"The load imposed on the crust is also causing regional-scale subsidence. The ground level today will be 1 km under water in 0.5 Ma, UNLESS you allow the river to flow through town and build it up with sediments. That's 10m (a storey) in 5,000 years, or faster on a local basis.

There aren't enough trucks in the USA to economically deliver that volume of crushed rock and keep building it up. You have to rely on the massive and free power of mother nature."

I posted about this on Current Events:
http://www.habitablezone.com/currentevents/messages/394180.html
[I made a simple mistake resulting in being off by a factor of 10, but I think the general idea is valid.]
I don't think we need to design cities to last 5000 years, and I think 500 years is excessive. If you want a city lasting 5000 years I suggest the cheapest solution is building this city on the Moon.
Thinking ahead a decade or three is about the normal way things are done. A century into the future is far sighted.

And you right about not enough trucks to deliver crushed rock, but I see little reason for using dump trucks or crushed rocks. [But I did wonder a little bit about using a lot concrete- I'll mention this later]. Now trucking the landfill a mile or two and using huge off road dump trucks, such as 160 ton vehicle, would quite different matter than hauling tens of miles. Now, New Orleans is near a big river, and this river is dregged often. Instead of dumping these barges somewhere to get rid of this material, you could use it for landfill material in New Orleans.
In looking specific data on this I ran across this:
"With Permit Number P-2247, the applicant proposes to dredge approximately between 150,000 - 200,000 tons (100,000 - 133,333 cubic yards) of sand/gravel per year. Dredging will be conducted in the Mississippi River between miles 182.0 and 188.0 above the mouth of the Ohio River. Sand will be accumulated on barges then transported and stored on the left descending bank, Beelman Terminal, Venice, Illinois at river mile 182.8. Dredging in this reach of the river has been conducted and authorized since approximately 1964. Plans submitted by the applicant have been reproduced on the attached sheets."
http://www.mvs.usace.army.mil/permits/pn/p-2247.htm

So this is one example of normal dredging routiuely done one particular location on Mississippi River. Instead you want project 100 times this scale- millions of cubic yards.
Triva: " Waterborne commerce on the Mississippi rose from 30 million tons in 1940 to almost 400 million in 1984. "
http://www.mvn.usace.army.mil/pao/bro/misstrib.htm

So scale of this project would significantly add to this this traffic in the order of 100 millions of tons per year, but it's not if as you were starting from stratch. There is a lot of dredging that needs to be done. And more dredging would result is less flooding in other areas of the country.
Another quote:
"Critics argue that railroads or trucks could pick up much of the commerce now shipped along the Mississippi. But the river moves 80 million tons of goods a year, including two-thirds of all U.S. grain exports. It would take 225 rail cars -- or a convoy of tractor-trailers 34 miles long -- to carry the load in a single barge tow."
http://www.sfgate.com/cgi-bin/article.cgi?file=/chronicle/archive/2000/05/01/MN20360.DTL

Point is barges can move a lot of tonnage. Also compare 80 million tons of goods against 400 million. This probably means that currently about 300 million tons of gravel or other bulk type material is being moved yearly. So the scale here is a squared kilometer of land raised 10 meter requires 10 million cubic meters of material.

Now, concrete. Orginally I thought about concrete, as a way to describe how cheap landfill would be- it's obviously cheaper than concrete. And then I wondered whether you could actually lay concrete as a way stablizing the landfill & compact it. I dismissed the idea. But
then when you mentioned "As the buildings foundered, you'd pump cement and clean waste into the basements to counter the pressure of sediment outside, or simply let the windows pop and the mud slump in."
It reminded me of the idea, but with one additional improvement. So here's the plan:
First you build mounds. Once you build up area so it's at the level of sea level, you build a slab of concrete one or two feet thick on top of this, then add more landfill on top of this. With this done, you can increase the elevation decades into the future by pumping material beneath this concrete slab and thereby raising the elevation.