The river officially begins in a place called Canoga Park, in the San Fernando Valley. 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 () where the Los Angeles River officially begins. At this point, the river already flows in a concrete channel. In times of flood, the channel can move between per hour to up to 