Did they overflow the banks because of roads that were built (as stated in the OP)? Nope!
Did they overflow because they didn't release water from the reservoirs early enough and fast enough? Yep! The government officials admit they miscalculated the amount of rainfall and when it would hit.
https://www.washingtonpost.com/news/post-nation/wp/2017/08/28/houston-releases-water-from-two-dams-in-attempt-to-prevent-uncontrolled-overflow/?utm_term=.3beca802cc7e