The Euripus Strait is a narrow channel of water separating the Greek island of Euboea in the Aegean Sea from Boeotia in mainland Greece. The strait's principal port is Chalcis on Euboea, located at the strait's narrowest point. The strait is subject to strong tidal currents which reverse direction approximately four times a day. Tidal flows are very weak in the Eastern Mediterranean, but the strait is a remarkable exception. Water flow peaks at about, either northwards or southwards, and lesser vessels are often incapable of sailing against it. When nearing flow reversal, sailing is even more precarious because of vortex formation. The Swiss scholar François-Alphonse Forel contributed to an understanding of the enigmatic phenomenon by his study of limnology and the discovery of seiche, where layers of water of differing temperature oscillate in thickness in a confined body of water. But the problem was solved completely only by D. Eginitis, director of the Athens Observatory, who published his conclusions in 1929.
Bridges
There are two road bridges across the strait, both at Chalcis. One is the Euripus Bridge or Chalcis Bridge, a two-pylon, cable-suspended bridge built south of town in 1992, and commonly called the "New" or "High" bridge, with a span of about 215 m. The strait is 160 m wide at this point. The bridge is accessible via a fork on the main road at Aulis. The "Old" or "Low" or "Sliding" Bridge lies across midtown, and can slide away to allow shipping traffic. It is located at the narrowest point of the strait, where it is only 38 m wide. It accommodates two lanes of vehicular traffic. It was originally built as a retractable bridge in 1858, replaced by a rotating one in 1896. The existing, originally wooden bridge was built in 1962 and was extensively refurbished in 1998.
History
The current consensus is that the Euripus was closed by a dike of coarse sediment until about 6000 years ago. It was opened following an earthquake and remained open until 411 BC, when the Euboeans decided to renounce their status as an island subject to Athenian hegemony and make themselves part of Boeotia. There is no trace of this either in Thucydides or in Xenophon Diodorus mentions specifically that gaps had to be left in the dike to allow the Euripus tides to flow through and that the current became much more intense owing to the narrowness of the passage and says that a single passage was left just wide enough for a single ship. Strabo wrote of some later time when there was a bridge two plethra long. Some vestiges of the two ends of the dike of 411 probably remained, so that this later bridge was probably narrower than the channel that existed before 411 BC. We have no information about the depth, but even in the case of a channel about 50 m wide under Strabo's bridge, the depth could have been scoured out to a level entirely sufficient for ancient shipping. It is not until the time of the Emperor Justinian I, that we have evidence of two channels in the Euripus, the large original channel and a new, narrow cleft to the east of it, so narrow that it could be crossed on a plank of wood. This later stream is what was eventually widened to make the present shipping channel. At the time when Procopius wrote, the name of the fortress on the Euripus was probably "Euripus," which had become "Egripos" by 1204, and was adopted and slightly altered to "Nigriponte" by the Latins who occupied the place in 1205. In 1395, Nicola di Martoni came to Negropont during the return from his pilgrimage to Egypt and Palestine. He is clear that the main shipping channel in the Venetian period was on the side of the Boeotian mainland, and mentions the mills on the narrower channel, which he says were sometimes broken in the speed and turbulence of the flow there. We have further information about the shipping channel and its single wooden bridge from various documents in the archives of the Venetian Empire. In 1408, the formation of a reef under the bridge severely affected shipping and in 1439 there was concern over the tendency of the current to erode the surroundings of the pilings that supported the bridge . Evliya Çelebi, in his Travel Journal, tells us that the narrow channel was first opened out enough for a galley to pass through at some time in the late 16th century, and was still just barely wide enough at the time of his visit in 1668 for a galley to squeeze through, even though the old shipping channel had been abandoned. By the end of the 18th century it was well on its way to being the width of the modern channel.
