Hidden infrastructure headaches: who's responsible for unmapped drainage systems?

Unidentified and unmaintained drainage systems are causing flooding headaches for homeowners and risk management authorities.

In case law, riparian rights grant specific privileges to landowners bordering a waterway like a river or stream. These rights centre around the concept of "reasonable use" of the water on or flowing across their property. Examples include access for activities like swimming, boating, or fishing.

However, this approach also applies to culverted systems. Riparian rights traditionally apply to well-defined waterways, but hidden and undocumented streams can create murky legal territories. Determining ownership, access, and responsibility for maintaining these watercourses becomes crucial, especially as they can significantly impact surrounding land. Navigating the complexities of case law and water management around riparian ownership is not on the agenda, but I argue it should be.

When flooding hits – who do you call?

For many people being the victim of flooding, it’s the first time it will have happened. They may have heard of some public and private bodies responsible for flood risk management, however it’s unlikely that they will know them all or who they should report the incident to.

They are very unlikely to be flood prepared and will be unsure how to navigate conversations with their insurance company if they are fortunate enough to be able to claim against the damages. Once the victim starts to come to terms with the shock of the incident, it’s common to look to blame someone for this flooding event, "this has never happened before, and it’s rained harder than this is the past – so something must have happened to cause this".

In my experience, particularly in relation to surface water flooding in urban areas; highways infrastructure is firstly accused, followed by a lack of maintenance of above ground fluvial infrastructure. This is visible on the surface, and after an event it’s likely to be full of debris. There is also a common assumption that this is and should be managed and maintained by the state.

A hidden infrastructure with vague ownership

However, as practitioners, we know that this isn’t the case and not all river and drainage infrastructure is above ground, in fact, there is a complicated network of main rivers, ordinary watercourses and drainage that’s been culverted or put into small pipes to facilitate development.

This hidden infrastructure may not be known to the landowner, and the infrastructure could pass close or even under property. It may not even be known to a Risk Management Authority, and they are only made aware of is existence when it has either failed or it’s the identified conveyance route to a flooded property.

Risk Management Authorities therefore then need time to collaborate with others to help determine what this unidentified infrastructure is. This may sound straight forward, however in practice this can be incredibly time consuming and can include legal representation to help decide what the original purpose/function of the asset was, as they will not necessarily want to assume ownership and take on additional maintenance responsibilities.

This isn’t just related to the aftermath of flooding, as developers wanting to discharge existing unmapped infrastructure are unable to if the planning authority is unable to determine if the asset will continue to be maintained for the life of the development.

Shared riparian responsibilities impractical

There are several outcomes in this type of scenario, with either a risk management authority taking responsibility, a riparian owner being identified or the asset becoming abandoned, with no owner identified. Abandoned assets are all too common, and they are a victim of being left off maps and lists when transitions have taken place between authorities or when new infrastructure replaces the existing function of the asset (a combined sewer becoming a separate foul or surface sewer system for example).

However, how practical, and effective is it to rely on shared riparian responsibilities on drainage and watercourse infrastructure? How likely is it that a group of residents will be able to raise the funds to maintain this ageing infrastructure and have the technical ability to undertake any remedial works? In practice, it’s rare that this will be possible, with risk management authorities needing to take difficult decisions to spend budget on infrastructure they are not responsible for, but knowing that if they don’t, repeat flooding is likely.

One of the significant benefits of enacting Schedule 3 of the Flood and Water Management act is ensuring that the maintenance of any new drainage infrastructure could be adopted by a government body.

However, there is no plan to try and address this issue with existing infrastructure, and it would be great to hear other practitioners’ views on the matter, to ascertain if more should be done to try and address this issue.

Author: Ryan Thomas BSc MSc MCIWEM C.WEM

Associate Director at Waterman Aspen with 17 years’ experience working in Flood Risk Management. Ryan undertook a part-time MSc in Flood and Coastal Risk Management at Lancaster University and wanted to explore alternatives to riparian responsibilities as part of his research project. Even though the research demonstrated that change would provide a positive impact, no silver bullet was found from practitioners participating in the research.

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