I'm on the northwest side of Houston. Most of the houses in our subdivision are on gentle slopes 12-18" above street and gutter level. The water still got high enough to put a couple of inches into the garage and laundry room but thankfully just short of entering the main living areas.
I feel sorry for all the people who had to abandon their vehicles on the freeways. Night visibility in a rainstorm on Houston freeways is poor. So a lot of people pull over to the shoulder and wait for the rain to slow down. But it didn't, and most of the frontage roads and bottom stacks of the interchanges flood first, so you get trapped on the mainlanes with no way off and then those flood and you have to abandon the car if you don't want to drown.
Though certain low lying spots here flood pretty easily, the bayou system works fairly well and moves huge quantities of water. Much of the waters receded within a few hours though the damage was already done. Flood control estimated that over 162 billion gallons of water fell in the county in the span of four to five hours.