The collapse of the bank to Valkenburgse Lake suddenly seemed to be, but was actually to be expected

The Valkenburgse is more and takes the Valkenburgse more. Such as the island on the southwestern bank, where surfers sometimes started to pick blackberries. Spring that was no longer there, – according to the return function of Google Earth.

But as rough as on April 1, the lake did not struck before: dozens of meters of banks were swallowed up in the depth of the Zandwinningplas in the South Holland municipality of Katwijk. On one movie A man who walks his dog can be seen how a tree is swallowed up. As far as we know, the man was the only witness to the bank of the bank. Nobody got into the water. Not the dog either.

A week and a half later, Dijkgraaf Rogier van der Sande has no news for Arjan Planje from Surfschool and Winkel Gearfreak. In this case there is no news, bad news. The advice of the water board to the mayor is that the emergency regulation around the lake remains in force as long as the bank stability is doubted. « Very sad, » says De Dijkgraaf. « It’s about his sandwich here. »

A runner in the fluorescent outfit runs past the Surfwinkel. Apparently she has the fault of the deposition ribbons. For almost two weeks it has been forbidden to be present around the lake. On Easter Monday (April 20), according to an announcement at the Smalspoor Museum Valkenburg, the steam train will again beamed around the lake. A glance at the rails along the swallowed bank, where the sleepers float above the water, is sufficient to establish that the train is not going to run for the time being.

Altitude lines

The collapse of the southwestern bank looks a lot like an announced calamity. The Water Board of Rijnland, the water board between Amsterdam and The Hague, had already warned in 2007 that sand extraction in the lake was approaching its borders. It Leidsch Dagblad written last week About worries that were already expressed at the beginning of this century about the « slope stability. »

Nevertheless, the Province of South Holland was awarded the expansion of sand extraction at the beginning of this century to Van Herwaarden from Hillegom, legal predecessor of the now active company Xella. In addition, it would be expanded more, but it remained with floor for the time being. An initiate who wants to remain anonymous notes that the lake was also operated by other parties in the last century. For example, by Rijkswaterstaat, which has won Zand for the construction of the adjacent A44. Investigations already showed that a subsidence « can happen once, » he says. « If something would hit, then it would be that zone. »

Geography teacher Bart Vermeulen was a member of the States for the SP and opponent of granting the permit at the time. He still has a deep survey card from 2005. The height lines are very close together in some places, indicating steep parts in the bottom. « This was the situation in 2005, » he says. « I have no insight into what it looks like since then. »

Shifting chance

At the beginning of this century, the operator received a permit to suck up 4.7 million cubic meters of sand. The lake would be ten meters deeper, forty meters in total. « As deep as our North Sea, » says Van der Sande.

The slightly slopes were allowed to become steeper, and went to 1: 4, or every four meters further down the lake in one meter. Earlier it was 1: 6. The more sloping the bottom, the more sand -lime brick sand can be won. The disadvantage is the greater risk of shear. « That understands everyone who has ever dug a channel on the beach, » says Van der Sande.

The water board had no objection to this in 2003. Later, in proceedings against the permit for further expansion of the lake, the « advancing insight » existed that a buffer zone of twenty meters had to be arrested at one of the slopes. If the soil were to slide, the bank line would not be immediately affected. But the administrative court found that necessity insufficiently substantiated.

Dijkgraaf van der Sande is now not going to get the right from his water board. There is a lesson to be drawn, he thinks. The advice of water boards must be anchored more strongly. « They can now be put aside too easily. We are on the boundaries of the soil water system. That can take its toll, especially with the current weather extremes. » Although in this case, the weather – the record dried in March, for example – probably did not play a role.

Loss of turnover

What then? The Advisory Administrative Law Foundation for Environment and Spatial Planning, which the administrative court advised, called the slope of 1: 4 « metastable ». That means that something has made the slope unstable, « for example, a careless action with a sand cleaner. » Coincidentally, Boskalis had just started sucking again, about a hundred meters from the southwestern bank.

Surfshop owner Planje has drone images of two weeks before the bank of the bank, when the sand dredger is even stillag at the depot on the other side of the lake. On or just before April 1, he says, the sand extraction was restarted.

Dijkgraaf van der Sande advises Planje to engage an expert, in case liability can be established and he can recover the loss of turnover. « Unfortunately, I can’t mean more. »

Research into the circumstances is in full swing, the province of South Holland says. The companies involved Xella and Boskalis make no statements before the investigation into the circumstances has been completed. « One thing is certain, » according to the spokesperson for Xella. « We have adhered to the regulations of the permit. »

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