The Los Angeles River 's official beginning is at the confluence of two channelized streams - Bell Creek and Arroyo Calabasas - in the Canoga Park section of the city of Los Angeles , just east of California State Route 27 , at 34 ° 11 ′ 43 ″ N 118 ° 36 ′ 07 ″ W \ / 34.1952 ° N 118.601838 ° W \ / 34.1952 ; -118.601838 .
Bell Creek and Calabasas Wash ( Arroyo Calabasas or Calabasas Creek ; Calabasa is Spanish for `` pumpkin '' ) flow from opposite sides of the valley to a point ( 34 ° 11 ′ 43 ″ N 118 ° 36 ′ 07 ″ W \ / 34.1952 ° N 118.601838 ° W \ / 34.1952 ; -118.601838 ) where the Los Angeles River officially begins .