Читать книгу Taming the Flood: Rivers, Wetlands and the Centuries-Old Battle Against Flooding - Jeremy Purseglove - Страница 11

Rivers and streams have been straightened and evened out as never before. This work has been carried out by water authorities, internal drainage boards, and many councils, in part to reduce flooding of roads and houses, but largely to increase farm yields. In the years between 1971 and 1980, an annual average of 207,217 acres was estimated to have been drained, of which ‘new’ drainage of wetlands comprised around 20,000 acres per year.¹² One straightened stream begins to resemble another. River organisms’ ability to survive the disruption of floods was never evolved to withstand this kind of onslaught. Repeated dredging has removed the weedy margins upon which dragonflies depend. In the last twenty-five years, four dragonfly species have become extinct in England, while many others have shown a marked decline. Reduction of such insect populations will in turn reduce the fish population, which depends on a diversified, rather than a straightened and uniform, channel. With the loss of the fish, we can expect to lose the electric-blue flash of the kingfisher. The dredgings are put in the bottoms of furrows or are used to fill in ponds. With the virtual disappearance of the farm pond, frog populations in some parts of England declined drastically between the 1950s and the 1970s.^fn7

Many streams have been stripped of their ancient boundary trees, and the knock-on effect of the drainage schemes has been to encourage farmers to turn their farms into prairies. Between 1946 and 1963, around 85,000 miles of hedges were grubbed out.¹³ The lowering of water levels to allow ploughing of damp pasture has removed the nesting habitat of many birds that we used to take for granted, such as snipe, lapwing, and redshank. A survey of Oxfordshire in 1982¹⁴ found only 15 breeding pairs of redshank, compared to 112 pairs in a similar survey in 1939.^fn8

Studies have shown that the water vole, ‘Ratty’ of The Wind in the Willows, has become scarce in many areas, due to intensive management of river banks.¹⁵ Indeed, Ratty’s emotional, if not his ecological, headquarters, the river Pang between Reading and Newbury, where Kenneth Grahame wrote his classic, has been subjected to a notoriously insensitive drainage scheme.^fn9

In some counties, such as Staffordshire, a previously common wetland plant such as reed has become a rare sight. The remains of water mills have been consistently removed; the weirs that hold up river levels have been dismantled; and millponds and millraces have been filled with the dredgings. On the Worcestershire Stour, ten mill sites have been removed in as many years. The ancient fords which hold up the water are dredged out, along with their water crowfoot. In the late 1970s, the Anglo-Saxon ‘stretford’ of Stratford-upon-Avon was taken out.

The inexorable desiccation of the Fens, the Somerset Levels, and the Lancashire mosses is exposing remarkable artefacts of early civilization, long preserved in the wet peat. But in the absence of an effective liaison between drainage engineers and archaeologists, there is a danger that such remarkable finds as the Bronze Age settlement built on a timber ‘island’ recently rescued at Flag Fen near Peterborough could be broken up by diggers or left to crumble on exposure to the atmosphere.^{16 fn10}

Major wetlands are obvious victims of drainage. Casualties since the Second World War have included the river Idle washlands in Nottinghamshire and large parts of Romney Marsh, Otmoor, and the Lancashire mosses. Major debates have been held since the late 1970s over the future of wetlands in Sussex, Somerset, Yorkshire, and East Anglia. Wetlands under threat have included a variety of landscapes: swamps of tall reed or reed sweet-grass; marshes of rush and sedge, which sometimes develop into scrub of willow and bog myrtle; fens, whose lush vegetation is nourished by alkaline groundwater, and which range from open pools, often the remains of peat cutting, to grazed beds of meadowsweet and iris, grading in turn to the wet woodlands known as alder ‘carr’. Additionally threatened are mires such as the mosses of the north-west, whose deep peatlands support sphagnum moss and heather, scattered with glades of birch, the favourite haunt of nightjars. Finally, there are flowery hay meadows and damp pastures, intersected by dykes patrolled by dragonflies in summer and all submerged in winter by the silver flood, which draws in dark clouds of wildfowl and companies of wild white swans. The destruction of such places in our time has been startling.

In 1983 the chief scientist of the Nature Conservancy Council, the Government’s watchdog on conservation, produced a definitive report on the destruction of habitat in Great Britain since 1949.¹⁷ Among the casualties wholly or partly attributable to drainage were 97 per cent of herb-rich hay meadows, 50 per cent of lowland fens, and 60 per cent of lowland raised mires, all lost in the space of a generation. In the mid-1980s the Norfolk Broads were losing an average of 1,500 acres per year.^fn11

All this has happened because enormous sums of public money available for drainage schemes since the Second World War have combined with a revolution in technology with which we have not yet fully come to terms. I will always remember standing one early spring day near the river Severn, arguing with a drainage officer who had previously maintained watercourses, which were now due to be reshaped as part of an expensive new scheme. This man had as little sympathy for the environment as a pike might have kind feelings towards a minnow. Yet the point he rightly argued was that, for the previous thirty years, he had personally controlled the maintenance of the ditches and hedges of this parish, so why should he now consider newfangled ideas about nature conservation? I looked at what he had created. In spite of his indifference, it was exquisite: the ditch banks were creamy with cowslips and lilac with cuckoo flower. Chiffchaffs were arriving to nest in the spangled scrub of blackthorn. There was a badger sett under some old pear trees. I asked him how he managed the place. It turned out that he had a small dredger, an even smaller budget, and a very primitive brand of mowing machine. With this equipment he had efficiently kept water flowing through his ditches. I lost the argument that day. Within a week the big machines had moved in, and that corner of his parish could have been one of thousands of others in modern England – any place, anywhere.

The lesson was clear. Of course, the countryside must continue to be a working landscape; but if most people’s definition of a river as something more than just a drain is valid, then that broad definition must be consciously built into the brief of those who wield this mighty technology of the JCB, the Hymac, and the Swamp-dozer. Only then can we guide the evolution of the countryside within legitimately broad terms of reference and continue the age-old process of civilizing the rivers. And why not? The big machines are only powered by the ratepayers’ money, and the woman who threatened to tie herself to a willow tree represents thousands of ratepayers who share her (and Constable’s) convictions about the essential nature of a river.

Over the last half-dozen years there has been a quiet revolution in the water industry as this simple realization has dawned upon engineers, farmers, digger-drivers, and even the legislators in Westminster. Of course, there are still places where the old-style canalizing approach to river management is being pushed through; and the conflict of values that underlies this whole issue raises a number of questions which are not easy to answer. No-one can seriously suggest that we turn back the clock entirely and return to the world of Constable’s hay wain, where there was a good deal of misery and hunger amidst all that beauty. We admire and cherish an environment that we also depend on for food. We may reduce the dredging of rivers, but if we stop it altogether, floods will return to overwhelm us. We are therefore committed to continue managing rivers, as we are to managing every square mile of the English countryside. It is the way we do so which counts.^fn12