Amsterdam is definitively below sea level, existing within a larger low-lying region of the Netherlands. The land is a complex system of engineered terrain situated beneath the level of surrounding water bodies. Significant portions of the city are naturally susceptible to flooding from the North Sea, rivers, and groundwater seepage. The city’s existence today is a testament to a meticulously managed hydraulic defense system.
The Dutch Benchmark: NAP
Understanding Amsterdam’s elevation requires knowing the country’s zero reference point, the Normaal Amsterdams Peil (NAP). NAP, which translates to “Normal Amsterdam Level,” serves as the national vertical datum for all height measurements in the Netherlands and much of Western Europe. This reference level is approximately equal to the average sea level of the North Sea.
The zero point of NAP was originally established in the 17th century based on measurements of the water level in Amsterdam’s River IJ. Although the sea level has changed since then, the NAP remains the fixed standard against which all elevations are measured. Many areas of Amsterdam itself are several meters below this zero level.
How Amsterdam’s Land Was Created
The very ground Amsterdam sits on was created through an extensive process of human intervention and drainage. The original landscape consisted primarily of marshy peat bogs and shallow lakes, making the area naturally waterlogged and unstable. In the Middle Ages, communities began constructing dikes to protect their settlements, but the underlying peat soil dried out and compacted, causing the land to sink further below the water table.
The widespread creation of reclaimed land, known as polders, became common practice, especially during the 17th century. Polders are areas of land surrounded by a ring dike, from which water is pumped out to keep the interior dry. This engineering process required innovative technology, with Dutch engineers perfecting the use of windmills to power the scoop wheels and Archimedean screws that lifted water out of the polder and into higher-level canals.
The result of this constant drainage and reclamation is that the ground itself was engineered to exist at a lower elevation than the surrounding water. Examples like the Beemster Polder, just north of Amsterdam, demonstrate how large lakes were entirely drained and transformed into geometrically planned, productive farmland lying far below sea level. The city’s growth, including expansions over filled-in waterways, means its foundations rest on this historically engineered, low-lying subsoil.
The Infrastructure Keeping the City Dry
Keeping Amsterdam dry today relies on a complex, multi-layered system of hydraulic engineering that requires continuous operation. The primary defense against the sea and major rivers comes from an extensive network of main dikes and immense storm surge barriers, which protect the region from catastrophic high water events. These large-scale barriers, such as those that are part of the Delta Works system protecting the wider region, form the outer shell of the defense.
Behind these outer defenses, a secondary system of internal dikes and canals, often called water rings, manages the water within the low-lying areas. This network collects seepage and rainfall, maintaining a specific, controlled water level within the polders. Water is constantly being moved from the lowest ditches and canals to the higher-level storage basins, or “boezem,” before being released into the sea or major rivers.
The core of the daily operation is the modern electric pumping stations, or gemalen, which have largely replaced the historic windmills. These powerful pumps work non-stop to remove excess water, preventing the land from returning to its natural waterlogged state. This entire system is overseen by regional water boards, or Waterschappen, which are independent governmental bodies responsible for maintaining the dikes, pumps, and water quality.