I've ridden the entire Katy the last 5 years. For the most part it's in good condition, but sometimes local flooding messes it up. From what I gather, there's a 4-mile stretch near Augusta that's closed. There's also a closed section around mile marker 35 between St. Charles and Machens. It is walkable.

You can find the latest Katy information in this forum. Plus the web site is very informational.
Katy Trail Forum - questions, answers, and discussions about