I was camping at Roaring River State Park in September of 08, when hurricane Ike came through. The lower campground was evacuated, they told us to leave. Being from St Louis, and my 30th birthday, I didn't want to go home. Had no idea how much rain was coming, went to the higher campground. I should have went home. The lower campground lantern holders were under water, could not see the tops. Bad deal.
Be safe, listen to those who tell you to leave. Don't drive through water, it can be deadly. We had a couple people die south of St Louis last week due to water quickly rising.