Runoff Rates Research Articles

Assessment of the Impact of LID Techniques on Water Cycle Recovery in Industrial Complexes

Urbanization and industrialization have significantly disrupted the natural water cycle, leading to increased runoff, flooding, and groundwater depletion. Research on LID (Low Impact Development) techniques is ongoing in order to address these challenges. This study has analyzed the improvement in the water cycle system by applying LID techniques to the Daejeongcheon watershed in Ulsan. Using SWMM, this study has assessed the long-term effects of LID on runoff reduction and water cycle recovery rate improvement. Based on local climate data, topographical information, and regional characteristics, LID elements such as permeable pavements, green roofs, bioretention, and vegetative swales were applied. The results showed that the LID techniques reduced runoff by 8.44% and also improved the water cycle recovery rate by 13.52%. Additionally, the study confirmed that LID techniques effectively contributed to managing runoff from the 25.5 mm rainfall management target. LID techniques are expected to serve as sustainable water management strategies in urbanized and industrialized areas, offering effective restoration and management solutions.

Response of Runoff, Sediment Yield, and Runoff‐Related Dissolved Organic Carbon Loss to Variable Straw Mulching Rates on Sloping Lands of Regosols

ABSTRACTDissolved organic carbon (DOC), an organic carbon fraction with high activeness and mobility, migrated by runoff is a key part in carbon cycle. A rational straw mulching rate can be regulated to obtain maximum benefits while controlling runoff and sediment yield on sloping lands. However, little remains known about the optimal straw mulching rates required for effectively reducing the loss of DOC in runoff. Therefore, to overcome the existing limitations, this study investigated the effects of modified maize straw mulching rates on the loss of DOC during runoff, utilizing indoor rainfall simulation. Five mulching rates, including 0, 0.2, 0.4, 0.6, and 0.8 kg m−2 [control (CK) and treatments (T1, T2, T3, and T4), respectively], were tested in combination with three slope gradients (10°, 15°, and 20°) to evaluate how straw mulching rate influences runoff, sediment yield, and runoff‐related DOC loss under a heavy rainfall intensity of 90 mm h−1. Our results showed that various straw mulching rates did not significantly differ runoff rates; however, straw mulching significantly reduced sediment concentration and yield. Moreover, the reduction in sediment yield increased with an increase in mulching rate. Compared to the CK, T1 resulted in a 63% increase in DOC loss at a slope of 20°. Additionally, T2 caused an 8% and 7.2% increase in DOC loss at both 10° and 15° slopes. Conversely, T3 and T4 reduced DOC loss by 54.1%–80.8% and 51.1%–65.2%, respectively, across all slope gradients. These results suggested that mulching rates of 0.2–0.4 kg m−2 may potentially increase DOC loss in runoff on the sloping lands. Our results hold significant importance in optimizing the use of straw mulching for sustainable management practices in agricultural lands.

Stormwater runoff volume reduction and pollutant removal efficiency via bioretention cell using rock wool as the media

ABSTRACT Bioretention cells have been widely used in stormwater management. Media plays an important role in stormwater runoff reduction and pollutant removal. A novel bioretention media of rock wool has been proposed, and its effect on stormwater runoff reduction was investigated via a laboratory-scale experiment. The results showed that compared with the conventional bioretention (CB) using medium sand as media, the volume capture ratio of annual rainfall (VCRAR) of the rock wool bioretention (RWB) was 2.66–5.5% higher, and the peak flow reduction rate was 2.97–11.32% higher. The removal efficiency rates of the RWB on COD, NH4+ -N, TN, and TP were 25–30%, 10–31%, 20–40%, and 5–14% higher than the CB, respectively. The removal efficiency of the RWB on botht Pb and Zn was >99%. The microbial high-throughput sequencing results showed that the RWB can provide a better breeding environment for Bacteroides and Actinobacteria, which is conducive for the removal of pollutants. The RWB had a better stormwater runoff volume reduction rate and pollutant removal efficiency than the CB, therefore, it could be used as a better media for bioretention cells to improve stormwater management efficiency by using rock wool, obtained from construction waste, as the media.

A modified Soil and Water Assessment Tool Plus (M-SWAT+) model for sediment yield estimation

ABSTRACT The Soil and Water Assessment Tool Plus (SWAT+) model depends on the Modified Universal Soil Loss Equation (MUSLE), which in turn depends on the peak runoff rate for the estimation of soil loss from a catchment. The SWAT+ model generates a random number for each day in the process of peak runoff rate estimation from the catchment. On the other hand, the model provides calibration parameters like the peak rate adjustment factor for sediment routing in the tributary channels and main channels. There is uncertainty that how likely the SWAT+ model estimates the actual peak runoff rates. An improved MUSLE does not depend on the peak runoff rate, and, therefore, it minimizes uncertainty related to the peak runoff rate when estimating soil loss from the catchment in the SWAT+ environment. On the other hand, the effect of the topographic factor of the MUSLE or improved MUSLE on soil erosion and sediment transport is not explicitly explained. Therefore, we modify the source code of the SWAT+ model for sediment yield estimation by replacing the improved MUSLE and the best-fitted equations of the topographic factor in the source code. The modified SWAT+ model showed better performance than the original SWAT+ model.

Stormwater retention performance of tree integrated infiltration trenches designed for suburban streetscapes

The volume of stormwater generated by streetscapes in cities is a primary driver of urban stream degradation. Large infiltration trenches can be integrated into streetscapes to potentially retain large volumes of runoff and increase growth rates of nearby trees. To test this, a field study was conducted where three structural soil infiltration trenches receiving runoff (12 m long, 0.6 m wide and 0.6 deep) were installed alongside a carpark in Melbourne, Australia, with sizing determined by space constraints in a typical streetscape. The three structural soil trenches had raised outflow drainage, which created internal water storage for runoff received from a carpark. To separate the effects on tree growth of i) the presence of structural soil from ii) passive irrigation into the structural soil, three structural soil trenches (6 m long, 0.6 m wide and 0.6 deep) not receiving runoff and without outflow drainage were also installed. Runoff capture, exfiltration, outflow and tree growth was monitored over 19 months. Only one system performed close to the design intent and retained 18 % of runoff, due to slow soil exfiltration rates (<0.1 mm h−1). Compacted soil generated pervious-area runoff that filled the structural soil trenches not receiving impervious-area runoff from the carpark. Tree growth near these structural soil trenches was poor (59 % relative growth) compared with trees receiving runoff from the carpark (112 % relative growth), due to a lack of drainage, emphasising the need for drainage of stormwater systems in heavy textured soils to promote tree growth. This study highlights that options for creating storage for stormwater in streetscapes have the potential to meet local runoff infiltration targets. However, meeting local runoff volume reduction targets will require alternative ways to reduce surface runoff.

Effects of inoculation with Bacillus arenosi on physical and biochemical properties of soil, and surface runoff and erosion in degraded forestlands of Northern Iran

A viable practice to improve key properties of soil, and reduce runoff generation and erosion may be inoculation with selected bacteria. However, no previous studies have evaluated whether the direct inoculation of Bacillus arenosi K64 (hereafter simply indicated as B. arenosi) to soil impacts the main physical and biochemical properties of soil as well as the runoff and erosion rates. This study has measured the infiltration rate (IR), tensile strength (TS), mean weight diameter (MWD), polysaccharides (PS) and important enzymes of soil (β-glucosidase, N-acetyl glucosaminidase, phosphatase and arylsulphatase) in degraded forest soils (Northern Iran) inoculated with B. arenosi in comparison to untreated soils (control). Moreover, the runoff coefficient and soil loss have been measured in plots with soil sampled in those sites under natural rainfalls. IR, TS and MWD increased by 65 % to 160 % in treated soils compared to the control. PS and enzymes were significantly higher (by 20 % to 200 %) after soil inoculation. A noticeable decrease in both surface runoff and soil loss (both by 45 %) in the inoculated soils resulted from those changes. High correlations between the hydrological response of soil on one side, and the measured physical and biochemical variables on the other side were observed. A derivative variable calculated by the Principal Component Analysis can be considered as a meaningful parameter to estimate the changes in soil properties and response due to inoculation with bacteria. Agglomerative Hierarchical Cluster Analysis clearly discriminated the treated from the untreated soils. This study has demonstrated that soil inoculation with B. arenosi plays a significant role in reducing runoff generation and soil erosion under the experimental conditions, thanks to the general improvement in physical and biochemical properties of soil.

A Low-Impact Development-Based Modeling Framework for Flood Mitigation in a Coastal Community

Urbanization is known to increase the volume of stormwater runoff and peak flow rates, which leads to changes in the natural flow regime and increases the likelihood of flooding. Low-impact development (LID) practices seek to reduce runoff volume and peak flow and are generally considered to be a more sustainable solution for urban stormwater management. In this study, we present a systematic approach to address nuisance flooding issues in small cities and communities. As an application, the effectiveness of two LID practices, rain barrels and permeable pavements, were explored in mitigating the urban flooding problem of a highly urbanized small coastal watershed in Alabama, USA. The EPA Stormwater Management Model (SWMM) was first calibrated for water depth using data collected at multiple sites within the watershed during the 2014–2015 period. The calibrated model was then used to first identify the areas prone to flooding using design storms with 1, 2, 5-, 10-, 50-, and 100-year return periods. Floodplain maps were generated for those design storms with HEC-RAS. Next, LID options upstream of those flood-prone areas were assessed to potentially minimize the flooding risks. The results indicate that LID controls can have considerable benefits for stormwater management by reducing runoff volume (1–24%), peak flow rates (18–25%), and water depth (5–15%), potentially returning watersheds to their natural flow regimes, thereby minimizing the flooding risk in urbanized areas. However, the effectiveness of LIDs, especially for the runoff volume, quickly diminishes as the return periods of the storms increase. Rain barrels were identified as the most economical and effective LID within the drainage system.

Land use transformations in the Brazilian Savanna: A decade of soil erosion and runoff measurements

Changes in land cover and land use (LULC) are one of the main drivers of erosion and runoff. How ever, most research has relied on short-term observations and only focused on one or two land cover types. We investigated the long-term trade-off between common agricultural land covers (sugarcane, pasture, and soybean), runoff, and soil loss rates. We compared these to native forest (wooded Cerrado) and bare soil. The field observations were done in 100 m2 experimental plots in Brazil maintained during the past 10 years. The paper provides three main contributions: (1) long-term runoff and soil loss rates of plots under different LULCs, (2) comparison of runoff, soil loss, and pedological characteristics between plots constructed 10 years apart, and (3) analysis of the trade-off between different LULCs. When ranking land covers based on runoff and soil loss rates, there is a shift in ranking positions, making it difficult to determine which one is more environmentally harmful. However, it is evident that whatever agricultural practice is used, there is a significant impact when compared to native forest. For example, the area converted to pasture resulted in almost 20 times higher runoff, while conversion to sugarcane resulted in 5 times higher soil loss. Not only land cover plays a major influencing factor, but also weathering exposing time. Areas under the same land cover and environmental conditions had different rates of soil loss and runoff due to long-term exposure effects such as soil crusting. Our findings have high relevance for the hydrological and agricultural community by demonstrating (i) the magnitude of trade-off in terms of soil loss and runoff due to land cover changes and (ii) that soil loss should not be assumed to be a linear process over time, as it is commonly assumed.

Multi-objective optimization of distributed green infrastructure for effective stormwater management in space-constrained highly urbanized areas

Green infrastructure (GI) is essential for stormwater management, but its implementation in highly urbanized areas is challenging due to the limited space available for GI retrofitting. There is a lack of comprehensive evaluations that assess the spatial adaptability, functionality, and cost-benefit of various GI measures, and optimize their placement to achieve the maximum reduction rate of total runoff (RTR) and reduction rate of pollution load (RPL) while minimizing life cycle cost (LCC) in space-constrained highly urbanized areas (SCHUA). To address this issue, a novel concept of infiltration, retention, and storage integrated GI (IRS-GI) for SCHUA was proposed, and a framework coupling the Storm Water Management Model (SWMM) with multi-objective optimization algorithms was developed to determine the optimal IRS-GI layout, focusing on the objectives of RTR, RPL, and LCC. The impacts of different GI type, size, and location, rainfall return periods, and algorithms (NSGA-II and NSGA-III) were then examined. The results showed that IRS-GI could achieve satisfactory RTR and RPL results while single-type GI may struggle to meet requirements. Optimization outcomes were significantly influenced by rainfall return periods, with cost-benefit decreasing as return periods increasing. Besides, the optimization results of NSGA-II and NSGA-III showed differences, and the comprehensive Pareto frontier obtained by reapplying non-dominated sorting could achieve more comprehensive results for determining the optimal IRS-GI configuration. Under the urban drainage design standard, the optimal IRS-GI layout, covering 32.97 % of the green spaces, 38.57 % of the rooftop, and 60.98 % of the ordinary roads and squares, respectively, could achieve a RTR of 50.09 %, RPL of 57.00 %, and LCC of 0.79 × 108 CNY/yr. Additionally, the optimal configuration suggested that a higher proportion of GI downstream of drainage system may contribute to better cost-benefit, emphasizing the need for location-specific GI solutions. This research offers valuable insights for optimizing GI in SCHUA, advancing sustainable urban stormwater management.

Study on Soil Stabilization and Slope Protection Effects of Different Plants on Fully Weathered Granite Backfill Slopes

The slope erosion in the distribution area of completely weathered granite is often relatively severe, causing serious ecological damage and property loss. Ecological restoration is the most effective means of soil erosion control. Taking completely weathered granite backfill soil as the research object, two types of slope protection plants, Vetiver grass and Pennisetum hydridum, were selected. We analyzed these two herbaceous plants’ soil reinforcement and slope protection effects through artificial planting experiments, indoor simulated rainfall experiments, and direct shear tests. The test results showed that the runoff and sediment production rates of the two herbaceous plant slopes were significantly lower than those of the bare slope, with the order of bare slope &gt; Vetiver grass slope &gt; Pennisetum hydridum slope. Compared with the bare slope, the cumulative sediment production of the Vetiver grass slope at 60 min decreased by 56.73–60.09%, and the Pennisetum hydridum slope decreased by 75.97–78.45%. The indoor direct shear test results showed that soil cohesion decreases with increasing water content. As the root content of Vetiver grass roots increases, soil cohesion first increases and then decreases, reaching a maximum value when the root content is 1.44%. As the root content of Pennisetum hydridum increases, soil cohesion increases. The internal friction angle increases slightly with increasing water content, while the root content does not significantly affect the internal friction angle. Therefore, the shear strength of soil decreases when the water content increases. The shear strength of the Vetiver grass root-soil composite reaches a peak at a root content of 1.44%, while the shear strength of the giant king grass root-soil composite increases as the root content increases. At the same root content, the shear strength of the Vetiver grass root-soil composite is slightly higher than that of giant king grass. The reinforcement effect of roots on shallow soil is better than on deep soil. Both herbaceous plants have an excellent soil-fixing and slope-protecting impact on the fully weathered granite backfill slope. Pennisetum hydridum’s soil and water conservation effect is significantly better than that of the Vetiver grass. In contrast, Vetiver grass roots slightly outperform Pennisetum hydridum in enhancing the shear strength of the soil. The research results can provide a theoretical basis for the vegetation slope protection treatment of fully weathered granite backfill slopes.

Surface Runoff Estimation in Kubaisa Watershed Using SWAT, Western Desert, Iraq

Surface runoff significantly impacts the region's ecosystem and is closely linked to sustainable development and human well-being. The mathematical model SWAT running in an ArcGIS environment was used to estimate surface runoff in the Kubaisa watershed. The period simulated in this model is 31 years, sufficient to give good results regarding surface runoff volume and water yield contribution from each sub-watershed. The Kubaisa watershed has an area of 2485.50 km2 and comprises six sub-watersheds. The watershed consists of 172 HRUs distributed among sub-watersheds depending on the variation in soil layers, land use, vegetation, and slope. The volume of water calculated from the annual surface runoff rate for the simulation period was about 2699 million cubic meters, and its value was higher than the volume of water calculated from surface runoff due to lateral flow, groundwater discharge, and the contribution of each sub-watershed to the water yield. The highest value in water yield was in 2012, and the largest contribution was made by the sixth sub-watershed; thus, the difference is temporal and spatial in terms of water yield. Finally, through the analysis of multiple scenarios, the difference in hydrological response units is controlled by the difference in surface runoff, discharge, and water yield to the watershed. For this purpose, the SWAT model divides the watershed into many different units and starts the simulation on their basis.

Optimizing stormwater runoff treatment: The role of two-stage tandem rain gardens

Regarded as a superior urban stormwater management solution, rain gardens can effectively store rainfall runoff and purify water quality. However, the efficiency of traditional rain gardens (TRG) in regulating runoff and removing nitrogen and phosphorus varies under different hydrological conditions. In this study, the TRG was retrofitted to construct a two-stage tandem rain garden (TTRG). Based on the experimental monitoring of rain gardens under natural rainfall from 2011 to 2013, results indicated a significantly higher runoff reduction capacity for the TTRG compared to the traditional garden (p < 0.05), with average runoff and peak flow reduction rates increasing by 42.8% and 36.2%, respectively. Rainfall characteristics significantly impacted the runoff reduction of the TRG (p < 0.05), but not the TTRG (p > 0.05), demonstrating the enhanced control and stability of the TTRG in managing rainfall runoff. The concentration removal efficiency of nitrate nitrogen (NO3--N) was significantly improved (p < 0.05), whereas the total phosphorus (TP), ammonium nitrogen (NH3-N) and total nitrogen (TN) were not significantly changed (p > 0.05). The first-order kinetic model was used to fit the removal effect of different pollutants before and after retrofitting the rain garden, and the removal of NO3--N by the TTRG was better than that of the TRG. The TTRG showed significantly higher load removal efficiencies for TP, NO3--N, and NH3-N compared to TRG (p < 0.05), with average load removal rates increasing by 49.92%, 75.02%, and 14.81%, respectively. The TTRG can regulate urban rainfall runoff more efficiently and stably. By changing the water flow path in the rain garden, the TTRG has a better runoff reduction ability and pollutant purification effect.

Response of Surface Runoff Evolution to Landscape Patterns in Karst Areas: A Case Study of Yun–Gui Plateau

To control and improve the phenomena of rocky desertification and soil erosion in karst landform areas, which are caused by a series of human factors that include social and economic development and human activities, China has successively introduced many policies, resulting in spatial and temporal changes in the landscape pattern of the southern karst area. In this study, land use transfer intensity maps, the grid method, the sample line method, the semivariogram method, and the Spearman analysis method are used to explore the spatial and temporal evolutions in surface runoff as responses to landscape pattern and policy factors in karst landform area. Therefore, this study provides theoretical and policy support for improving the regional landscape structure, optimizing the landscape layout, introducing regional policies, reducing surface runoff, and alleviating soil erosion. The results show that the best scale for the study of landscape patterns in the southern karst area is 3000 m. Forests are the land type that make up the highest proportion in the southern karst area, and they have the strongest interception capacity for surface runoff. The spatial and temporal distributions of the surface runoff are significantly different, and urban expansion has led to an increase in impervious runoff year over year. Runoff is positively correlated with the Shannon diversity index (SHDI), patch density (PD), and landscape shape index (LSI). The stronger the landscape heterogeneity, the more runoff. DIVISION is positively correlated with forest runoff and negatively correlated with other land types. The higher is the degree of aggregation of impervious patches, the higher the regional runoff rate. The more dispersed the forest patches are, the smaller the area proportion, and the greater the runoff. In addition, policy factors have a significant impact on surface runoff.

Runoff Control Performance of Three Typical Low-Impact Development Facilities: A Case Study of a Community in Beijing

The development of sponge cities advocates for sustainable urban rainwater management, effectively alleviating urban flood disasters, reducing non-point-source pollution, and promoting the recycling of rainwater resources. Low-Impact Development (LID) serves as a key strategy in this context, providing essential support for urban rainwater control and pollution reduction. To investigate the runoff control effects of LID measures and to reveal the relationship between facility runoff control performance and installation scale, this study focuses on a sponge community in Beijing. A SWMM model was constructed to analyze the rainwater flood control and pollutant load reduction effects of different LID facilities, including bio-retention cells, green roofs, and permeable pavements. Using evaluation indicators such as surface runoff, node overflow, and pollutant control rates, this study examined how facility performance varies with installation scale under different rainfall conditions. The combination scheme of LID equipment optimal configuration is designed by using multiple criteria decision analysis (MCDA) and cost–benefit theory. The results indicate significant differences in performance among the various LID facilities across different rainfall scenarios. Specifically, the optimal installation proportion for runoff and overflow control of permeable pavements were found to be between 30% and 70%. Green roofs demonstrate superior performance in handling extreme rainfall events, while bio-retention cells exhibit significant effectiveness in controlling Total Suspended Solids (TSSs). Through comprehensive performance evaluation, this study identified the optimal combination scale under a 3-year rainfall recurrence interval as 30% permeable pavements, 20% green roof, and 60% bio-retention cells. This combination effectively leverages the strengths of each facility, ensuring system stability and efficiency while also demonstrating optimal management efficiency in cost–benefit analyses. The findings of this research provide valuable insights for future urban water management and infrastructure development.

How vertical drainage positions of extensive green roofs affect the runoff control performance

The capacity of extensive green roofs (EGRs) in runoff reduction and pollutants control significantly decreased with increasing rainfall intensity. This is attributed to most of EGRs are the lower-drainage method and use a thinner substrate layer because of the structural load-bearing limits of buildings. Existing solutions depend on increasing the rainwater storage by thickening the substrate layer of EGRs, or replacing the substrate materials. We propose to enhance the water retention capacity of EGRs by adjusting vertical drainage positions and moving the lower-drainage at the bottom to upper-drainage over the substrate layer. To test the runoff control performance of EGRs with the upper-drainage method, we designed three EGR models with two different (upper- and lower-) drainage methods based on the common EGR’s structure in practice and carried out total 48 experiments under different rainfall intensities with an artificial rainfall simulator. The experimental design also included adjusting structural factors of the EGR to further explore the influences of roof slope, status of vegetation growth (height and canopy cover ratio), and model size. The average runoff retention rate for the upper-drainage EGR was 61.82 %, which was much higher than the 23.94 % for the lower-drainage EGR. The concentrations of TN and TP in runoff with the upper-drainage were 2.83 and 0.18 mg/L, which were much lower than the 8.47 and 2.10 mg/L for the lower-drainage EGR. EGRs with upper-drainage overall performed better in runoff control than EGRs with lower-drainage. Vegetation height and model size did not significantly affect the rainwater control performance for different drainage methods, while the change of slope affected the rainwater interception of the EGRs with upper-drainage method.

Simulation and Prediction of Snowmelt Runoff in the Tangwang River Basin Based on the NEX-GDDP-CMIP6 Climate Model

In this study, the future snowmelt runoff in the chilly northeast region’s Tangwang River Basin was simulated and predicted using the SWAT model, which was built and used based on the NEX-GDDP-CMIP6 climate model. This study conducted a detailed analysis of the spatial and temporal distribution characteristics of snowmelt runoff using high-resolution DEM, land use, and soil data, along with data from historical and future climatic scenarios. Using box plots and the Bflow digital filtering approach, this study first determined the snowmelt runoff period before precisely defining the snowmelt periods. Sensitivity analysis and parameter rate determination ensured the simulation accuracy of the SWAT model, and the correlation coefficients of the total runoff validation period and rate period were 0.75 and 0.76, with Nashiness coefficients of 0.75 for both. The correlation coefficients of the snowmelt runoff were 0.73 and 0.74, with Nashiness coefficients of 0.7 and 0.68 for both, and the model was in good agreement with the measured data. It was discovered that while temperatures indicate an increasing tendency across all future climate scenarios, precipitation is predicted to increase under the SSP2-4.5 scenario. The SSP2-4.5 scenario predicted a decreasing trend regarding runoff, while the SSP1-2.6 and SSP5-8.5 scenarios showed an increasing trend with little overall change and the SSP5-8.5 scenario even showed a decrease of 6.35%. These differences were evident in the monthly runoff simulation projections. Overall, the findings point to the possibility that, despite future climate change having a negligible effect on the hydrological cycle of the Tangwang River Basin, it may intensify and increase the frequency of extreme weather events, creating difficulties for the management of water resources and the issuing of flood warnings. For the purpose of planning water resources and studying hydrological change in this basin and other basins in cold regions, this study offers a crucial scientific foundation. An in-depth study of snowmelt runoff is of great practical significance for optimizing water resource management, rational planning of water use, spring flood prevention, and disaster mitigation and prevention, and provides valuable data support for future research on snowmelt runoff.

Exploring rational vegetation configuration to relative increase runoff, reduce erosion and soil organic carbon loss in gully-slopes on the Chinese Loess Plateau

In order to solve the water shortage, uncoordinated runoff-sediment relationship, and prevent carbon loss in the Yellow River Basin, there is an urgent need to explore the rational vegetation configuration in order to relative increase runoff, reduce sediment and prevent soil organic carbon loss in the gully-slopes on the Loess Plateau. To solve these problems, the simulated rainfall experiments with an intensity of 60 mm·h−1 were conducted in four types of plots: shrub-grass (SG), tap root grasses (GT), fibrous root grasses (GF) and bare land (CK). Four types of plots were built on one gully-slope with a slope of 35°–40° in situ. Compared with CK (mean runoff rate: 0.61 mm·min−1), the runoff reduction benefits of SG (0.27 mm·min−1), GT (0.04 mm·min−1) and GF (0.17 mm·min−1) plots were 54.9 %, 71.7 %, 92.2 %. Compared with GT and GF plots, the total runoff of SG plots was 1.6–5.8 times. Compared with CK, the sediment reduction benefits of three vegetation plots were more than 98 %. Shrub-grass is a more suitable vegetation combination for soil and water conservation: reducing sediment and relative increasing runoff. The soil organic carbon loss has been well alleviated through vegetation restoration, and vegetation plots all prevented over 98 % of soil organic carbon loss compared with the bare plot. Soil organic carbon loss equation based on runoff and sediment was established and validated. The R2, P and NSE results of the equations were 0.92–0.95, <0.001, 0.85–0.86, respectively, indicating that the fitted equations can be considered acceptable. The soil organic carbon loss in the gully-slopes was mainly from sediment (more than 85 %) compared with runoff. Therefore, controlling sediment is more effective than controlling runoff in preventing soil organic carbon loss in the gully-slopes on the Loess Plateau. These results can provide a basis for decision-making of high-quality development of contemporary soil and water conservation on the Loess Plateau.

Soil hydro-physical variables and crop residues determinate runoff, soil loss, and glyphosate and AMPA concentration in the aqueous phase under simulated rainfall events.

Soil structural degradation and water erosion processes were observed even in no-tillage schemes in the Pampas region. Within these conservation systems, agrochemical application per hectare is one of the highest globally. Thus, this entails a serious risk of water contamination. The objectives of this study were to (1) test the hypothesis that the hydrological dynamics and sediment concentration related to surface runoff were conditioned by soil structure regardless of the presence of maize (Zea mays L.) crop residue and (2) assess the incidence of maize crop residue on glyphosate and aminomethylphosphonic acid (AMPA) concentration in runoff. The soil under study corresponded to Arroyo Dulce Series (Typic Argiudoll silty loam soil). Rain simulations were performed in the laboratory on undisturbed soil samples. Total runoff and infiltration rate were similar between treatments with C(+) and without C(-) maize crop residues (C(+) 1381.40mL and 14.27mm h-1, C(-): 1529.70mL and 21.67mm h-1). The C(-) treatments showed a higher sediment concentration than C(+) (1.58 and 0.42g 100mL-1, respectively). Glyphosate and AMPA average values in runoff were 15.9 and 33.9µg L-1. High variability of the hydro-physical properties and occurrence of soil structure, particularly platy ones, were detected. The hydrological variables were conditioned mainly by the occurrence of platy structures regardless of crop residue presence. Glyphosate concentration was increased in the first runoff event by the presence of corn residues, while AMPA concentrations were higher in the second runoff event in both residue treatments. In this study, maize residue on the soil surface protected the soil from sediment detachment but did not change runoff or infiltration. Thus, the implementation of agricultural management practices that promote vegetative residue cover has shown positive results to erosion.

Enhanced resilience in urban stormwater management through model predictive control and optimal layout schemes under extreme rainfall events

Optimizing the layout of urban stormwater management systems is an effective method for mitigating the risk of urban flooding under extreme storms. However, traditional approaches that consider only economic costs or annual runoff control rates cannot dynamically respond to the uncertainties of extreme weather, making it difficult to completely avoid large accumulations of water and flooding in a short period. This study proposes an integrated method combining system layout optimization and Model Predictive Control(MPC)to enhance the system's resilience and effectiveness in flood control. An optimization framework was initially built to identify optimal system layouts, balancing annual average life cycle cost (AALCC) and resilience index. The MPC was then applied to the optimal layout selected using the Technique for Order Preference by Similarity to Ideal Solution (TOPSIS) method, aiming to alleviate inundation cost-effectively. The adaptability of MPC to varying sets of control horizons and its efficacy in managing the hydrograph and flood dynamics of urban drainage system were examined. Conducted in Yubei, Chongqing, this study revealed patterns in optimal layout fronts among various extreme design rainfalls, showing that peak position rate and return period significantly influence system resilience. The contribution of MPC to the optimal system layout was particularly notable, resulting in improved instantaneous and overall flood mitigation. The application of MPC increased the resilience index by an average of 0.0485 and offered cost savings of 0.0514 million yuan in AALCC. Besides, our findings highlighted the importance of selecting an optimal set of control horizons for MPC, which could reduce maximum flood depth from 0.43m to 0.19m and decrease conduit peak flow by up to 14% at a flood-prone downstream location.

Integrating topographic factors for effective urban sponge construction in mountainous regions: A case study

The construction of sponge cities in mountainous areas is crucial to achieving high-quality development in these regions. Owing to rugged terrain, significant changes in elevation, and uneven distribution of cities, the construction of sponge cities in mountainous areas faces challenges such as difficulties in clearing mountains and roads, high cost, and varying regional development requirements. However, there is currently limited research focusing on the impact of terrain on sponge city construction plans. In this study, we developed an optimal low impact development (LID) system layout method based on the annual runoff control rate. This study suggests implementing LID plans in stages to balance cost-effectiveness and enhance resilience. The optimized case1_100 scheme, which takes regional differences into account, can effectively achieve a runoff control coefficient of less than 0.25 in 98.86% of the area. Remarkably, this achievement comes at a significantly lower total cost of only 1.22 billion RMB compared to the unoptimized case2_100 scheme (which does not consider regional differences) with a cost of 3.03 billion RMB. Interestingly, the optimized case1_100 plan, selected using the Technique for Order of Preference by Similarity to Ideal Solution (TOPSIS) method, has an LID layout that is closely related to the surface terrain. Structural equation modeling analysis indicates that terrain affects land types, which in turn impacts the surface impermeability and runoff coefficients, ultimately influencing the corresponding LID deployment plan. The coefficients of relative elevation and slope on the final plan are determined as −0.13 and −0.77, respectively, with a high overall explanatory power of 0.84. This indicates that terrain characteristics have a significant impact on the spatial patterns and surface features of typical mountainous cities in China and the optimal LID strategy largely depends on the initial terrain conditions. This study provides valuable insights for optimizing LID construction in sponge cities, particularly in the context of new mountainous urban planning.