Letting Go of What You Know To Prepare for a Once-in-a-Thousand-Years Storm

Trust Mark Twain to hit the nail on the head in his inimitably folksy way. Sometimes what you know never was true; sometimes it used to be true but conditions have changed and it's no longer true. But confirmation bias keeps us clinging to those beliefs even in the face of new information. We pay attention to any signals or data that support our belief and firmly disregard anything that challenges those beliefs. Furthermore, as Kathryn Schulz puts it in her book Being Wrong, "But the point is not that we are bad at saying "I don't know" (a fact she has just spent some pages illustrating). The point is that we are bad at knowing we don't know."

We can see this unwillingness to let go in emotionally-laden politics. We can see it in companies that persevere with business models that are clearly no longer tenable. You might think of Kodak, where digital photography was invented, refusing to acknowledge the assault on their film-based business model.  

Then, there's the Netherlands. As far back as the Iron Age, people in the Netherlands have been building dikes of ever increasing sophistication. This is not surprising in a country with a quarter of its land below sea level and fully one half is less than one meter above sea level. Building dikes to keep out the water or to reclaim land is part of their national DNA. Yet the Dutch have abandoned dike building as their main defence against devastating storms and floods and generally rising sea levels. They've let go of what they know - at least as the only solution.

A 1953 flood, when a major storm coincided with a high spring tide in the middle of the night, resulted in the loss of 1,836 people mostly over the space of a few hours (Katrina's death toll was 1833). This was their wake-up call.  They initiated Delta Works, a project to protect the Netherlands against a once-in-a-1,000-years storm. (As a reference point, Katrina was a once-in-hundred-years-storm and Hurricane Harvey has been described as a once-in-a-500-years storm.)

1  As a reference point, here is a photo of traditional dikes along a river and lower lying land from a recent trip to the Netherlands. (Also worth nothing is the fact that there are two bike lanes but only one lane for cars).

After the 1953 storm, the Dutch concluded that they just couldn't build the river dikes high enough for full protection. And besides it would be much too expensive. They had to stop the water before it reached the rivers. They still use sand dunes as a natural barrier along the sea shore. These large dunes needed to be reinforced annually, a significant task to dump the sand all kilometres of coastline. But the Dutch are so clever. They observed where sand was distributed naturally by tides and currents and concluded they could simply dump sand in a few strategic places and let nature distribute it where needed.

2 To protect further against the sea, they first built two dams south of Rotterdam. But this approach was problematic. Where once there had been a gradual change from salt water to fresh water, now there are two totally separated ecosystems on either side of the dam. The types of fish the fishermen used to fish disappeared. Solid dams were clearly not the answer.

3  Further south, at Oosterschelde, a different approach was taken in the 70s: to build gates that 

stay in a raised position normally but would be lowered during a storm. This allows the fish - and their predators the fishermen - to pass through freely. An excellent movie at the visitors' centre at Ooseterschelde describes how huge piers were placed on the ocean floor, sitting on ‘mattresses’ made of material filled with rocks to form a firm foundation. The mattresses were laid by being uncoiled off huge rollers on the back of special boats. The piers were built on shore on a huge dry dock, then towed out to sea after the dry dock was submerged. Then each pier was lifted off the dock and precisely placed on the mattress floor between the piers.  Lastly, a road  was laid on top.

4 The solution of gates that could be raised and lowered between fairly closely set piers wouldn't work at the mouth of the Rotterdam port. Once the largest ports in the world, Rotterdam is now surpassed by ports in Asia, but it’s still impressive. The day before, with many kilometres of piers b (numbered from 1 to 9900), that seem to stretch endlessly off the main road. 

The problem of protecting Rotterdam from the sea was difficult. Proposals were invited for techniques to close off the mouth of the river as required in the case of big storms, but leave it open for shipping. The winning proposal involved two huge arms (the size and twice the weight of two Eiffel Towers) which are swung in from either side of the estuary to close it off completely if there is a risk of the water level rising 3 metres in Rotterdam. It's designed to protect Rotterdam in the case of seas rising five meters above normal! You can see the scale of the arms that support the barrier from the picture of me standing by them.

These massive blocks of concrete are swung in by equally massive ball bearings, which can move in several directions, like shoulder joints. They have to move sideways to swing the barrier across the channel, an exercise which takes half an hour. Then the ball bearings have to be able to move up and down, as the concrete wall is filled with water and descends to fit on the concrete block on the bottom over an hour and a half. Here's a diagram from the New York Times article showing how everything fits together.

The system is tested once a year, and various disaster scenarios  each year. This bottom block gathers a metre of sediment every year. As the barrier slowly descends, the water is compressed and gathers speed and washes away the sediment. This is the reason for the slow descent. Brilliant.

This amazing piece of engineering was completed in 1997 after 6 years of construction, on time and on budget. Equally amazing. All the pieces were build in Holland, except for the massive ball bearings, which were made by Skoda in Czech Republic. The Canadian software firm CGI provided the software to control the barrier (a CGI employee told me this, but I have not independently verified).

The risk of flooding is assessed every ten minutes to check water levels and the risk of a big storm. When the software was designed in 1997, it took ten minutes to complete the calculations! Today the calculations complete in seconds, but the Dutch have not felt the need to do the calculation more often. When there is a risk, a warning is sent out to all ships with four hours notice so that they can determine if they have time to get past the barrier before closing. (Tug boats are on standby to haul ships away if there is a risk they’ll get caught as the barrier closes). At two hours, the decision to close becomes irrevocable and the countdown starts.

5 Having completed all these projects, the Dutch still didn't feel they had enough protection against flooding in an era of climate change and the inexorable rise in sea levels. So they had to overturn all their past thinking again. If you can't keep the water out, then you have to learn to live with it. So you start projects with another approach to the problem and brand them Room for the River. That's another radical change in thinking. They are building catchment areas for when, not if, there is flooding. Some of these catchment areas are lakes designed to overflow, some are used as recreational areas, some even as parking lots. It's another stage in the remarkable evolution of their thinking.

The Dutch have turned their preoccupation with water into an exportable expertise.The Dutch have consulted on water management for a long time; in fact, long ago, they helped the English drain the fens. And they are consulting around the world about this approach today (as described in this wonderful New York Times article). Toronto has also adopted the Dutch 'Live with the Water' approach in dealing with the threat of flooding of the Don River, as described here. Let's hope their expertise helps save many shores threatened by rising sea levels.