One of the aspects we love about UDM events is the deep discussion fostered by inspirational topics. We’ve set aside time in the conference program for you to join in these discussions during 1-hr Special Sessions and Workshops. Look for these topics in the conference program: 

  • Workshop: Performance Metrics for Green Stormwater Infrastructure 
  • Workshop: Community-driven Open-source SWMM, Where Next? 
  • Special Session: Moving towards an open urban water modeling paradigm: perspectives from academia and industry
  • Special Session: A decade of collecting data on trace contaminant in wet weather discharges – are we ready to model them?
  • Special Session: Modelling for a More Resilient Stormwater System-A basic introduction to real-time modelling and digital twin concepts

Scroll through this page for a description of each session. 

Workshop: Performance Metrics for Green Stormwater Infrastructure

Convenor: Prof. Virginia Stovin, University of Sheffield 

In most jurisdictions, conventional stormwater infrastructure for runoff quantity control (i.e. underground pipes and tanks) is designed based on idealized high return period design storms.  Often the system is assumed to be ‘empty’ prior to the start of rainfall. There are several reasons why this approach may be inappropriate for the design and approval of SuDS/LIDs: 

  • SuDS/LID devices are typically reliant on natural hydrological processes (infiltration and/or evapotranspiration) to restore their retention capacity.  These may occur more slowly compared with drain-down times associated with conventional drainage systems, such that the SuDS/LID will not always be at full retention capacity when the next storm occurs. Depending on assumption made (0-100% capacity available), the system will be over-or under-designed respectively. 
  • A focus on high return period events may rule out SuDS/LID options unable to achieve such stringent requirements, whilst ignoring multiple other hydromorphological and water quality benefits that could be achieved through the effective management of routine events.  

The aim of this workshop is to consider alternative approaches to setting performance targets.  It is expected that suitable metrics would be derived from simulated responses to long duration (10 yr+) high temporal resolution (5 min) continuous rainfall inputs.  What are the right metrics to use in a drainage design/regulatory context? These could include probabilistic performance targets based on flow duration curves, or multiple metrics aimed at characterizing runoff volumes and runoff rates for events with lower return periods (e.g. annual) (Stovin et al., 2017; Quinn et al.,2021).  We expect the discussion to focus mainly on stormwater runoff quantity, but implications for water quality and other (multiple) benefits should be noted. While continuous simulation is feasible at the device/development scale, its computational expense prevents such approaches being applied at the city/catchment scale.  Simplified/surrogate modelling techniques are potentially useful in this context.  

The format of the workshop will be a brief introductory presentation followed by an open discussion. It is anticipated that the workshop discussions will lead to a position paper being submitted to a relevant academic journal. 

Workshop: Community-driven Open-source SWMM, Where Next? 

Convenor: Prof. Ben Hodges, University of Texas at Austin 

This workshop aims to gain insight into the community perceptions on the future development of open-source SWMM. Although EPA-SWMM is formally maintained and distributed by the US EPA, it is (and always has been) a public-domain open-source model. The new development of SWMM5+ and the establishment of the Center for Infrastructure Modelling and Management (CIMM) as a US-based 501c(3) non-profit (charitable) organization has the potential to jump-start community involvement in improving the SWMM code. This objective of this workshop is to establish whether or not the community is interested in participating in open-source code development for SWMM.  The end product of the workshop will be a short paper that provides a discussion of community perceptions, consensus, and disagreements.  

Of particular interest are opinions on:  

  1. What new capabilities are needed in SWMM?  
  2. What people/organizations are interested in making open-source contributions?  
  3. What are some of the funding sources that the community might look to?  
  4. What are recommended “best practices” for integrating the community product with EPA?   

The workshop is looking to document diverse opinions rather than establish a consensus on such complex topics. The work product of the workshop will be a short paper. The draft paper prepared by the convenors and reported out at the close of the conference to all participants. The convenors will circulate the draft for comments among all conference participants and prepare a final version incorporating feedback within 30 days of the conference completion. 

Special Session: Moving towards an open urban water modeling paradigm: perspectives from academia and industry


Abhiram Mullapudi, Ph.D., Xylem Inc.

Sara C. Troutman, Ph.D., Xylem Inc.

Sara P. Rimer, Ph.D, Argonne National Laboratory

Caleb Buahin, Ph.D, Xylem Inc.

Ruben Kertesz, Ph.D., Xylem Inc.

Bryant E. McDonnell, Xylem Inc.

Branko Kerkez, Ph.D., University of Michigan


  1. Industry and open source: a win-win for smart sewers?

Bryant E. McDonnell, Ruben Kertesz, Caleb Buahin

  1. Breaking barriers to adoption: leveraging open source tools to build smart and resilient urban water infrastructure

Branko Kerkez, Sara P. Rimer, Sara C. Troutman, Abhiram Mullapudi

Objectives of the Special Session

This special session aims to provide the attendees an insight into the current state of open-source in urban drainage modeling and have a directed discussion on the role of open-source in ushering a new era of smart urban water systems. Smart water technologies are emerging as a viable alternative for addressing the challenges associated with climate change and urban sustainability. The advent of these smart technologies is creating the merger of the digital and physical worlds. Unlike the classical infrastructure systems, software and simulation tools are integral to the operation of smart urban water infrastructure systems. Hence, ensuring that these tools remain open and accessible to the various stakeholders is essential for transitioning smart water technologies into adoption and improving the trust of stakeholders in these technologies.

This session is divided into two segments. The first segment comprises two talks; these talks draw on the expertise from academia and industry to provide a holistic perspective on the state of open source in urban water modeling. This segment also leans on the experience of the maintainers of open-source tools to discuss the challenges of maintaining open-source projects in the urban water domain. The second segment discusses the role of open source in the future of urban water modeling. This discussion is not limited to but focuses on the following questions:

  • How does one get started with open source?
  • How does the industry benefit from supporting open source?
  • What is the cost of open-source, and who shoulders it?
  • How do we ensure the sustainability of open-source projects?

We hope this session will provide a fruitful discussion on the role of open source in urban drainage modeling and help us chart a course for moving towards a future where urban drainage modeling tools are open and accessible to communities worldwide. We plan to submit a position paper to a relevant academic journal based on the discussions in this session.

Special Session: A decade of collecting data on trace contaminant in wet weather discharges – are we ready to model them?


Luca Vezzaro, Ph.D., Technical University of Denmark (DTU)

Lena Mutzner, Ph.D., Technical University of Denmark (DTU)


  1. What have we learnt from past monitoring studies? Lena Mutzner (DTU)
  2. The efforts to identify relevant trace contaminants – the analytical and eco-toxicological perspective. Charles Wong (SCCWRP)
  3. How can we use these data in our models? Luca Vezzaro (DTU)

Objective of the Special Session

In the last decade, large efforts have been made to collect data on trace contaminants (micropollutants) in wet-weather discharges. The increasing data availability will allow us to build models to simulate trace contaminants concentration in wet-weather discharges, their removal in blue-green infrastructure systems, and their impacts on the status of receiving water bodies. Such models are needed to inform stormwater managers, water utilities and regulators in a wide range of applications (planning of investments, discharge regulations, dimensioning, etc.).

The aim of this session is to collect and discuss recommendations for future monitoring efforts based on the data requirement by modellers. Through the discussion in the session, we aim to draft a shared understanding on data availability and quality, necessary data documentation and meta data collection as well as model requirements and expectations for different applications. In the session we will present the current state of data on trace contaminants, what we can learn from this data, what is the effort required for data collection and analysis, and what are the implications for modellers.

Special Session: Modelling for a More Resilient Stormwater System: A basic introduction to real-time modelling and digital twin concepts

Convenor: Ryan Brown, Innovyze, An Autodesk Company

Objectives of the Special Session Develop a better understanding of what is a digital twin, how it can be used, and how real time (live) modelling can improve system design and management to save costs associated with damage from flooding events and prevent loss of life through both concept description and applied case studies.