Piave (pyäˈvā) [key], river, c.137 mi (220 km) long, rising in the Carnic Alps, Venetia, NE Italy, and flowing generally S, past Belluno, to the Gulf of Venice. The upper Piave basin is subject to severe seasonal flooding (see Vaiont Dam). Hydroelectric power is produced along the upper Piave; the lower river is used for irrigation. In World War I, after their defeat at Caporetto (1917), the Italians withdrew to the Piave. Despite fierce onslaughts by the Austrians, the line was held until Oct., 1918, when the Austrians were routed by a combined Allied attack.