I have read about the massive storm surge that could cause flooding as far as Houston and even if it doesn't come that far, it will hold back the drain-off from the bayous that drain Houston into the Gulf. If looks like Houston will be on the "wet" side of the eye of Rita so Houston will most likely get hit not only from strong winds but also heavy rains. Flooding can be expected.
In 2001, Tropical Storm Allison dumped 20-30 inches of rain on Houston in a short period of time. Massive flooding. This picture is from 2001 and is just west of downtown Houston. Buffalo Bayou is flooding over a large green belt area. Buffalo Bayou becomes the Houston Ship Channel just a few miles to the East of downtown Houston. The storm surge is expected to be more concentrated in the Ship Channel and so downtown Houston will be in the middle of the surge from the sea and the run-off of the rain.
This image is a underpass at Houston Avenue and Memorial Drive...again just West of downtown Houston. The traffic through this underpass includes buses and 18-wheelers. This picture was taken after the water had receded from the bridge which is now crossable.