Where two worlds meet: metrology and urban drainage

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Successful urban drainage depends on diverse monitoring under the heading of metrology. Jac van Tuijn hears from editors of a recent book on this topic about the issues the book has sought to address, and the huge collaborative effort that has brought these insights together.

For real-time decision making in urban drainage and stormwater management, it is crucial to have a reliable monitoring system that includes weather predictions, rainfall, water levels and discharge data. It also helps when scientists and practitioners have a good understanding of this area of monitoring – metrology, say three experts who have brought together a comprehensive book on this crossover of two worlds: Metrology in Urban Drainage and Stormwater Management: Plug and Pray.

Informative and critical

The book began life following a conference on Urban Drainage Modelling in Montreal, Canada in 2015, in an initiative to bring together the existing scientific knowledge and experiences in applied metrology in the field of urban drainage and stormwater management. Some five years later, and having brought together 50 contributions from experts, the book has recently been published by IWA Publishing. The three editors hope that the book helps urban drainage managers to better design and operate monitoring networks that include weather, rainfall and discharge data to improve the performance of their urban drainage and systems.

The book is highly informative, but it is also critical. “We also aimed at sharing doubts and criticism,” says Mathieu Lepot, one of the three editors, who is a researcher on urban drainage at the National Institute of Applied Sciences (INSA) in Lyon, France. “Sensor manufacturers and sellers often use the phrase ‘plug and play’. We subtitled our book ‘plug and pray’, as a warning against too much optimism.”

Fellow editor Jean-Luc Bertrand-Krajewski, Professor of Urban Hydrology at INSA Lyon, emphasises the importance of understanding the crossover: “Metrology as a discipline or field of competences is not sufficiently taught as part of education and training in the field of urban water. A real need exists for improvement of knowledge, skills, implementation, and best practice.”


The editors acknowledge that the physical situation of each urban drainage system is unique, and monitoring systems are designed to meet the requirements of local regulations. This limits the technical possibilities and parameters that need to be measured. Yet, they want to challenge urban drainage managers to go beyond the minimal requirements and look for additional value.

“Proper monitoring can provide important insights into the actual performance of existing systems”

The third editor, Francois Clemens, Professor of Urban Drainage at Delft University of Technology and senior researcher with Deltares, says: “The main issue is that, in many organisations, the added value of monitoring is not recognised and is often only seen from the perspective of cost. We hope the book helps people in these organisations to address all aspects of monitoring, including ways to set up monitoring projects that produce the type of information that really has value for the tasks being managed by the organisation they operate,” says Clemens. “Making budget estimates in terms of personnel and materials and operation, allows for rational decision making to avoid disappointments as much as possible.”

Bertrand-Krajewski challenges practitioners and scientists to use data for better protection of the environment. “Using data and information beyond minimalist regulatory requirements can produce such a higher value in order to better manage the system for the protection of the environment.” Bertrand-Krajewski mentions the importance of skilled and trained staff. “The staff should, as much as possible, be involved in data processing and information production, and at least have some feedback on the outputs and results delivered by the monitoring system,” he suggests. “In this respect, I see metrology is a real field of expertise and not a secondary task that anyone can be in charge of without competences.”

The three editors call upon urban drainage managers to identify any weakness, source of bias and incorrect methods that could affect the quality of recorded data. In their book, they include warnings and feedback on plausible issues.

Interactive design process

The book covers the whole process to design and implement a monitoring system that starts with writing the specifications, for the short, mid and long term, and stating the different goals and purposes. According to Bertrand-Krajewski, these specifications may need adjustments over time. “It often occurs that monitoring at new locations reveals unexpected hydraulic conditions, or processes emerge. Reality is always more complex. The design of a performing monitoring system is an iterative process, during which experience helps to improve the initial design. This iterative approach should be accounted for and not be considered as a failure,” says Bertrand-Krajewski. He recommends the use of preliminary or provisional equipment as an option to save time and money and to make the best choices for the final monitoring system.

Clemens has an additional recommendation for the scientific community. He advocates for a uniform use of monitoring data and protocols. “This allows good accessibility in an efficient manner.” He sees international sharing of protocols and standards as an important step to enhance analysis of systems on a large scale. “As things are now, every new project is being designed from scratch, hampering individual choices. Virtually every researcher is spending much time, budget and other means in reinventing the wheel,” he says.

Sharing experiences

“Proper monitoring can provide important insights into the actual performance of existing systems,” Clemens continues. “This not only allows us to manage them more efficiently, but it also allows us to judge alternative designs or alternative options in daily operation and management. Given global urbanisation and climate change, these insights need to be gained in the relative short term to be able to face them in a timely way,” he warns.

Clemens underlines the importance for scientists and practitioners to appreciate the need to share their knowledge and experiences. “In many scientific projects, there is little focus on technology and practicalities. This can be a source for error, especially in the new and fast developing fields such as blue-green infrastructures and sustainable urban drainage systems (SUDS). Here, academics and practitioners certainly have a strong mutual interest in sharing their latest understanding,” Clemens observes.


In their book, the editors encourage all experts, both practitioners and scientists in both worlds, to share their experiences. Monitoring of urban drainage systems seems straightforward, but that is not the case. The book warns of common setbacks and sets out the best ways to navigate them.

The editors hope that their book will contribute to a global standard that allows data sharing on a large scale. Given the diversity of systems and the wide range of different and dynamic conditions, it requires huge amounts of accessible data to enable the application of data-driven methods for modelling the behaviour of urban drainage systems.

Here, Clemens draws a comparison with astronomy and particle physics: “Academics in these fields conduct joined-up research and add value to each other’s data. Cooperation and data sharing can accelerate developments; possibly, we do not have the luxury not to do something similar.” •


Six key messages drawn from case studies

  • Keep urban drainage-metrology projects going
  • Harmonise data handling
  • Include sufficient budget for metrology issues
  • Harmonise guidelines for better comparisons
  • Identify and plan for continuity issues
  • Use cheap sensor technology but include redundancy


Metrology in Urban Drainage and Stormwater Management: Plug and Pray

Edited by Jean-Luc Bertrand-Krajewski, Francois Clemens-Meyer and Mathieu Lepot

IWA Publishing

DOI: doi.org/10.2166/9781789060119

ISBN electronic: 9781789060119

Publication date: August 2021


Seven cases from around the world

The book presents seven cases showing the different usage and settings of monitoring systems with flow sensors and rain gauges for real-time control. One case describes a field laboratory in Switzerland that combines traditional monitoring techniques with Internet of Things-driven approaches. The five-year project aims at the collection of consistent datasets and the development of low-power sensor technology. One of the preliminary findings is that low-power sensor technology in combination with low-power wide-area network allows data collection in underground infrastructure.