As long asI may have missed it but how did you address Houston's storm water discharge requirements with respect to impervious surfaces?
1) you are in zone x (outside flood zone)
2) your lot is less than 15000sf
3) and you do not cover more than 75% with concrete or decking (house foundation, driveway, patio, etc.)
you don't need to have any engineered drainage plans or special permits
The only rule will be that your property has to be able to bring water to the front street somehow instead of dumping it onto your neighbors. Whether you do that by grading / sloping around your house or by putting in pvc drain pipes is up to you.