My thoughts after some analysis.
1. Flooding from Harvey different from local flooding. Harvey was 50 inches in 4 days and Lake Houston went to 53 ft level from 42 ft normal. Water seeks own level and homes at 53 ft level flooded from backed up bayous . Look at Lake Houston level and compare with your home elevation and good idea of flooding. L. Houston designed for water supply not flood control. Only many more flood gates in Lake Houston Dam will solve problem.
2. Local flooding is a different problem. Drains only can handle about 3 inches per hour and we in Kingwood had 6 in. per hour so built up. I suspect drainage has changed due to all the building and not following drainage codes and many drainage ditched filled up over the years. Big problem. My street flooded big time but drained in front in ½ hour which indicated drains themselves probably were not plugged.
Any thoughts? No profanity please. Thanks. 

I think it's safe to say that no area in the whole world can handle four feet of rain in 4 days without a buildup. The flooding was caused by a multitude of issues compounding.

If you're interested in real time continuous analysis of all of Kingwood's flooding issues let me suggest this website. Reduce Flooding dot Com

It is updated with blog posting and analysis daily.

The flooding was caused by a multitude of issues compounding. 

Thanks Joe Blow, I agree. Good reference. 

Lots of other good data available like Joe Blow has shown. For example drone footage and analysis of Elm Grove.
https://reduceflooding.com/2019/05/09/elm-grove-looks-for-answers-and-doesnt-have-to-look-far/?fbclid=IwAR03JpPlGyVoVBnp8YPjR2INDQw8AEJhcQP0WLe7-pIvH3HrLfCP4ruzMds

Sorry just copy and stick it in your browser. Hope it works.