Good point LoveChild.
If someone were to take a gander at Google Earth and zoom in from Canyon Lake to Seguin, then one cause would become evident. It's called "pavement" and there's a lot of it around New Braunfels that wasn't there before which causes runoff.
So, if this is a cause, how would it be remedied? Tear down subdivisions and shopping centers?
It wasn't all that long ago that 10 inches of rain fell in New Braunfels, wreaking havoc on the river. Dozens of boats and RV's plummeted over the dam on Lake Dunlap (Guadalupe River). Check out this YouTube link http://www.youtube.com/watch?v=2uh4gZ...
The topographical layout of the land and the obstructions in the river are the cause for the flooding. God made it that way. We need another big flood to wash out the rivers and clean the waterways. If you live in a flood proned area, move! Or you will be flooded again and again. There is a flood plain for a reason.
My guess would be too much water and my solution is to move the town away from the river. Can I have my $2 million now ?
Could it be rain and urban development?