On the west edge of Downey is a finger of land that is known as "the island," surrounded on one side by the Rio Hondo River and on the other by the Los Angeles River. It makes for a different kind of river walk adventure.
According to Wikipedia, the Rio Hondo was once known as the "Old River," because it was the old course of the San Gabriel River. The Old River School was named for it, and Old River School Road was named for the school. The "New River" is the present course of the San Gabriel River.