That's about it in a nutshell.

There are other factors involved in land los in LA, too. Petroleum extraction causes a very local land loss, some (extreme) sites subsided a couple of feet in a year or so over several hundred acres. You can look through the water and see marsh grasses below. But this is not a common phenomenon and is pretty local. Also all of the canals built for access to the Gulf and inland waterways allows rapid movement of saline water into fresh marshes, which quickly kills fresh marsh vegetation. This phenomenon is ubiquitous in S. LA and parts of TX. And of course, the whole coastline is subsiding and not being replenished by overbank flooding of the MS River. Oh yeah, there's also the sea level rise as a result of melting snowpacks and glaciers. The combined effect is a huge rate of landloss, on the order of acres per hour if looked at linearly since the 1950's. (But it is not linear, it proceeds in a downward stairway fashion because local events work with subsidence).

It is hugely complicated. But the whole problem may solve itself naturally. Either through massive spring floods overwhelming the flood control system of a Cat 5 hurricane slowly moving up the MS to NOLA and Baton Rouge. That's when we'll enjoy the TV spectacular of 10's of thousands, perhaps hundreds of thousands of people dying. Then we'll all wring our hands and wail our laments and blame politicians for not doing something.