The river is moving away from the city. The city is sinking because of its weight, because no upbuilding by new muck for many decades, because of being cut off from the fresh water, because it is sliding off a cliff (the Continental Shelf), and because the Oil and Gas Industry is extracting oil out from under it. It is a city that for all intents and purposes is now Sea domain.
Ignore the tree-hugger stuff. The facts concur with other neutral authors, but the article summarizes things nicely.