If you look at the old B&W photos from the 1930s, 40s, and through the 1950s in many different books, you would see from the old photos that ANGC was manicured during those periods.
Cannot explain the creek in the video, but old photos showed the creek banks were maintained.
The old B&W photos from 30s through 50s, show much fewer trees as compared to the the 90s.
Stan Byrdy's book and Frank Christian's book are good references.