While I don't yet live in the Austin/Lake Travis area, it is my plan to move there in the near future. Your question raises some concerns as to what area I choose.
I know this will not help, but I did find some information on the change.
There was a study done by the University of Texas at Austin-Department of Geography, by Justin Kockritz and Ryan Reynolds.
Lake Travis, Changing the 100 year Floodplain.
Thank you and good luck