The glaring errors in the "nobody plans for 50 inches of rain" excuse are twofold. 

First, Houston has been warned for years about catastrophic hurricanes being a when-not-if proposition. Hurricane Ike in 2008 sounded alarms which produced no actions. http://grist.org/climate-energy/houston-is-a-sitting-duck-for-the-next-big-hurricane-why-isnt-texas-ready/

Second, the average rainfall over the Houston area during Harvey was 24 inches--less than half of 50 the inches used to excuse poor preparedness. Public health? Who needs it? CEO bonuses are what's important.