That's really an exit at 43 and I-10. If you take 43 north, then you hit 603 north of Kiln (the exit might say 603 on it though).

Anyway...the land that exit is on is at 5 ft elevation. So even if I-10 was 25 feet higher it would still only jibe with the 30-ft surge number.

The damage from the surge there is not surprising and probably doesn't have to do with velocity so much...water is quite heavy. One cubic foot is about 62 pounds, and a cubic yard weighs as much as a car. Water doesn't compress for all practical purposes. For this reason moving water packs quite a large force, which can do seemingly amazing things (such as in Mobile float an oil rig downriver and wedge it under a high bridge).

So...with all the water towers that have survived, I'm wondering if the new model for successful beachfront homes is steel girders sunk into the ground and a house built to withstand strong winds that can be raised and lowered on that framework. Not cheap, but would it work. I think the houses that were already on wooden piers washed away because they weren't high enough above the surge and coastal waves.