Hooge Boezem Haastrecht natural climate buffer

Hooge Boezem is a nature reserve on the outskirts of the Krimpenerwaard and Lopikerwaard polders. In 2014, the Stichtse Rijnlanden district water control board constructed a water storage area here, in collaboration with the Het Zuid-Hollands Landschap nature organisation: the Hooge Boezem natural climate buffer near Haastrecht. This water storage area adds to the resilience and climate-proofing of the regional water system. Furthermore, the area attracts a wide range of meadow birds.

Haastrecht 1

Use of calamity culvert during high water

A calamity culvert has been constructed to enable water discharge during extremely high water in the Gekanaliseerde Hollandsche IJssel. The calamity culvert is a passage connecting the Hollandsche IJssel river to the Vlist stream. During high water, the culvert can be opened to allow water from the Hollandsche IJssel to flow into the Vlist. Culverts have also been placed in the Vlist; these culverts allow the water to flow back into the water storage area. The overall area is capable of temporarily storing a maximum of 73,000 m3 of water: enough to fill thirty Olympic-sized swimming pools.

What happens after the high water event?

Once the Hollandsche IJssel water level falls, the water is discharged to the Lopikerwaard polder. There, the Keulevaart pumping station pumps the water back into the Hollandsche IJssel river. Expectations are that such a situation will arise once every five years.

Haastrecht 2

What other measures have been taken?

In addition to the construction of a calamity culvert, 28,000 m3 of soil have been excavated to create the water storage area in the new nature reserve. This soil has been used to construct embankments in the area and to raise a footpath through the polder. The nature reserve comprises three sections: pasture, flowery grassland, and reedy land. During extreme weather, the authorities can thus choose which section to flood.

What results have been achieved?

The main result of this climate buffer is that it has boosted the resilience of the regional water system, which is now better prepared for extreme weather. In addition, the area features increasingly more water plants and waterside plants. The organisations expect that this will improve the water quality. Furthermore, by redeveloping the Hooge Boezem into a water storage area, they are tying in with an old water management tradition which dates back to the fifteenth century.

Contact person

Hoogheemraadschap De Stichtse Rijnlanden
Mathijs van de Griendt
Gebiedsmanager IJssel / Lopikerwaard
030 634 57 00

Project type
Completed measure
Hoogheemraadschap De Stichtse Rijnlanden & Zuid-Hollands Landschap
Urban flooding, Waterlogging