Input (grade 13): Most of the Rio Hondo is a concrete-lined channel to serve its primary flood control function, but in two places the river flows over open ground: the Peck Road Water Conservation Park, and the Whittier Narrows Recreation Area.
Output (grade 7): Most of the Rio Hondo is lined with concrete, but there are two places the river is free-flowing. These are the Peck Road Water Conservation Park and the Whittier Narrows Recreation Area.