Twelve Mile Circle decided to stick with the aqueduct theme once again after the recent discussion of England’s Barton Swing Aqueduct. There were other structures, equally fascinating in their own distinct ways. Some were large, some were unusual, and some offered elements of both. Many of those innovative structures seemed to concentrate in western Europe, an obvious leader in navigable inland waterways.
Longest Navigable Aqueduct
Magdeburg Water Bridge seen from a kite by Pierre Lesage on Flickr (cc)
Aqueducts designed simply to move water were interesting by themselves, however I was considerably more fascinating by those designed to carry boat traffic above the surrounding terrain, akin to a bridge for boats for a lack of better words. For more than a century the title of longest navigable aqueduct had been held by the Briare aqueduct of the Canal latéral à la Loire, the canal over the Loire River in France (map). It was a magnificent masonry structure with a steel trough stretching 662 metres (0.4 miles). Then came Germany’s Kanalbrücke Magdeburg, or Magdeburg Water Bridge in 2003 (map), considerably longer at 918 metres (0.6 miles) albeit more utilitarian than beautiful.
Upon it’s opening, the German broadcaster Deutsche Welle proclaimed,
In what’s being hailed as an engineering masterpiece, two important German shipping canals have been joined by a giant kilometer-long concrete bathtub… The water bridge will enable river barges to avoid a lengthy and sometimes unreliable passage along the Elbe. Shipping can often come to a halt on the stretch if the river’s water mark falls to unacceptably low levels.
The Magdeburg Water Bridge provided a vital direct connection between two separate canals on either side of the River Elbe, the Mittellandkanal and the Elbe-Havel, essentially connecting eastern and western Germany directly by water as well as to nations beyond its borders from Poland to France and the Benelux region. The possibility had been envisioned at the turn of the last century when construction first began. Two World Wars and the politics of a protracted Cold War completely halted the dream. German reunification provided an impetus to renew and complete this effort, nearly a century after initial construction first began. Now it’s a reality.
Zandvlietsluis & Berendrechtsluis; Antwerp, Belgium
Belgium’s Port of Antwerp locked-up (pun alert) the title for the world’s largest canal lock. It handled 200 million tonnes of cargo in 2015, enough to make Antwerp one of the Top 20 busiest ports in the world, and it "aims to keep growing," Locks were necessary to protect the port from strong tidal actions pushing in and out along the Scheldt River. The locks kept water levels constant on the port side of the structures. Oceangoing cargo container ships kept growing larger so the locks had to follow suit in a continual game of catch-up. They became truly mammoth.
Antwerp first claimed the largest lock title with the construction of the Zandvlietsluis, or Zandvliet Lock, in 1967. That remained sufficient for a solid three decades until a new class of larger ships threatened to diminish the port’s usefulness. The port authority responded by opening a new lock parallel to the Zandvlietsluis in 1989, the Berendrechtsluis, or Berendrecht Lock. It was great enough to accommodate Post Panamax container ships (Panamax being an official set of dimensions for the largest ships that can navigate the Panama Canal). The Berendrecht Lock, currently the largest lock in the world, is 68 metres (223 ft) wide, about 11 metres (36 ft) wider than the Zandvliet Lock.
Right on schedule, however, container ships grew once again to an even larger behemoth class called New Panamax. Elsewhere in the Port of Antwerp, engineers are building the Deurganckdoksluis, or the Deurganckdok Lock. It will encompass the same length and width as Berendrecht, and in addition it will be four metres deeper to accommodate the extra draft of New Panamax ships. The Deurganckdok Lock was undergoing testing at the time I posted this article and was expected to open in April 2016.
Obviously Twelve Mile Circle fixated on superlatives like the world’s longest navigable aqueduct and the world’s largest lock, although the real reason for this article centered on a combination of the two: the worlds longest/largest aqueduct with a built-in lock. Actually there was but a single example of such an unusual structure currently, the Netherlands’ Naviduct. The concept was so new that the term stood on its own. THE Naviduct.
Naviduct on Houtribdijk
The whole situation seemed odd. The Netherlands was renowned for land reclamation and that figured indirectly into the creation of the Naviduct. The nation planned to drain a 410 km2 (158 mi2) polder — about the size of the Caribbean island of Barbados — to be called Markerwaard. It went so far as to create a 27 km (17 mi) dike between Enkhuizen and Lelystad that it completed in 1975 and called the Houtribdijk, resulting in two large lakes, Markermeer and IJsselmeer. However the project stalled and the Netherlands abandoned its plan altogether a couple of decades later. Nonetheless the nation still had a long dike which, by that time, carried the new N302 Motorway that separated two large lakes. Authorities also built a lock between the two lakes, a necessary step because prevailing winds affected the lakes differently even though they were at the same elevation. However ships and cars couldn’t cross the point at the same time. It created a transportation mess.
Thus, Dutch officials faces simultaneous dilemmas of their own creation: a problematic connection between two bodies of water; and a transportation bottleneck impacting maritime and automotive traffic. They responded by designing an aqueduct with a lock built within it, the Naviduct. Motorway traffic flowed below the aqueduct while ships sailed across it. I don’t know why they didn’t simply build either a tunnel or a bridge for the motorway. Regardless, their preferred solution was infinitely more interesting and it went into service in 2003. The structure remains the only Naviduct for the time being although it has been considered as a possible solution for other locations in the Netherlands. It would be hard to imagine its usefulness elsewhere since few other places face the same set of extreme geographic challenges. We should simply enjoy its existence.