Nice detective work as always Melissa!
I wouldn't have the faintest idea of where, definitively, to go, and can only suggest trying Google.
But one piece of info that might help is that the NBI shows that the current span on Route 2004 crossing this bayou - listed as FM 2004 - was built in 1965. Maybe the straightening was done in conjunction with the construction of replacing the truss bridge?
I am trying to figure out what agency or company straighten Bastrop Bayou and when it was done. I have been in Brazoria county since 1941 as a baby. I remember fishing there but was not straighten at that time 1953, I do not think, (but that was a long time ago). However, in my high school days I remember the fresh dirt on the banks after leaving bridge at Hoskins Mound rd. all way to Lost Lake or Intercoastal Canal (the ditch).
Please see if you can provide me with information or where I can go to secure the information.
Thank you, bill
Thank you Tony...it was minimal effort at best