The term flood defence evokes the idea of a defence against floods these days.
When Vauban designed the fortress town of Saarlouis in the 1680s, he envisaged something else. Rather than defending against floods, he designed a bridge which could create floods.
The bridge remains in place just outside the fortified old town. When you walk around the oxbow lake, you can see channels running down each pillar of the bridge. These acted as guide tracks for large sluices.
The sluices could be dropped to stop the river Saar. This raised the water level and flooded the area outside the city fortress. Attackers would be prevented from reaching the city.
That the original bridge with the channels remains in place is as impressive as the idea.
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