scholarly journals Assessment of LID practices for restoring pre-development runoff regime in an urbanized catchment in southern Finland

2015 ◽  
Vol 71 (10) ◽  
pp. 1485-1491 ◽  
Author(s):  
Mingfu Guan ◽  
Nora Sillanpää ◽  
Harri Koivusalo
Keyword(s):  
Low Impact Development ◽  
Urban Runoff ◽  
Flow Conditions ◽  
Runoff Generation ◽  
Flow Rates ◽  
Storm Water Management Model ◽  
Runoff Regime ◽  
Reduction Effect ◽  
Development Levels ◽  
Negative Impacts

This study quantifies the effects of common stormwater management techniques on urban runoff generation. Simulated flow rates for different low impact development (LID) scenarios were compared with observed flow rates during different urban construction phases in a catchment (12.3 ha) that was developed from natural forest to a residential area over a monitoring period of 5 years. The Storm Water Management Model (SWMM) was calibrated and validated against the observed flow rates in the fully developed catchment conditions, and it was then applied to parameterize the LID measures and produce scenarios of their hydrological impacts. The results from the LID scenarios were compared with the observed flow rates in the pre-development and the partially developed catchment conditions. The results show that LID controls reduce urban runoff towards the flow conditions in the partially developed catchment, but the reduction effect diminishes during large rainfall events. The hydrographs with LID are still clearly different from the observed pre-development levels. Although the full restoration of pre-development flow conditions was not feasible, a combination of several measures controlling both volumes and retention times of storm runoff appeared to be effective for managing the stormwater runoff and mitigating the negative impacts of urban development.

scholarly journals SWMM-Based Assessment of Urban Mountain Stormwater Management Effects under Different LID Scenarios

Water ◽  
2022 ◽  
Vol 14 (1) ◽  
pp. 78
Author(s):  
Yangyang Yuan ◽  
Yu Gan ◽  
Yuhan Xu ◽  
Qining Xie ◽  
Yuqing Shen ◽  
...  
Keyword(s):  
Urban Areas ◽  
Low Impact Development ◽  
Peak Discharge ◽  
Mountain Region ◽  
Runoff Generation ◽  
Storm Water Management Model ◽  
Mountainous Regions ◽  
Nanjing City ◽  
Runoff Control

The types of urban mountains are diverse, and the surrounding environment is complex. The conditions of runoff generation and convergence in different regions of the same mountain vary. Using the Lijia Mountain in China’s Nanjing City as a case study, this study investigates the effects of such mountain-region-based LID (Low Impact Development) systems. Based on the hydrological analysis of this mountain region, SWMM (Storm Water Management Model) software is used to model and compare the runoff control effects of two LID systems schemes, namely segmental detention and retention and terminal detention and retention. The study’s findings demonstrate that the terminal detention and retention scheme can effectively delay the time of peak flooding and partly reduce peak discharge. In contrast, the segmental detention and retention scheme has a limited delay effect on flood peaks but significantly reduces the peak discharge. This research breaks through the limitations of the previous construction of a single LID scheme for mountainous regions in built-up urban areas. It serves as a theoretical model and technical reference for selecting LID scenarios in response to different mountain conditions.

Large-Scale Application of Biofiltration Swale Runoff Management Practices

2007 ◽  
Vol 2 (2) ◽  
Author(s):  
William C. Lucas
Keyword(s):  
Large Scale ◽  
Management Practices ◽  
Peak Flow ◽  
Low Impact Development ◽  
Urban Runoff ◽  
Management Model ◽  
Check Dams ◽  
Runoff Reduction ◽  
Impervious Area ◽  
Hydrologic Responses

Retaining rainfall where it lands is a fundamental benefit of Low Impact Development (LID). The Delaware Urban Runoff Management Model (DURMM) was developed to address the benefits of LID design. DURMM explicitly addresses the benefits of impervious area disconnection as well as swale flow routing that responds to flow retardance changes. Biofiltration swales are an effective LID BMP for treating urban runoff. By adding check dams, the detention storage provided can also reduce peak rates. This presentation explores how the DURMM runoff reduction approach can be integrated with detention routing procedures to project runoff volume and peak flow reductions provided by BMP facilities. This approach has been applied to a 1,200 unit project on 360 hectares located in Delaware, USA. Over 5 km of biofiltration swales have been designed, many of which have stone check dams placed every 30 to 35 meters to provide detention storage. The engineering involved in the design of such facilities uses hydrologic modeling based upon TR-20 routines, as adapted by the DURMM model. The hydraulic approach includes routing of flows through the check dams. This presentation summarizes the hydrological network, presents the hydrologic responses, along with selected hydrographs to demonstrate the potential of design approach.

scholarly journals Net-exergetic, hydraulic and thermal optimization of coaxial heat exchangers using fixed flow conditions instead of fixed flow rates

2021 ◽  
Vol 9 (1) ◽  
Author(s):  
Tobias Blanke ◽  
Markus Hagenkamp ◽  
Bernd Döring ◽  
Joachim Göttsche ◽  
Vitali Reger ◽  
...  
Keyword(s):  
Reynolds Number ◽  
Laminar Flow ◽  
Mass Flow ◽  
Flow Rate ◽  
Heat Exchangers ◽  
Circular Ring ◽  
Flow Conditions ◽  
Flow Rates ◽  
Mass Flow Rates ◽  
Pipe Radius

AbstractPrevious studies optimized the dimensions of coaxial heat exchangers using constant mass flow rates as a boundary condition. They show a thermal optimal circular ring width of nearly zero. Hydraulically optimal is an inner to outer pipe radius ratio of 0.65 for turbulent and 0.68 for laminar flow types. In contrast, in this study, flow conditions in the circular ring are kept constant (a set of fixed Reynolds numbers) during optimization. This approach ensures fixed flow conditions and prevents inappropriately high or low mass flow rates. The optimization is carried out for three objectives: Maximum energy gain, minimum hydraulic effort and eventually optimum net-exergy balance. The optimization changes the inner pipe radius and mass flow rate but not the Reynolds number of the circular ring. The thermal calculations base on Hellström’s borehole resistance and the hydraulic optimization on individually calculated linear loss of head coefficients. Increasing the inner pipe radius results in decreased hydraulic losses in the inner pipe but increased losses in the circular ring. The net-exergy difference is a key performance indicator and combines thermal and hydraulic calculations. It is the difference between thermal exergy flux and hydraulic effort. The Reynolds number in the circular ring is instead of the mass flow rate constant during all optimizations. The result from a thermal perspective is an optimal width of the circular ring of nearly zero. The hydraulically optimal inner pipe radius is 54% of the outer pipe radius for laminar flow and 60% for turbulent flow scenarios. Net-exergetic optimization shows a predominant influence of hydraulic losses, especially for small temperature gains. The exact result depends on the earth’s thermal properties and the flow type. Conclusively, coaxial geothermal probes’ design should focus on the hydraulic optimum and take the thermal optimum as a secondary criterion due to the dominating hydraulics.

scholarly journals Temperature log simulations in high-enthalpy boreholes

2019 ◽  
Vol 7 (1) ◽  
Author(s):  
Jia Wang ◽  
Fabian Nitschke ◽  
Maziar Gholami Korzani ◽  
Thomas Kohl
Keyword(s):  
Heat Transfer ◽  
Temperature Distribution ◽  
Temperature Gradient ◽  
Flow Rate ◽  
Fluid Loss ◽  
Flow Conditions ◽  
Flow Rates ◽  
High Enthalpy ◽  
Fluid Losses ◽  
Lateral Heat

Abstract Temperature logs have important applications in the geothermal industry such as the estimation of the static formation temperature (SFT) and the characterization of fluid loss from a borehole. However, the temperature distribution of the wellbore relies on various factors such as wellbore flow conditions, fluid losses, well layout, heat transfer mechanics within the fluid as well as between the wellbore and the surrounding rock formation, etc. In this context, the numerical approach presented in this paper is applied to investigate the influencing parameters/uncertainties in the interpretation of borehole logging data. To this end, synthetic temperature logs representing different well operation conditions were numerically generated using our newly developed wellbore simulator. Our models account for several complex operation scenarios resulting from the requirements of high-enthalpy wells where different flow conditions, such as mud injection with- and without fluid loss and shut-in, occur in the drill string and the annulus. The simulation results reveal that free convective heat transfer plays an important role in the earlier evolution of the shut-in-time temperature; high accuracy SFT estimation is only possible when long-term shut-in measurements are used. Two other simulation scenarios for a well under injection conditions show that applying simple temperature correction methods on the non-shut-in temperature data could lead to large errors for SFT estimation even at very low injection flow rates. Furthermore, the magnitude of the temperature gradient increase depends on the flow rate, the percentage of fluid loss and the lateral heat transfer between the fluid and the rock formation. As indicated by this study, under low fluid losses (< 30%) or relatively higher flow rates (> 20 L/s), the impact of flow rate and the lateral heat transfer on the temperature gradient increase can be ignored. These results provide insights on the key factors influencing the well temperature distribution, which are important for the choice of the drilling data to estimate SFT and the design of the inverse modeling scheme in future studies to determine an accurate SFT profile for the high-enthalpy geothermal environment.

scholarly journals Carotid Bifurcation Hemodynamics in Older Adults: Effect of Measured Versus Assumed Flow Waveform

2010 ◽  
Vol 132 (7) ◽  
Author(s):  
Yiemeng Hoi ◽  
Bruce A. Wasserman ◽  
Edward G. Lakatta ◽  
David A. Steinman
Keyword(s):  
Magnetic Resonance ◽  
Older Adult ◽  
Blood Flow Rate ◽  
Carotid Bifurcation ◽  
Flow Waveform ◽  
Flow Conditions ◽  
Flow Rates ◽  
Relative Residence Time ◽  
Contrast Magnetic Resonance ◽  
Dynamics Models

Recent work has illuminated differences in carotid artery blood flow rate dynamics of older versus young adults. To what degree flow waveform shape, and indeed the use of measured versus assumed flow rates, affects the simulated hemodynamics of older adult carotid bifurcations has not been elucidated. Image-based computational fluid dynamics models of N=9 normal, older adult carotid bifurcations were reconstructed from magnetic resonance angiography. Subject-specific hemodynamics were computed by imposing each individual’s inlet and outlet flow rates measured by cine phase-contrast magnetic resonance imaging or by imposing characteristic young and older adult flow waveform shapes adjusted to cycle-averaged flow rates measured or allometrically scaled to the inlet and outlet areas. Despite appreciable differences in the measured versus assumed flow conditions, the locations and extents of low wall shear stress and elevated relative residence time were broadly consistent; however, the extent of elevated oscillatory shear index was substantially underestimated, more by the use of assumed cycle-averaged flow rates than the assumed flow waveform shape. For studies of individual vessels, use of a characteristic flow waveform shape is likely sufficient, with some benefit offered by scaling to measured cycle-averaged flow rates. For larger-scale studies of many vessels, ranking of cases according to presumed hemodynamic or geometric risk is robust to the assumed flow conditions.

scholarly journals Simulation of Low Impact Development (LID) Practices and Comparison with Conventional Drainage Solutions

Proceedings ◽  
2018 ◽  
Vol 2 (11) ◽  
pp. 640 ◽  
Author(s):  
Ioannis M. Kourtis ◽  
Vassilios A. Tsihrintzis ◽  
Evangelos Baltas
Keyword(s):  
Water Management ◽  
Design Process ◽  
Low Impact Development ◽  
Green Roofs ◽  
Storm Water ◽  
Management Model ◽  
Storm Events ◽  
Storm Water Management Model ◽  
Runoff Volume ◽  
Peak Runoff

The present work aims at quantifying the benefit of Low Impact Development (LID) practices in reducing peak runoff and runoff volume, and at comparing LID practices to conventional stormwater solutions. The hydrologic-hydraulic model used was the Storm Water Management Model (SWMM5.1). The LID practices modeled were: (i) Green roofs; and (ii) Permeable pavements. Each LID was tested independently and compared to two different conventional practices, i.e., sewer enlargement and detention pond design. Results showed that for small storm events LID practices are comparable to conventional measures, in reducing flooding. Overall, smaller storms should be included in the design process.

scholarly journals A Comprehensive Review of Low Impact Development Models for Research, Conceptual, Preliminary and Detailed Design Applications

Water ◽  
2018 ◽  
Vol 10 (11) ◽  
pp. 1541 ◽  
Author(s):  
Sahereh Kaykhosravi ◽  
Usman Khan ◽  
Amaneh Jadidi
Keyword(s):  
Spatial Data ◽  
Spatial Scales ◽  
Low Impact Development ◽  
Model Development ◽  
Point Of View ◽  
Tree Canopy ◽  
Balance Model ◽  
Runoff Generation ◽  
Development Models ◽  
Model Features

This review compares and evaluates eleven Low Impact Development (LID) models on the basis of: (i) general model features including the model application, the temporal resolution, the spatial data visualization, the method of placing LID within catchments; (ii) hydrological modelling aspects including: the type of inbuilt LIDs, water balance model, runoff generation and infiltration; and (iii) hydraulic modelling methods with a focus on the flow routing method. Results show that despite the recent updates of existing LID models, several important features are still missing and need improvement. These features include the ability to model: multi-layer subsurface media, tree canopy and processes associated with vegetation, different spatial scales, snowmelt and runoff calculations. This review provides in-depth insight into existing LID models from a hydrological and hydraulic point of view, which will facilitate in selecting the best-suited model. Recommendations on further studies and LID model development are also presented.

scholarly journals Evaluation of the Main Function of Low Impact Development Based on Rainfall Events

Water ◽  
2020 ◽  
Vol 12 (8) ◽  
pp. 2231
Author(s):  
Meiyan Feng ◽  
Kwansue Jung ◽  
Fengping Li ◽  
Hongyan Li ◽  
Joo-Cheol Kim
Keyword(s):  
Low Impact Development ◽  
Hydrological Process ◽  
Main Function ◽  
Storm Events ◽  
Rapid Urbanization ◽  
Rainfall Events ◽  
Hydrological Balance ◽  
Storm Water Management Model ◽  
Cycle System ◽  
Positive Effect

Low Impact Development (LID) is one of the sustainable approaches to urban stormwater management in areas with rapid urbanization. Although LID has been shown to have a positive effect in flood reduction, the hydrological balance regulation effect of LID under a variety of rainfall events is not fully understood. In this study, we assessed the hydrological efficiency of LID at two residential–commercial mixed sites in Korea to investigate the main function of LID in terms of diverse rainfall characteristics. Storm Water Management Model (SWMM) was constructed to simulate the hydrological process numerical simulations in the pre-development, post-development and LID design scenarios, respectively. The model was calibrated and validated by using five observed rainfall–runoff events. Then, four single and four multiple LID practices (LIDs) were used to estimate their effectiveness under seven different designed rainfall events. The results indicate that LIDs substantially influence the hydrology cycle system, while the regulating effect varies with rainfall amounts. The efficiency of LIDs in flood reduction is proved to be more effective during lower storm events. However, LIDs should be designed to primarily prioritize the restoration of hydrological balance when the rainfall return period is longer.

scholarly journals Effectiveness of low-impact development for urban inundation risk mitigation under different scenarios: a case study in Shenzhen, China

2018 ◽  
Vol 18 (9) ◽  
pp. 2525-2536 ◽  
Author(s):  
Jiansheng Wu ◽  
Rui Yang ◽  
Jing Song
Keyword(s):  
Local Governments ◽  
Risk Mitigation ◽  
Low Impact Development ◽  
Green Roofs ◽  
Rapid Urbanization ◽  
Storm Water Management Model ◽  
Inundation Depth ◽  
High Hazard ◽  
Hazard Level ◽  
Hazard Levels

Abstract. The increase in impervious surfaces associated with rapid urbanization is one of the main causes of urban inundation. Low-impact development (LID) practices have been studied for mitigation of urban inundation. This study used a hydrodynamic inundation model, coupling SWMM (Storm Water Management Model) and IFMS-Urban (Integrated Flood Modelling System–Urban), to assess the effectiveness of LID under different scenarios and at different hazard levels. The results showed that LID practices can effectively reduce urban inundation. The maximum inundation depth was reduced by 3 %–29 %, average inundation areas were reduced by 7 %–55 %, and average inundation time was reduced by 0 %–43 % under the eight scenarios. The effectiveness of LID practices differed for the three hazard levels, with better mitigation of urban inundation at a low hazard level than at a high hazard level. Permeable pavement (PP) mitigated urban inundation better than green roofs (GRs) under the different scenarios and at different hazard levels. We found that more implementation area with LID was not necessarily more efficient, and the scenario of 10 % PP+10 % GR was more efficient for the study area than other scenarios. The results of this study can be used by local governments to provide suggestions for urban inundation control, disaster reduction, and urban renewal.

scholarly journals Developing a Reliability Index of Low Impact Development for Urban Areas

Water ◽  
2020 ◽  
Vol 12 (11) ◽  
pp. 2961
Author(s):  
Yang Ho Song ◽  
Jung Ho Lee ◽  
Eui Hoon Lee
Keyword(s):  
Urban Areas ◽  
Distance Measure ◽  
Low Impact Development ◽  
Drainage System ◽  
Reliability Evaluation ◽  
Nonpoint Source ◽  
Evaluation Technique ◽  
Storm Water Management Model ◽  
Primary Reference ◽  
Urban Catchments

A defining characteristic of the urbanization is the transformation of existing pervious areas into impervious areas during development. This leads to numerous hydrologic and environmental problems such as an increase in surface runoff due to excess rainfall, flooding, the deterioration of water quality, and an increase in nonpoint source pollution. Several studies propose supplementary measures on environmental change problems in development areas using the low impact development technique. This study investigated the reduction of nonpoint source pollutant loads and flooding in catchments through urban catchment rainfall–runoff management. For the quantitative assessment of flood disasters and water pollution problems, we propose a reliability evaluation technique. This technique refers to a series of analysis methods that determine the disaster prevention performance of the existing systems. As the two factors involve physical quantities of different dimensions, a reliability evaluation technique was developed using the distance measure method. Using the storm water management model, multiple scenarios based on synthetic rainfall in the catchment of the Daerim 2 rainwater pumping station in Seoul, South Korea, were examined. Our results indicate the need for efficient management of natural disaster risks that may occur in urban catchments. Moreover, this study can be used as a primary reference for setting a significant reduction target and facilitating accurate decision making concerning urban drainage system management.

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