KWT Engineering in the new DriemansPolder in the area of Zoetermeer en The Hague.
In an high density populated area around the capital of the area in South-Holland, The Hague, was a urge for a large retention bay for heavy rainfall and stormwater.
The water board HH van Rijnland put out an contract for the technical design and development of the immens retention bay and recreational facility.
If there are high water levels in combination with storm/heavy rainfall, the retention area can be filled up with 10.000 liters of water per second, this will occur approximately once every 7 years.
The property of 300 hectares, is a former agraculter and now developed as an nature en recreational area.
With the development of the retention area in the new Driemandspolder, the contractor of “De Dijkencombi” enhances the safety of flooding in the region of South-Holland, and a few bottlenecks will be solved, together with the retention area of ” the Haarlemmermeerpolder”.
KWT Designed, engineerd and produced tilting weirs of 7.000 x 2.300 mmm wich will function as a normal overflow levelcontrol.
During the filling of the retention area, the water board will lower the tilting weirs and they will let in a staggering 5.000 l of water in per tilting weir!
The retention bay will hold 2.000.000 cubic meters of water, and fill within 2 days.
The tilting weirs are designed trough the high standard of EUROCODE consequential class (CC) 3, with a lifespan of 100 years duty.
For KWT this ment that not only the design has to be validated as a current 3D model and detailed force simulations, but also the fatigue calculations for materials and drivetrain had to be calculated for the next 100 years. This was a part of a validationprocess in the VISE program.
The climate is changing rapedly, the predictions of 2006 for heavy rainfall in the year 2050 became a reallity in 2015.
The scope of the project “Driemanspolder” at the point of the contract was a retention use once every 25 years.
The current expectation is the retention area will be used once every 6 to 7 years.