Those two dams protect Houston. Houston will be flooded anyway, just like 10 years ago with Allison. What I'm more worried about is not the San Jacinto or Brazos, but the Colorado. If you look at the numbers now near to Austin it had already has a flow of 40.000cfs (!) and a height of 25ft. This is not sustainable, and more will come. The problem will be nationwide if the Colorado dams break, the flooding will be above 40ft and the STP nuclear power plant will not be able to shut down properly. I don't trust them at all. It is besides Palo Verde the most dangerous plant in the world. 2 highly experimental 1.3GW vessels (normal is 800MW) without cooling towers, cooled by seawater, and a series of security problems, which were all downplayed by management for decades. This is different to Fukushima. The wind direction goes over Houston, Austin and Dallas over Oklahoma to all major cities in the middle East (Chicago, New York). The USA will be no more after an accident there.
The STP sits right in the eye of the hurricane so it gets all the water.
This is from 2012, has anything been done to remedy the situation since then?