Inside a sprawling warehouse on the outskirts of Vicksburg, Mississippi, a 15,000-square-foot model of New Orleans is getting very, very wet. Since February, researchers with the U.S. Army Corps of Engineers have been re-creating Hurricane Katrina’s wrath in miniature. Their goal has been to emulate the size and speed of the storm’s waves to understand why the levees crumbled and how to fortify them against future storms.

One startling finding, revealed in a 6,000-page tome released in June, is that nearly two thirds of the flooding could have been prevented had the Corps simply fortified the weak soil conditions that ultimately caused the levees to collapse. Since then, the Corps has installed “T-walls” around the levees that will bolster them against smaller storms, yet its long-term defense plan for Katrina-style nightmares, illustrated here, could be at least another decade, and potentially billions of dollars, away from completion.

Rebuild the Barrier Islands
Deployment: 2017 at the earliest
Cost: Undetermined
Probably the most ambitious arm of the Army Corps’s long-term defense plan begins 85 miles east of New Orleans in the Gulf of Mexico. An archipelago of uninhabited barrier islands, the Chandeleurs, would be fortified with sediment to weaken the storm surge long before it reached the city limits.

Install Sea Gates
Deployment: 2017 at the earliest
Cost: $500 million to $1 billion
Another proposal is to resurrect an idea first put forward in the 1960s: Insert a pair of navigable sea gates (think Panama Canal–size locks) between Lake Pontchartrain and the Gulf of Mexico. Even if a storm surge overtopped the barrier islands, the sea gates would minimize the flow of floodwaters entering the lake.

Fortify Levees with T-Walls
Deployment: June
Cost: $85 million
The Katrina simulations revealed that it wasn’t the pounding waves that toppled the levees, as experts had assumed. Most of the levees withstood the hurricane’s initial volley, only to collapse when water cascading down their dry side eroded the soil around their foundations. The discovery of this “scouring effect” led to another fix: Replace weaker sections of levees with inverted T-walls that form a scoop at ground level to channel water away from their foundations.

Create Floodwalls
Deployment: July
Cost: $150 million
Perhaps the simplest and most immediately feasible of all the defense options are retractable floodwalls positioned where the 17th Street Canal meets Lake Pontchartrain. The gates should reduce wave energy by 20 percent—enough to give the levees a fighting chance.