h4 par 1 The threat of the water
Chapter 4
Cities and countryside in the Netherlands
Par 1 The threat of the water
1953: the big flood in the Netherlands
Combination of storm and spring-tide
Big part of Zeeland and South Holland were flooded because the dykes broke.
18-01-13
flood disaster
1953
Big parts of the Netherlands are below sea level, most of them in the west and southwest. But also parts of Friesland are below sea level, and parts of the
Netherlands along the main rivers.
Protection (1)
In the early ages people protected their homes and churches against flooding by building a terp.
That is a man-made hill built from earth and waste. These terps could be more than 8 metres high.
Terps were build before there were dykes otherwise these terps wouldn't be necessary.
Most terps can be found in Friesland and
Groningen, but also along the main rivers.
Protection (2)
Dykes have been build since 1200 AD to protect the people from seawater and from flooding rivers.
Connecting terps by dykes led to the first polders .
In a polder the waterlevel can be regulated with windmills and later on pumping stations.
When the waterlevel is too high in a polder the drained water can be temporarily
(tijdelijk) stored in a boezem.
This could be ditches (sloten), canals and lakes in the surrounding area.
Land reclamation (landaanwinning)
Since 1200 AD the Dutch have reclaimed land from the sea.
1. Silting up or dyke enclosure
At the seaside of a dyke new land is formed due to the tides. After each flood, the sea leaves behind a layer of silt (sand and clay). Eventually this new land is high enough that it won't be flooded anymore and vegetation starts to grow on it.
These pieces of land are called tidal marches
(kwelders). New dykes are formed around the new land.
2. Polderized lakes
In the 16 th century the invention windmills which could pump up water gave the opportunity to drain large,deep lakes.
3 or 4 Windmills stood in a row and each mill could pump up the water for 0.5-0.8 metres. In Dutch this is called a molengang.
Polderized lakes are surrounded by 2 dykes with a ring canal (ringvaart) in-between.
Nowadays this new land is perfectly suited as arable land. .
In our surrounding areas beautiful examples of poldarized lakes are:
The Heerhugowaard
The Schermer
The Beemster
