Our flooding problems will be with us for years

Opinion: hard engineering is not the answer to our flooding crisis – and has been a large part of the problem

Urban flooding: one of the causes is that we have covered huge areas with a hard shell of stone, concrete and asphalt. Photograph: Bryan O’Brien

Urban flooding: one of the causes is that we have covered huge areas with a hard shell of stone, concrete and asphalt. Photograph: Bryan O’Brien

Mon, Feb 17, 2014, 00:01

The metaphors we use so casually in our daily conversations often reveal more than we realise. They also influence how we try to solve problems. Inappropriate metaphors are misleading, and sometimes downright dangerous.

While the recent floods were wreaking their havoc, I heard someone say on radio that we “need to find the plughole to let the water out”.

Of course the speaker was not being completely literal. He didn’t think we should all be searching for a giant bung buried somewhere north of Limerick.

But his graphic turn of phrase betrayed a common misconception about the natural world, one that creates environmental crises rather than resolving them. It suggests that hard engineering is always the answer, when it is often part of the problem.

We don’t need plugholes, we need sponges. Let me explain: You find plugholes in basins and baths, which have uniform, hard, impermeable surfaces. That is the way we often think about our landscapes and water: as though we were dealing with a closed system within a rigid and predictable structure.

But the system is not closed. We are part of a global climate, which is changing dramatically and fast, subjecting us to increasingly unpredictable and exceptional weather events.

In that context, it is vital that we understand that our island is not constructed like a bath or a basin at all, at least not the way nature originally made it.

Our land mass is diverse and complex, but most of it is soft and absorbent, easily conducting water to streams. There are relatively few naturally impermeable areas, and here water has usually sculpted deep channels over millennia, feeding rivers that drain off into the sea.

The rate at which water reaches those rivers is – or rather was – greatly slowed by the sponge-like function of wetland bogs and marshes. When flows are seasonally high, flood plains cope – or used to cope – with the excess water.

A Martian equipped with only this information might wonder why we have a serious flooding problem at all.

The answer is that we have re-engineered much of the country on an ever-accelerating scale. We have covered huge areas with a hard shell of stone, concrete and asphalt. We have drained most of the wetlands that used to arrest the flow of water.

We have forced rivers into narrow, faster-flowing channels, straightening the meanders that slowed them, to “reclaim” natural flood plains. We have buried urban streams in constricted culverts that cannot cope with exceptional rainfall.

And then we built more homes and farms in the very places the water used to rest – wetlands – or overflow –floodplains. We have built cities horizontally rather than vertically, encasing much more land than we needed to.

In recent decades, we have systematically suburbanised the countryside with individual dwellings, many surrounded by swathes of hermetically sealed parking space.

Today, the consequences of such environmentally insensitive developments are converging with climate change to produce an ongoing series of perfect storms.

Even in the unlikely event of radical global action being taken, right now, to reverse the human contribution to climate change, the best evidence suggests Ireland would still face increasing rainfall and wind speeds for decades to come. We aren’t going to find any plugholes.

Flood control
Hard engineering has a role in flood control, of course. Barriers, booms and dredging will produce some short-term solutions, and even some long-term ones. But we must think far outside such rigid boxes to meet the massive challenge we are facing.

Some “soft” engineering solutions are already becoming familiar. Enlightened county councils and developers have introduced sustainable drainage systems (SuDS). If you build car parks on grid of open bricks, for example, storm water can sink into the ground between them instead of generating floodwater off a sealed hard surface.

But we need to do a lot more than insist on SuDS in all new construction. We need to restore drained wetlands, and even create new ones, recognising their huge potential as giant absorbent pads for protecting villages and towns from storm surges. We need to start working with natural forces for our own benefit, instead of vainly attempting the hubristic task of containing them in concrete.

We need sponges, not plugholes. And we need them very soon.

Paddy Woodworth is the author of Our Once and Future Planet: Restoring the World in the Climate Change Century (University of Chicago Press).

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