Banks of Yalu--Korean side. 'Yalu River or Amnokkang in eastern Asia, forming most of the boundary between North Korea and China. About 790 km (490 mi) long, it rises on the southern slopes of the Changbaeksan mountains, flows in a generally southern and southwestern direction, and empties into Korea Bay, an arm of the Yellow Sea, just south of Andong (An-tung), China.