They work, oh yeah… well, sometimes.
I suppose that I should say that my bias is reflected from spending a lot of time growing up near the Mississippi, and doubting that we could really effectively control the whole flow of that massive body of water with a few levee’s. For the most part, they do work – and to reasonable effect. The downside is that too many people assume they’re foolproof and in my opinion don’t have enough respect for the power of the river. I spent some time myself doing sandbagging in the Flood of ’93 – but my respect for the sheer force of the river goes back a lot farther than that.