Nothing is practical. The beach at Kitty Hawk is in a different place than when the wright Brothers flew there!
An 8 foot deep concrete wall would be undercut within a few minutes by a storm surge (ever heard of them). The wave interaction would then begin its destructive work on your "floating" roadway. Dead man anchors are good for a small project, but to rely on their stability along miles of roadway is not practical in the face of such reality.
There is a significant difference between making a proper airfoil on a lightweight frame, and constructing your "floating roadway". For an example of a hurricane's destructive power, look at the bridge across Lake Ponchartrain... or the beaches of NC after a storm...
I'm sure they were designed by an architect... sitting in a room with his pipe spewing smoke!
Your picture proves the point : the heavy concrete bridge sections FLOATED off of the support stanchions. If they had been tied down by piano hinges on one side they would have just floated up and then settled back down again. As to the depth of the concrete wall, it can be 8', 12', 20'...whatever depth is deemed necessary. The dead man anchors can be 20', 50', 100'...whatever is deemed necessary. But you are amoung the "fearful and unbelieving", even if I did it for you and yours for FREE you'd still be in denial(not the river in Egypt),so go ahead and drown, I'll read about it in the paper...one more expensive hurricane disaster that the whole country is expected to pick up the tab for...