Houston, TX

Hurricane Harvey deposited more than 60 inches of rain on parts of the Houston metro in August 2017—the largest rainfall total ever recorded from a US tropical cyclone. Houston's flood score of 95 sits at the 99th national percentile. That ceiling reflects a geography problem: the city is built on flat clay prairie with limited natural drainage gradients, cut by bayous that fill quickly and empty slowly. Harvey was catastrophic. It was also preceded by two major flood events in 2015 and 2016, confirming that the problem is systemic—not episodic. We checked twice: the real Houston buyer question is not whether a property sits in a FEMA Special Flood Hazard Area. It is whether it has flooded before, and what the drainage behavior looked like at the specific address during Harvey. River Oaks and Memorial area properties along Buffalo Bayou have prior flood histories that high valuations do not erase. The Washington Avenue corridor's rapid infill has changed runoff assumptions in ways that older flood maps have not yet captured. Annual premiums range from $2,400 to $7,000, with flood insurance worth pricing even outside mandatory zones. Prior flood history can change a transaction more than the base premium alone. Heat at the 88th national percentile adds a year-round operating pressure: Houston's humidity extends the effective cooling season, and grid reliability during peak demand months is a genuine resilience variable. Harvey reset insurance markets in this city. Those resets have not fully returned to pre-2017 pricing, and the underlying geography that produced them has not changed. Bayou location—not zip code—is the first filter every Houston buyer should apply.

— Open Data Collective