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Publications (10 of 27) Show all publications
Broekhuizen, I., Leonhardt, G., Marsalek, J. & Viklander, M. (2019). Calibration event selection for green urban drainage modelling. Hydrology and Earth System Sciences Discussions
Open this publication in new window or tab >>Calibration event selection for green urban drainage modelling
2019 (English)In: Hydrology and Earth System Sciences Discussions, ISSN 1812-2108, E-ISSN 1812-2116Article in journal (Refereed) Submitted
Abstract [en]

Calibration of urban drainage models is typically performed based on a limited number of observed rainfall-runoff events, which may be selected from a longer time-series of measurements in different ways. In this study, 14 single- and two-stage strategies for selecting these events were tested for calibration of a SWMM model of a predominantly green urban area. The event selection was considered in relation to other sources of uncertainty such as measurement uncertainties, objective functions, and catchment discretization. Even though all 14 strategies resulted in successful model calibration, the difference between the best and worst strategies reached 0.2 in Nash–Sutcliffe Efficiency (NSE) and the calibrated parameter values notably varied. Most, but not all, calibration strategies were robust to changes in objective function, perturbations in calibration data and the use of a low spatial resolution model in the calibration phase. The various calibration strategies satisfactorily predicted 7 to 13 out of 19 validation events. The two-stage strategies performed better than the single-stage strategies when measuring performance using the Root Mean Square Error, flow volume error or peak flow error (but not using NSE); when flow data in the calibration period had been perturbed by ±40 %; and when using a lower model resolution. The two calibration strategies that performed best in the validation period were two-stage strategies. The findings in this paper show that different strategies for selecting calibration events may lead in some cases to different results for the validation period, and that calibrating impermeable and green area parameters in two separate steps may improve model performance in the validation period, while also reducing the computational demand in the calibration phase.

Place, publisher, year, edition, pages
Copernicus Publications, 2019
National Category
Water Engineering
Research subject
Urban Water Engineering
Identifiers
urn:nbn:se:ltu:diva-73294 (URN)10.5194/hess-2019-67 (DOI)
Projects
Reliable modeling of green infrastructure in green urban catchments
Funder
Swedish Research Council Formas, 2015-121
Available from: 2019-03-25 Created: 2019-03-25 Last updated: 2019-04-16
Gavric, S., Leonhardt, G., Marsalek, J. & Viklander, M. (2019). Processes improving urban stormwater quality in grass swales and filter strips: A review of research findings. Science of the Total Environment, 669, 431-447
Open this publication in new window or tab >>Processes improving urban stormwater quality in grass swales and filter strips: A review of research findings
2019 (English)In: Science of the Total Environment, ISSN 0048-9697, E-ISSN 1879-1026, Vol. 669, p. 431-447Article in journal (Refereed) Published
Abstract [en]

Increasing interest in urban drainage green infrastructure brings attention to grass swales and filter strips (GS&GFS) and their role in stormwater management. While the understanding of the hydrology and hydraulics of these stormwater control measures is adequate for current needs, there are knowledge gaps in understanding the water quality processes in GS&GFS and such a finding motivated preparation of the review paper that follows. The review revealed that most of the empirical studies of GS&GFS flow quality focused on the removal of pollutants associated with road runoff, and particularly solids, with relatively few studies addressing nutrients, traffic associated hydrocarbons, oxygen demanding substances, chloride, and faecal indicator bacteria. The reported results suffer from limitations caused by experimental conditions often representing a steady flow used to irrigate GS&GFS and generate runoff, non-submerged flows, no lateral inflows along swale side slopes, constant dosing of solids, emphasis on larger-than-typical solids, incomplete descriptions of experimental conditions, and limited attention to experimental uncertainties. Besides settling, other treatment processes, like adsorption/desorption, plant uptake, chemical precipitation and microbial degradation are often acknowledged, but without attempting to quantify their effects on flow quality. The modelling of GS&GFS flow quality would be beneficial for an improved understanding of green urban drainage infrastructure, but currently it is infeasible without a better knowledge of stormwater quality processes in GS&GFS facilities.

Place, publisher, year, edition, pages
Elsevier, 2019
Keywords
Green infrastructure, Pollutant transport, Runoff treatment, Stormwater management, SolidsTrace metals
National Category
Water Engineering
Research subject
Urban Water Engineering
Identifiers
urn:nbn:se:ltu:diva-73262 (URN)10.1016/j.scitotenv.2019.03.072 (DOI)30889442 (PubMedID)2-s2.0-85063001613 (Scopus ID)
Note

Validerad;2019;Nivå 2;2019-03-21 (johcin)

Available from: 2019-03-21 Created: 2019-03-21 Last updated: 2019-04-05Bibliographically approved
Broekhuizen, I., Leonhardt, G., Marsalek, J. & Viklander, M. (2019). Selection of Calibration Events for Modelling Green Urban Drainage. In: Giorgio Mannina (Ed.), New Trends in Urban Drainage Modelling: UDM 2018. Paper presented at International Conference on Urban Drainage Modelling, UDM 2018, Palermo, Italy, 23-26 September 2018 (pp. 608-613). Cham: Springer
Open this publication in new window or tab >>Selection of Calibration Events for Modelling Green Urban Drainage
2019 (English)In: New Trends in Urban Drainage Modelling: UDM 2018 / [ed] Giorgio Mannina, Cham: Springer, 2019, p. 608-613Conference paper, Published paper (Refereed)
Abstract [en]

Urban drainage models are often calibrated using a limited number of rainfall-runoff events, which may be selected in different ways from a longer observation series. This paper compares 13 different single- and two-stage strategies for selecting events used to calibrate a SWMM model of a predominantly green urban area. Most led to successful calibration, but performance varied for various validation events. Most selection strategies were insensitive to the choice of Nash-Sutcliffe Model Efficiency or Root Mean Squared Error as the objective function. Calibrating impervious and green area parameters separately in two-stage strategies can help improve prediction of low-flow events in validation.

Place, publisher, year, edition, pages
Cham: Springer, 2019
Series
Green Energy and Technology
National Category
Water Engineering
Research subject
Urban Water Engineering
Identifiers
urn:nbn:se:ltu:diva-70715 (URN)10.1007/978-3-319-99867-1_105 (DOI)978-3-319-99866-4 (ISBN)978-3-319-99867-1 (ISBN)
Conference
International Conference on Urban Drainage Modelling, UDM 2018, Palermo, Italy, 23-26 September 2018
Available from: 2018-09-03 Created: 2018-09-03 Last updated: 2018-09-03Bibliographically approved
Broekhuizen, I., Rujner, H., Roldin, M., Leonhardt, G. & Viklander, M. (2019). Towards using soil water content observations for calibration of distributed urban drainage models. In: : . Paper presented at NOVATECH 2019.
Open this publication in new window or tab >>Towards using soil water content observations for calibration of distributed urban drainage models
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2019 (English)Conference paper, Published paper (Refereed)
Abstract [en]

Fully distributed urban drainage models can be used to analyse and predict the behaviour of green urban drainage infrastructure such as swales, but they need to be calibrated for specific study sites. Using only drainage outflow measurements may not provide enough information to do this in an optimal way, so additional types of measurements have to be considered. This study identifies different approaches to including soil water content (SWC) observations in the calibration process and investigates how they affect parameter identifiability and the predictive uncertainty of the calibrated model. This is done using the Generalized Likelihood Uncertainty Estimation methodology applied to a model of a large urban swale. It was found that setting initial conditions based on the SWC measurements improved the fit between observed and simulated SWC, but also reduced the accuracy of the simulated amount of infiltration. Including SWC observations allowed to identify one parameter (saturated moisture content of the swale bottom) that was not identifiable from outflow measurements alone. Including SWC observations in the derivation of predictive uncertainty bounds made those bounds narrower (more precise), but where SWC had been used to set initial conditions the uncertainty bound failed to capture the observations. It is concluded that SWC observations can provide useful information for the calibration of distributed urban drainage models.

Keywords
calibration, distributed models, parameter identifiability, predictive uncertainty, soil water content
National Category
Water Engineering
Research subject
Urban Water Engineering
Identifiers
urn:nbn:se:ltu:diva-73293 (URN)
Conference
NOVATECH 2019
Projects
Reliable modeling of green infrastructure in green urban catchmentsAssessment and modelling of green infrastructure for urban catchments
Funder
Swedish Research Council Formas, 2015-121Swedish Research Council Formas, 2015-778
Note

An extended abstract was submitted to the conference and accepted for presentation, but the type of presentation (oral or poster) has not been assigned yet as of 2019-03-25.

Available from: 2019-03-25 Created: 2019-03-25 Last updated: 2019-08-27
Broekhuizen, I., Muthanna, T. M., Leonhardt, G. & Viklander, M. (2019). Urban drainage models for green areas: Structural differences and their effects on simulated runoff. Journal of Hydrology X, 5, Article ID 100044.
Open this publication in new window or tab >>Urban drainage models for green areas: Structural differences and their effects on simulated runoff
2019 (English)In: Journal of Hydrology X, ISSN 2589-9155, Vol. 5, article id 100044Article in journal (Refereed) Published
Abstract [en]

Mathematical stormwater models are often used as tools for planning and analysing urban drainage systems. However, the inherent uncertainties of the models must be properly understood in order to make optimal use of them. One source of uncertainty that has received relatively little attention, particularly for increasingly popular green areas as part of urban drainage systems, is the mathematical model structure. This paper analyses the differences between three different widely-used models (SWMM, MOUSE and Mike SHE) when simulating rainfall runoff from green areas over a 26-year period. Eleven different soil types and six different soil depths were used to investigate the sensitivity of the models to changes in both. Important hydrological factors such as seasonal runoff and evapotranspiration, the number of events that generated runoff, and the initial conditions for rainfall events, varied significantly between the three models. MOUSE generated the highest runoff volumes, while it was rather insensitive to changes in soil type and depth. Mike SHE was mainly sensitive to changes in soil type. SWMM, which generated the least runoff, was sensitive to changes in both soil type and depth. Explanations for the observed differences were found in the descriptions of the mathematical models. The differences in model outputs could significantly impact the conclusions from studies on the design or analysis of urban drainage systems. The amount and frequency of runoff from green areas in all three models indicates that green areas cannot be simply ignored in urban drainage modelling studies.

Place, publisher, year, edition, pages
Elsevier, 2019
Keywords
Model structure uncertainty, Urban drainage, Green areas, Runoff, Infiltration, Stormwater models
National Category
Water Engineering
Research subject
Urban Water Engineering
Identifiers
urn:nbn:se:ltu:diva-76902 (URN)10.1016/j.hydroa.2019.100044 (DOI)2-s2.0-85075487371 (Scopus ID)
Funder
Swedish Research Council Formas, 2015-121Vinnova, 2016-05176
Note

Validerad;2019;Nivå 1;2019-11-28 (johcin)

Available from: 2019-11-28 Created: 2019-11-28 Last updated: 2019-12-09Bibliographically approved
Rujner, H., Leonhardt, G., Marsalek, J. & Viklander, M. (2018). High-resolution modelling of the grass swale response to runoff inflows with Mike SHE. Journal of Hydrology, 562, 411-422
Open this publication in new window or tab >>High-resolution modelling of the grass swale response to runoff inflows with Mike SHE
2018 (English)In: Journal of Hydrology, ISSN 0022-1694, E-ISSN 1879-2707, Vol. 562, p. 411-422Article in journal (Refereed) Published
Abstract [en]

The feasibility of simulating the hydrological response of a grass swale to runoff inflows was examined using the hydrological model Mike SHE and the available input data from 12 irrigation events mimicking runoff from block rainfalls. The test swale channel had a trapezoidal cross-section, bottom slope of 1.5%, length of 30 m, and was built in loamy fine sand. The irrigation events consisted in releasing two equal constant inflows to the swale: a concentrated longitudinal flow at the upstream end and a distributed lateral inflow along the swale side slope adjacent to the contributing drainage area. The total inflows approximated runoff from two events with return periods of 2 months and 3 years, respectively, for durations of 30 min. Irrigation experiments were done for two states of the initial soil moisture, dry or wet antecedent moisture conditions (AMC). Mike SHE has been extensively used on catchments of various sizes, but rarely for small stormwater management facilities and their detailed topography investigated in this study. The latter application required high spatial and temporal resolutions, with computational cells of 0.2 × 0.2 m and time steps as short as 0.6 s to avoid computational instabilities. For dominant hydrological processes, the following computational options in Mike SHE were chosen: Soil infiltration – the van Genuchten equation, unsaturated zone flow – the one-dimensional Richards equation, and overland flow – the diffusive wave approximation of the St. Venant equations. For study purposes, the model was calibrated for single events representing one of four combinations of low and high inflows, and dry and wet AMC, and then applied to the remaining 11 events. This was complemented by calibration for two events, representing high inflow on wet AMC and low inflow in dry AMC. The goodness of fit was statistically assessed for observed and simulated peak flows, hydrograph volumes, Nash-Sutcliffe model efficiencies (NSE), and soil water content (SWC) in swale soil layers. The best fit (NSE > 0.8) was obtained for high inflows and wet AMC (i.e., when the primary swale function is flow conveyance); the least fit was noted for low inflows and dry AMC, when the primary swale function is flow attenuation. Furthermore, this observation indicates the overall importance of correct modelling of the soil infiltration. The effects of spatial variation of SWC on the swale discharge hydrograph could not be confirmed from simulation results, but high topographical accuracy was beneficial for reproducing well the locations of the observed water ponding. No significant increases in simulated SWC at 0.3 m or greater depths were noted, which agreed with field observations. Overall, the results indicated that Mike SHE was effective in process-oriented small-scale modelling of grass swale flow hydrographs.

Place, publisher, year, edition, pages
Elsevier, 2018
Keywords
Grass swale, Distributed modelling, Mike SHE, Soil water content, Stormwater management
National Category
Oceanography, Hydrology and Water Resources Water Engineering
Research subject
Urban Water Engineering
Identifiers
urn:nbn:se:ltu:diva-68751 (URN)10.1016/j.jhydrol.2018.05.024 (DOI)000438003000031 ()2-s2.0-85046868673 (Scopus ID)
Projects
GrönNano
Funder
Swedish Research Council Formas, 2015-778
Note

Validerad;2018;Nivå 2;2018-05-16 (andbra)

Available from: 2018-05-16 Created: 2018-05-16 Last updated: 2019-09-13Bibliographically approved
Moghadas, S., Leonhardt, G., Marsalek, J. & Viklander, M. (2018). Modeling Urban Runoff from Rain-on-Snow Events with the U.S. EPA SWMM Model for Current and Future Climate Scenarios. Journal of cold regions engineering, 32(1), Article ID 04017021.
Open this publication in new window or tab >>Modeling Urban Runoff from Rain-on-Snow Events with the U.S. EPA SWMM Model for Current and Future Climate Scenarios
2018 (English)In: Journal of cold regions engineering, ISSN 0887-381X, E-ISSN 1943-5495, Vol. 32, no 1, article id 04017021Article in journal (Refereed) Published
Abstract [en]

A methodological study of modeling runoff from rain-on-snow events was conducted using the northern Swedish city of Kiruna as a test case, with respect to physiographic, drainage system, and the current and projected future climate data. Runoff simulations were carried out with the PCSWMM, which is a geographic information system (GIS) supported version of the U.S. EPA Storm Water Management Model (U.S. EPA SWMM5) developed by Computational Hydraulics International (CHI). In total, 177 simulations were run covering four scenario categories: eight rain events, three climates (the current and two projected), three soil infiltration rates, and five snow water equivalent (SWE) values. Simulation results were analyzed with respect to influential rainfall/snowmelt/runoff factors and the noted differences were statistically tested for significance. Result analysis revealed new findings concerning the differences between runoff generated by rain-on-snow and summer thunderstorm events. In particular, it was noted that a relatively frequent rain-on-snow event, with a return period of 1.4 year, caused fewer flooded nodes and surcharged pipes in the catchment sewer system, but almost five times greater runoff volume, when compared to the same drainage system performance indicators corresponding to a 10-year event occurring in the summer. Depending on the physical characteristics of the snow cover, among which the depth appears the most important, rainwater and snowmelt may be retained in, or released from, the snowpack, which acts as a dynamic reservoir controlling the generation and release of runoff. Smaller snow depths produce smaller volumes of melt, smaller storage capacity and less effective insulation of soils, which may freeze to greater depths and become practically impervious, until the process of soil thawing has been completed. The impacts of climate change in the study area, described by increases in precipitation and air temperatures, are likely to cause more frequent runoff problems attributed to the future rain-on-snow events. Even though the runoff tendencies reported here reflect the characteristics of the study area and climate, they suggest the need to consider rain-on-snow events in sewer design and storm water management in regions with seasonal snow covers, certainly with respect to runoff volumes.

Place, publisher, year, edition, pages
American Society of Civil Engineers (ASCE), 2018
National Category
Water Engineering
Research subject
Urban Water Engineering
Identifiers
urn:nbn:se:ltu:diva-66278 (URN)10.1061/(ASCE)CR.1943-5495.0000147 (DOI)000428257200007 ()2-s2.0-85032174474 (Scopus ID)
Projects
GREEN / BLUE CITIES - GreenBlue Infrastructure for Sustainable, Attractive Cities
Funder
Swedish Research Council Formas, 1173214VINNOVA, 1173214
Note

Validerad;2017;Nivå 2;2017-10-26 (andbra)

Available from: 2017-10-26 Created: 2017-10-26 Last updated: 2018-04-12Bibliographically approved
Sun, S., Leonhardt, G., Sandoval, S., Bertrand-Krajewski, J.-L. & Rauch, W. (2017). A Bayesian method for missing rainfall estimation using a conceptual rainfall–runoff model. Hydrological Sciences Journal, 62(15), 2456-2468
Open this publication in new window or tab >>A Bayesian method for missing rainfall estimation using a conceptual rainfall–runoff model
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2017 (English)In: Hydrological Sciences Journal, ISSN 0262-6667, E-ISSN 2150-3435, Vol. 62, no 15, p. 2456-2468Article in journal (Refereed) Published
Abstract [en]

The estimation of missing rainfall data is an important problem for data analysis and modelling studies in hydrology. This paper develops a Bayesian method to address missing rainfall estimation from runoff measurements based on a pre-calibrated conceptual rainfall–runoff model. The Bayesian method assigns posterior probability of rainfall estimates proportional to the likelihood function of measured runoff flows and prior rainfall information, which is presented by uniform distributions in the absence of rainfall data. The likelihood function of measured runoff can be determined via the test of different residual error models in the calibration phase. The application of this method to a French urban catchment indicates that the proposed Bayesian method is able to assess missing rainfall and its uncertainty based only on runoff measurements, which provides an alternative to the reverse model for missing rainfall estimates.

Place, publisher, year, edition, pages
Taylor & Francis, 2017
Keywords
Bayesian method, conceptual ra infall–runoff model, missing rainfall data, rainfall estimates, uncertainty
National Category
Other Civil Engineering Water Engineering Other Environmental Engineering
Research subject
Urban Water Engineering
Identifiers
urn:nbn:se:ltu:diva-66031 (URN)10.1080/02626667.2017.1390317 (DOI)000418482200003 ()
Projects
Assessment and modeling of green infrastructure for urban catchments (2016-2018)
Funder
Swedish Research Council Formas, 2015-778
Note

Validerad;2017;Nivå 2;2017-11-28 (rokbeg)

Available from: 2017-10-10 Created: 2017-10-10 Last updated: 2019-09-11Bibliographically approved
Leonhardt, G., Moghadas, S., Marsalek, J. & Viklander, M. (2017). An exploratory study of snowmelt runoff modelling in an urban catchment using the US EPASWMM model. In: 14th IWA/IAHR International Conference On Urban Drainage: . Paper presented at 14th IWA/IAHR International Conference On Urban Drainage, Prague, Czech Republic, September 10-15 2017 (pp. 78-81).
Open this publication in new window or tab >>An exploratory study of snowmelt runoff modelling in an urban catchment using the US EPASWMM model
2017 (English)In: 14th IWA/IAHR International Conference On Urban Drainage, 2017, p. 78-81Conference paper, Oral presentation with published abstract (Refereed)
Keywords
melt condition, model calibration, snowmelt model, SWMM
National Category
Other Civil Engineering Water Engineering Other Environmental Engineering
Research subject
Urban Water Engineering
Identifiers
urn:nbn:se:ltu:diva-66033 (URN)
Conference
14th IWA/IAHR International Conference On Urban Drainage, Prague, Czech Republic, September 10-15 2017
Projects
Reliable modeling of green infrastructure in green urban catchments - Calibration, validation and uncertainty assessment
Funder
Swedish Research Council Formas, 2015-121
Available from: 2017-10-10 Created: 2017-10-10 Last updated: 2018-02-26Bibliographically approved
Zischg, J., Goncalves, M. L. R., Bacchin, T. K., Leonhardt, G., Viklander, M., van Timmeren, A., . . . Sitzenfrei, R. (2017). Info-Gap robustness pathway method for transitioning of urban drainage systems under deep uncertainties. Water Science and Technology, 76(5), 1272-1281
Open this publication in new window or tab >>Info-Gap robustness pathway method for transitioning of urban drainage systems under deep uncertainties
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2017 (English)In: Water Science and Technology, ISSN 0273-1223, E-ISSN 1996-9732, Vol. 76, no 5, p. 1272-1281Article in journal (Refereed) Published
Abstract [en]

In the urban water cycle, there are different ways of handling stormwater runoff. Traditional systems mainly rely on underground piped, sometimes named ‘gray’ infrastructure. New and so-called ‘green/blue’ ambitions aim for treating and conveying the runoff at the surface. Such concepts are mainly based on ground infiltration and temporal storage. In this work a methodology to create and compare different planning alternatives for stormwater handling on their pathways to a desired system state is presented. Investigations are made to assess the system performance and robustness when facing the deeply uncertain spatial and temporal developments in the future urban fabric, including impacts caused by climate change, urbanization and other disruptive events, like shifts in the network layout and interactions of ‘gray’ and ‘green/blue’ structures. With the Info-Gap robustness pathway method, three planning alternatives are evaluated to identify critical performance levels at different stages over time. This novel methodology is applied to a real case study problem where a city relocation process takes place during the upcoming decades. In this case study it is shown that hybrid systems including green infrastructures are more robust with respect to future uncertainties, compared to traditional network design.

Place, publisher, year, edition, pages
IWA Publishing, 2017
Keywords
city transformation, green/blue infrastructure, hybrid systems, Info-Gap robustness pathway method, network transitioning, SWMM
National Category
Other Civil Engineering
Research subject
Urban Water Engineering
Identifiers
urn:nbn:se:ltu:diva-65300 (URN)10.2166/wst.2017.320 (DOI)000409346700028 ()28876269 (PubMedID)2-s2.0-85029094937 (Scopus ID)
Projects
GREEN / BLUE CITIES - GreenBlue Infrastructure for Sustainable, Attractive Cities
Funder
Swedish Research Council Formas, 1773241VINNOVA, 1773241
Note

Validerad;2017;Nivå 2;2017-09-11 (svasva)

Available from: 2017-08-24 Created: 2017-08-24 Last updated: 2018-07-10Bibliographically approved
Organisations
Identifiers
ORCID iD: ORCID iD iconorcid.org/0000-0003-0367-3449

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