I'm actually betting that it's more on the order of a 1000 or 2500 year flood. The 1900 Galveston hurricane was not as bad, and that is considered a benchmark for flooding in the area.
I’m betting that they are using an inappropriate statistical model to decide how unusual these events are. If you naively use a normal distribution, based on the standard deviation of usual rainfall, and the distribution is actually fat tailed, you will underestimate the likelihood of big flooding events.
800-1000 year flood.
I have lived in Pasadena Tx, in this house since 1988. I’ve lived in the Pasadena/Deer Park area since 1972. There is always rain and some flooding and rarely trudging through water to get where I need to be.
This house has NEVER flooded. In Allison, it was approaching the garage. This time it was with in inches. As of 3:00 PM today we got 42.6 inches of rain since Thursday. That has never happened. Not Even Close
I am so tired, I hope I make sense.