Can stormwater harvesting restore pre-development flows in urban catchments in South East Queensland?

2013 ◽  
Vol 67 (2) ◽  
pp. 446-451 ◽  
Author(s):  
S. Ashbolt ◽  
S. Aryal ◽  
K. Petrone ◽  
B. S. McIntosh ◽  
S. Maheepala ◽  
...  
Keyword(s):  
Flow Distribution ◽  
High Rate ◽  
Storm Events ◽  
Flow Conditions ◽  
Impervious Area ◽  
Stormwater Harvesting ◽  
Urban Catchments ◽  
The Mean ◽  
Flow Frequency ◽  
Impervious Areas

Increases in the impervious area due to urbanisation have been shown to have negative impacts on the physical and ecological condition of streams, primarily through increased volume and frequency of runoff. The harvesting and detention of runoff has a potential to decrease this impact. This paper describes the effects of urbanisation on catchment flow and of stormwater harvesting on reducing those adverse impacts on a stream in South East Queensland (SEQ), Australia. A largely undeveloped catchment located southeast of Brisbane city was calibrated and validated using the Stormwater Management Model (SWMM). This model was used to investigate the effect of a range of future increases in urbanisation (represented by impervious area) on stream hydrology as well as the potential of stormwater harvesting to return the catchments to predevelopment flow conditions. Stormwater harvesting was modelled according to flow frequency measures specified in current SEQ development guidelines. These guidelines stipulate the capture of the first 10 mm of runoff from impervious areas of 0–40% and the first 15 mm from impervious areas of 40% or greater for urban developments. We found that increases in the impervious area resulted in increases in the mean, frequency and duration of high flows, and an increase in the mean rate of rise and fall for storm events in the catchment. However, the predevelopment (non-urbanised) flow distribution was very flashy in comparison with all urbanised scenarios; i.e. it had the quickest response to rainfall indicated by a high rate of rise to and fall from peak flow volume, followed by a return to zero flow conditions. Capturing the runoff according to the development guidelines resulted in a reduction in flow towards the flow distribution of a lower impervious area, however this was insufficient to meet predevelopment conditions. This suggests a stronger influence of impervious areas in this catchment on the volume of runoff than flow frequency measures are able to ameliorate.

scholarly journals Contribution of directly connected and isolated impervious areas to urban drainage network hydrographs

2013 ◽  
Vol 17 (9) ◽  
pp. 3473-3483 ◽  
Author(s):  
Y. Seo ◽  
N.-J. Choi ◽  
A. R. Schmidt
Keyword(s):  
Mass Balance ◽  
Additional Contribution ◽  
Runoff Hydrograph ◽  
Impervious Area ◽  
Width Function ◽  
Direct Interpretation ◽  
Balance Analysis ◽  
Urban Catchments ◽  
Runoff Hydrographs ◽  
Impervious Areas

Abstract. This paper addresses the mass balance error observed in runoff hydrographs in urban watersheds by introducing assumptions regarding the contribution of infiltrated rainfall from pervious areas and isolated impervious area (IIA) to the runoff hydrograph. Rainfall infiltrating into pervious areas has been assumed not to contribute to the runoff hydrograph until Hortonian excess rainfall occurs. However, mass balance analysis in an urban watershed indicates that rainfall infiltrated to pervious areas can contribute directly to the runoff hydrograph, thereby offering an explanation for the long hydrograph tail commonly observed in runoff from urban storm sewers. In this study, a hydrologic analysis based on the width function is introduced, with two types of width functions obtained from both pervious and impervious areas, respectively. The width function can be regarded as the direct interpretation of the network response. These two width functions are derived to obtain distinct response functions for directly connected impervious areas (DCIA), IIA, and pervious areas. The results show significant improvement in the estimation of runoff hydrographs and suggest the need to consider the flow contribution from pervious areas to the runoff hydrograph. It also implies that additional contribution from flow paths through joints and cracks in sewer pipes needs to be taken into account to improve the estimation of runoff hydrographs in urban catchments.

scholarly journals Contribution of directly connected and isolated impervious areas to urban drainage network hydrographs

2013 ◽  
Vol 10 (5) ◽  
pp. 5605-5641
Author(s):  
Y. Seo ◽  
N.-J. Choi ◽  
A. R. Schmidt
Keyword(s):  
Mass Balance ◽  
Additional Contribution ◽  
Runoff Hydrograph ◽  
Impervious Area ◽  
Width Function ◽  
Direct Interpretation ◽  
Balance Analysis ◽  
Urban Catchments ◽  
Runoff Hydrographs ◽  
Impervious Areas

Abstract. This paper addresses the mass balance error observed in runoff hydrographs in urban watersheds by introducing assumptions regarding the contribution of infiltrated rainfall from pervious areas and isolated impervious area (IIA) to the runoff hydrograph. Rainfall infiltrating into pervious areas has been assumed not to contribute to the runoff hydrograph until Hortonian excess rainfall occurs. However, mass balance analysis in an urban watershed indicates that rainfall infiltrated to pervious areas can contribute to direct runoff hydrograph, thereby offering an explanation for the long hydrograph tail commonly observed in runoff from urban storm sewers. In this study, a hydrologic analysis based on the width function is introduced, with two types of width functions obtained from both pervious and impervious areas, respectively. The width function can be regarded as the direct interpretation of the network response. These two width functions are derived to obtain distinct response functions for directly connected impervious areas (DCIA), IIA, and pervious areas. The results show significant improvement in the estimation of runoff hydrographs and suggest the need to consider the flow contribution from pervious areas to the runoff hydrograph. It also implies that additional contribution from flow paths through joints and cracks in sewer pipes needs to be taken into account to improve the estimation of runoff hydrographs in urban catchments.

scholarly journals Analysing the impact of urban areas patterns on the mean annual flow of 43 urbanized catchments

2015 ◽  
Vol 370 ◽  
pp. 29-32 ◽  
Author(s):  
B. Salavati ◽  
L. Oudin ◽  
C. Furusho ◽  
P. Ribstein
Keyword(s):  
Landscape Metrics ◽  
Urban Areas ◽  
The United States ◽  
Spatial Changes ◽  
Urban Catchments ◽  
The Mean ◽  
Flow Changes ◽  
The Impact ◽  
Impervious Areas ◽  
Historical Flow

Abstract. It is often argued that urban areas play a significant role in catchment hydrology, but previous studies reported disparate results of urbanization impacts on stream flow. This might stem either from the difficulty to quantify the historical flow changes attributed to urbanization only (and not climate variability) or from the inability to decipher what type of urban planning is more critical for flows. In this study, we applied a hydrological model on 43 urban catchments in the United States to quantify the flow changes attributable to urbanization. Then, we tried to relate these flow changes to the changes of urban/impervious areas of the catchments. We argue that these spatial changes of urban areas can be more precisely characterized by landscape metrics, which enable analysing the patterns of historical urban growth. Landscape metrics combine the richness (the number) and evenness (the spatial distribution) of patch types represented on the landscape. Urbanization patterns within the framework of patch analysis have been widely studied but, to our knowledge, previous research works had not linked them to catchments hydrological behaviours. Our results showed that the catchments with larger impervious areas and larger mean patch areas are likely to have larger increase of runoff yield.

scholarly journals Antecedent flow conditions and nitrate concentrations in the Mississippi River Basin

2013 ◽  
Vol 10 (9) ◽  
pp. 11451-11484 ◽  
Author(s):  
J. C. Murphy ◽  
R. M. Hirsch ◽  
L. A. Sprague
Keyword(s):  
River Basin ◽  
Mississippi River ◽  
Nitrate Concentration ◽  
Mississippi River Basin ◽  
Storm Events ◽  
Flow Conditions ◽  
Continental Scale ◽  
Antecedent Moisture ◽  
Nitrate Concentrations ◽  
The Mean

Abstract. The influence of antecedent flow conditions on nitrate concentrations was explored at eight sites in the Mississippi River Basin, USA. Antecedent moisture conditions have been shown to influence nutrient export from small, relatively homogenous basins, but this influence has not been observed at a regional or continental scale. Antecedent flow conditions were quantified as the ratio between the mean daily flow of the previous year and the mean daily flow from the period of record (Q ratio), and the Q ratio was statistically related to nitrate anomalies (the unexplained variability in nitrate concentration after filtering out season, long-term trend, and contemporaneous flow effects) at each site. Nitrate anomaly and Q ratio were negatively related at three of the four major tributary sites and upstream in the Mississippi River, indicating that when the previous year was drier than average, at these sites, nitrate concentrations were higher than expected. The strength of these relationships increased when data were subdivided by contemporaneous flow conditions. Five of the eight sites had significant negative relationships (p ≤ 0.05) at high or moderately high contemporaneous flows, suggesting nitrate that accumulates in these basins during a drought is flushed during subsequent storm events. At half of the sites, when flow during the previous year was 50% drier than average, nitrate concentration can be from 9 and 27% higher than nitrate concentrations that follow a year with average daily flow. Conversely, nitrate concentration can be from 8 and 21% lower than expected when the previous year was 50% wetter than average. These relationships between nitrate concentration and Q ratio serve as the basis for future studies that can better define specific hydrologic processes occurring during and after a drought, which influence nitrate concentration, such as the duration or magnitude of low flows, and the timing of low and high flows.

scholarly journals Forensic Investigation of Four Monitored Green Infrastructure Inlets

Water ◽  
2021 ◽  
Vol 13 (13) ◽  
pp. 1787
Author(s):  
Leena J. Shevade ◽  
Franco A. Montalto
Keyword(s):  
Measurement Uncertainty ◽  
Green Infrastructure ◽  
Stormwater Management ◽  
Catchment Area ◽  
Low Flow ◽  
Inflow Rate ◽  
Forensic Investigation ◽  
Flow Conditions ◽  
The Mean

Green infrastructure (GI) is viewed as a sustainable approach to stormwater management that is being rapidly implemented, outpacing the ability of researchers to compare the effectiveness of alternate design configurations. This paper investigated inflow data collected at four GI inlets. The performance of these four GI inlets, all of which were engineered with the same inlet lengths and shapes, was evaluated through field monitoring. A forensic interpretation of the observed inlet performance was conducted using conclusions regarding the role of inlet clogging and inflow rate as described in the previously published work. The mean inlet efficiency (meanPE), which represents the percentage of tributary area runoff that enters the inlet was 65% for the Nashville inlet, while at Happyland the NW inlet averaged 30%, the SW inlet 25%, and the SE inlet 10%, considering all recorded events during the monitoring periods. The analysis suggests that inlet clogging was the main reason for lower inlet efficiency at the SW and NW inlets, while for the SE inlet, performance was compromised by a reverse cross slope of the street. Spatial variability of rainfall, measurement uncertainty, uncertain tributary catchment area, and inlet depression characteristics are also correlated with inlet PE. The research suggests that placement of monitoring sensors should consider low flow conditions and a strategy to measure them. Additional research on the role of various maintenance protocols in inlet hydraulics is recommended.

scholarly journals Quantifying the Effects of Wave—Current Interactions on Tidal Energy Resource at Sites in the English Channel Using Coupled Numerical Simulations

Energies ◽  
2021 ◽  
Vol 14 (12) ◽  
pp. 3625
Author(s):  
Jon Hardwick ◽  
Ed B. L. Mackay ◽  
Ian G. C. Ashton ◽  
Helen C. M. Smith ◽  
Philipp R. Thies
Keyword(s):  
Wave Model ◽  
Tidal Energy ◽  
English Channel ◽  
Flow Conditions ◽  
Mean Flow ◽  
Radiation Stress ◽  
Large Wave ◽  
Stress Gradients ◽  
The Mean ◽  
Flow Power

Numerical modeling of currents and waves is used throughout the marine energy industry for resource assessment. This study compared the output of numerical flow simulations run both as a standalone model and as a two-way coupled wave–current simulation. A regional coupled flow-wave model was established covering the English Channel using the Delft D-Flow 2D model coupled with a SWAN spectral wave model. Outputs were analyzed at three tidal energy sites: Alderney Race, Big Roussel (Guernsey), and PTEC (Isle of Wight). The difference in the power in the tidal flow between coupled and standalone model runs was strongly correlated to the relative direction of the waves and currents. The net difference between the coupled and standalone runs was less than 2.5%. However, when wave and current directions were aligned, the mean flow power was increased by up to 7%, whereas, when the directions were opposed, the mean flow power was reduced by as much as 9.6%. The D-Flow Flexible Mesh model incorporates the effects of waves into the flow calculations in three areas: Stokes drift, forcing by radiation stress gradients, and enhancement of the bed shear stress. Each of these mechanisms is discussed. Forcing from radiation stress gradients is shown to be the dominant mechanism affecting the flow conditions at the sites considered, primarily caused by dissipation of wave energy due to white-capping. Wave action is an important consideration at tidal energy sites. Although the net impact on the flow power was found to be small for the present sites, the effect is site specific and may be significant at sites with large wave exposure or strong asymmetry in the flow conditions and should thus be considered for detailed resource and engineering assessments.

Scaphoid Nonunion Is a Disabling Problem in a Military Population

Hand ◽  
2021 ◽  
pp. 155894472110031
Author(s):  
Nicholas H. Lake ◽  
Rafae Khan ◽  
Kyle W. Mombell ◽  
Mary Fergus ◽  
Dominic Gomez-Leonardelli
Keyword(s):  
Functional Outcome ◽  
Military Service ◽  
Functional Outcomes ◽  
High Rate ◽  
Scaphoid Nonunion ◽  
Military Population ◽  
Outcome Scores ◽  
The Mean ◽  
Return To Duty

Background Scaphoid nonunion can occur in up to 55% of displaced scaphoid fractures. Long-term functional outcomes of this injury are lacking. In addition, no study has published rate of return to active military service after this injury. Our goal was to educate providers and patients on expected functional outcomes and return to duty after treatment of scaphoid nonunion. Methods We conducted a retrospective review of patients who underwent scaphoid nonunion repair at our institution from 2008 to 2017. The primary outcome measures were union rates, return to duty rates, and functional outcome scores obtained by telephone call. A total of 144 patients were included and 40 responded to our call for long-term follow-up. Results A total of 72% of patients achieved union after surgery, 18% required revision surgery, and 74% of patients were able to return to full duty after surgery. However, this number progressively decreased at 1, 2, and 5 years after surgery. At an average of 5.9 years after surgery, the mean Quick Disabilities of the Arm, Shoulder, and Hand (qDASH) score was 23.9. The mean qDASH for patients who achieved union (21.9) was significantly lower than those with persistent nonunion (29.2) ( P = .0115). Conclusion Scaphoid nonunion is a difficult problem in the military. We found a high rate of persistent nonunion often requiring revision to partial or full wrist arthrodesis. In addition, our long-term functional outcome scores demonstrate significant disability after this injury, even when union is achieved. This information can help us better counsel our patients and set expectations after treatment of this injury.

The Estimation of Discharge in an Experimental Open Channel

2014 ◽  
Vol 905 ◽  
pp. 369-373
Author(s):  
Choo Tai Ho ◽  
Yoon Hyeon Cheol ◽  
Yun Gwan Seon ◽  
Noh Hyun Suk ◽  
Bae Chang Yeon
Keyword(s):  
Unsteady Flow ◽  
River Discharge ◽  
Open Channel ◽  
Flow Conditions ◽  
Mean Velocity ◽  
Velocity Equation ◽  
The Mean ◽  
Loop Form

The estimation of a river discharge by using a mean velocity equation is very convenient and rational. Nevertheless, a research on an equation calculating a mean velocity in a river was not entirely satisfactory after the development of Chezy and Mannings formulas which are uniform equations. In this paper, accordingly, the mean velocity in unsteady flow conditions which are shown loop form properties was estimated by using a new mean velocity formula derived from Chius 2-D velocity formula. The results showed that the proposed method was more accurate in estimating discharge, when compared with the conventional formulas.

Abstract 16884: Evaluating the Effectiveness of Atrial Fibrillation Ablation Guided by Spatiotemporal Electrogram Dispersion

Circulation ◽  
2020 ◽  
Vol 142 (Suppl_3) ◽  
Author(s):  
Brian Liu ◽  
Arismendy Nunez-Garcia ◽  
Cao Tran ◽  
Michael Wu
Keyword(s):  
Atrial Fibrillation ◽  
Atrial Tachycardia ◽  
Statistical Significance ◽  
Univariate Analysis ◽  
External Validation ◽  
Posterior Wall ◽  
High Rate ◽  
Single Center Experience ◽  
The Mean

Introduction: Catheter ablation of atrial fibrillation (AF) guided by spatiotemporal dispersion (SD) of electrograms has been proposed as an ablation strategy to treat patients with persistent AF. However, external validation of this technique is lacking. Here we report a single center experience using ablation by SD. Hypothesis: Targeting regions with SD is associated with a high rate of termination and favorable freedom from AF among patients with persistent AF. Methods: Patients with persistent AF who underwent SD from November 2018 to January 2020 were included in this study. All patients underwent pulmonary vein isolation (PVI) in addition to targeting areas of SD. Lesions on areas of electrogram dispersion were anchored to the PVI or to mitral or posterior wall lines where appropriate. EKG, Holter, event monitors or device interrogations were obtained at 3 and 6 months to assess for arrhythmia recurrence. Results: 44 patients met the inclusion criteria and were included in the study. The patients had a mean age of 69±8 years and were 68 % male. The prevalence of comorbidities was as follows: hypertension (89%), diabetes (21%), OSA (37%) and CAD (26%). Average CHADSVASC score was 2.9±1.4, LVEF was 53±11% and left atrium (LA) diameter was 5.2±1 cm. The recurrence rate of AF at 6 months was 14% whereas the recurrence of atrial tachycardia was 20%. Acute AF termination was observed in 73% of the patients. Termination to sinus occurred in 38% of the patients and the remaining terminated to atrial tachycardia which was subsequently ablated to sinus. The mean procedure duration was 240±90 minutes. Univariate analysis showed recurrence was associated with LA diameter (r=.52; p<.001). No recurrences were observed among patients with a LA diameter < 5 cm. Termination rates were higher among patients with LA diameter < 5 cm when compared to LA diameter ≥ 5 cm. However, it did not reach statistical significance (80% vs. 60%; p=.21). Conclusions: The target of electrograms with SD during AF ablation added to PVI was associated with a high termination rate and a good freedom from AF recurrence at 6 months. The ideal candidate for this procedure may be those with LA diameter < 5 cm among persistent AF. The long-term efficacy of this technique merits further studies in larger populations.

scholarly journals Numerical Modeling of Flow Over a Rectangular Broad-Crested Weir with a Sloped Upstream Face

Water ◽  
2018 ◽  
Vol 10 (11) ◽  
pp. 1663 ◽  
Author(s):  
Lei Jiang ◽  
Mingjun Diao ◽  
Haomiao Sun ◽  
Yu Ren
Keyword(s):  
Numerical Simulations ◽  
Discharge Coefficient ◽  
Separation Zone ◽  
Turbulence Models ◽  
Numerical Results ◽  
Upstream Face ◽  
Flow Conditions ◽  
Flow Features ◽  
The Mean ◽  
Absolute Percent Error

The objective of this study was to evaluate the effect of the upstream angle on flow over a trapezoidal broad-crested weir based on numerical simulations using the open-source toolbox OpenFOAM. Eight trapezoidal broad-crested weir configurations with different upstream face angles (θ = 10°, 15°, 22.5°, 30°, 45°, 60°, 75°, 90°) were investigated under free-flow conditions. The volume-of-fluid (VOF) method and two turbulence models (the standard k-ε model and the SST k-w model) were employed in the numerical simulations. The numerical results were compared with the experimental results obtained from published papers. The root mean square error (RMSE) and the mean absolute percent error (MAPE) were used to evaluate the accuracy of the numerical results. The statistical results show that RMSE and MAPE values of the standard k-ε model are 0.35–0.67% and 0.50–1.48%, respectively; the RMSE and MAPE values of the SST k-w model are 0.25–0.66% and 0.55–1.41%, respectively. Additionally, the effects of the upstream face angle on the flow features, including the discharge coefficient and the flow separation zone, were also discussed in the present study.

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