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.
What have developers done across the Greater Houston area over the past few decades that may have contributed to some of these recent major flood events?
Boullion: We have research that shows that rainfall hasn’t increased dramatically over the last 30 years. The nice thing about Harris County is all the stream flow gauges we have, and a lot of them have been in place for decades, so we can go back and look at data from decades back. We don’t see the significant increase in rainfall, and we look at that as an organization and say, ‘Is there a climate thing happening here?’ But what we do see is dramatic changes in peak flows and especially on bayous like Greens that have had the gauges for the longest amount of time, we can see some real upswing in peak flow. I think it goes back to the development and the fact that we weren’t looking at things in a holistic way and impervious surfaces causing more higher peak flows.
What role does climate change play in the severity of recent flooding?
Lindner: There is good consensus that the earth is warming. Where we start to get into disagreements is why the earth is warming, but there’s little denying the earth is warming. Science will tell you that if the temperature is warming, the atmosphere can hold [more] moisture—that’s a fact. So you would expect an increase in rainfall from a warmer climate. But can you say Hurricane Harvey is a result of climate change? No, you cannot say that a particular event is the result of climate change.
Since the hurricane season is only a few months away now, what short-term flood mitigation projects already have funding in place?
Costello: We have a lot of plans ongoing for the city and the frustration that we have, has to do with the bureaucratic process. When [Hurricane] Harvey impacted us, the government allocated $15 billion to the region right away. We haven’t seen any of that money.
The public is expecting us to get things accomplished, and we haven’t had any recovery money. We have over $2.5 billion of facilities that were damaged, and just like when you negotiate with an insurance agent on damage to your house, it’s a negotiation process.
It’s not something that happens right away. This could take five, six, seven years of full recovery period. But the district has a number of federal projects ongoing that they could use advanced funding for, and so, if you go back and you go to the flood control district’s website, they have a federal briefing document that shows all the projects they’re working on that they’re advocating for advanced funding for.
Why do some counties lack a flood control district, and how would the creation of one aid with flood mitigation projects and funding?
Costello: I publicly have gone before the Texas House Committee on Natural Resources and said that’s not a good idea to create another taxing entity, and I say that because if you compare Harris County to all of the other counties, Harris County Flood Control District has the largest engineering firm in comparison to private practices in stormwater management. We could easily create interlocal agreements between each county and have Harris County be the lead, just like we do with toll roads—HCTRA is the lead agency for all the other toll roads. We can do the same thing without creating another taxing entity, and this way, we can have these interlocal agreements because, everyone knows this: Water doesn’t follow political boundaries, it follows watershed boundaries.
Boullion: And it’s a regional issue. It’s not a city of Houston-only issue. It’s not a Harris County issue. It’s a regional issue, and we need to cross those political boundaries and work with other entities.