You don't know which direction the flood waters came from. North, south, east, west -- even from the skies! -- they may have come from any or all directions. So as I see it they could most certainly have carved the Grand Canyon in what seems like contradicting ways.

Your rebuttal in no way diminishes the factual authenticity of the biblical flood.

Think you of the fact that a deaf person cannot hear. Then, what deafness may we not all possess? What senses do we lack that we cannot see and cannot hear another world all around us?
-The Orange Catholic Bible