Posted on October 23 2018
Water covers about three quarters of the Earth, so it doesn’t seem too greedy that folks in Netherlands wanted to convert some of that to dry land. But before we get to that undertaking, how did that area evolve to where it became necessary to dry out land in the first place? The Netherlands, sometimes called Holland, have always been territory of low relief. Their soils were wet, as you would expect of near sea-level land at the edge of a rainy continent, and mostly composed of peat bogs. These bogs contained land that was at least a few feet above sea level, raised by thousands of years of moss and other wetlands vegetation growing and putting down dead material layer by layer since the close of the last ice age. The anaerobic state of the soaked vegetation kept each season’s dead material more or less intact for lack of decomposition. Because they required a great deal of modification to serve as farmland, few bothered with these “nether” lands. About a thousand years ago, climatic and social conditions developed that encouraged more farming, and people looked to these once-ignored areas to raise crops. They drained the watery bogs into nearby rivers to make them farmable. Plowing the rich peat provided fertile ground for farmers, but the exposure of the old plant material to oxygen hastened decomposition. The peat that had maintained its volume for many centuries began to shrink within a few hundred years, lowering the elevation of the land. Land that had been previously dried out for farming by draining it into lower water bodies was now too low to keep drained.
Initially, the water that began to invade this deflating land was the fresh water of precipitation, lakes and rivers. The farmers learned to build dikes around flooded land and pump out the unwanted water by means of power from windmills. In the 17th century, Netherlands was a prosperous place thanks to trade, and money was available for a legion of these windmills to help dry out land that had either subsided or had been lowered by the extraction of peat for fuel. Given the success of converting low freshwater-invaded land into farmable dry land, engineers began to encircle areas of salt water with dikes and berms, draining them with pumps for the same purpose. The salt-soaked soil then had to be treated to make it palatable to crops. These reclaimed lands, called polders, added many square miles to the Netherlands’ size. The fortifications built to hold back the water were made of piled and stacked soil, but were also lined or strengthened with wooden timbers. Around 1730, the Dutch experienced at the water’s edge what wooden ships had long contended with at sea: Teredo navalis, the shipworm.
One of the members of a family of wood-boring bivalves, they made a honeycombed skeleton of the wooden elements of the ramparts that kept Netherlands from being inundated. Expanded shipping trade to distant areas had brought the mollusk to the area as a stowaway. Drought, which resulted in lower river flow, allowed salinity to increase nearshore, giving the marine animal greater access to the dikes. With dike systems under the threat of imminent collapse, engineers moved quickly to design new protections that involved building with more soil, and with a lower angle facing the water. These earthworks were buttressed with piled stones instead of wooden piers and planks. Eventually, the end of the drought period drove Teredo seaward again, and the re-engineered dikes were now stronger than ever.
As technology advanced, cement and steel came into play, and the pumps that kept the constantly seeping and accumulating water back were fueled by steam and electricity rather than wind. The Dutch by now were masters in the science and construction of barriers to the sea, and development of polders. Beginning in the 1920s and ‘30s, portions of what would be the Zuiderzee project were begun. The Zuiderzee, or South Sea, was an inlet of the North Sea. The partitioning of the area by multiple dike-building projects produced over 620 square miles of polders. The land has been used for agriculture, but also housing, industry, and recreation. In 1953, however, the triumph of man over the sea took a mighty setback. A combination of storms, voluminous runoff, and high tides created breaches in the dike system of southern Netherlands, flooding hundreds of square miles, and killing 1,800 people. The Dutch bounced back with plans to make the dikes stronger and more comprehensive, which they continue to do. The history of dike building in the Netherlands is vastly more complicated than told here, and involves feats of engineering that boggle the mind. With its long history of reclamation, more than half of its land is at or below sea level. It is said that God made the world, but the Dutch made Holland. They truly have built a country by wresting land back from the sea. But the challenges that face the Netherlands will get no easier as climate change raises sea levels, and the increased power of storms press harder against man-made ocean barriers. There is ample motivation for the effort, though, as the very existence of the country depends upon the construction and vigilant maintenance of this brilliant and elaborate system.
Take a trip to the Low Countries to see the dikes and polders—and spend some time in Amsterdam! Let this Freytag & Berndt map guide your wanderings. It’s available from Maps.com.
caption: Netherlands in 1682; north is to right. Dikes were in place, but the large polders in “De Zuyder Zee” were still in the future.
source: Wikimedia Commons: Nicolaas Visscher (Public domain)
caption: An example of what shipworms can do to wood. Dutch dikes were in serious trouble when they arrived.
source: Wikimedia Commons: Rosser1954 (CC by SA 3.0 Unported)
caption: By means of dikes, canals and pumps, farmland and living space is wrested from underwater.
source: Wikimedia Commons: Jan Arkesteijn (Public domain)
caption: Picturesque windmills once did the pumping, but power pumps have increased the capacity to dry out land.
source: pxhere: Unknown (CC0)
caption: Engineering projects like the 20-mile long Afsluitdijk, a dike and highway across the sea, are a Dutch specialty.
source: Wikimedia Commons: C messier (CC by 4.0 International)