scholarly journals The Impact of Rainfall Movement Direction on Urban Runoff Cannot Be Ignored in Urban Hydrologic Management

Water ◽  
2021 ◽  
Vol 13 (20) ◽  
pp. 2923
Author(s):  
Yesen Liu ◽  
Yaohuan Huang ◽  
Yuanyuan Liu ◽  
Kuang Li ◽  
Min Li
Keyword(s):  
Heavy Rainfall ◽  
Rainfall Intensity ◽  
Urban Runoff ◽  
Temporal Variations ◽  
Movement Direction ◽  
Urban Floods ◽  
Peak Runoff ◽  
Hydrologic Management ◽  
The Impact

Urban floods have been exacerbated globally, associated with increasing spatial-temporal variations in rainfall. However, compared with rainfall variabilities of intensity and duration, the effect of rainfall movement direction is always ignored. Based on 1313 rainfall scenarios with different combinations of rainfall intensity and rainfall movement direction in the typically rainy city of Shenzhen in China, we find that the effect of rainfall movement direction on the peak runoff may reach up to 20%, which will decrease to less than 5% under heavy rainfall intensity conditions. In addition, our results show that the impact of rainfall movement direction is almost symmetrical and is associated with the direction of the river. The closer rainfall movement direction is to the Linear Directional Mean of rivers, the larger is the peak runoff of section. Our results reveal that rainfall movement direction is significant to urban peak runoff in the downstream reaches, which should be considered in urban hydrological analysis.

scholarly journals The impact of RMD on urban runoff cannot be ignored in urban hydrologic management

2021 ◽  
Author(s):  
Yesen Liu ◽  
yaohuan huang ◽  
yuanyuan liu
Keyword(s):  
Rainfall Intensity ◽  
Urban Runoff ◽  
Temporal Variations ◽  
Hydrologic Model ◽  
Urban Floods ◽  
Spatial Feature ◽  
Peak Runoff ◽  
Hydrologic Management ◽  
The Impact

Abstract Urban floods have been exacerbated globally, associated with increasing spatial-temporal variations of rainfall. However, compared with rainfall variabilities of intensity and duration, the effect of RMD is always ignored. Based on 1313 rainfall scenarios with different combinations of rainfall intensity(RI) and RMD in a typical rainy city of Shenzhen in China, we investigate the urban runoff response in relation to RMD and the spatial feature of rivers. Our results show that the effect of RMD on the peak runoff may reach up to 20%, which will decrease to less than 5% under heavy RI conditions. In addition, we find that the impact of RMD is almost symmetrical and is associated with the direction of the river. The closer RMD is to the Linear Directional Mean of upstream, the larger peak runoff of section is. Our results reveal that RMD is significant to urban peak runoff in the downstream reaches, which should be considered in urban hydrologic model.

scholarly journals Prediction of factors affecting activation of soil erosion by mathematical modeling at pedon scale under laboratory conditions

2020 ◽  
Vol 10 (1) ◽  
Author(s):  
Saeed Shojaei ◽  
Zahra Kalantari ◽  
Jesús Rodrigo-Comino
Keyword(s):  
Soil Loss ◽  
Rainfall Intensity ◽  
Quadratic Function ◽  
Interactive Effects ◽  
Soil Protection ◽  
Single Factor ◽  
Rainfall Events ◽  
Rainfall Duration ◽  
The Impact ◽  
Runoff Production

AbstractSoil degradation due to erosion is a significant worldwide problem at different spatial (from pedon to watershed) and temporal scales. All stages and factors in the erosion process must be detected and evaluated to reduce this environmental issue and protect existing fertile soils and natural ecosystems. Laboratory studies using rainfall simulators allow single factors and interactive effects to be investigated under controlled conditions during extreme rainfall events. In this study, three main factors (rainfall intensity, inclination, and rainfall duration) were assessed to obtain empirical data for modeling water erosion during single rainfall events. Each factor was divided into three levels (− 1, 0, + 1), which were applied in different combinations using a rainfall simulator on beds (6 × 1 m) filled with soil from a study plot located in the arid Sistan region, Iran. The rainfall duration levels tested were 3, 5, and 7 min, the rainfall intensity levels were 30, 60, and 90 mm/h, and the inclination levels were 5, 15, and 25%. The results showed that the highest rainfall intensity tested (90 mm/h) for the longest duration (7 min) caused the highest runoff (62 mm3/s) and soil loss (1580 g/m2/h). Based on the empirical results, a quadratic function was the best mathematical model (R2 = 0.90) for predicting runoff (Q) and soil loss. Single-factor analysis revealed that rainfall intensity was more influential for runoff production than changes in time and inclination, while rainfall duration was the most influential single factor for soil loss. Modeling and three-dimensional depictions of the data revealed that sediment production was high and runoff production lower at the beginning of the experiment, but this trend was reversed over time as the soil became saturated. These results indicate that avoiding the initial stage of erosion is critical, so all soil protection measures should be taken to reduce the impact at this stage. The final stages of erosion appeared too complicated to be modeled, because different factors showed differing effects on erosion.

Regulation and Critical Threshold of Grass Cover on Slope Runoff in LoessHilly Gully Region under Artificial

2021 ◽  
Author(s):  
Qiufen Zhang ◽  
Xizhi Lv ◽  
Rongxin Chen ◽  
Yongxin Ni ◽  
Li Ma
Keyword(s):  
Soil Erosion ◽  
Rainfall Intensity ◽  
Climatic Conditions ◽  
Vegetation Coverage ◽  
Critical Threshold ◽  
Runoff Generation ◽  
Grassland Vegetation ◽  
Slope Flow ◽  
The Impact ◽  
Slope Runoff

<p>The slope runoff caused by rainstorm is the main cause of serious soil and water loss in the loess hilly area, the grassland vegetation has a good inhibitory effect on the slope runoff, it is of great significance to reveal the role of grassland vegetation in the process of runoff generation and control mechanism for controlling soil erosion in this area. In this study, typical grassland slopes in hilly and gully regions of the loess plateau were taken as research objects. Through artificial rainfall in the field, the response rules of slope rainfall-runoff process to different grass coverage were explored. The results show that: (1) The time for the slope flow to stabilize is prolonged with the increase of vegetation coverage, and shortened with the increase of rainfall intensity; (2) At 60 mm·h <sup>−1</sup> rainfall intensity, the threshold of grassland vegetation coverage is 75.38%; at 90 mm·h<sup> −1</sup> rainfall intensity, the threshold of grassland vegetation coverage is 90.54%; at 120 mm·h <sup>−1</sup> rainfall intensity, the impact of grassland vegetation coverage on runoff is not significant; (3) the Reynolds number and Froude number of slope flow are 40.07‒695.22 and 0.33‒1.56 respectively, the drag coefficient is 1.42‒43.53. Under conditions of heavy rainfall, the ability of grassland to regulate slope runoff is limited. If only turf protection is considered, about 90% of grassland coverage can effectively cope with soil erosion caused by climatic conditions in loess hilly and gully regions. Therefore, in loess hilly areas where heavy rains frequently occur, grassland's protective effect on soil erosion is obviously insufficient, and investment in vegetation measures for trees and shrubs should be strengthened.</p>

scholarly journals Absorption coefficient of urban aerosol in Nanjing, west Yangtze River Delta, China

2015 ◽  
Vol 15 (23) ◽  
pp. 13633-13646 ◽  
Author(s):  
B. L. Zhuang ◽  
T. J. Wang ◽  
J. Liu ◽  
Y. Ma ◽  
C. Q. Yin ◽  
...  
Keyword(s):  
Absorption Coefficient ◽  
Urban Area ◽  
Yangtze River ◽  
Temporal Variations ◽  
Yangtze River Delta ◽  
River Delta ◽  
Near Surface ◽  
Absorbing Aerosols ◽  
The Impact ◽  
532 Nm

Abstract. Absorbing aerosols can significantly modulate short-wave solar radiation in the atmosphere, affecting regional and global climate. The aerosol absorption coefficient (AAC) is an indicator that assesses the impact of absorbing aerosols on radiative forcing. In this study, the near-surface AAC and absorption Ångström exponent (AAE) in the urban area of Nanjing, China, are characterized on the basis of measurements in 2012 and 2013 using the seven-channel Aethalometer (model AE-31, Magee Scientific, USA). The AAC is estimated with direct and indirect corrections, which result in consistent temporal variations and magnitudes of AAC at 532 nm. The mean AAC at 532 nm is about 43.23 ± 28.13 M m−1 in the urban area of Nanjing, which is much lower than that in Pearl River Delta and the same as in rural areas (Lin'an) in Yangtze River Delta. The AAC in the urban area of Nanjing shows strong seasonality (diurnal variations); it is high in cold seasons (at rush hour) and low in summer (in the afternoon). It also shows synoptic and quasi-2-week cycles in response to weather systems. Its frequency distribution follows a typical log-normal pattern. The 532 nm AAC ranging from 15 to 65 M m−1 dominates, accounting for more than 72 % of the total data samples in the entire study period. Frequent high pollution episodes, such as those observed in June 2012 and in winter 2013, greatly enhanced AAC and altered its temporal variations and frequency distributions. These episodes are mostly due to local emissions and regional pollution. Air masses flowing from northern China to Nanjing can sometimes be highly polluted and lead to high AAC at the site. AAE at 660/470 nm from the Schmid correction (Schmid et al., 2006) is about 1.56, which might be more reasonable than from the Weingartner correction (Weingartner et al., 2003). Low AAEs mainly occur in summer, likely due to high relative humidity (RH) in the season. AAC increases with increasing AAE at a fixed aerosol loading. The RH–AAC relationship is more complex. Overall, AAC peaks at RH values of around 40 % (1.3 < AAE < 1.6), 65 % (AAE < 1.3 and AAE > 1.6), and 80 % (1.3 < AAE < 1.6).

Herbicide loss in runoff: effects of herbicide properties, slope, and rainfall intensity

Soil Research ◽  
2004 ◽  
Vol 42 (1) ◽  
pp. 17 ◽  
Author(s):  
K. Müller ◽  
M. Trolove ◽  
T. K. James ◽  
A. Rahman
Keyword(s):  
Rainfall Intensity ◽  
Water Solubility ◽  
Small Scale ◽  
Herbicide Application ◽  
Rainfall Events ◽  
Kd Values ◽  
Loam Soil ◽  
The Impact ◽  
Field Plots ◽  
Dissolved Form

Runoff potential of 5 herbicides (acetochlor, atrazine, hexazinone, pendimethalin, and terbuthylazine) was evaluated in a small-scale study under simulated rainfall on a cultivated Hamilton clay loam soil. At 24 h after herbicide application, rainfall events of different intensities were simulated to 0.5-m2 field plots with 20% (70, 88, and 111 mm/h) and 30% (60, 70, and 80 mm/h) slope, respectively. The objective of this study was to compare the behaviour of pesticides covering a range of properties under identical hydrodynamic conditions. Sediment amounts and herbicide concentrations were determined in the runoff samples. As the transported sediment amounts were not sufficient for chemical analyses, herbicide residues attached to sediment were estimated using Kd values determined locally for the soil. Whereas pendimethalin concentrations followed no noticeable pattern, the concentrations for the other herbicides were highest in the first runoff samples, and decreased exponentially with further rain. Results show that herbicides were primarily transported in their dissolved form with the exception of pendimethalin. Slope affected cumulative runoff, sediment, and herbicide losses significantly (P < 0.05). The impact of increased rainfall intensity on runoff initiation followed a similar trend, but herbicide losses from plots exposed to different intensities were not always significant. Losses dissolved in runoff from plots with 20% slope were ≤1% of the applied herbicide, whereas on plots with 30% slope the maximum recorded loss was 65%. Here, losses for all herbicides ranged between 1 and 7% at 60 mm/h and 8 and 65% at 80 mm/h. Exports of herbicides with moderate solubility were negatively correlated with their Kd values and their water solubility.

scholarly journals Analysis of Stormwater Retention on Green Roofs / Badania Retencji Wód Opadowych Na Dachach Zielonych

2012 ◽  
Vol 38 (4) ◽  
pp. 3-13 ◽  
Author(s):  
Ewa Burszta-Adamiak
Keyword(s):  
Life Sciences ◽  
Green Roofs ◽  
Retention Capacity ◽  
Runoff Reduction ◽  
Science And Education ◽  
Peak Runoff ◽  
The Impact ◽  
Stormwater Retention ◽  
Maximum Runoff ◽  
Sewage Systems

Abstract This study presents the results of tests conducted in 2009 and 2010 on experimental sites installed on the roof of the Science and Education Building of the Wroclaw University of Environmental and Life Sciences. The aim of the analysis was to determine the retention capacity of green roofs and the runoff delays and peak runoff reduction during rainfall recorded in Wroclaw conditions. The research shows that green roofs allow to reduce the volume of runoff stormwater in comparison to conventional roofs, that they delay the runoff in time and influence the reduction of the maximum runoff intensity, and thus may limit the impact of stormwater on the stormwater drainage and combined sewage systems.

scholarly journals Effectiveness of Three Post-Harvest Rehabilitation Treatments for Runoff and Sediment Reduction on Skid Trails in the Hyrcanian Forests

2020 ◽  
Vol 41 (2) ◽  
pp. 309-324
Author(s):  
Meghdad Jourgholami ◽  
Masoumeh Ahmadi ◽  
Farzam Tavankar ◽  
Rodolfo Picchio
Keyword(s):  
Leaf Litter ◽  
Sediment Yield ◽  
Rainfall Intensity ◽  
Regression Equations ◽  
Negative Effects ◽  
Diverse Range ◽  
Straw Mulch ◽  
The Impact ◽  
Different Levels ◽  
Runoff And Sediment Yield

Ground-based skidding operations can lead to soil compaction and displacement, which could cause negative effects on forest soil. Hence, some efforts such as forestry best management practices (BMPs) must be implemented in the prone area to mitigate these possible impacts. Several materials and treatments have been adopted to suppress these adverse effects by increasing the ground cover. However, the effects of mulch treatments on runoff and sediment yield are inconclusive with a diverse range of effectiveness. For these reasons, in this research mulch treatments were tested as to determine how the application of organic mulch amendments such as straw and leaf litter and contour-felled logs would alleviate the runoff and sediment yield on machine operating trails and ensure successful hillslope stabilization. The aims of the study were to analyse and compare the effectiveness of leaf litter (LM) and straw mulch (SM) rate and different distances of contour-felled logs (CFL) to mitigate the runoff and sediment yield, and examine the impact of rainfall intensity on effectiveness of litter mulch, straw mulch, and contour-felled logs. Totally, 30 bounded runoff plots in the machine operating trails and four treatments including litter mulch (LMR1: 0.62, LMR2: 1.24, and LMR3: 1.86 kg m-2), straw mulch (SMR1: 0.45, SMR2: 0.92, and SMR3: 1.34 kg m-2), contour-felled logs (CFL10: 10, CFL20: 20, and CFL30: 30 m), and untreated area were established in triplicate with 4 m width and 100 m length. During the study period, the runoff and sediment yield in the untreated trails (U) were 2.36 mm and 11.84 g m-2. Straw (from 41.5 to 60.6%) and litter mulch (from 38.1 to 55.1%), and contour-felled logs treatments (from 70.8 to 88.1%) significantly decreased the runoff, compared to U treatment. Results show that mulch treatments with three different levels of Litter Mulch Rate, LMR1, LMR2, and LMR3 decreased mean sediment by 46.6, 64.0 and 71.8%, in the treatments with three different levels of Straw Mulch Rate, SMR1, SMR2, and SMR3 decreased mean sediment by 42.9, 62.1, and 69.9%, and in the treatments with three different distances of Contour-Felled Logs, CFL10, CFL20, and CFL30 decreased mean sediment by 90.6, 94.7 and 88.3% comparing to U, respectively. The relationships of the runoff and sediment responses to increasing mulching rate of litter and straw followed as negative logarithmic curves, but the decreasing-increasing trends were observed in runoff and sediment yield as the distance between contour-felled logs increased from 10 to 30 m. Polynomial regression equations were developed for predicting the runoff and sediment yield as a function of the application rate of litter and straw mulch and the distance between contour-felled logs, and rainfall intensity. We concluded that contour-felled logs treatment was more effective than both litter and straw mulch to mitigate the runoff, runoff coefficient, and sediment yield on machine operating trails. As a management measure, it could be possible to propose that the contour-felled logs with a distance of 20 m be prescribed to protect the machine operating trails from the negative effects of surface waterflow.

scholarly journals Spatial and temporal variations of CO<sub>2</sub> mole fractions observed at Beijing, Xianghe and Xinglong in North China

2021 ◽  
Author(s):  
Yang Yang ◽  
Minqiang Zhou ◽  
Ting Wang ◽  
Bo Yao ◽  
Pengfei Han ◽  
...  
Keyword(s):  
Seasonal Variations ◽  
Human Activities ◽  
North China ◽  
Terrestrial Ecosystem ◽  
Temporal Variations ◽  
Spatial And Temporal Variations ◽  
Boundary Layer Height ◽  
The Mean ◽  
The Impact ◽  
First Time

Abstract. Atmospheric CO2 mole fractions are observed at Beijing (BJ), Xianghe (XH), and Xinglong (XL) in North China using the Picarro G2301 Cavity Ring-Down Spectroscopy instruments. The measurement system is described comprehensively for the first time. The geo-distances among these three sites are within 200 km, but they have very different surrounding environments: BJ is inside the megacity; XH is in the suburban area; XL is in the countryside on a mountain. The mean and standard deviation of CO2 mole fractions at BJ, XH, and XL between October 2018 and September 2019 are 448.4 ± 12.8 ppm, 436.0 ± 9.2 ppm and 420.6 ± 8.2 ppm, respectively. The seasonal variations of CO2 at these three sites are similar, with a maximum in winter and a minimum in summer, which is dominated by the terrestrial ecosystem. However, the seasonal variations of CO2 at BJ and XH are more affected by human activities as compared to XL. By using CO2 at XL as the background, CO2 enhancements are observed simultaneously at BJ and XH. The diurnal variations of CO2 are driven by the boundary layer height, photosynthesis and human activities at BJ, XH and XL. Moreover, we address the impact of the wind on the CO2 mole fractions at BJ and XL. This study provides an insight into the spatial and temporal variations of CO2 mole fractions in North China.

scholarly journals Investigating pedestrians’ obstacle avoidance behaviour

2020 ◽  
Vol 5 ◽  
Author(s):  
Abdullah Alhawsawi ◽  
Majid Sarvi ◽  
Milad Haghani ◽  
Abbas Rajabifard
Keyword(s):  
Physical Environment ◽  
Simulation Models ◽  
Avoidance Behaviour ◽  
Movement Direction ◽  
Total Speed ◽  
Lateral Direction ◽  
Video Recordings ◽  
High Speeds ◽  
The Impact ◽  
Pedestrian Simulation

Modelling and simulating pedestrian motions are standard ways to investigate crowd dynamics aimed to enhance pedestrians’ safety. Movement of people is affected by interactions with one another and with the physical environment that it may be a worthy line of research. This paper studies the impact of speed on how pedestrians respond to the obstacles (i.e. Obstacles avoidance behaviour). A field experiment was performed in which a group of people were instructed to perform some obstacles avoidance tasks at two levels of normal and high speeds. Trajectories of the participants are extracted from the video recordings for the subsequent intentions:(i) to seek out the impact of total speed, x and yaxis (ii) to observe the impact of the speed on the movement direction, x-axis, (iii) to find out the impact of speed on the lateral direction, y-axis. The results of the experiments could be used to enhance the current pedestrian simulation models.

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