OK, let's start out with the Grand Canyon. True enough, there are many, many layers of horizontal sedimentary rocks. large angular unconformity - or other sedimentary layers that were subsequently tilted, eroded and then they became a depositional surface. In addition, if there was a singular, great flood, there would be a transgression and regression sequence in the Grand Canyon - rocks would go from shallow-water to deep-water depositional forms and then back again in a singular sequence. Instead, you see many different depositional environments, including some terrestial sandstones. How does the Genesis account of the flood account for this?
I don't think Genesis has anything to say about the GC. Creationist geologists don't say that it was carved out by the flood itself, but by an ancient lake draining suddenly through the canyon.