Water level and boezem
The water level in the canals of Delft is the same height as the water in the surrounding storage boezem. This means that when the water level rises, the city water cannot be transported away. In the past this resulted in flooding in the old city centre. However, nowadays if the water level in the city centre is too high, a single press of a button ensures that eight hydraulic tilting flood barriers can be engaged that isolate (compartmentalise) a part of the historic city centre of Delft from the surrounding water system.
As the water in the compartmentalised area cannot discharge of its own accord via the Schie to the North Sea or the Nieuwe Waterweg, a pumping station has been built at the end of the Kantoorgracht canal (at the Duyvelsgat bridge). Here the excess water is pumped into the Schie. The increasing instability of the climate means this may be needed more often.
Hydraulic research showed that this is the best location for discharging water into the Schie. The maximum capacity of this pumping station is 85 m3/minute. The station comprises two pumps that are suspended under water.
This bridge was replaced in 2006. This new construction made it possible to integrate the new pumping station in the land abutment (support) of the bridge. This makes it almost invisible, so that the street scene is not disrupted.
Impressions
Picture captions (from left to right):
1. Film: Water in Zicht 1, 2018 explanation of tilting flood barriers in Delft, Duyvelsgat bridge at 15:49
2. Tilting flood barrier
3. ‘Compartmentable’ city centre surrounded by boezem water (shown in blue)