Raising New Orleans

I listened to a discussion about raising the portions of New Orleans that are below sea level to above sea level on a the radio the other day.

The question was: could land fill be used to accomplish the task. Not surprisingly, the number of truck loads of fill and the ability to truck them to New Orleans from across the country made this one a financial and logistical mission: impossible.

But it did get me thinking. Are there other alternatives. I came up with one that I would like to throw out here. I'm no engineer, so I have no idea about practicality, but at least this one is good for brain storming:

Is if possible to create a device that crosses the Mississippi north of New Orleans (but still allows for shipping to go through) that would trap all that wonderful and abundanat silt heading down the river to the gulf, so that it could be used to raise New Orleans?

Look, this one may be a bit "over the top" (literally), but desperate times deserve desperate measures. Is this one even a remote possiblity?>