Spanning more than 25 miles of shoreline and covering 41 square miles, the Port of Rotterdam is largest shipping berth in all of Europe, the fifth-busiest in the world, and a major interchange for the region's energy supplies. But keeping the North Sea's fury in check is no easy feat. So to keep the port open for business, the Netherlands has installed two monumentally mammoth surge barriers. Huge doesn't even begin to cover it.
Known as the Maeslantkering, this massive storm surge barrier is a monster machine in every sense of the word, and constitutes one of the single largest things humanity has ever built. It spans across the mouth of the River Scheur where it intersects with the Nieuwe Waterweg waterway just outside the city of Rotterdam. The €440 million Maeslantkering was designed and built as a last-minute addition to the region's extensive Delta Works project. This system was meant to supplement the low-lying country's numerous dikes and levees, keeping flood waters out of coastal towns and agricultural fields. When the dikes and levees originally planned to protect Rotterdam and Antwerp harbors proved insufficient to the task, the movable flood gate idea was floated.
Measuring 22 metres tall and 210 metres long apiece, these steel storm doors are so large that they had to be built on-site in specially constructed dry docks beginning in 1991. Additionally, engineers welded on a series of steel trusses measuring 237 metres in total, which acted as a skeletal frame to support the doors. Each truss, stood on end, is the same height as the Eiffel Tower, albeit twice its weight. Each truss runs back to a single hinge that operates atop a single gigantic ball bearing measuring 10 metres in diameter and tipping the scales at 680 tonnes—the largest in the world, in fact.
The barrier mechanism is deployed as needed by an automated weather-tracking computer system. When sea levels reach a critical level—three metres above average—the system will engage its doors, swinging them across the 360 meter-wide gap. The gates themselves are hollow, which allows them to float easily across the river mouth and then be flooded once they're together. This sinks the gates to the river bottom, sealing back the tides and multiplying the gates' mass.
The Maeslantkering entered operation in 1997 with the expectation that it would be employed maybe once every decade or so, though thanks to climate-change induced rising sea levels and enhanced storm systems they've required closing at double the estimated pace.
In the $50 billion aftermath of Hurricane Sandy, a similarly drastic engineering solution might be in the works for New York Harbor as well. It certainly beats sandbags and prayers.[Wiki 1, 2 - Keringhuis - Holland]