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Why are dikes built around a polder before water is pumped out?
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land reclamation
The Yser River flowing through reclaimed farmland in Belgium.
Dikes are constructed around a polder to create a physical barrier that isolates the target area from the surrounding body of water. This enclosure is essential for two primary reasons:12
- Isolation: By building dikes roughly parallel to the shoreline, engineers create a contained space that prevents the re-entry of water from the sea or adjacent water bodies.13
- Controlled Drainage: Once the area is enclosed, the water trapped inside can be systematically removed through drainage systems, such as tide gates or pumping stations. For lands located below low-tide level, pumping is the only way to lift the water over the dikes to expose the land.13
Without these dikes, it would be impossible to maintain the dry conditions necessary for land reclamation, as the water would continuously flow back into the area. Once the water is pumped out, the land can be further prepared for agricultural use by removing salt and installing internal drainage channels.123