The second map is from an adjacent quad but has no contour lines. Instead of labeling the contour interval at the bottom, there is simply a note that says "Entire Area Below 5 Feet". And, in the corner you'll notice that there is no legend for roads, either. But they still made the map. The USGS didn't say, "Oh there isn't muc land there" or "there is absolutely no topography there". They made the maps. And I bet these maps get used too.
Be careful, the linked images are quite large. But if you want to go back to the source, you can head over to Libre Map to get all of the topos for Louisiana.