| Tanaro | |
|---|---|
| Origin | Ligurian Alps, on the slopes of Monte Saccarello |
| Mouth | Po near Bassignana (AL) |
| Basin countries | Italy |
| Length | 276 km |
| Avg. discharge | 123 m³/s |
| Basin area | 8,234 km² |
The Tanaro (Italian pronunciation: [ˈtaːnaro]), known as Tanarus in ancient times, is a 276 km-long river in northwestern Italy. It rises in the Ligurian Alps, close to the border with France and is the most significant right-side tributary to the Po in terms of length, size of drainage basin (partly Alpine, partly Apennine) and discharge.
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The Tanaro proper begins in Liguria at the confluence of two small torrents whose sources are in Piedmont: the Tanarello and the Nerone.
The main source of the Tanarello is on the slopes of Monte Saccarello above Monesi, a village belonging to the commune of Triora (IM). This mountain straddles the French département of Alpes-Maritimes, the Piedmontese province of Cuneo and the Ligurian province of Imperia and marks the juncture of the watersheds between three drainage basins: that of the Tanaro itself, that of the Roya (Italian Roia), which rises in France but enters the sea at Ventimiglia; and the Argentina which flows into the Ligurian Sea at Taggia.
The sources of the Negrone are some 10 km to the north, very close to the French border and south of Punta Marguereis.
The main tributaries to the Tanaro are the Stura di Demonte from the left, and the Bormida and Belbo from the right.
The Tanaro flows past the towns Ceva, Alba, Asti and Alessandria before entering the Po near Bassignana in the Province of Alessandria.
The discharge is subject to a great deal of seasonal variation. Although, uniquely among the Po’s right-side tributaries, the river has an Alpine origin, the Ligurian Alps are of an insufficient altitude, and too close to the sea, to allow for the formation of snow fields or glaciers large enough to provide a steady source of water during the summer. Furthermore the Alpine zone forms only a part of the basin drained by the Tanaro. The seasonal regime of the river is therefore more typical of an Apennine torrent, with a maximum discharge (which can reach 1,700 m³/s) in spring and autumn and a very small rate of flow in the summer.
The river is highly prone to flooding. During the two hundred year period 1801–2001 parts of the Tanaro basin were affected by floods on 136 occasions, the most devastating being those of November 1994 when the whole of the river valley was affected by severe flooding and the town of Alessandria was especially stricken.
The left bank of the Tanaro River near Asti is the scene of the Battle of Pollentia on April 6, 402.
LUINO F. (1999): “The flood and landslide event of November 4–6, 1994 in Piedmont Region (North-West Italy): causes and related effects in Tanaro Valley”. XXII General Assembly dell’European Geophysical Society, Vienna (Austria). 21–25 April 1997. Ed. Elsevier Science Ltd, Vol. 24, N. 2, p. 123-129.