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•A dynamic von Mises-based model considering trend-caused nonstationarity was proposed to assess the temporal variations of flood timing (FT).•The advanced impact of urbanization on the peak timing ... of floods is slightly stronger in the Huaihe River Basin sites than in the Yangtze River Basin.•In contrast to the modest advancement resulting from urbanization, climate change factors such as the timing of soil moisture (TSM) and maximum rainfall (TPRE) play a predominant role in contributing to a delayed trend observed at HRB and YRB.•Compared to the effect of TPRE, the timing of soil moisture plays a more impartant role in determining the timing of floods in both the HRB and the YRB. The combined effect of global warming and urbanization have an impact on the occurrences of floods in the Yangtze River Basin (YRB) and Huaihe River Basin (HRB), causing potential risks to the safe operation of watersheds. Therefore, this study proposed a dynamic von Mises-based (DvM) framework for detecting the impact of urbanization and climate change on flood timing (FT) across HRB and YRB from the nonstationary frequency included: (1) visualization of empirical probability of FT series to ascertain the number of mixed von Mises distributions; (2) selection of the multi-covariate-based model in consideration of the combined effect of multiple physical covariates, following the phase-wise strategy which involves the likelihood ratio test, Kolmogorov-Smirnov goodness-of-fit test, and the Akaike information criterion; (3) development of the linear regression-based comparative approach to isolate and distinguish the delaying and advancing effects of various factors (mainly climate change and urbanization-induced impact) on FT. In terms of the urbanization-induced impact on peak flow timing, HRB suffered an advanced effect by 4% and YRB suffered an advanced effect by 2%, which can be attributed to the divergence of the urbanization development level quantified by the impervious surfaces of sub-basins controlled by the stations in these two basins. In contrast to the modest advancement caused by urbanization (4% for HRB and 2% for YRB) in influencing the timing of flood peaks in the two basins, climate change factors, specifically the timing of soil moisture (TSM) and maximum rainfall (TPRE), play a more significant role in contributing to a delayed trend observed at a total of seven stations in the Huaihe River Basin and Yangtze River Basin. The main driver behind the trend towards delayed flood timing in both the Huaihe River Basin (HRB) and the Yangtze River Basin (YRB) is predominantly influenced by the timing of soil moisture. According to TSM, this factor contributes 16% in HRB and 10% in YRB. In contrast, the timing of rainfall has a lesser impact, accounting for 13% in HRB and 8% in YRB according to TPRE. more

The scaling of peak flows associated with a probability of exceedance (Qp) or a specific rainfall‐runoff event (QR) with respect to drainage area (A) is known as flood scaling and it has been widely ... used in peak flow regionalization. The attenuation and aggregation processes within the hillslopes and river network in a rainfall‐runoff event, provide a framework to test the scaling of QR. Although scaling of Qp has been reported in empirical studies, its physical interpretation is compromised, since Qp at each site could come from different rainfall‐runoff events. To address this problem, the authors explored the effect of actual variabilities of rainfall and soil moisture fields, and the effect of the river network structure, in the scaling of peak flows of 85 rainfall‐runoff events and peak flow quantiles that were observed in the Iowa River Basin at 43 streamflow gauges. The authors established empirical evidence that addresses two questions: (1) What does control the performance of the scaling of observed QR? (2) What is the interplay between sampling errors and the selection of explanatory variables in the construction of regional regression models for QR and Qp? For the first question, the authors found that the slope magnitude in the scaling of the rainfall intensity fields with respect to A controls the scaling' performance of QR. Regarding the second question, the authors demonstrate that the inclusion of river network descriptors should improve the regional equations to estimate peak flow quantiles unless stream gauging sampling errors affect the analysis. Key Points The performance of the scaling of peak flows from rainfall‐runoff events is explained by the scaling structure of rainfall intensity fields The river network structure represented by width function descriptors can improve the regional equations to estimate peak flow quantiles The selection of width function descriptors in regional equations is hampered by sampling errors and limited number of streamflow gauges more

•First SWAT review on hydro-climatic extreme studies.•Lack of SWAT assessment on extreme flows simulations.•Comparison of SWAT+ and SWAT should be conducted.•Incorporation of CMIP6 GCMs in SWAT ... hydro-climatic studies.•Integration of artificial intelligence within SWAT modelling. Hydro-climatic extremes, such as droughts and floods, have most likely increased due to climatic change and could lead to severe impacts on socio-economic, structural and environmental sectors. With nearly 4000 publications, the Soil and Water Assessment Tool (SWAT) is clearly one of the most extensively used ecohydrological models worldwide. The model has been widely used for projecting the impacts of future hydro-climatic changes, but application for extreme streamflow conditions is still rarely reported. To date, SWAT application reviews have focused on compilations of SWAT studies for specific or relatively new applications such as eco-hydrological modelling, ecosystem services, sub-daily simulations, and pesticide fate and transport simulations. However, no existing SWAT review studies have focused on simulation of hydro-climatic extremes. Therefore, this research aims to bridge this gap by compiling and reviewing the findings of studies reporting SWAT hydro-climatic extremes including highlighting the performance and future research needs. A total of 111 articles have been identified since 1999; most of these studies were conducted in the United States and China. These articles can be divided into extreme flow assessments, drought studies, flood studies, drought and flood studies, SWAT coupling with other models, and SWAT improvements. Most of the extreme performance assessment studies reported “satisfactory” performance, with a particular emphasis on peak flow comparisons. Future research needs regarding this topic include: (1) a unified SWAT extreme performance assessment framework; (2) SWAT improvements that result in improved replication of peak and low flows; (3) reliability assessment of global and satellite products for SWAT extreme simulations; (4) bias correction of CMIP6 and regional climate projections; (5) comparison of SWAT+ and SWAT for extreme flow simulations in different types of basins; (6) development of an extreme flow module within an overall SWAT modelling system; and (7) integration of artificial intelligence within SWAT modelling. Display omitted more

Green roof is an important measure in “Sponge Cities” to reduce the runoff and improve the runoff quality. The runoff quantity and quality control capacity of five types of extensive green roofs ... (EGRs) were analyzed in Beijing for 51 nature rainfall events and 6 simulated events from July 2017 to October 2018. Different module scales (sizes) and substrate depths were examined to study their correlation to runoff retention, peak flow reduction, pollutant event mean concentration (EMC) and load reduction performance of EGRs. In general, both the single-field rainfall events and the long-term monitoring showed that as the module scale and substrate thickness increased, the retention capacity of the EGRs increased. As the module scale increased, the peak flow reduction rate (Pfrr) of the EGR modules increased, while the thickness of the substrate appeared to have less of an effect on Pfrr. When water quality effect was considered, compared with module scale, the substrate thickness had a more obvious effect on the average EMC of different pollutants. As the substrate thickness increased, the EMC of pollutants decreased. Under six simulated design rainfalls, EMC reduction rate of suspended solid (SS) of all types of EGRs ranged from 64.3%–73.1% while no reduction was found in the EMC of chemical oxygen demand (COD). The EMC trends of ammonia nitrogen (NH4+-N), nitrate nitrogen (NO3−-N), total nitrogen (TN) and total phosphorus (TP) were almost the same, and their EMCs decreased with increasing total rainfall depth. When the pollutant load was considered, the EGRs in this study were a sink of NH4+-N, NO3−-N, TN, and TP but a source of COD. Display omitted •Runoff quantity and quality effect of extensive green roofs (EGRs) was conducted.•Both EGR scale and substrate thickness affected EGRs' runoff retention capacity.•EGRs had strong capacity to reduce concentration and pollutant load of SS.•The concentration of COD, N and P in EGR runoff was higher than that in normal roof.•The EGRs were the sink of TN, NH4+-N, NO3−-N and TP but the source of COD. more

快速城市化驱动的不透水面比例增加是引起流域洪峰和径流总量增加的直接原因,海绵城市建设通过生态基础设施网络构建增加流域透水面比例,是重构流域生态水文过程的重要途径.但是海绵城市建设在流域海绵体生态水文过程中发挥的作用尚不清楚.以深圳市布吉河流域洪湖片区为例,通过雨季水文过程要素在线连续监测来确定海绵城市建设是否改善洪湖片区生态水文过程.结果表明,中观尺度上,雨季降雨量对洪湖片区地表径流总量无直接影响,降雨强度显著影响洪湖片区地表径流峰值流量(P<0.05),日降雨量对布吉河水质影响极显著(P<0.01).洪湖片区通过28.3％(0.85 km2)海绵面积建设,透水面比例提升,以生物滞留设施和透水铺装等强化片区蒸散和下渗过程,减少雨季径流97.2％(248.72万m3),削减典型降雨峰值流量98.2％以上,降低易涝点积水水位至7.8 cm以下,2.8％形成河川径流(布吉河),海绵面积(比例)和地表径流量削减无直接量化关系.洪湖片区污染物截留时空随保水能力得到提升,控制排放悬浮物月均浓度均低于15.60 mg/L,污染物通过径流裹挟进入布吉河的总量和速率降低,促使布吉河黑臭消除、水质提升至IV类.海绵城市建设对微观尺度生态水文过程的影响与中观尺度存在差异,降雨量等因素与典型项目生态水文过程量化关系不明显.学校、道路和社区公园利用绿色屋顶、透水铺装等强化下渗、蒸散,可削减雨季径流99.0％以上、削减峰值流量97.0％以上,控制悬浮物月均浓度低于17.10 mg/L.总之,以上研究结果强烈表明海绵城市中微观尺度源头减排设施和调蓄设施的耦合建设模式可以削减洪湖片区径流总量、峰值流量、积水水位和径流污染,是一种改善相似流域生态水文过程的有效途径.

•Peak flows were reduced by 3–17% for variable soil, structural storage, and rainfall.•Initial soil moisture has an important effect on peak flow scale invariance.•Extrapolation of scale invariance ... revealed reductions dissipated 2km downstream. This research systematically analyzed the influence of antecedent soil wetness, rainfall depth, and the subsequent impact on peak flows in a 45km2 watershed. Peak flows increased with increasing antecedent wetness and rainfall depth, with the highest peak flows occurring under intense precipitation on wet soils. Flood mitigation structures were included and investigated under full and empty initial storage conditions. Peak flows were reduced at the outlet of the watershed by 3–17%. The highest peak flow reductions occurred in scenarios with dry soil, empty project storage, and low rainfall depths. These analyses showed that with increased rainfall depth, antecedent moisture conditions became increasingly less impactful. Scaling invariance of peak discharges were shown to hold true within this basin and were fit through ordinary least squares regression for each design scenario. Scale-invariance relationships were extrapolated beyond the outlet of the analyzed basin to the point of intersection of with and without structure scenarios. In each scenario extrapolated peak discharge benefits depreciated at a drainage area of approximately 100km2. The associated drainage area translated to roughly 2km downstream of the Beaver Creek watershed outlet. This work provides an example of internal watershed benefits of structural flood mitigation efforts, and the impact the may exert outside of the basin. Additionally, the influence of $1.8 million in flood reduction tools was not sufficient to routinely address downstream flood concerns, shedding light on the additional investment required to alter peak flows in large basins. more

Subsurface flows, particularly hyporheic exchange fluxes, driven by streambed topography, permeability, channel gradient and dynamic flow conditions provide prominent ecological services such as ... nitrate removal from streams and aquifers. Stream flow dynamics cause strongly nonlinear and often episodic contributions of nutrient concentrations in river‐aquifer systems. Using a fully coupled transient flow and reactive transport model, we investigated the denitrification potential of hyporheic zones during peak‐flow events. The effects of streambed permeability, channel gradient and bedform amplitude on the spatio‐temporal distribution of nitrate and dissolved organic carbon in streambeds and the associated denitrification potential were explored. Distinct peak‐flow events with different intensity, duration and hydrograph shape were selected to represent a wide range of peak‐flow scenarios. Our results indicated that the specific hydrodynamic characteristics of individual flow events largely determine the average positive or negative nitrate removal capacity of hyporheic zones, however the magnitude of this capacity is controlled by geomorphological settings (i.e., channel slope, streambed permeability and bedform amplitude). Specifically, events with longer duration and higher intensity were shown to promote higher nitrate removal efficiency with higher magnitude of removal efficiency in the scenarios with higher slope and permeability values. These results are essential for better assessment of the subsurface nitrate removal capacity under the influence of flow dynamics and particularly peak‐flow events in order to provide tailored solutions for effective restoration of interconnected river‐aquifer systems. Key Points Reactive transport model predicts stream geomorphological impacts on hyporheic denitrification potential High frequency observations of nutrient fluxes improve predictions of denitrification potential Controls of duration and intensity of peak‐flow events on denitrification potential vary between geomorphological settings more

Spirometry and peak expiratory flow measurement (PEF) are combined during functional respiratory assessments. The new digital peak flow meter (DPM) evaluates the forced expiratory volume in the first ... second (FEV 1 ) and PEF. To compare lung function measurements using spirometry and DPM. This cross-sectional analytical study assessed FEV 1 and PEF in children with and without asthma. Statistical analysis was performed to assess the agreement between the measures using the intraclass correlation coefficient (ICC), Bland-Altman, and survival agreement plot. 125 (3-12 y) and 196 (6-18 y) children without and with asthma, respectively, were studied. In children without asthma, the ICC for FEV 1 and PEF were 0.89 and 0.86, respectively, while the corresponding values were 0.87 and 0.79, respectively, in patients with asthma. The Bland-Altman method showed a difference of −0.4 to 0.5 for FEV 1 in patients without asthma, with a tendency to increase as the FEV 1 increased to a certain extent. In patients with asthma, the pattern was similar for FEV 1 , and the PEF had a greater dispersion than among those without asthma; however, a good agreement pattern was maintained. In the survival agreement plot, when accepting a tolerance of 0.150 mL for FEV 1 , there was an agreement of close to 55% in both groups. Likewise, when accepting a tolerance of 0.5 L/s for PEF, an agreement of close to 60% and 50% was observed in patients without and with asthma, respectively. DPM was effective as a measure of lung function in pediatric patients with and without asthma. more

Storm direction modulates a hydrograph's magnitude and duration, thus having a potentially large effect on local flood risk. However, how changes in the preferential storm direction affect the ... probability distribution of peak flows remains unknown. We address this question with a novel Monte Carlo approach where stochastically transposed storms drive hydrologic simulations over medium and mesoscale watersheds in the Midwestern United States. Systematic rotations of these watersheds are used to emulate changes in the preferential storm direction. We found that the peak flow distribution impacts are scale‐dependent, with larger changes observed in the mesoscale watershed than in the medium‐scale watershed. We attribute this to the high diversity of storm patterns and the storms' scale relative to watershed size. This study highlights the potential of the proposed stochastic framework to address fundamental questions about hydrologic extremes when our ability to observe these events in nature is hindered by technical constraints and short time records. Plain Language Summary Estimating the likelihood of extreme events such as floods is becoming more challenging because climate change affects storm patterns worldwide. This study focuses on understanding how storm direction affects the probability distribution of peak flows, which is essential for floodplain mapping and engineering design of resilient infrastructure under future climate. Our results suggest that storm direction has minor implications for these probability distributions in medium‐sized watersheds or smaller (order of 4,000 km2) but can significantly affect larger watersheds, particularly for the largest flood events. Our findings point to avenues for future interdisciplinary analyses of the complex, dynamic role of rainfall structure in flooding. Key Points The importance of storm direction in peak flow distribution is mainly driven by the relative difference of storm and watershed size Expected changes in predominant storm trajectories can significantly modify peak flow distributions Regionalization of peak flow distributions should account for the effects of the relative orientation of storms and watersheds more

The floods of the Lahdar river cause repeated inundations and damage to road infrastructures, particularly crossing structures in the territorial center of Had Msila. Our study involved the ... application of various methods to estimate flood flows for different return periods along the Lahdar river. The selected flows were chosen after a comparative analysis of values calculated by the different methods used. These results served as the basis for hydraulic modeling aimed at assessing water levels to establish risk zone mapping. This step is crucial in flood risk assessment. Two main approaches were distinguished: hydrometeorological methods, based on regional parameters derived from rainfall data, and empirical methods, used in the absence or with limited data on flood flows in a given region. Hydraulic modeling was carried out using two software programs: a Geographic Information System (GIS) such as Arc-GIS, and a specific river modeling software like Hec-Ras, allowing for the numerical representation of the natural state of the territory. The results obtained serve as the foundation for all river hydraulic modeling, thereby facilitating flood prediction and hydrological risk management in floodplains. Modeling Lahdar river floods in the studied sections enables the prediction of flood risk and its impacts on constructions and infrastructure in the Had Msila Center. more