You do realize that where we have deserts now was not always a desert, same with mountains? Where I live, in Wisconsin, at one time was under an inland sea and at another time was buried under a mile of ice. Mountains rise as plates collide, areas that were fertile or even under water dry up as the plates move them to less temperate areas.
If there was a flood that swept the entire planet, there is way WAY more evidence that should be found. In fact, there is A LOT of evidence against it. Just because you can point to one fact and create a story around it that could support a global flood doesn't mean you get to ignore all the evidence that shows there wasn't one or the other theories that explain that fact, especially if those theories have a lot of evidence for them.