The map of the south part of the spillway has been divided into four zones. Such a division facilitates the study of the area. Zone 1 Zone 1 is a strip parallel to the murals and adjacent to them. The north edge of this zone is a line roughly from the north end of Boardwalk 1 to the tenth metal post to the south of the south gate. Here the thin top soil was apparently left in place.
Less bedrock is exposed and grasses and other plant cover most of the area.
Zone 2 Zone 2 is a broader zone just north of Zone 1 with a northern border extending from Boardwalk 6 to the tenth post north of the south gate. This zone is characterized by more intense erosion with bedrock and boulders exposed. Vegetation is usually restricted to protected areas such as depressions and crevices. Many geological structures are exposed in this zone. Zone 3 Zone 3 is just north of Zone 2 and bordered on is northern edge by a line extending roughly from the angle of BW7 to about 17 post north of the central gate.