bare Soil slope, Withered Herbs slope, and Fresh Herbs slope. The sediment yield intensity was positively correlated with runoff intensity, but its variation peak lagged slightly behind the latter. The runoff intensity and sediment yield was influenced by the dual effects of rainfall intensity and rainfall time, and sometimes the impact of rainfall time was higher than that of rainfall intensity. A research assistance in can be hopefully provided in this study on protecting earthen sites from rainfall erosion through plant covering.

Runoff generation and erosion processes at the rock–soil interface of outcrops with a concave surface in a rocky desertification area

Rock surface flow, originating from outcrop surfaces during rainfall, represents a distinctive form of runoff influencing surface erosion and subsurface soil leakage in karst rocky desertification areas. Despite their significance, the processes governing runoff generation and erosion at the rock–soil interface (RSI) under the influence of rock surface flow remain poorly understood. This study aims to elucidate the generation and transformation of runoff at the RSI, along with their scouring erosion effects influenced by rock surface flow from concave-shaped outcrops. Artificial rainfall experiments were conducted on simulated rock–soil structural units featuring exposed rock surfaces and unexposed RSIs of outcrops with concave shapes. Two driving factors, namely rainfall intensity (R) and the inclination of the rock surface (IRS), were manipulated to investigate the formation and output processes of runoffs and sediments from the surface, RSI, and non-RSI (a site away from the RSI). The presence of an exposed rock surface altered the distribution pattern of rainfall–infiltration–runoff. An increase in the IRS led to a significant decrease in surface runoff (p < 0.05). When the IRS was close to vertical, the rainfall-runoff was primarily in the form of surface runoff; however, for inclinations less than 90°, the primary contributors to rainfall-runoff were the RSI and non-RSI runoffs. Surface soil erosion emerged as the predominant form of soil loss, with runoff yield demonstrating a linear positive correlation with sediment production. Both the IRS and R were identified as significant factors affecting surface runoff and soil erosion. Notably, when the IRS was less than 45°, the total soil loss reached its minimum. Therefore, runoff generation at the RSI led to a reduction in surface runoff and an increase in subsurface runoff, contributing to soil leakage at the RSI. Nevertheless, surface erosion remained the primary mechanism of soil loss.

Subsurface flow aggravates the soil erosion on steep slopes in karst post-mining areas

On karst steep slopes, subsurface flow frequently emerges at the rock-soil interface, thereby exacerbating soil erosion. However, there have been few studies that quantitatively assess the impact of subsurface flow on soil erosion in this region. We conducted indoor artificial rainfall experiments to observe runoff and sediment yield under two conditions: with subsurface flow (SF) and without subsurface flow input (WSF). We considered various rainfall intensities (30 mm h−1, 60 mm h−1, 90 mm h−1) and slope gradients (30°, 35°, 40°). The results demonstrated that the presence of subsurface flow significantly amplified both surface runoff and sediment yield, while also intensifying the influence of rainfall intensity and slope gradient on runoff and sediment yield. Compared to WSF, under SF conditions, surface runoff increased by 1.55 to 4.43 times, and sediment yield increased by 4.60 to 8.72 times. Slope gradient played a substantial role in soil loss, while rainfall intensity primarily impacted surface runoff. Under WSF conditions, soil loss only occurred at a 40° slope gradient or under a rainfall intensity of 90 mm h−1, whereas under SF conditions, soil loss could occur at a 30° slope gradient or under a rainfall intensity of 30 mm h−1. This research provides a scientific foundation for a more profound understanding of the mechanisms driving soil erosion on karst slopes, particularly in the context of subsurface flow.

Experimental study on the failure of loose accumulation landslides under rainfall conditions

Rainfall plays a pivotal role in triggering the failure of loose accumulation landslides. To understand their stability, it is essential to explore the deformation, failure patterns, fine particle migration, and infiltration behavior of such landslides under rainy conditions. Employing the Yuqiupo landslide as a case study, this research dissects the fundamental attributes of the Yuqiupo landslide through geological examinations. Moreover, the study replicates the failure of the loose accumulation landslide via artificial rainfall experiments. By employing acquired data on soil volumetric water content and matrix suction from these experiments and observing measurable shifts in the landslide’s failure progression and rainfall circumstances, the water-hydraulic conditions of the accumulation landslide are meticulously dissected. The conducted experiments disclose that the failure of the loose accumulation landslide emanates from the combined effects of preferential flow and matrix flow within unsaturated conditions. Rainfall triggers an elevation in soil moisture content and a concurrent decrease in matrix suction, compromising the slope’s stability and ultimately causing the landslide. Furthermore, our research includes a quantitative analysis of changes in particle size distribution before and after the landslide’s failure. This endeavor underscores the influence of distinct failure modes on the migration of fine particles, with these migration patterns distinctly shaped by prevailing rainfall conditions.

Glyphosate spraying exacerbates nitrogen and phosphorus loss in karst slope farmland.

Glyphosate herbicide is an indispensable material in agricultural production. In order to explore the potential environmental effects of glyphosate application in karst slope farmland, this paper used a variable slope steel tank to simulate the surface microtopography and underground pore structure characteristics of karst slope farmland, and combined with artificial rainfall experiments to explore the migration path of glyphosate in karst slope farmland and the impact of spraying glyphosate on soil nitrogen and phosphorus loss. The results showed that under the condition of heavy rain, glyphosate in karst slope farmland was mainly transported and diffused by surface runoff, supplemented by underground runoff; secondly, in different hydrological paths, glyphosate directly affected the content of nitrogen and phosphorus in runoff, and all showed extremely significant positive correlation (p < 0.001). In addition, rainfall conditions such as rainfall intensity, rainfall duration, and runoff affected the content of nitrogen and phosphorus in runoff to varying degrees. In conclusion, the application of glyphosate significantly increased the content of nitrogen and phosphorus in different runoff and accelerated the loss of nitrogen and phosphorus from soil, which not only led to soil degradation, but also threatened the safety of aquatic ecosystem. Therefore, in the prevention and control of agricultural non-point source pollution, the threat of glyphosate to the surrounding aquatic ecosystem cannot be ignored, especially in karst areas with frequent rainstorms and serious water erosion, long-term monitoring and risk assessment of glyphosate are needed.

Exploring watershed structural variation during watershed evolution process under artificial rainfall experiment

Exploring watershed structural variation during watershed evolution process under artificial rainfall experiment

Response relationship between vegetation structure and runoff-sediment yield in the hilly and gully area of the Loess Plateau, China

The structure of the vegetation has a significant impact on how much runoff and sediment is produced. Choosing the right parameters to evaluate the correlations between vegetation and runoff-sediment yield, however, is fraught with uncertainty. We chose 18 vegetation plots with a range of vegetation types and structural characteristics for this study to investigate the applicability of various vegetation structure parameters in identify in the response relationship between vegetation and runoff-sediment yield through field artificial rainfall experiments. The vegetation coverage, stratified vegetation cover index (Cs), species diversity and functional diversity were among the criteria of vegetation structure. The findings revealed that: (1) There was a significant difference in the runoff start time and sediment yield differed significantly between vegetation types, with shrub communities having a longer start time and the lowest sediment yield; (2) The vegetation coverage of the community had a significant impact on the runoff start time and, when combined with Cs, explained 48% of the runoff start time. (3) Simpson index (D) and functional richness (FRic) significantly influenced the total runoff yield and along with Cs explained 46% of the total runoff yield. Cs, coverage and FRic also positively influenced the runoff end time, with a total explanation of 29%. Functional divergence (FDiv) had a significant negative effect on the total sediment yield. Together with coverage and Cs, FDiv explained 66% of the total sediment yield. These results demonstrated how biodiversity consideration helped to clarify connections between vegetation structure and runoff-sediment yield.

Forecasting the Failure Time of an Expansive Soil Slope Using Digital Image Correlation under Rainfall Infiltration Conditions

Expansive soil is one of the most widely distributed special soils in the world. It is widely developed in Henan, Anhui, Guangxi and other places in China, and highly overlaps with densely populated and economically active areas. Expansive soil is considered a typical “problematic soil” because its mechanical behaviour is very sensitive to water content changes; such behaviour mainly manifests as swelling upon wetting and shrinking upon drying, so the presence of expansive soil is an important factor in mountain landslide disasters in southern China. Because the particularities of its constituent materials are related to typical physical and mechanical properties, forecasting the failure times of expansive soil slopes remains a global problem. In this study, a series of in situ artificial rainfall experiments were conducted on an excavated expansive soil slope; then, the digital image correlation (DIC) method was applied to monitor the slope surface deformation and crack development. Finally, the failure time of the slope was forecasted using the inverse velocity (INV) and slope (SLO) models. The study results show that the deformation and failure processes of the analysed expansive soil slope had an obvious crack control effect, and the displacement–time curve derived by the DIC method had an obvious “phased change law”. The data points calculated by the INV method were discrete and had high linear fitting requirements, resulting in large failure time forecasts. When the SLO method was used to forecast the failure time, because the values derived in the stable deformation stage were relatively concentrated in the calculation process, an obvious linear relationship was found in only the accelerated deformation stage, so the prediction results were more accurate. Therefore, the SLO method should be preferentially used to forecast the failure of expansive soil slopes with “step-like” displacement. These results enabled us to characterize slide processes and identify the mechanism responsible for the movement of a rainfall-induced expansive soil landslide. The stage deformation and failure mode of expansive soil landslide under rainfall infiltration: “slow deformation—stable deformation—accelerated deformation—instability failure” was revealed. This study is helpful for determining the deformation and failure mechanism of rainfall-induced expansive soil landslide and forecasting expansive soil landslides and providing guidance for controlling landslide hazards in expansive soil areas.

Experimental study of rock wool on the farmland soil erosion and crop growth of winter wheat and its comprehensive evaluation

Introduction: Droughts and flooding occur frequently due to climate change and human activities, which have significantly affected the ecological environment of farmland and crop production. Rock wool (RW) has some properties like high porosity and water retention capacity, and it is widely used in green roofing and agricultural production to reduce flood and drought disaster.Methods: We set 24 artificial rainfall experiments to analyze the impact of RW on the farmland runoff, soil water storage capacity (SWSC), nitrogen and phosphorus loss and crop growth. Finally, the Critic-Entropy comprehensive evaluation method was used to select the best solution for RW embedding.Results: The result shows that RW could reduce the runoff by 49.6%–93.3%, and it made the SWSC increase by .2%–11% Vol in the 10–70 cm depth. During the runoff process, the concentration of nitrogen and phosphorus decreased with the increase of the RW volume, while the nitrogen and phosphorus loss reduced by 51.9%–96.6% and 72.4%–96.4% respectively when RW was buried in the farmland, so RW could effectively promote soil and water conservation. Finally, RW increased the plant biomass and yield by a maximum of 12.1% and 20.4% respectively due to the large retention of water and nutrients. Therefore, combined with the above experimental result, this study indicates that RW could obtain the best comprehensive benefit in the embedding volume of 536.73 m3/ha.Discussion: When the volume of RW embedding was too large, RW easily caused insufficient water storage in short-duration rainfall or irrigation, which made the RW unable to release water to alleviate the soil water deficit during the critical growth period, which may result in drought events being aggravated and crop yield reduced. Overall, this study is conducive to clarifying the comprehensive application effect of RW in agricultural production, pollution control, and urban landscape, and it provides an important basis for expanding its application field and promoting the stability of farmland ecosystems.

Investigating the effect of biochar application on raindrop-driven soil erosion under laboratory rainfall experiments

Rainfall soil erosion is mainly initiated by raindrop splashing. Many studies have addressed the role of biochar in water and soil conservation; however, the processes and mechanisms of soil erosion via raindrop splashing with biochar application remain unclear. Thus, this study investigated raindrop-driven erosion in a silt loam red soil mixed with different ratios of biochar (i.e., 0, 3 %, and 5 %) and groups with different biochar particle sizes (i.e., <0.5, 0.5–1, and 1–2 mm) under artificial rainfall experiments with a high rainfall intensity (68.5 mm/h). A Hydrus 1D combined Rose soil erosion model was employed to explain the hydro-erosion processes. Our experimental results showed that the maximum suspended sediment concentration (SSC) eroded in the surface runoff increased from 12.77 to 14.15 and 15.41 g/L as the amount of biochar application increased from 0 to 3 % and 5 %, respectively. Owing to the decreased infiltration capability, increased surface runoff volume and SSC resulted in the largest amount of suspended sediment (SS) in the 5 % biochar group. Moreover, the biochar grain size also affected raindrop-driven erosion. The mid-sized biochar (0.5–1 mm) had the highest effect on the SSC and the total amount of SS; however, the finer biochar (<0.5 mm) inhibited SS accumulation. Model simulations indicated that biochar application potentially increased the fraction of erodible particles and soil detachability, thereby enhancing raindrop splash erosion. Given that contaminants could diffuse as solid bound (i.e., soil and biochar) and dissolved forms, the trade-off between decreased leaching and increased surface load, or vice versa, under biochar application requires further research to evaluate the associated environmental transport and fate.

Near surface roughness estimation: A parameterization derived from artificial rainfall experiments and two-dimensional hydrodynamic modelling for multiple vegetation coverages

Roughness is the key parameter for surface runoff simulations. This study aims to determine robust Manning resistance coefficients (n) on the basis of consecutive artificial rainfall experiments on natural hillslopes available in literature, obtained at 22 different sites with different degrees of vegetation cover and type. The Manning resistance coefficient is particularly important in the context of two-dimensional (2D) hydraulic heavy rainfall simulations. Since there is a wide range of possible resistance values available leading to significantly different results regarding the accumulation of surface runoff, especially for shallow water depths. The planning of flood protection structures is directly affected by these uncertainties. This work also improves the knowledge between roughness and the shape of the hydrograph allowing a better calibration of infiltration models. As flow velocity, water depth, and infiltration rate were not observed during the rainfall experiments, only the outflow of the test field and rain intensity are known. For this purpose, a framework was developed to parameterize shallow water depth (<1 cm) -dependent roughness coefficients. To test the robustness of the framework, three different formulations of depth-dependent roughness and a constant Manning coefficient are used by comparing the measured discharge under different rainfall intensities with simulations in a 2D-hydraulic model. We identified a strong dependency of Manning’s n on the degree of vegetation cover and -type as well as an influence of consecutive rainfall events. This finally leads to a more robust parameterization of near surface roughness for hydrodynamic modelling, which is particularly important for the simulation of heavy rainfall events.

Effects of subsurface rock fragment layers caused by simulated hoeing on near-surface rainfall-runoff processes

In hilly agricultural landscapes with shallow soil, cultivation activities can cause the fragmentation of bedrock and induce vertical spatial heterogeneity of rock fragments, modifying the hillslope architecture and flow paths. Previous research mainly focused on the impact of rock fragments in the topsoil on surface runoff, but the role of subsurface rock fragments in rainfall-runoff processes has received less attention. In order to investigate the role of the subsurface rock fragment layer in rainfall-runoff processes through artificial rainfall experiments, we used sieved soil to establish soil layers with thickness of 10 cm and subsurface rock fragment layers related to hoeing depths from 10 to 16 cm under the soil layer. Additionally, a rubber plate was employed to initiate subsurface flow and deep percolation during the rainfall experiments. Results show that the presence of subsurface rock fragment layers mainly influenced the runoff partitioning between subsurface flow and deep percolation, but had little effect on surface flow. When there was no subsurface rock fragment layer, the yields of subsurface flow and deep percolation were in the ranges of 2.78–5.32 mm and 6.35–25.52 mm, respectively, under 15° slope and 15–120 mm h−1 rainfall intensities. The presence of subsurface rock fragment layers resulted in a 30–110% increase of subsurface flow, compared with no subsurface rock fragment layer, and it resulted in deep percolation decreasing by 4–48%. Subsurface rock fragment layers with substantial thickness and content of coarse rock fragments facilitated runoff partitioning into subsurface flow, but reduced the fraction of deep percolation. Rainfall intensity and slope steepness both exerted positive effects on the magnitude of subsurface flow and deep percolation within the thresholds of 60 mm h−1 and 15°, respectively. With increasing rainfall intensity (or slope steepness), subsurface flow yield increased apparently for the thick subsurface layer with substantial coarse rock fragments. It indicates that the thick subsurface rock fragment layer with high content of large-sized particles together with the great rainfall intensity (or steep slope) can result in substantial lateral subsurface flow. This study has important implications for the management of water and environment in hilly agricultural landscapes.

Effects of the extreme rainfall events on particle size selectivity on the simulated Gobi surface using indoor rainfall experiments

Understanding the particle size selectivity characteristics by rainfalls in the Gobi is of significance to the assessment and projection of the potential sources for the dust emissions. The particle size selectivity characteristics by extreme rainfall events and their correlations with rainfall characteristics and erosion processes were specifically investigated using indoor artificial rainfall experiments. The soils were collected from the Ala Shan Gobi, where was recognized as the major potential sources of dust emissions in Central Asia. The fine particles (<50 μm) on-slope after rainfall event were significantly (P < 0.05) higher than the original value at rainfall intensity of 15 mm h−1, but they were significantly (P < 0.05) lower than the original value at other rainfall intensities (except 60 mm h−1) with different particle sorting mechanisms. The selectivity of the fine particles (<50 μm) by rainfall was higher under 20 mm h−1 and 40 mm h−1, as the medium particle size (d50) of the eroded sediment was significantly (P < 0.05) lower than the original value and the fine particles (<50 µm) enrichment ratio (ERf) of the eroded sediment was dramatically high (4.3 ± 1.0 at 20 mm h−1 and 3.5 ± 0.9 at 40 mm h−1). No significant fine particle sorting was showed both on-slope and in the eroded sediment at 60 mm h−1. The correlation analysis suggested that fine particle selectivity in the eroded sediment was more related with rainfall intensity, runoff rate and flow hydrodynamics. Implications of these findings for effects of the extreme rainfalls on the potential dust sources in the Ala Shan Gobi were presented and it could provide the scientific basis for the prediction of potential dust emission in the Ala Shan Gobi areas in the future.

Hydraulic modeling of water flow in the thick vadose zone under precipitation

Data from field monitoring and artificial rainfall experiments suggest that the thick vadose zone can be divided into two sub-zones based on soil water variation, namely the active and steady zones. The soil water content of the top active zone (2–5 m depth) is sensitive to precipitation and evaporation and dominated by transient water flow. Soil water content of the underlying steady zone remains constant over time and there is a steady flow under the force of gravity. However, since the transition from transient flow to steady flow is difficult to observe in nature, the physical mechanism of this transition remains poorly understood. This study establishes a hydraulic model to visually demonstrate water flow in the entire vadose zone under multiple infiltration events. The model comprises of a series vertically aligned water tanks, each with a small outlet at the bottom, and each representing a soil unit. The water level in a tank represents the water content and the related permeability of the soil unit. The results of an experiment conducted with the model clearly show that transient flow in the upper active zone will transfer to steady flow. A zoomed out data with an annual rainfall record at a site in the central Chinese Loess Plateau is applied in the model to simulate the water content and the flow state of the vertical profile, and the results are in accordance with in-situ monitoring data. The outcomes of this study suggest that although water content in the steady zone remains unchanged, there is a constant steady flow seeping downward through the zone, acting as a typical source of groundwater recharge in the loess region.

Rainfall Infiltration under Various Building Layouts Using Concrete Microseepage Wells

Low-impact development measures are a kind of ecological technology system that can easily realize urban rainwater collection and utilization to alleviate the contradiction between flooding/water logging disasters and water shortages. But most of the low-impact development measures are difficult to solve the problem of deep soil infiltration and fully utilize runoff regulation and seepage benefits. Therefore, this paper proposes the concrete microseepage well with the optimum proportion of crushed stone, cement, and water of 1 : 0.13 : 0.11 and 2% steel fiber content. The artificial rainfall experiment is applied to verify the high-infiltration of concrete microseepage well in deep soil. The numerical analysis shows that the concrete microseepage well around a single building and two adjacent buildings can all decrease 15%–40% of the pore water pressure, decrease 11%–33% of total head, and improve 43–55 times of infiltration velocity. The concrete microseepage well with 0.1 m in diameter and 1 m in height can affect the infiltration area of 1 m2. Each building being surrounded by seepage wells is the optimal layout scheme to alleviate the flooding/water logging disasters. This study provides a scientific reference for the development of sponge cities with low-impact development measures to reduce the problem of flooding/water logging disasters and water shortages.

Phosphorus fluxes in two contrasting forest soils along preferential pathways after experimental N and P additions

The assessment of impacts of an altered nutrient availability, e.g. as caused by consistently high atmospheric nitrogen (N) deposition, on ecosystem phosphorus (P) nutrition requires understanding of P fluxes. However, the P translocation in forest soils is not well understood and soil P fluxes based on actual measurements are rarely available. Therefore, the aims of this study were to (1) examine the effects of experimental N, P, and P+N additions on P fluxes via preferential flow as dominant transport pathway (PFPs) for P transport in forest soils; and (2) determine whether these effects varied with sites of contrasting P status (loamy high P/sandy low P). During artificial rainfall experiments, we quantified the P fluxes in three soil depths and statistically analyzed effects by application of linear mixed effects modeling. Our results show that the magnitude of P fluxes is highly variable: In some cases, water and consequently P has not reached the collection depth. By contrast, in soils with a well-developed connection of PFPs throughout the profile fluxes up to 4.5 mg P m−2 per experiment (within 8 h, no P addition) were observed. The results furthermore support the assumption that the contrasting P nutrition strategies strongly affected P fluxes, while also the response to N and P addition markedly differed between the sites. As a consequence, the main factors determining P translocation in forest soils under altered nutrient availability are the spatio-temporal patterns of PFPs through soil columns in combination with the P nutrition strategy of the ecosystem.

Effects of spatial variations in rock fragments related to tillage on hydrological processes and sediment transport

Cultivation activities play an important role in shaping the spatial distribution of rock fragments in hilly agricultural landscapes. The spatial variation in rock fragment contents (SVRFC) can exert strong effects on the spatial heterogeneity of soil properties with great implications for hydrological fluxes and soil erosion. However, previous research always assumed that rock fragments were homogenously distributed, but little has been known concerning the SVRFC over the hillslope and its influence on hydrological and erosional processes. In this study, simulated rock fragment contents (RFCs) in soil layers at the upper (0.6 kg kg−1) and lower slope positions (0, 0.2, 0.4 and 0.6 kg kg−1) were established in combination with artificial rainfall experiments, to investigate the influence of RFC difference between the upper and lower slope positions on hydrological and erosional processes. Results show that the decreasing RFC difference reduced the yield of surface flow (5–100%), but increased yields of subsurface flow (58–792%) and deep percolation (19–130%). Additionally, the decreasing RFC difference reduced the runoff velocity of surface flow and surface erosion rate, but aggravated subsurface erosion. Especially under the 0 kg kg−1 RFC difference, the intense soil loss occurred at the subsurface which may be due to the highly developed preferential flow. With increasing rainfall intensity, great increments in yields of subsurface flow, deep percolation and subsurface sediments were found under the small RFC difference which had small increments in yields of surface flow and surface sediments. These results suggest that the changing SVRFC related to tillage erosion can exert strong influence on behaviors of hydrological and erosional processes. Our study provides a better understanding of the interaction between agricultural cultivation and soil–water loss in hilly agricultural landscapes.

Diffuse nutrient export dynamics from accumulated litterfall in forested watersheds with remote sensing data coupled model

Nutrients exported from forest litterfall significantly contribute to the global cycling of elements and the water quality in watersheds. Simulating the watershed discharge load is challenging because of the combined effects of the decomposing litterfall and topographic heterogeneity. We quantified the contribution of diffuse nutrient export from forest litterfall in a low temperature watershed using artificial rainfall experiments and watershed territorial modeling with remote sensing data, and therefore, the critical spatial factors and corresponding nutrient export dynamics were identified. Rainfall intensity and terrain slope were found to be the key factors for nutrient export under different litterfall decomposition conditions. Based on the moderate resolution imaging spectroradiometer data and field observations, the temporal patterns of litterfall biomass of two types of dominant forests (broad-leaved and mixed) were interpreted. The spatial patterns of total organic carbon (TOC), total nitrogen (TN), and total phosphorus (TP) exports from watershed litterfall were simulated by coupling the observed discharge parameters under artificial rainfall conditions and watershed surface flow modeling with the hydrological characteristics of the forested areas. The average watershed TOC, TN, and TP loads exported from the litterfall were approximately 58.22, 7.89, and 0.37 kg ha−1 a−1, respectively. The exported loads of TOC, TN, and TP varied with the forest types, and the loads from the litterfall of deciduous broad-leaved forest were found to be ∼50–70% of loads from the litterfall of mixed forest. A comparison with similar studies worldwide also indicated that low temperature decreased the litterfall decomposition rate and diffuse nutrient export. This study indicated that litterfall nutrients were a key contributor to watershed water pollution, and their spatial discharge trend varied intensively with the terrestrial conditions. The modified simulation methods were found to accurately assess the cycling of nutrients from the forest litterfall on a watershed scale.

Unprecedented Retention Capabilities of Extensive Green Roofs—New Design Approaches and an Open-Source Model

Green roofs are a proven measure to increase evapotranspiration at the expense of runoff, thus complementing contemporary stormwater management efforts to minimize pluvial flooding in cities. This effect has been quantified by numerous studies, ranging from experimental field campaigns to modeling experiments and even combinations of both. However, up until now, most green roof studies consider standard types of green roof dimensions, thus neglecting varying flow length in the substrate. For the first time, we present a comprehensive investigation of green roofs that involves artificial rainfall experiments under laboratory conditions (42 experiments in total). We consider varying flow length and slope. The novelty lies especially in the consideration of flow lengths beyond 5 m and non-declined roofs. This experimental part is complemented by numerical modeling, employing the open-source Catchment Modeling Framework (CMF). This is set-up for Darcy and Richards flow in the green roof and calibrated utilizing a multi-objective approach, considering both runoff and hydraulic head. The results demonstrate that through maximizing flow length and minimizing slope, the runoff coefficient (i.e., percentage of rainfall that becomes runoff) for a 100 years design rainfall is significantly decreased: from ~30% to values below 10%. These findings are confirmed through numerical modeling, which proves its value in terms of achieved model skill (Kling-Gupta Efficiency ranging from 0.5 to 0.95 with a median of 0.78). Both the experimental data and the numerical model are published as open data and open-source software, respectively. Thus, this study provides new insights into green roof design with high practical relevance, whilst being reproducible.

RETRACTED ARTICLE: Rainfall soil erosion based on color image super resolution and rural revitalization design

Based on the super-resolution color image, this paper studies the design of rainfall soil erosion and rural revitalization. The steep slope system of the Loess Plateau is not only an important cause of soil erosion by rain, but also an important area for landslides, debris flows, and other natural disasters. In this study, high and steep slope system was used as the research object. Through indoor artificial rainfall experiments, under the conditions of intermittent rainfall, outflow and sediment yield characteristics, soil moisture content changes, and rainfall erosion dynamic parameters, the appearance of steep slope system under various conditions was studied from the beginning of rainfall to slope crack stage. At the same time, the development of agriculture and rural areas is not only an important foundation and support for the realization of national modernization, but also an important factor affecting economic and social development. At present, the development level of China’s agriculture and rural areas is still relatively backward, which is a significant defect in the development of China’s modernization. According to the relevant research results of domestic and foreign researchers, this study takes the main content of Rural Revitalization Strategy as the starting point, and, based on the explanation of development background and implication, deeply analyzes the development background of rural complex model and local economic revitalization strategy. At the same time, taking the rural complex as the main carrier to implement the rural revitalization strategy, this paper studies the theoretical source of the rural complex model in detail, and briefly summarizes the significance and characteristics of the rural complex model. This paper expounds the important role of the development of rural complex facilities in the implementation of China’s rural revitalization strategy.