I know a woman whose mother was here illegally. Mom arranged for a coyote (smuggler) to bring in her daughters.
My friend swam the Rio Grande at age 9 with her 8 year old and 2 year old sister on a very cold Christmas Eve (the coyote thought the Border Patrol would take the night off).
Cold and exhausted, she and her little sisters marched across 20 miles of desert to the pickup point.
She is a citizen now, and you know what she says?
She says, “BUILD THE WALL. Without the Wall, immigrants will continue to attempt the dangerous crossing and many will die”.
And that fact puts lie to the claims that the Rio Grande is a natural barrier and no wall is needed along much of the river. I remember news reports going back many years about illegals wading across parts of the river, coming over in all sorts of boats and even coyotes bringing folks across with jet skis.
I don't know the terrain along the Rio Grande at all, but I'd bet there needs to be a wall on the US side along most of the river.