The risk of flooding from rivers, the sea and surface water can have a major impact on people, businesses and communities. With a rapidly changing climate, the more we can understand residual uncertainties and better inform flood risk management decisions, the more we can improve our overall resilience.
Residual Uncertainty Analysis Practitioner Guidance
When designing safety-critical infrastructure such as flood defenses its essential designs are adapted to account for uncertainty – to help inform investment decisions and deliver schemes better able to protect local communities.
The current Residual Uncertainty Analysis (RUA) guidance published by the Environment Agency (in 2017 sets out approaches and methods for assessing uncertainty in flood models (such as Flood Modeller by Jacobs) when used to evaluate and design flood alleviation schemes.
The guidance defines residual uncertainty as: “Evidence supporting flood risk management decisions will always have some degree of uncertainty associated with it because flooding mechanisms might be poorly understood, or flood information is incomplete or inaccurate. Some of these uncertainties will have been addressed through standard design and appraisal procedures; others will not. Those uncertainties that remain are called residual uncertainties.” (Environment Agency, 2021)
Hydraulic models are an essential tool used when developing flood management schemes, informing many key aspects of the design. No matter how refined and enhanced the models are, there will always remain inherent uncertainties in the results; it is important to understand and quantify this.
We are bringing Jacobs’ flood risk management expertise to support the Environment Agency and develop supplementary practitioner guidance, including associated automated tools and case studies, to complement the existing guidance and provide direction to flood risk professionals in the delivery and review of RUA. We are independently developing the functionality of our Flood Modeller software in parallel to support the rapid undertaking of the RUA Practitioner Guidance project, and ensure consistency and compatibility with its new guidance and tools. Ultimately this guidance (and associated tools) is expected to enhance the quality and confidence in new flood alleviation schemes delivered across the U.K.
“It is essential to understand the remaining uncertainties so that these can be managed effectively and proportionally in scheme design to optimize construction costs and mitigate risk of failure, and ultimately provide more robust and reliable protection to those at risk of flooding,” says Jacobs Director of Flood Products and Water Catchment Management Dr. Richard Crowder.
“This is a nationally significant project that will drive the direction of uncertainty assessment within the U.K., simplifying and demystifying residual uncertainty to bring about consistency in application and drive widespread adoption”, says Ian Perkins, Senior Technical Advisor, Evidence & Risk, Environment Agency (Project Executive.)
Strategic Modelling and Analytics
Jacobs is also contributing to another strategic, long-term national plan to improve understanding of flood risk mapping and modelling data through the Strategic Modelling and Analytics project. The project’s findings will support development of a Modelling Roadmap to be produced by the Environment Agency. Through research, surveys, interviews and workshops, the project aims to understand the current challenges that the U.K.’s flood modelling community faces, with the objective of creating a shortlist of actions to improve best practice, enabling more informed decision-making with future risk management and areas of investments, and ultimately optimizing flood resilience for our communities.
Through a collaborative process encompassing a wide range of industry stakeholders, including the Environment Agency, other U.K. regulators and flood risk management authorities, water companies and academia, the project team assembled a significant amount of data and worked with the Environment Agency to identify key challenges to be prioritized.
“With a mounting climate crisis, this project is improving our understanding of flood risk. It provides greater confidence in our flood risk mapping and modelling data, which will enable better decisions in future flood risk management,” says Jacobs Head of Water Catchment Management Amy Bentley.
“This review project has undertaken comprehensive engagement across our industry and provided us with a detailed set of future user needs. It is a very timely project that will support the formation of a long-term improvements plan. It helps strengthen our understanding of how flood risk management will evolve, and how to embed better technology to manage this risk,” adds Ian Perkins.