I’m not sure if this area is involved, but there is a big chunk of swamp down there.
https://www.youtube.com/watch?v=6_tM0mWBg2U
That is exactly the area that will be closed off by this segment (Just a few hundred yards South of the Morelos Dam).
The lady in the video reports that about 4,000 family units per month were coming through there at one point.