WHY NATURE ALWAYS HAS THE UPPER HAND
There’s no magic wand to solve our f looding woes, which have been with us since time began. Instead, this writer argues, we have to retreat from f lood plains
BANDON is destroyed,’ said the tall garda rather theatrically as he sent us miles further inland from our planned itinerary from Cork to Schull for a New Year’s break little more than a week ago. And not just Bandon was destroyed. We passed through mile after mile of flooded fields, homes and roads and faced even more diversions until we finally and circuitously reached our goal, via Bantry, no less.
But the earlier part of the journey, from Dublin to Cork city had already convinced us that something apocalyptic had indeed happened to the landscape. Flooding was visible everywhere. As yet more inundated properties loomed into view I gave quiet thanks that I live on the east of the island, on the side of a hill, miles from a big river, and in an area with the second lowest rainfall in the country.
The car radio crackled that day with phone-ins peppered with calls for ‘Enda to come and see this...’ as though he possessed some magic bucket which would drain the land in minutes. The truth is that, apart from re-engineering the entire island overnight, there was very little that even Enda could do. The nation was experiencing a national disaster. Kansas gets whirlwinds, Nepal earthquakes, other countries have volcanic eruptions or droughts but we get lots of rain and flooding.
Indeed, in scientific terms we could not be worse placed to receive the Atlantic storms which nature hurls at us. In an ideal world, Enda the Wizard would shift the entire island several hundred miles to the south and safely out of the way of the salvo of depressions that the Atlantic launches at us every year.
LAST month it was easy to lose track of the storms, there were so many. But the weather statistics told their own tale. Many places experienced three and half times more rain than the average month of December and it often fell in a matter of hours, not days or weeks. A total of 300mm on average poured on our heads from above.
Let me try to place that in perspective. Pretend that, overnight, Ireland became completely flat with a big wall around it preventing last month’s rainwater from escaping to the sea. The entire island, every inch of it, would then be flooded to a depth of 300mm, or one foot. That’s nearly up to the top of your wellies, everywhere in the country. It would seep into every house.
Now, let us magically remove the big wall and instantly grow back the hills and mountains and force all that water to drain away. On the east coast of the country relatively short, fast-flowing downhill rivers like the Boyne, the Liffey, the Dodder, the Dargle and the Slaney would quickly deal with the wellie-deep water in their catchments and funnel it to the Irish Sea without too much flooding.
In the Midlands and the hilly country further to the south, things are very different. Geogra- phy, which favours drainage on the east coast, works against it elsewhere. More than a third of the rainfall falling on the Republic can only go one way, into the long River Shannon, which meanders though a flat plain, draining some or all of 17 counties with a fall of only a few metres between Carrick-on-Shannon and Killaloe, 170km driving distance apart.
Drop a tennis ball in the upper reaches of a flooded River Liffey and it could be in the sea within 24 hours. A tennis ball dropped off the bridge at Carrick-on-Shannon could take weeks to reach the sea, so slowly does the current move. While a flood dramatically accelerates the flow of the Liffey, on the Shannon it simply causes it to develop the watery equivalent of middle-aged spread as it extends out across the landscape, flooding the central plains like it has done for millennia.
In the south, especially in West Cork, rivers are funnelled through valleys running largely towards the east which occasionally reach rock-bound bottlenecks, causing the water to pile up – as it does in the centre of luckless Bandon. Bear in mind also that hilly country, as in West Cork, usually attracts heavier rainfall – which drains rapidly into these valleys contributing to a form of flash flooding.
Many locals have blamed the Shannon flooding on the multiplicity of government and local agencies which administer the river and their alleged failure to co-operate, but a recent consultancy study carried out on behalf of the Office of Public Works’ CFRAM project has declared the actions of those agencies has made little difference one way or the other. If anything, their policies mostly tend to reduce, not exacerbate, flooding.
Still, practically every flood news report brings further criticism of local and national authorities but while Bandon, in the words of the policeman, was ‘destroyed’ twice last month, it couldn’t be blamed on any lack of effort on the part of Cork County Council which, following similar flooding in 2009, commissioned flood defences.
WORK was due to commence earlier last year but was delayed (and still is) following legal action by a disgruntled contractor who is contesting the legality of the tendering system.
But new flood defences for Fermoy convincingly saved the town from a bad drenching last month showing that someone is finally getting things right. Defences also appear to have spared Athlone from suffering Bandon’s fate.
Saving large centres of population from the worst flooding has got to get priority and it’s interesting to note that Cork City, whose turn to be destroyed came in 2009, escaped a repeat ducking last month, despite rainfall of biblical proportions in the Lee catchment during December. It is smaller, rural settlements, or
single one-off homes, often farmhouses, that need to worry as the cost per head of protecting them is enormous, compared to preventing flooding in larger towns and cities.
And the question has to be asked: is it better for those homes and farms to be abandoned to their fate and their occupants re-homed like abandoned puppies on higher ground, or in larger towns where flood defences are more effective? The answer is probably yes. Indeed, Enda Kenny has already suggested as much and he deserves some credit for having the political courage to say it.
Many of these properties are on flood plains of one form or another and they are flooding more, not less – often because we are not only losing the battle against nature but also contributing to our own defeat. Shannon flooding comes courtesy of, let’s call it, the Law of Unintended Agricultural Consequences.
To explain, let me wind back a few hundred years when large areas of the midlands were covered with peat bogs. In periods of high rainfall, these acted like a giant sponge, holding back some of the excess water which was then released slowly into the rivers. Many of those bogs have since been either drained for agriculture, or by way of turf cutting, thus reducing their sponge-like properties. The result is that more and more water is flooding immediately into the rivers instead of trickling in more slowly.
IT’S not just the bogs. Farmers have always drained land to make it more productive but the availability of efficient machinery and, in many cases, government grants, accelerated the process exponentially in recent years. But that soggy land played a vital role in storing excess water in the landscape, not in the river. We need to minimise that land drainage.
As TV weathermen never tire of telling us, flooding is more likely when the soil is saturated with water after a long period of rain. Because of that saturation, additional rain simply runs directly into watercourses: and our taming of the land may be accelerating this process. Heavy stocking of cattle compacts the soil, reducing its water-carrying properties. Giant farm machines also contribute their share.
Clearing scrubland and felling trees doesn’t help either and the concept of set-aside may need revisiting in a more innovative light. There’s evidence that healthy vegetation contributes significantly to the water-holding capacity of the soil, because of the penetration of roots and the way leaves evaporate moisture back into the air.
It’s impossible to tell how much earlier flood protection schemes are contributing to the flooding of the Shannon. These usually involved the dredging and draining of tributary rivers and streams to prevent local flooding of farms but all they often achieved was to cause water to reach the river even quicker and flood all the sooner. Sometimes it just flooded back up the tributary as the main river burst its banks even more rapidly and spread out over the plain, a further example of that law of Unintended Agricultural Consequences.
Flood defence engineers will have to be careful not to repeat the same mistakes. Mrs Byrne, say, outside Athlone may be lucky in persuading the authorities to build a giant Dutch-style dyke all around her farm but the acres of waist-high water displaced by that dyke will simply move down the river a bit and flood someone else’s land which has never flooded before. Then that owner will bellow on the airwaves for a dyke or some other flood-prevention solution and someone else’s land then gets flooded in a pattern that gets repeated ad infinitum all along the river.
I’m not ruling out the possibility that engineers might come up with some wizard wheeze that fixes the Shannon problem, perhaps involving a neat combination of calculus and trigonometry and lots of pumps, but neither am I rushing to the bookies to put bets on it.
I don’t believe drainage is the answer but rather the opposite. We need to find more ways of slowing down the accelerating rush of water into the river, and in the meantime, to admit defeat and abandon attempts to prevent flooding in areas where it traditionally floods.
I’m quite happy for the Shannon flood plain to be used for agriculture, but when it rains too much, we should allow the old lady of the skies to spread her skirts on the land as she has done for thousands of years, while we respectfully retreat to higher ground. ÷ Gerry Byrne is the winner of three science journalism awards in Ireland and the USA.