Sure. It’ll take 84 years to build a small sea wall.

Galveston is just now starting a multi-billion dollar project to protect the island. They already have a sea wall and habe already raised the level of the entire downtown area (in wake of 1900 storm)

This project will lengthen the sea wall and raise it higher. They’re also adding beach berms beyond the sea wall, gigantic pumps to be able to drain lower areas of the city- an increasing problem that is happening more frequently in rainstorms that increasingly back up the storm sewers due to rising sea level.
But perhaps the biggest and most expensive part of the project (collectively known as “The Big Dike”) is the one mile long gate that will be istalled across the Houston Ship Channel at the opening to Galveston Bay.

Anchored by Galveston Island on the ssw, and Boliver Peninsula on the ENE, this gate will normally remain open to ship and boat traffic, but will be closed during hurricanes.

The purpose? To block waters flowing into Galveston Bay that would flood the bayside of the island. They even have consulted with Dutch engineers who have a long history of constructing such things.

The problems, of course, in addition to the initial expense of billions, will be the cost of operation and replentishment of the sand berms and dunes which form an integral part of the strategy.

And of course, there’s an underlying problem- the increasing rate of sea level rise (which you didn’t account for when you did the math).