Jill Boullion, executive director of the Bayou Land Conservancy; Jeff Lindner, meteorologist with the Harris County Flood Control District; and Stephen Costello, chief resilience officer with the city of Houston, answered questions on area flooding for Coffee With Impact, Community Impact Newspaper’s ongoing series of Q&A interviews with community leaders.
Why has Houston had so many 100- and 500-year flood events recently?
Costello: What most people don’t know in stormwater management is that we’re basing the rainfall on the statistical analysis.
In theory, a 100-year rainfall is using 100 years of records. It means you have that one point—that’s the 100-year rainfall. What happens is a lot of times we don’t have that database available so there’s a statistical correction you make. But we do know that we’re anticipating right now is that our design rainfall—our new 100-year—is going to change.
We’ve been advised by [the National Oceanic and Atmospheric Administration] that they’ve estimated our new 100-year rainfall will be close to what our 500-year rainfall is today. I always tell the public that our maps are what we call “living maps”—they always change as we get more knowledge of our design frequency. You’re seeing that now in Harris County and other cities proposing changing our regulations in terms of floor elevations in anticipation of our maps changing in the future.









