I haven't made an effort to research this, but so far, I've heard nothing at all about storm surge damaging anything. And Houston is a good little ways from where the hurricane actually came in, so I don't know how much surge they had there.
When I was in high school, I think it was a hurricane blowing past on one side or the other that brought about 13" of rain to our area, but dumped about 27" of rain up in Alvin, just south of Houston. And yes, it flooded stuff. If I remember, that was 27" in 24 hours. Some of the rain numbers I'm hearing from the current situation are over the whole week or so, so it's hard to compare.
One problem with the information I see, it's obvious that there's a lot of water and flooding down there, but not obvious if that's 2% of Houston, or 10% or 90% or 98% or what.
My folks live south of there, and they haven't been flooded out- the major issue down that way has not been rain, but prediction of some of the rivers flooding from rain farther up the way.