Big Waterfall Support Walls
Because of the big size of this waterfall, the rocks, and the amount of earth to support it, a solid frame has to be built. Each of these cinder block cores in this support wall is to be filled with concrete and capped to reinforce against outward pressure from fill dirt and rocks. The larger the structure, the more reinforcement needed. Smaller normal size residential waterfalls generally don't need this much support. However, too much is always better than not enough.
Each step down the support wall is double rowed and will support the heavy spillway rocks placed directly on top of them. unlike the surrounding dirt filled cells, there will be no chance of them settling or moving in the future. This factor magnifies the importance of the cell dirt being compacted to an extreme density. The cell fill must support the rest of the waterfall elements without settling. Even in smaller waterfall projects, if settling occurs, the entire waterfall should move together.
Also See: How To Build A Waterfall