The Tiber is the principle river of cental Italy. It rises in Tuscany, at the south of the Monte Fumajolo in the Province of Arezzo, about 30 miles east of the source of the Arno, at an altitude of more than 3,600 feet above the level of the sea, and flows towards the south in a winding course, across Perugia (Umbria). After receiving the waters of many small streams, at Orte, where it is joined by the Nera (the ancient Nar) it forms the boundary between Umbria and Rome, enciricling Mount Soracte and entering the Campagna Romana. About three miles above Rome it is swelled by the Anio (now Ariene or Teverone) then passes through the city of Rome, where it forms an island, the Insula Tiberina (now Isola di San Bartolommeo) and enters the Tyrrhenian Sea about 26 miles below. The total length of the Tiber is 245 miles; its breadth at Rome is about 250 feet. It is a swift-running stream, carrying down an enormous amount of alluvial matter, which, in solution, gives the water that yellowish color for which the flavus Tiberis was renowned. The sediment deposited at the mouth of the Tiber is pushing out the land at the rate of about 10 feet a year, so that the ruins of Ostra, the ancient harbor of Rome, are now more than 4 miles inland. The delta is formed of two mouths, the fuimicino, originally a channel dug by Trajan for his harbor (Port Traiani) now the larger and navigable branch, and the fuimara, now almost choked by sand banks; and these inclose the Isola Sacra, a desolate and unhealthful island once sacred to a Venus. The Tiber is navigable by small steamers as far as Rome and by smaller craft 60 miles higher up. It is subject to frequent and often disastrous inundations, of which the ancient writers have recorded no less than 23. Among the more famous floods are that mentioned by Horace, when the water at Rome rose 51 1/2 feet, and in 1900 when it reached a flood height of almost 54 feet. To remedy this evil the government, beginning in 1876, constructed massive embankments at Rome, at the expense of more than $25,000,000; but the carefully planned work has proved defective. The stream on the north of the Tiber island has become clogged with sand, and in the flood of 1900 fully a quarter of a mile of the south embankment was carried away by the water.
