Bart Schultz
The Bethunepolder - 545 hectares, reclaimed between 1858 and 1880 - lies northeast of Maarssen, the Horstermeerpolder - 610 hectares, reclaimed in 1882 - lies west of Hilversum, and the Koekoekspolder - 600 hectares - lies east of Kampen. A contribution about the Horstermeerpolder was pubiished earlier on Flevolands Geheugen.
The Koekoekspolder originally formed part of the Mastenbroekpolder. In its natural state, the entire area was a swamp forest on the northeast side of the IJssel estuary. During high discharges, the area was mainly flooded from River IJssel, but it could also be flooded during storms on the former Zuiderzee.
Around 1384 the area was reclaimed. The northwestern part of the Mastenbroekpolder was released for excavation of peat in 1752, which gradually created an ever larger lake in the polder. Around 1850 the lake was drained and the Koekoekspolder was created. After that the polder was flooded several times. In 1945 the Koekoekspolder was finally drained and it gradually became a horticultural area with mainly greenhouses.
As mentioned, a large amount of seepage occurs in the Koekoekspolder. The seepage here amounts to almost 20 millimetres per day. For the Bethunepolder a seepage of 17 millimetres per day has been calculated and for the Horstermeerpolder of 15 millimetres per day. Based on this, it can be stated that the Koekoekspolder is probably the polder with the largest amount of seepage per unit of surface area in the Netherlands.
The surface level of the Koekoekspolder is now between 2.50 and 3.00 metres below mean sea level, which is about two metres lower than the surface level in the Mastenbroekpolder. From the latest edition of the Waterstaat map it can be deduced that a summer water level and a winter water level are maintained in the watercourses of the Koekoekspolder. These levels are, with some deviations in sub-areas, respectively 3.65 and 3.85 metres below mean sea level. The Koekoekspolder is therefore certainly not the deepest polder in our country, but due to the soil situation it is the polder with the most seepage per unit of surface area.
