According to the Houston City Flood Map linked in an earlier thread, the eastern side of Houston will surge flood from a Cat 5 and possibly from a Cat 4. There are also various low parts in town that will flood due to rain. These are areas that normally flood when it rains.
That's why I said SOME parts of Houston are safe from the STORM SURGE. Not all areas (especially those East of I-45 and the Beltway up to I-10). And other areas are not necessarily safe from ancillary flooding or wind damage. But I'd rather be in my house than trapped in a broken down car on an Interstate during a hurricane.