Very clever idea! Each 'rock' has a slightly different mold so yours might not have that exact high point as shown in the photo. I have several from different manufacturers and Backyard X-Scapes products have the best natural and irregular look of any. The measurements have always been spot-on so, if this size is sufficient for your waterfall, I think it might work. Be sure to protect it from erosion of a continuous flow of water by using an outdoor spray coating and angle it to minimize force of water striking the surface.