Creationist here. The grand canyon was formed by the waters receding from the earth and with just the Bible one could of predicted canyons etc everywhere in 1500 B.C.
Yaro in post 25 beat me to the punch that there are canyons here and there demonstrationing a concentrating of water overflow as the Grand.
Also the present water level of the sea is higher then it would of been after the flood. The level then needed to be lower for animals to spread about quickly. I've read that in the water indeed way down beside present continents there are hugh canyons. I can't quote.
I would add that the previous ideas about these great canyons being formed by slow processes is not only without evidence of any depth to back it up but it is unreasonable when looking at such holes to imagine anthing but a water disaster.
Truly it was just the premise that the present is the clue to the past that brought the error. And present slow water work would need time indeed. And also floods today can cause big change anyway so this should of been figured into the options.
Rob