Yup, the delta is endangered as it is. Much of the farming area in the delta has the same elevation problems as New Orleans: they are up to 20' below average sea level. The predictions say if there is a catastrophic levee failure, the amount of water that will flood into one of the "islands" in the delta will draw so much water so fast that salt water from the SF Bay will intrude most of the delta, killing fish, vegetation &c. The new "lake" in the delta would be too deep for even aquatic vegetation to grow, so would be a dead spot permanently.
There are communities on the west side of Stockton (just about anything west of I-5) that are within 5 feet of sea level. I live at about +20 or so.