According to a persistent myth, the Dutch reclaimed their land from the sea. But it could be argued that the Dutch themselves destroyed their country only to rebuild it by means of dikes and pumping plants.
According to a persistent myth, the Dutch reclaimed their land from the sea. It is true though that looking at the elevation map, or rather the depression map, one gets the impression that the Netherlands ends roughly at the line Zwolle-Amersfoort-Breda. Everything to the west of this line lies below sea level, with the lowest point – near the residence of Prime Minister Balkenende – almost seven metres below sea level. This conjures up the image of powerful engineers building a huge ring of sand and stone in the sea before pumping the entire western part of the Netherlands dry.
The truth is that the basic shape of the Netherlands dates back from after the last Ice Age. Approximately ten thousand years ago, the sea level began to rise significantly. Britain became isolated from mainland Europe again, and the tides deposited sand at approximately the current location of the Netherlands in the form of beach ridges running parallel to the coastline. After two and a half thousand years, the Dutch coast had roughly reached its current outline. When the sea-level rise came to a halt, the sand barriers grew together to form the so-called Old Dunes, which over time became covered with dense forests. The salt marshes and mud flats behind those dunes slowly silted up and turned into soil through the formation of peat. In Roman times, the coastline of the Netherlands was made up of an extensive range of unbroken dunes that also included the current West Frisian or Wadden Islands. Behind these dunes lay a vast plain with meandering rivers and waterlogged peat areas. Though not very firm or stable, these areas clearly lay above sea level.
It was not until later that the sea surged further inland. The slowly rising sea level played a part in this, but much more destructive was the persistent land reclamation by the Dutch themselves. The reclamation and drainage of the delta caused the peat soil, which apart from a scanty fifteen percent of plant debris consisted of water, to subside many metres. The tide could thus penetrate the land deeper and deeper, scouring out the tidal inlets four times a day.
From the ninth century onwards, storm tides broke away parts of the coastline, and the water swallowed large stretches of land. This is how the Wadden Sea came into being, the Zuyderzee (Zuiderzee) – which later became a freshwater lake called the IJsselmeer – and the estuaries in the Province of Zeeland. It could be argued, therefore, that the Dutch themselves destroyed their country only to rebuild it by means of dikes and pumping plants.
The first dikes were not built along the coast or even along the rivers but in the peat lands behind the coastal areas. People had for some considerable time been enjoying a relatively safe life on the terps, but to make the surrounding land suitable for field cropping and cattle breeding, it had to be drained, which required the construction of ditches and low dikes. It was not until 1000 A.D. that people actually started cutting and stacking sods to form low embankments. The favourite building material was fatty clay because the fatter the clay the smaller the risk of washout. The biggest problem in this were not the dikes themselves – they were simply raised again and again to form ring dikes enclosing several villages – but the construction of sluices to drain the redundant water.
The very first sea dike was probably built in the present province of Zeeland, after the storm flood of 1134, which turned the province into an archipelago of islands. It took more than half a century to dike the four large islands and recover the old cultivated landscape from the sea. The dikes were built on old creek ridges further inland so that they were burdened only during high tide. We do not know exactly how these dikes were built: archaeological research is difficult, because these dikes have largely been incorporated into the new dikes, which obviously cannot be excavated. Around 1930, however, a dam dating back from the initial period was found, which not only appeared to consist of clay but was also strengthened with a launching apron.
In the course of the fifteenth century, the dike builders introduced apart from clay and stone a third building material: brushwood. They bundled and plaited the thin, flexible twigs of willow and alder into fascines: long sausage-shaped bundles of 50 centimetres in diameter, bound together with osiers. The fascines were used as mats for the foundation of sluices. Cleverly stacked, the fascines formed dams to close off gaps, and groins and breakwaters, which running perpendicular to the dike, controlled the current.
Along the Zuyderzee, where the shortage of good fatty clay had forced people to use less suitable peat, new forms of dike revetment came into use. The dike exterior was covered with slikker – stiff, tough boulder clay collected in the mud flats – or with layers of seaweed kept in place by means of poles. Sometimes even straw was used, which had to be replaced every year.
The real innovation, however, came once again from Zeeland, and it was not so much the material application that was innovative but the standardisation. Gradients, crest level, and width were laid down in standard profiles, and at the most threatened places dikes were equipped with a zeebek: a gently ascending slope on the open-water side of the dike. The construction of dikes was put out to public tender in pieces of eighty metres long and a scenario had been drawn up to regulate the cooperation between the contractors. The ‘Zeeland’ dike was so successful that later on the system was also implemented in Holland and Friesland.
From the seventeenth century onwards, the focus of water management shifted from the dike to the foreshore, because even the strongest dike could collapse if the soil subsides or moves. The solution was found in fascine mattresses, large mats of plaited brushwood that, weighted with stones or clay sods – so-calledkloetingen – were sunk on the foreshore of the dike. Especially on the unstable soil in the Zeeland delta, the plaited mats, which were sometimes many metres in diameter, proved to be invaluable. Without the fascine mats Zeeland – and with it eventually also the hinterland – would have been doomed.
However heroic the toilsome labour with clay, stones, and brushwood, the construction of dikes proved not the only way to protect the Netherlands against the water: from the late Middle Ages, the insights into the role of nature as a defensive force became more and more solid. The planting of marram grass appeared a good way of controlling the New Dunes, which from the ninth century onwards had been piled up by high winds and which were much higher and more rugged than the Old Dunes. Marram grass was initially planted to prevent arable land from being covered with drifting sand, but later on also to stabilise the dunes themselves, which especially near the North Holland village of Petten tended to crumble away. The coast defenders found out that they could also build dunes themselves. With sand and marram grass, they built inner or safety dikes, which if constructed in the right place, could be the starting point for new dune formation. The year 1506 seemed a turning point in the fight against the water: the Hof van Holland (Council of Holland) decided to withstand the sea. Instead of filling up the eroding dunes on the landside with sand and accepting the slow eastward advance of the coastline, they decided to defend the dunes more actively. Scandinavian timber and Belgian natural stone were used to build breakwaters in the sea over a length of two kilometres.
In the end, all efforts appeared to no avail: the storm flood of 1570 wreaked havoc on the line of defence. Fortunately, the inner dike behind the dunes held out, preventing North Holland from being inundated. The flood put an end to the active coastal defence; the Netherlands, still licking its wounds, moved backwards and forwards with the advancing sea, and it would take until 1880 before a sturdy stone-lined dike was built here: the Hondsbossche Zeewering. The art of dike construction seemed to be more or less crystallised out in those days: a dike consisted of tamped clay applied in layers of 35 to 40 centimetres thick. Its height should be 1 to 1.75 metre above the highest storm flood level, its width at least three metres, the open-water side should slope down by twenty percent, and in dangerous places the foot of the dike should stretch into the water for a length of 300 to 375 metres. The dike ended in a toe of poles that had to prevent it from sliding down.
The dike revetment was standardised as well: the top and the interior side were covered with sods on which sheep were allowed to graze. Cows and horses were banned because they would trample the top layer. In the southern part of the Netherlands, the open-water side of the dike was covered with Belgian natural stone, and in the northern part with German basalt columns. In short, the Dutch dike had attained its classical form.
The Zuyderzee Flood of 1916 put an end to the feeling of security that had pervaded the Netherlands, and gave an impetus to the scientification of dike construction. Experiments in laboratories and research stations proved that dikes do not have to be made of clay at all, as sand is at least equally suitable provided the covering is firm enough. This was how eventually the construction of the Afsluitdijk (Closure Dike) could begin, a plan that had been presented as early as 1667 by Hendric Stevin, the son of the famous mathematician Simon Stevin.
Sand was soon to be followed by concrete. The Allies had bombed the dikes of Walcheren, and in the winter of 1944-1945 the breaches had grown larger and larger. As there was no time or material to close the dikes in the traditional way, the people saw no other way but to use the floating caissons left after D-Day. The [These] concrete boxes were sailed to the breaches, sunk on a threshold of gravel and stone, and filled up with minestone from Limburg. A daring exploit, pulled off splendidly. The knowledge acquired during this enterprise proved particularly useful during the next disastrous storm surge, the North Sea Flood of 1953, which took nearly eighteen hundred lives. It was this particular flood that led to the construction of the Deltaworks. As it happens, this closure too had been included in Stevin’s wish list three centuries earlier.
Natural stone appeared to have been dismissed completely: for the closure of the Haringvliet concrete blocks of one cubic metre were cast, to which four hooks were attached. A cableway transported the blocks to the right place and plunged them into the water. During the next closure – the ‘open’ Oosterschelde barrier – the site with its concrete pillars looked more like a city under construction than a dike. Dike construction had become a thoroughly professionalised industry; nothing bad could happen to the Netherlands ever again.
Without being prodded into action by a disaster – in the Netherlands a sure wake-up call – a new Delta Committee presented in 2008 their findings on the safety of the country. A quarter of the dikes appeared not to meet the standards set by the original Delta Committee, and it proved impossible to assess the condition of another third part adequately. In addition, the Delta Committee 2008 stipulated that the safety standards should at least be improved by a factor of 10 to ensure that even if the soil continues to subside and the sea level rises by 1.3 metres in the next century, the chance of drowning in a flood is smaller than one in a million per year. The Netherlands must remain the safest delta in the world. The new Delta Committee, however, does not come with proposals for the construction of the super dike mentioned five years ago: a 350 kilometres long dike located twenty kilometres off the coast, with a storage lake between beach and dike. Also the plans for artificial islands in sea – in the shape of a tulip, for example – did not make it. Instead of all this, the committee comes up with the cheapest building material of all: sand, or rather, mud.
Since 1990, the Dutch coast has been maintained by means of sand replenishment, which involves spraying a mixture of sand and water in strategic places to counteract coastal erosion and enable the coast to restore itself. Unlike a dike, the shape of the coast is subject to change: wind, waves, and currents determine the appearance of the new coastline. The new trump card in this engineering project are ‘sand engines’: large quantities of sand deposited in strategic places off the coast. In 2010 a pilot project is to start south of The Hague.
To withstand the expected sea-level rise, 85 million cubic metres of sand are required per annum. The Delta Committee, however, is planning to take further actions: the sand replenishment of an additional forty million cubic metres per year will ensure that in one hundred years’ time the Dutch coast is one kilometre wider. Then the Dutch can rightfully say that they have reclaimed the land from the sea. And paradoxically enough, this time it will be as if human hands had nothing to do with it.
Introduction to the book Dutchscapes by photographer Jan Koster. The book is available through Jap Sam Books