Polders

• Aardrijkskunde
• Middelbare school
• havo, vwo
• Leerjaar 2

Polders

At the end of this lesson

-You can explain what a ' Polder' is

-You can name the difference between a drainage and a peat polder

-You can explain the problem of subsidence 

www.topotijdreis.nl

Polder

• Land where the water level is carefully controlled.
• by a mill or a pumping station
• Without pumping the land will flood.

1.Peatpolder

• Peat= a type of soil made up of partially decomposed plant matter.
• ' mined' from the 10th century. Digging canals.
• Ground level was sinking
  
• Result?> Subsidence
• We are sinking!!!

A polder is a piece of land surrounded by dikes. The waterlevels are managed in between these dikes.

2.Drainagepolder

• Pieces of lakes or sea have been drained
• First, building dikes around the lake and than pump for several years
• Used for agriculture or housing.
• Flevoland in the IJsselmeer is an example.

Drainage polder

ijsselmeerpolder

• 20th century
• Used to be Zuiderzee (sea)
• Flevoland/Noord-Oostpolder
  

Subsidence (Süllyedés)

• Sinking of the ground caused by pumping out groundwater or extracting minerals.

Subsidence

• Lowering groundwater level
  
  
• Soil will composite when water is gone. 
  
  
• Peat polders are most likely to subside because most water is pumped out.

Building on wooden poles 

To do
1. Solve the mysteries. There are two stories. You need to put the strips in order

2.Than fill in the numbers 1 to 10 on the worksheet, can you name the interior of the polders?

Wordlist:

Subsidence= Süllyedés
Meadow= Rét
Irregular= Szabálytalan
Narrow= Keskeny
Reclaimed= Visszanyert
Groundwater=Talajvíz

The story of a drainage polder

-Once there was a lake that was four metres deep. A dike was built around it, the ring dike.

-By building the dike, a ring canal was created. Windmills were used to drain the water from the lake into the ring canal.

-After a while, the lake was dry. A drainage polder was created.

-A drainage polder is reclaimed land: the water level is artificially controlled. Today, pumping stations pump the water away instead of windmills.

The story of a peat polder

-A peat polder looks a lot different from a drainage polder. There are many, many drainage ditches, and the plots of land have irregular shapes, or they are long and narrow.

-Like a drainage polder, the water level is artificially controlled. The network of ditches and lakes where water is stored temporarily is called the drainage pool.

-The water flows from the drainage pool into open water. That open water could be one of the major rivers, the sea or the IJsselmeer.

-In the past, windmills pumped the water out of the drainage ditches in the polder.

-Today, pumping stations are used to drain polders.

At the end of this lesson

-You can explain what a ' Polder' is

-You can name the difference between a drainage and a peat polder

-You can explain the problem of subsidence