How the Netherlands Turned a Sea into a Province | Maps in Motion #04
Short answer
- The Dutch dammed the Zuiderzee into a lake, then enclosed parts of it and pumped them dry, making about one-twentieth of the country's land.
- Closing the sea in 1932 added no land; the land came as four polders that fell dry between 1930 and 1968.
- The polders still lie about 4 m below sea level, and the outlines of the old islands survive in the ground height.
Also calledZuiderzee Workshow Flevoland was madeDutch poldersAfsluitdijkland below sea level
Video
Pressing play loads the YouTube player on this page. Watch on YouTube
Explained
In the video
- 0:00Rewind a province, and it turns into sea
- 0:34The Zuiderzee: a shallow saltwater sea
- 1:07Why close off the sea? (the 1916 flood and food)
- 1:28How a polder is made (and how it differs from landfill)
- 1:57The first island and the first polder (1924–1930)
- 2:331932: the sea becomes a lake (no new land)
- 3:02Noordoostpolder: islands become part of the land (1939–1942)
- 4:081945: the land floods again
- 4:27Eastern Flevoland: the lakebed emerges (1956–1957)
- 5:28The last polder, and the polder that was mapped but never built
- 6:101986: a province is born, and towns grow
- 6:47The old islands, still visible in the ground
- 7:32People made one-twentieth of the Netherlands' land
Almost all of the land in Flevoland, a province of the Netherlands, was seabed 100 years ago. The video fast-forwards on a map from a 1905 sea chart to today's ground heights, showing how the Zuiderzee was dammed into a lake and how parts of it were then enclosed with dikes and pumped dry. This page lists the values and sources behind the maps.
Timeline (what happens on the map)
| Date | Event | Map change | Source |
|---|---|---|---|
| 1905 | Zuiderzee sea chart (revised by S. Mars). Islands: Wieringen, Urk, Schokland, Marken (and Pampus) | Sea, islands and depths | RWS (digitized 1905 chart) |
| January 1916 | A storm surge floods Marken and parts of North Holland | Markers only (flood extent not drawn) | IamExpat / RWS |
| 14 June 1918 | The Zuiderzee Act is published (close off the sea and make new land) | — | Nieuw Land National Park / RWS |
| 31 July 1924 | The Amsteldiepdijk closes; Wieringen is no longer an island | Dike line, island outline | RWS / quarterly report 1932 |
| July 1929 | The Wieringermeer ring dike is closed | Ring dike, water inside | RWS / nl.wikipedia |
| August 1930 | The Wieringermeer falls dry (the sea outside is still open) | Mud → reclaimed land | RWS |
| 28 May 1932 | The last gap in the Afsluitdijk is closed (13:02). The Zuiderzee becomes the IJsselmeer (about 3,500 km², about 11.9 billion m³ of water) | Sea colour → lake colour (no new land) | RWS / quarterly report 1932 |
| 3 October 1939 | The Lemmer–Urk dike is closed; Urk is no longer an island | Dike line, island outline | Nieuw Land / quarterly report 1939 |
| 13 December 1940 | The Noordoostpolder ring dike is closed | Ring dike, water inside | Quarterly report 1940 |
| 9 September 1942 | The Noordoostpolder is officially dry (Schokland is now surrounded by land) | Draining reconstruction → reclaimed land | Nieuw Land / quarterly report 1942 |
| 17 April 1945 | German troops blow up the Wieringermeer dike in two places; within days the polder is level with the lake | Land → water | Quarterly report 1945 / NH Nieuws |
| 11 December 1945 | The Wieringermeer is dry again (breaches closed 5 August, pumping from 9 August) | Water → land | Quarterly report 1945 / NH Nieuws |
| 13 September 1956 | Pumping begins in Eastern Flevoland; the Veluwemeer is left between the polder and the old land | Ring dike, pumping stations | Limosa 1958 / quarterly report 1956 |
| Late May 1957 | Reed seed is sown from aircraft over more than 8,000 ha | Aircraft symbol (area not drawn) | Limosa 1958 / RIJP 1970 |
| 29 June 1957 | Pumping in Eastern Flevoland is considered finished (shallow puddles remained) | Mud | Limosa 1958 / quarterly report 1957 |
| 1957 | Marken is linked to the mainland by a dike | Dike line, island outline | NH Nieuws |
| 25 October 1967 | The last gap in the Southern Flevoland ring dike is closed (delayed from the 18th by a storm) | Ring dike | Quarterly report 1967 |
| 29 May 1968 | Southern Flevoland is declared dry | Mud → reclaimed land | Quarterly report 1968 |
| 4 September 1975 | The last gap in the Houtribdijk is closed, creating the Markermeer | Dike line, lake names | RWS / quarterly report 1975 |
| 1 January 1986 | Flevoland becomes the 12th province (an administrative date, not when the land was finished) | Provincial border (also across the lakes) | Nieuw Land |
| 2003 | The government decides not to build the Markerwaard (the fifth polder) | Label | Commissie m.e.r. 2014 |
| August 2026 | Provincial population 465,921 (provisional) | Label 'about 470,000' | CBS StatLine |
Dates are given to the precision confirmed in primary sources such as the Zuiderzee Works quarterly reports (Rijkswaterstaat). The Wieringermeer dates are given to the month, as the quarterly report for 1930 was not found.
Polders: years and area
| Polder | Ring dike closed | Fell dry | Area (official · measured from shape) |
|---|---|---|---|
| Wieringermeer | July 1929 | August 1930 | About 20,000 ha (shape: 210 km²) |
| Noordoostpolder | 13 December 1940 | 9 September 1942 | About 48,000 ha (shape: 484 km²) |
| Eastern Flevoland | 13 September 1956 | 29 June 1957 (pumping considered finished) | About 54,000 ha (shape: 544 km²) |
| Southern Flevoland | 25 October 1967 | 29 May 1968 (declared dry) | About 43,000 ha (shape: 437 km²) |
| All four | — | — | About 165,000 ha (shape: 1,674 km²) |
Areas measured from the shapes are slightly larger, because today's boundaries include the dikes. The video uses the official figures.
Height and water (approximate)
| Polder | Height (lakebed c. 1935 → ground today, median) | Water inside at closure | Records |
|---|---|---|---|
| Wieringermeer | (land on the 1935 map) → NAP −3.9 m | — | — |
| Noordoostpolder | NAP −3.3 m → −3.8 m | Estimate 1.26–1.46 billion m³ (approx.) | Quarterly report: 97% of 1,376 million m³ removed by March 1942 |
| Eastern Flevoland | NAP −3.1 m → −4.0 m | Estimate 1.46–1.68 billion m³ (approx.) | Quarterly reports: about 1.64 billion m³ pumped (13 Sep 1956 – June 1957) |
| Southern Flevoland | NAP −2.8 m → −3.9 m | Estimate 1.04–1.22 billion m³ (approx.) | — |
Estimates assume a lake level of NAP 0 to −0.4 m. Recorded pumping volumes include rain and seepage during pumping and were derived from pump performance curves, not flow meters. Today's ground is lower than the lakebed around 1935, which is consistent with soil shrinking and compacting after drainage (the two sources use different methods). More than 98 percent of each polder lies below NAP.
The former islands
| Island | Area inside the 1905 chart outline | No longer an island (how) | Height today vs. surroundings (median) |
|---|---|---|---|
| Wieringen | About 25 km² (approx.) | 1924 (Amsteldiepdijk) | NAP +0.2 m / Wieringermeer −3.9 m |
| Urk | About 1.0 km² (approx.) | 1939 (Noordoostpolder dike) | NAP +0.4 m / surroundings −2.8 m (about 3 m higher) |
| Schokland | About 1.9 km² (approx.) | 1942 (Noordoostpolder drained) | NAP −2.1 m / surroundings −3.7 m (about 1.6 m higher) |
| Marken | About 2.6 km² (approx.) | 1957 (dike to the mainland) | — (not inside a polder) |
Buildings (BAG, buildings standing today)
| Polder | Built by 1959 | Built by 1979 | Today |
|---|---|---|---|
| Noordoostpolder | 8,324 | 21,537 | 46,586 |
| Eastern Flevoland | 118 | 25,304 | 90,148 |
| Southern Flevoland | 0 | 3,575 | 155,080 |
Counted by the construction year of buildings standing today; demolished buildings are not included. The oldest buildings in the Noordoostpolder are on the former islands of Urk and Schokland.
Maps and data used
| What | When | From |
|---|---|---|
| 1905 shorelines, islands and depths (chart revised by S. Mars) | 1905 | Rijkswaterstaat (digitized, CC0) |
| Lake shore and lakebed height around 1935 | c. 1935 | Rijkswaterstaat (digitized, CC0) |
| Kadaster topographic maps (in use in 1925, 1935, 1950, 1966) | Latest map in use each year | Kadaster (tiles by Esri Nederland) |
| Present-day ground height (AHN4) | Surveyed 2020–22 | AHN / PDOK (CC0) |
| Municipal boundaries (land only) | 2024 | CBS / PDOK (CC BY 4.0) |
| Provincial borders (including water) | Current | Kadaster / PDOK (CC BY 4.0) |
| Roads on dikes, towns, pumping stations | Retrieved October 2026 | OpenStreetMap (ODbL) |
| Neighbouring countries and borders | — | Natural Earth (public domain) |
| Zuiderzee Works quarterly reports (20 volumes) | 1931–1975 | Rijkswaterstaat archive (text CC0) |
| Buildings and construction years (BAG) | Buildings standing today | Kadaster / PDOK (CC0) |
| Photo of a pumping station today (Lovink) | 2014 | Wikimedia Commons (CC0) |
| Provincial population and area | August 2026 (population, provisional) / 2026 (area) | CBS StatLine |
| Greater London outline (size comparison) | December 2024 | ONS (Open Government Licence v3.0) |
Each Kadaster map is the latest map in use in that year. Maps were made from aerial photos and can lag by up to five years, and older maps were revised less often, so the survey may be older still (on the map in use in 1946, Urk and Schokland are still islands). That is why the animated map's shapes and years come from Rijkswaterstaat and CBS data and recorded dates, while the Kadaster maps are overlaid in the same position as "real map windows". The draining sequences are reconstructed from lake depths around 1935, with no dates on the intermediate shapes. For the Noordoostpolder, the reconstruction (69.9% dry at NAP −3.6 m) matches the project records (70%).
What this episode shows
- Closing off the sea in 1932 added no land; it only made a lake. The land came from enclosing parts of the lake and pumping the water out.
- The four polders make up about one-twentieth of the Netherlands' land. They still lie about 4 m below sea level and depend on pumps.
- Urk and Schokland became part of the polders, but the outlines of the old islands survive in the ground height.
Sources
Where the facts and numbers in the video and on this page come from.
References
- Historic shorelines, islands and depths: Rijkswaterstaat (digitized c. 1905 and c. 1935 maps, CC0)
- Present-day land and provincial borders: CBS / Kadaster (PDOK, CC BY 4.0)
- Ground height: AHN (Rijkswaterstaat · Het Waterschapshuis / PDOK, CC0)
- Building construction years: BAG (Kadaster / PDOK, CC0)
- Historic topographic maps: Kadaster (Historische topografische data, tiles by Esri Nederland)
- Dates and figures: Zuiderzee Works quarterly reports (Bron: Rijkswaterstaat) and others
- Dike lines, towns and pumping stations: © OpenStreetMap contributors (ODbL)
- Neighbouring countries: Natural Earth
- Greater London outline: Source: Office for National Statistics licensed under the Open Government Licence v.3.0
- Pumping station photo: Apdency, via Wikimedia Commons (CC0)
- Maps, draining reconstruction, diagrams and editing: Tamelabo
- Maps, draining reconstruction, diagrams and editing: Tamelabo (using AI and production tools)
Links
- Rijkswaterstaat, "diepte_ijsselmeergebied" (shorelines and depths c. 1905 and 1935) ((in Dutch) (CC0). Retrieved/checked: 2026-10-18)maps.rijkswaterstaat.nl/dataregister/srv/api/records/ab0d18ee-1…
- Rijkswaterstaat, "bodemhoogte_ijsselmeergebied" (depth grids) ((in Dutch) (CC0). Retrieved/checked: 2026-10-18)downloads.rijkswaterstaatdata.nl/bodemhoogte_ijsselmeergebied
- Rijkswaterstaat, "100 jaar Zuiderzeewet" ((in Dutch). Retrieved/checked: 2026-10-18)rijkswaterstaat.nl/water/waterbeheer/bescherming-tegen-het…
- Rijkswaterstaat, "Afsluitdijk" ((in Dutch). Retrieved/checked: 2026-10-18)rijkswaterstaat.nl/water/waterbeheer/bescherming-tegen-het…
- Rijkswaterstaat, "Houtribdijk" ((in Dutch). Retrieved/checked: 2026-10-18)rijkswaterstaat.nl/water/waterbeheer/bescherming-tegen-het…
- Zuiderzee Works quarterly reports, "Driemaandelijksch bericht betreffende de Zuiderzeewerken" (1931–1975, Rijkswaterstaat archive) ((in Dutch) (text CC0 (Bron: Rijkswaterstaat)). Retrieved/checked: 2026-10-18)open.rijkswaterstaat.nl
- Nieuw Land National Park, "Flevoland's history" (. Retrieved/checked: 2026-10-18)nationaalparknieuwland.nl/en/the-park/flevolands-history
- Limosa 31 (1958) on draining Eastern Flevoland ((in Dutch). Retrieved/checked: 2026-10-18)natuurtijdschriften.nl/pub/1027606/LIM1958031001004.pdf
- RIJP, "Toepassing van riet in de IJsselmeerpolders" (1970) ((in Dutch). Retrieved/checked: 2026-10-18)open.rijkswaterstaat.nl/@73115/toepassing-riet-ijsselmeerpolders
- Stichting Werelderfgoed Nederland, "Schokland en omgeving" ((in Dutch). Retrieved/checked: 2026-10-18)werelderfgoed.nl/werelderfgoed/schokland-en-omgeving
- NH Nieuws (Wieringermeer, 1945) ((in Dutch). Retrieved/checked: 2026-10-18)nhnieuws.nl/nieuws/260157/achter-de-foto-wieringerm…
- Commissie m.e.r. advice of 2014 (Markerwaard) ((in Dutch). Retrieved/checked: 2026-10-18)commissiemer.nl/docs/mer/p29/p2908/a2908rd.pdf
- CBS StatLine 37230ned (population) ((in Dutch). Retrieved/checked: 2026-10-18)opendata.cbs.nl/statline
- CBS StatLine 70072ned (area) ((in Dutch). Retrieved/checked: 2026-10-18)opendata.cbs.nl/statline
- PDOK (CBS municipal and Kadaster provincial boundaries, AHN, BAG) ((CC BY 4.0 / CC0). Retrieved/checked: 2026-10-18)pdok.nl
- Kadaster, "Historische tijdreis" tiles (Esri Nederland) ((credit: Kadaster). Retrieved/checked: 2026-10-18)tiles.arcgis.com/tiles/nSZVuSZjHpEZZbRo/arcgis/rest/serv…
- Rijkswaterstaat, "Normaal Amsterdams Peil" ((in Dutch). Retrieved/checked: 2026-10-18)rijkswaterstaat.nl/zakelijk/open-data/normaal-amsterdams-p…
- Rijkswaterstaat, IJsselmeer water level decision factsheet (2018) ((in Dutch). Retrieved/checked: 2026-10-18)open.rws.nl/publish/pages/39568/peilbesluit_ijsselm…
- Stichting Werelderfgoed Nederland, "Droogmakerij de Beemster" ((in Dutch). Retrieved/checked: 2026-10-18)werelderfgoed.nl/werelderfgoed/droogmakerij-de-beemster
- OpenStreetMap (roads on dikes, towns, pumping stations) ((© OpenStreetMap contributors (ODbL)). Retrieved/checked: 2026-10-18)openstreetmap.org/copyright
- Natural Earth ((public domain). Retrieved/checked: 2026-10-18)naturalearthdata.com
- Wikimedia Commons, "Gemaal Lovink.jpg" (Apdency) ((CC0). Retrieved/checked: 2026-10-18)commons.wikimedia.org/wiki/File:Gemaal_Lovink.jpg
- Office for National Statistics, Regions (December 2024) boundaries; Standard Area Measurements ((Open Government Licence v3.0). Retrieved/checked: 2026-10-18)ckan.publishing.service.gov.uk/dataset/3148e1cd-3ae0-4ce1-91aa-fa61956…
Voice, music, art
- Voice: Kokoro (synthetic narration)
- Music (OpenTracks): “近代的日本空間” by 伊藤ケイスケ, “あの日見た景色” by こばっと
- Sound effects: Tamelabo (generated in code)
- Fonts: Noto Sans JP, Source Serif 4, Shippori Mincho, M PLUS Rounded 1c (SIL OFL)
