The Attacking Ocean (33 page)

Serious dike work along the coast as a whole had begun as early as 1000 C.E. in response to rising sea levels and growing population. However, decentralized administration and the rudimentary technology of
the medieval farmer hampered large-scale construction. For five centuries, the fight against the attacking North Sea had been in the hands of major landowners and religious houses, which alone possessed the manpower, organization, and resources to build major dikes.
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They worked through a morass of local authorities, many of which were inefficient, even lazy. Pumping in particular was virtually nonexistent. For centuries, drainage depended on gravity. Nevertheless, by 1250, most coastal dikes formed a single defensive line. Once this rampart, however weak, was in place, the builders slowly moved the dikes seaward, taking advantage of the sediment built up by years of high and low tides. They would enclose the accumulating deposit, leaving the old dike as a secondary defense. Inside the perimeter, the drained soil consolidated and peat decomposed. As the land subsided, the difference between sea level and the land inshore increased, which was fine until a flood breached the dike or a high tide flowed over the top, in which case the destruction was far greater than before. Moving dikes seaward was sometimes impracticable, especially in delta areas where tides undermined sea defenses. Once this happened, inshore flood works became the primary defense and a great deal of land vanished.

By the early sixteenth century, a growing demand for peat as fuel for expanding cities and for industries such as brewing and pot manufacture led to serious environmental problems.
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Surface peat was in short supply; water tables were rising. When the peat was worked out, the diggings lay empty and soon filled with water, creating large lakes that threatened nearby dikes and settlements. Many villages and churches fell prey to slowly spreading water that undermined them.

There were occasional sea surges, but the period from about 1530 to 1725 witnessed a slower rise in sea levels, partly as a result of the colder conditions of the Little Ice Age, well illustrated by Dutch artists of the day. The landscape was ripe for reclamation schemes on a larger scale. More centralized hydrological administration helped change the equation. In 1544, King Charles V, ruler of the Burgundian Netherlands, reorganized water control efforts, a process that culminated in the formation of a single water control authority in 1565, which worked closely with polder boards and local communities.

By this time, hydraulic engineering was on the move, thanks to the experience of experts like Andries Vierlingh, dike master to William the Silent, Prince of Orange.
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Vierlingh spent his life working along the treacherous North Sea coast with its fast-running tides and currents and had also served as a member of several polder boards. His book on reclamation wrote of “roaring breaches.” He wrote, “Water will not be compelled by any force, or it will return that force unto you.” He added, “One must direct the streams from the shore without vehemence. With subtlety and sweetness you may do much more at low cost.”
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Vierlingh’s ambitious ideas coincided with the first widespread use of windmills to pump out polders.

THE NETHERLANDS ARE flat and windy, with an average wind speed of twenty-one kilometers an hour, an ideal environment for wind power. Most likely, the idea of a windmill arrived in the Netherlands in the hands of returning crusaders during the thirteenth century.
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At first they served as small corn mills, laboriously rotated to face the wind. Primitive windmill pumps lifted water at Alkmaar (today famous for its cheese) as early as 1408, but their scoops could lift water only a mere two meters, more if arranged in series. Over a century later, by 1574, the invention of the movable cap atop the mill allowed just the sails to be rotated, so windmills could be much larger, taller, and more efficient. Wind-driven water pumps led to the development of a new form of polder, created by surrounding shallow bodies of water with an embankment, then pumping them dry. Such polders required capital to build, but paid rich dividends when used for large-scale drainage, even if occasional storms wreaked havoc on embankments. By the later sixteenth century, rich urban merchants had begun to invest in land, as well as to finance large-scale reclamation, which they now considered a potentially lucrative investment as food prices rose and population growth caused shortfalls of good farming land. By 1640, twenty-seven lakes north of Amsterdam had been pumped dry.

Such reclamation works flourished under the direction of Jan Leeghwater of Burchardi storm fame, an accomplished millwright and expert on polder reclamation. He would construct an encircling dike and associated canal into which he would pump surplus water with windmills. Once dry, the peat was cut and sold as fuel. The exposed soil then became arable land and pasture. In 1607, Leeghwater began draining the 7,000-hectare, 3.5-meter deep Beemster Lake in North Holland. The encircling dike and canal took two years to construct. Twenty-two windmills began work before a storm surge destroyed the still-unconsolidated dike. Two years later, dike repairs allowed pumping to resume, this time with forty-two windmills. Trees planted on the flanking dike bound the earth together and provided a pleasant view. Hundreds of men labored with mattocks, spades, and wheelbarrows without any assistance, except from heavy pile drivers operated by teams of thirty to forty workers. Ox-drawn carts, sleds, and large wicker baskets moved clay for the dikes, and also the timber piles and willow wands used for reinforcement. Despite initial setbacks, the Beemster reclamation project was a spectacular success.
By 1640, 207 farmsteads, a hundred barns, ten hay or seed stores, a corn mill, two timber wharves, three schools, a church, and a parish hall flourished within the polder. There were even out-of-town houses for city dwellers to enjoy during the summer.
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Figure 14.2
Windmills at Laandam, Netherlands, 1898. James Batkin (creator). © The Print Collector/Heritage/The Image Works.

As drainage schemes proliferated, so accurate leveling became ever more important. In 1682, Johannes Hudde, the burgomaster of Amsterdam, organized the first systematic measurement of sea levels, the height being measured by eight large stones, the so-called Amsterdams Peil, the level from which all heights above and below sea level in the Netherlands have been measured ever since.
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SYSTEMATIC SEA LEVEL measurements were part of a far wider upgrade of both sea defenses and reclamation. Early sea defenses in the Low Countries were low embankments of tamped-down clay or earth. So were river dikes, which had to withstand not only wave action and tides but also long periods of high water when seepage was a problem. A clay core, gentle landward slopes, and a gravel-filled ditch at the base to catch seepage made them fairly effective.
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During the thirteenth century a form of mud dike, the
werdijken
, came into use in northern Holland. The builders piled turves or lumps of sticky clay to form a steep seaward face. A thick seaweed mattress, held in place with piles against the outer face, compressed and rotted into a solid residue that was surprisingly effective against attacking waves. Bricks or stones often reinforced the base, the seaweed piles sometimes extending as high as five meters over the face and top of the embankment. Seaweed clung to itself because of its weight, forming a sweating, elastic cushion that resisted waves. Reeds or wicker mats sufficed where seaweed was unavailable, but were not nearly as durable and had to be replaced every five years or so. Sometimes the builders used individual wooden piles, thirty centimeters square and up to six meters long. Some of these dikes appeared as early as 1440 and remained in use until the nineteenth century.

Sea defenses of earth and timber sufficed until 1731, when the teredo worm, inadvertently brought to the Netherlands by Dutch East India
Company ships, proliferated in Zeeland and elsewhere. This bivalve, which is actually not a worm at all but a saltwater clam, bores into wooden structures such as the hulls of ships immersed in seawater. Teredos ravaged the coastal defenses in short order. With a few years, wooden piles collapsed; seaweed and reed mattresses were washed away. By 1732, fifty kilometers of the Westfriese Zeedijk in North Holland had collapsed. Another twenty kilometers was seriously weakened. Memories of the Christmas flood of 1717 were fresh in everyone’s minds, when seventeen thousand people died and water poured into Amsterdam and Haarlem. “The blessed Netherlands … is in danger of being flooded because of a rare gnawing of worms,” lamented one observer in 1735.
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The only solution lay in imported stone, an expensive palliative but one offset by much greater durability.

Lengthy trials led to gently sloping stone revetments, walls that extended from the base of the dike to a meter or so above extreme high tide. After 1775, dike revetments consisted of irregular boulders, the cracks between them filled with rubble, the whole resting on a bed of straw, which served to absorb the shock of breaking waves and reduce erosion and seepage. Today’s dikes have a sand core, covered by a thick layer of clay to provide waterproofing and erosion resistance. Where there is now land in front of the dike, a layer of crushed rock lies below the waterline and slows water action. A layer of carefully laid basalt rocks or tarmac covers the front surface up to high water level. Grass mantles the rest of the dike, kept dense and short by grazing sheep.

The Industrial Revolution, with its fossil fuels and much more efficient pumps, eventually allowed the Dutch to undertake much larger reclamation projects. A steam pump imported from Looe in southwestern England came into use at Blijdorp near Rotterdam in 1787. At first the farmers opposed its use on the grounds that the noise would scare their cows from giving milk. Opposition soon evaporated when the pump successfully combated winter floods and seepage. Reclamation work had been at virtual standstill in many areas, but now resumed on a larger scale. The greatest impact of steam drainage came at the Haarlemmermeer in the south, which covered nearly eighteen thousand hectares and threatened the major cities nearby. In 1836, a southwesterly
gale blew water from the meer to the outskirts of Amsterdam. Another storm menaced Leiden a month later. Steam power now made the draining of the lake possible. An encircling lake and hundred-kilometer-long canal built between 1840 and 1854 allowed three large pumping stations to drain the Haarlemmermeer by 1852.
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The nineteenth century also witnessed a frenzy of canal building, aimed at improving access to Amsterdam and Rotterdam for larger oceangoing ships. Sandbanks in the Zuiderzee and circuitous approaches through delta channels made for hazardous, slow passages. Rotterdam was only thirty kilometers from the coast, but the approach by water twisted and turned for a hundred kilometers. Add the delays caused by tides and winds to the equation, and it could take an East Indiaman twenty-one days to reach the open sea and only a hundred more to reach the Indies. The Nieuwe Waterweg to the Rhine mouth was completed in 1872, in the hope that tidal scour would keep it deep, but shallowing began immediately. Only with the advent of steam dredgers did the canal link Rotterdam effectively to the Rhine. By 1876, the twenty-four-kilometer North Sea Canal punched through the coastal dunes and linked Amsterdam to the ocean and, with constant widening and improvements, has served as the main artery for the city’s port ever since.

THE MODERN ERA of sea defenses in the Netherlands can be said to have begun with two defining events—the Zuiderzee flood of 1916 and the flood of 1953. The Zuiderzee flood came on January 14, after several days of rough weather. Water levels rose; winds reached a velocity of over a hundred kilometers an hour. As dikes eroded on both sides, water inundated the island of Marken, where the only protection was low quays. Sixteen people died; fishing boats washed ashore. The material losses were far greater than fatalities, but the disaster stimulated a debate already in progress about reclaiming the Zuiderzee by building a dam across the mouth. On January 13, 1918, the Dutch Parliament passed a bill to start the work. The contractors built the thirty-two-kilometer Afsluitdijk of glacial boulder clay and rocks between 1920 and 1932, with drainage locks that allow excess water to pass into the Waddensee
outside. The Zuiderzee became a lake and was renamed the Ijsselmeer. Large polders then reclaimed extensive tracts of valuable farmland from the now freshwater lake.
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As the Zuiderzee works continued, a study by the state water authority in 1937 showed that sea defenses in the southwest were an inadequate defense against a major storm surge. The study proposed that all river mouths and sea inlets be dammed permanently in an expensive exercise that would shorten the coast by about four hundred kilometers. World War II intervened and it was not until 1950 that the first stage of dam construction was complete. Then came the second defining catastrophe—the great flood of 1953 that brought disaster to both coasts of the North Sea.