Harvey: Once-in-500-years-storm

In my recent post about the Dutch approach to preparing for storms and floods, I mentioned that their goal was to be ready for a once-in-a-thousand-years storm. We were told on a tour that America's goal is to be ready for a once-in-a-hundred-years storm. Since Harvey is being described as a once-in-500-years storm, it's not surprising Houston wasn't ready for it. I wonder if the Dutch would have coped?