In the evolving world of flood management, the phrase “Nature-based Solutions” (NbS) is everywhere. From conference panels to policy documents, from EU funding calls to pilot sites: green is in. The idea is simple — work with nature to manage water, restore habitats, and deliver benefits for people and ecosystems.

I support that idea. In principle.

This overview has been partially inspired by a LinkedIn post written by an NbS professional and professor at TU Delft who apparently start her presentations with saying ‘I do not want to talk about NBS!’ She must be struggling with her lectures.. But a great post to read.

The best engineering has always been nature-based — just not called that.

Many of the “innovative” measures now being promoted — riparian buffers, offline flood storage, reconnected floodplains, meandering channels — are not new to engineering practice. They’ve long been part of our toolbox. We implemented them, not because a grant called for green infrastructure, but because they worked.

Before it was fashionable, we were working with topography, soils, vegetation, and seasonal flows. We understood — and still understand — that floods are complex, living systems, not just water to be rerouted. But now, some of the same solutions are returning, with new language and new champions — sometimes, oddly enough, with engineers excluded from the conversation.

There’s a strange narrative taking hold in NbS discussions: that engineers only “move water,” while others — planners, ecologists, landscape architects — bring the social and ecological intelligence. False.

Good engineering has always been deeply social. We engage communities, assess impacts, adapt to constraints, and plan for future risk. Environmental and social assessments have been standard practice for decades — not because of new green mandates, but because they’re essential to building things that last.

What worries is the growing number of NbS projects being proposed — and even implemented — without a deep understanding of hydrology or hydraulics. In flashy, high-volume rural catchments, well-meaning interventions like willow planting or leaky dams can’t hold back a 50-year RP event. Floods don’t respond to ideology — they test your calculations.

There’s a risk that aesthetic “green” solutions are being treated as functional substitutes, when they may not offer meaningful risk reduction. And when that happens, communities suffer, not just budgets or reputations.

It’s over-simplifying, over-promising, and under-engineering.

Take for example the term “grey infrastructure.” It’s used too casually, often implying that engineers only build concrete canals and culverts. This stereotype ignores decades of adaptive, material-sensitive, and hybrid infrastructure design.

We use natural materials — timber, soil, vegetation — and combine them with structural integrity. We design to accommodate ecological processes while still protecting lives, property, and livelihoods.

Let’s stop talking about “grey vs green.” It’s an unhelpful and binary. What matters is performance, durability, function, and integration. A project should be judged by what it achieves, not by what colour metaphor it fits.

NbS Should Extend Engineering, Not Replace It

This is not an argument against NbS. On the contrary — I believe nature-based approaches are essential, especially under climate uncertainty. But they must be rooted in sound engineering and hydrological logic. Anything else is just landscaping with unrealistic expectations.

We need projects where engineers lead the hydraulic design, ecologists shape habitat outcomes, landscape architects enhance form and usability, and communities co-own the solution.

Nature-based Solutions should not be an ideological shift away from engineering, but a design evolution that invites engineers to lead — with new tools, new goals, and old wisdom.

Flood risk management is too important for professional turf wars — but it’s also too important to be led by green rhetoric over grounded hydrology. We need engineers at the centre of NbS, not pushed to the margins.

Nature works — but only when we understand it, model it, and design for it. And that’s what engineers have been doing all along.

One of the more frustrating trends I’ve observed is how many flood management Terms of Reference now mandate the inclusion of Nature-based Solutions — often written by individuals with no engineering background, no practical experience in flood management, and no direct involvement in schemes that have actually been built and tested under pressure.

These are often consultants or planners who have never had to sign off on a design, manage budget constraints, or feel legally and ethically responsible for how infrastructure performs in a real-world flood.

There’s a world of difference between drawing a nature-based concept on a map and being accountable for its performance in a 1-in-100-year event.

And yet, some of these ToRs now casually specify “solutions” as if they’ve reinvented flood management — dropping terms like “leaky barriers,” “floodplain reconnection,” or “natural attenuation” with no appreciation for the hydraulic consequences, land use trade-offs, or long-term maintenance challenges.

They’re not wrong to promote nature — but they are wrong to dismiss engineering insight, and wrong to assume that NbS is a universal substitute for the rigorous design and risk management that comes with infrastructure delivery.

Flood infrastructure is expensive, long-lived, and high-stakes. It’s not an ideological experiment.