; Trebia) is a river
and Emilia Romagna
in northern Italy
. It is one of the four main right-bank tributaries of the river Po
, the other three being the Tanaro
, the Secchia
and the Panaro
. The 1,150 km² (444 square miles) drainage basin is divided between Emilia Romagna (770 km², 300 mi²), Liguria (349 km², 135 mi²) and Lombardy
(31 km², 12 mi²). Its principal tributaries are the torrents
Aveto and Perino (from the right) and the torrent Boreca (from the left).
Its source is in the Ligurian Apennines on the hill called Monte Prelà, to the south of Monte Antola in the comune of Torriglia, Province of Genoa. From there it flows towards north-east for 105 km (65 miles), until it reaches the Po just to the west of Piacenza.
The main centres through which it flows before Piacenza are Ottone, Marsaglia (in the comune of Corte Brugnatella), Bobbio, Perino (a frazione of Coli), Travo and Rivergaro.
Between its source and Bobbio the river flows through a valley (the Val Trebbia) of great natural beauty, which attracts tourists for walking as well as for aquatic sports. The river valley then widens before merging with the Pianura Padana beyond Rivergaro.
Along its eastern banks in 218 BC was fought one of the battles of the Second Punic War: the Battle of Trebbia, where Hannibal defeated a Roman consular army.