And other threatened places.
One of the world's poorest and most vulnerable countries, Bangladesh, was able to drastically reduce flooding casualties by erecting simple elevated concrete platforms for elevation above floodwaters.
The mayor of Houston and others are getting grief for not ordering evacuations ahead of the predicted flooding. Actual flooding has probably been worse than the predictions, but it is incredibly difficult, if not impossible to evacuate a city of six million. A nation as rich as the US can afford a much more elaborate version of the Bangladesh solution. Sturdy, elevated structures should be constructed in all flood prone regions.
A portion of the funds could come from eliminating federally subsidized flood insurance, and building codes should strongly discourage building in flood prone regions.
The shelter buildings should be multiple use: schools, government buildings, hospitals, nursing homes, universities, and community centers should receive substantial subsidies to be built to hurricane and tornado proof standards and equipped with emergency supplies and prepared for rapid conversion to emergency shelters with beds, generators and so on. Where such buildings don't exist, subsidies for their construction as community centers should be provided.
This would be a multi-billion dollar infrastructure project, and would take decades to complete, but well worth it, in my opinion.
We don't know yet if Hurricane Harvey is a mass casualty event, but it's already certain to be one of the most costly disasters in American History.