The Netherlands' geography: a country that lowered its own ground

How the Dutch made the ground they stand on

About 6,500 square kilometres of the Netherlands consists of reclaimed land, the product of a water-management practice that Britannica dates back to medieval times. Along the coast, ground was taken from the sea. Inland, lakes and marshes were pumped dry, most of them beside the rivers. Every piece of that new ground was ringed with a dike and became a polder. The largest of the schemes were carried out in the second half of the nineteenth century and in the twentieth, once steam pumps, and after them electric and diesel pumps, took over from men, horses and windmills.

The result is a country whose lower half is flat in a way that has to be described in centimetres. More than half the total area lies no higher than about one metre above sea level, and about half of that area sits below it. On such ground a building cannot simply rest on the soil. It stands on a raft, or on concrete piles driven as much as twenty metres down into the silt.

Why draining the land lowered it

The relationship between drainage and depth runs the opposite way to the one most people expect. Relatively high-lying swampland was drained so that it could be farmed. The drainage dried the fertile peat beneath, the peat contracted, and the ground level fell. To keep the fields workable the groundwater had to be lowered again, which dried more peat, which dropped the surface further. Peat was also mined, dried and burned as fuel until the nineteenth century, and dredged as turf even out of ground that had already flooded, so the same material was being taken away from below while the drying went on above.

Most of the Dutch land that now lies under sea level was put there by that sequence and by peat extraction, and only in part by an advancing sea. A landscape that lowers itself every time it is made useful is the single fact from which the rest of this article follows.

Who has managed the water for centuries

The institutions are older than the machinery. In the first millennium AD villages and farmhouses were raised on artificial mounds called terps, and the terps were later joined up by dikes. From the twelfth century, local bodies called waterschappen, water boards, and hoogheemraadschappen took on the job of holding the water level and defending a district against flooding, and those agencies still exist. By the thirteenth century windmills were pumping, and mills were later turned on the lakes themselves, which is how the polders were drained. As the ground sank, the separate dikes grew and merged into one integrated system, because a dike that protects a single parish is a dike with an open flank.

Where the land still rises above the water

The high ground is in the east and the south, and it is not high. Layers of sand and gravel in the east were pushed sideways and upward by ice tongues of the Saale glacial stage, leaving elongated ridges that reach more than 100 metres and now form the principal relief of the Hoge Veluwe National Park. Only along the border zone of the Ardennes does the surface pass about 105 metres. The Vaalserberg, in the extreme south-eastern corner, reaches 322.7 metres, and that is the summit of the European Netherlands.

The highest point of the country as a whole is nowhere near it. Mount Scenery, 870 metres, stands on Saba in the Caribbean Netherlands, which covers 322 square kilometres in total. Saba and Sint Eustatius are volcanic and hilly, with little ground flat enough to farm; Bonaire belongs to the ABC islands in the Leeward Antilles off the Venezuelan coast, where the geology is mixed volcanic and coral. At the other end of the range, the lowest recorded point is the Zuidplaspolder at Nieuwerkerk aan den IJssel, seven metres below sea level.

The European Netherlands has a total area of 41,543 square kilometres including its water bodies and a land area of 33,481 square kilometres, and it lies between 50 and 54 degrees north and 3 and 8 degrees east. Land boundaries run to 1,027 kilometres, 577 of them with Germany and 450 with Belgium. The coastline is 451 kilometres and the exclusive economic zone 154,011 square kilometres. The country's record lists four neighbours, and two of them, France and Venezuela, are reached only across Caribbean water.

Even the land border is not fixed. In November 2016 the Netherlands and Belgium agreed to cede small uninhabited parcels to each other because the Meuse had shifted its course while the boundary drawn on it had not. The transfer took effect in 2018.

What three rivers built and still divide

Much of the country was formed by the estuaries of three large European rivers, the Rhine (Rijn), the Meuse (Maas) and the Scheldt (Schelde), together with their tributaries, and the south-west of the country is their shared delta. Nearly the whole of the western Netherlands is the Rhine and Meuse estuary. In the centre and the south those rivers unloaded thick layers of silt and gravel carried down from the European mountain chains. In the north, the Scandinavian ice sheet of the late Pleistocene, roughly 126,000 to 11,700 years ago, left moraine behind, and the cities of Arnhem and Nijmegen stand on the hill line it pushed up. Later, through the Holocene, clay settled in the sheltered lagoons behind the coastal dunes and peat formed on top of it.

The same rivers cut the country in two socially. The Rhine, its main branch the Waal, and the Meuse run west across the middle of the country, and they worked as a barrier between fiefdoms long enough to leave a cultural line behind them. The Dutch call them de Grote Rivieren, the Great Rivers, and phonetic traits are still recognisable on either side. A second line follows the IJssel, the Rhine branch that discharges into Lake IJssel: north-east of it people speak Dutch Low Saxon dialects, except in Friesland, which has a language of its own.

The river region has a character no other part of the country has. High dikes run along wide channels, orchards sit on the natural levees the rivers built, and long bridges carry the roads and railways that connect the central Netherlands to the southern provinces. It is the one Dutch landscape where the defence works are the scenery.

How the sea is kept out

The night of 1 February 1953 is the reference point for everything built since. A storm tide breached the dikes of the south-west in more than ninety places. More than 1,800 people drowned, some 162,000 hectares went under water, and the PBL Netherlands Environmental Assessment Agency puts the damage at more than 700 million euros. Zeeland, South Holland and North Brabant, much of which lies below sea level, took the worst of it.

What the Delta Works actually did

The answer was the Delta project, thirteen major flood-defence works begun in 1958 and largely finished in 1997 with the Maeslant barrier. Its arithmetic was blunt: raise 3,000 kilometres of outer sea dikes and 10,000 kilometres of inner, canal and river dikes, close off most of the sea inlets of the south-western delta, and shorten the coastline that has to be defended by some 725 kilometres. Ten dams and two bridges went up between 1960 and 1987. Two waterways were deliberately left open for the ports, the New Waterway to Rotterdam and the Western Scheldt to Antwerp, so the dikes along those had to be strengthened instead.

When the barriers get closed

The thresholds are set against NAP, Normaal Amsterdams Peil, which is roughly the average level of the North Sea. The Eastern Scheldt barrier closes when the water is expected to reach three metres above NAP. Its sixty-two gates come down from the control building on the artificial island of Neeltje Jans in about seventy-five minutes, and on average that happens once a year. The barrier rests on 65 piers, its gates are some 42 metres wide and 6 to 12 metres high and weigh between 260 and 480 tonnes each, and the whole structure is designed against a flood statistically unlikely to occur more than once in 4,000 years.

The Maeslant barrier, near Hoek van Holland, closes itself with no human intervention when the forecast reaches three metres above NAP at Rotterdam or 2.9 metres at Dordrecht. Each of its two gates is 210 metres wide, 22 metres high and 15 metres deep; when the barrier closes they fill with water and sink to the bottom within two hours, turning on ball-and-socket joints ten metres across that weigh 680 tonnes apiece. It was first closed in 2007.

None of this is a finished job. The Delta Fund set aside a budget of 15.2 billion euros for reinforcing and maintaining dikes and levees over the period from 2016 to 2028, around a billion euros a year, and roughly 60% of that sum is for additional reinforcement. The Delta Commission's action plan is written against a sea-level rise of 1.10 metres combined with a fall in land height of 10 centimetres, and answers it with 1.30 metres of extra protection on the existing dikes and dunes.

Where the tide is still allowed in

Not every inlet was closed. The Eastern Scheldt was originally to be dammed solid, and the design was changed to an open, movable barrier so that the estuary would keep its tides, keep its salt water and keep its fishery. About three-quarters of the tidal movement survives, and the estuary was designated a national park in 2002, covering 370 square kilometres. The former construction island of Neeltje Jans now sits inside that park.

The northern coast was never closed at all. Behind a chain of barrier islands lies the Wadden Sea, an unbroken system of intertidal sand and mud flats running along the Dutch, German and Danish coasts and inscribed on the UNESCO World Heritage list. It holds tidal channels, sandy shoals, sea-grass meadows, mussel beds, sandbars, salt marshes, estuaries, beaches and dunes, along with harbour seals, grey seals and harbour porpoises, and it is one of the few large intertidal systems where the natural processes still run largely undisturbed. A remote-sensing analysis put the Dutch tidal flat area at 1,025 square kilometres.

The rivers are being given room back as well. Under the Room for the River programme, Rijkswaterstaat is moving dikes inland at thirty locations, digging flood channels and lowering floodplains so that a peak can spread sideways instead of pressing on the defences. In the IJssel delta the shipping channel is being deepened and a flood channel built between two dikes to carry high water away faster. The handful of residents of the designated overflow areas have been moved to higher ground, some of it raised above the anticipated flood level for the purpose.

What the weather does to a flat country

The climate is temperate and maritime, with rain in every season. The prevailing wind is from the south-west and the sea moderates whatever it reaches, so the swing between summer and winter, and between day and night, is smallest along the coast and widest in the south-east. Britannica gives July an average near 17 °C and January near 2 °C, about 60 days of frost a year, roughly 790 millimetres of rain and about 25 clear days, with three-fifths of the sky clouded on an average day. Dutch landscape painting is full of that sky.

Wind meets very little resistance over flat ground, and only the hills in the south slow the coastal wind appreciably. The country also sits between the high-pressure air masses centred on the Azores and the low-pressure region centred on Iceland, which is why warm and polar air collide over it and why the weather refuses to settle.

The extremes are narrow by continental standards. The highest temperature on record is 40.7 °C, reached at Gilze-Rijen on 25 July 2019; the lowest is −27.4 °C, recorded at Winterswijk on 27 January 1942. Ice days, when the maximum stays below freezing, normally fall between December and February. Frost nights run from mid-November to late March and have been measured as early as mid-October and as late as mid-May, and snow is possible from November through April. Day length swings from barely eight hours in December to nearly seventeen in June, which organises the Dutch year more firmly than temperature does.

The averages are moving. The mean temperature in the Netherlands rose by more than 2 °C between 1901 and 2020, and droughts and heatwaves have both become more frequent over that period.

How the made ground gets used

Statistics Netherlands classified 49% of the surface as agricultural in 2020, mostly meadowland and arable fields. Built-up terrain, which covers buildings, industrial estates, roads and other infrastructure as well as public parks, took nearly 24%. Nature and semi-nature accounted for 16%, and fresh water, salt water and the coastal strip for the remaining 11%. Between 2013 and 2020 the country lost 244 square kilometres of agricultural land and 53 square kilometres of wooded area while nature and water gained 44, with the sharpest farmland losses in Noord-Brabant at 58 square kilometres and Gelderland at 38.

The Environmental Data Compendium's assessment for 2015 counted roughly two-thirds of the surface as agricultural and under 15% as built-up and infrastructural, with housing below 7% and building sites about 1%. The two counts disagree because they draw the line between built and green in different places, and the disagreement is itself informative in a country where a park, a road verge and a drainage ditch are all somebody's managed ground.

What survives as wild land is scarce and heavily managed. The last of the old original natural woods were cut down in 1871, and what stands today was planted on heaths and overgrazed drift sands. There are 21 national parks and several hundred other nature reserves, most of them held by Staatsbosbeheer, the state forestry and nature service, or by Natuurmonumenten, which buys and manages reserves privately. The Netherlands scored 0.6 out of 10 on the 2019 Forest Landscape Integrity Index, which measures how far a forest has been modified rather than how much of it there is. Nitrogen pollution is a standing problem, and the number of flying insects has fallen by around 75% since the 1990s.

The natural resources on the record are natural gas, petroleum, peat, limestone, iodised salt, sand and gravel, and arable land. Three of those seven are the ground itself.

Why almost everyone lives in one ring

The population was 17,942,942 as of 1 January 2024, at a density Wikipedia's geography article gives as 521 people per square kilometre against a base of 17.4 million. There is no single dominant metropolis. The four largest cities sit close together in the western provinces of North Holland, South Holland and Utrecht, with a ring of medium-sized towns between and around them, and the whole arrangement is called the Randstad. It takes up about 20% of the land area and holds about 45% of the population, at over 1,000 inhabitants per square kilometre, and it is laid out around an open interior the Dutch call the Groene Hart, the Green Heart. In November 2019 Amsterdam had 872,680 inhabitants, Rotterdam 650,711, The Hague 544,766, Utrecht 357,179 and Eindhoven 234,235. Government policy keeps the older towns and cities separated from one another by strips of agricultural or recreational land.

Outside the ring the country empties out quickly. Between 70 and 85% of the total land area is described as rural, and the northern provinces in particular are characterised by open space rather than by settlement.

The uncomfortable part is where the ring sits. It occupies the low ground, which is the ground that floods first. The PBL Netherlands Environmental Assessment Agency reckons almost 70% of the population lives in flood-prone areas, and that share has grown since 1953 as the economy and the population have grown with it. South Flevoland shows the arithmetic at a readable scale: a polder of 430 square kilometres on the edge of the IJsselmeer with 200,000 residents, where a dike that is overtopped instead of breached would flood roughly half as much land and reduce the potential number of casualties by around 95%.

Everything therefore stays conditional. Ninety years after it was closed in 1932, the Afsluitdijk is being re-clad along its whole length with concrete blocks weighing 6,500 kilograms each, so that it can take a storm expected once in 10,000 years, and a pumping station is being built inside it to move water from the IJsselmeer out into the Wadden Sea faster than the sluices alone can manage.