I-wall versus T-wall?

Post Katrina, the repaired breach site of the London Avenue Canal consists of a new flood wall in the T-wall design rather than I-wall design. A T-wall is a reinforced concrete structure supported by foundation pilings with a non-structural steel sheet pile assembly beneath the levee. T-walls are not typically earth supported, are a significantly sturdier design, and are also three or more times more expensive to build than I-walls. Drawing submitted courtesy of Levees.org