Transcript 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 16th 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