Ancient Tunnel and Diversion Channel in Seleuceia Pieria: A Flood Diversion System near Antiochia in Turkey

The diversion system at Cevlik, near Antakya in Turkey, had the purpose to prevent the siltation of the antique harbour of Seleuceia Pieria. This 875 m long system consists of a dam, a short approach channel, the first tunnel, a short intermediary channel, the second tunnel, a long discharge channel. The construction began in 1.century A.D. during the reign of Vespasianus, continued under his son Titus and several successors, completed in 2.century A.D. during the reign of another roman emperor, Antonius Pius. The tunnels of simple horseshoe and trapezoidal cross-sections, with dimensions in the order of 5 to 7 m, have a capacity of 150 m3/s. The capacity of the open channel section is computed as 70 m3/s, corresponding to a peak flood discharge with average recurrence interval of about 10 years.