Q+A: The Rising Risks of Urban Flooding


From existing data sources to flood mitigation practices, cities need to step up to respond to a national challenge.

Aerial view of flooding in New Orleans

U.S. Coast Guard.

From existing data sources to flood mitigation practices, cities need to step up to respond to a national challenge.

After two years of research with Gerald Galloway, "the godfather" of flood management and resilience in the U.S. and a team of researchers from the University of Maryland and Texas A&M University, flooding expert Sam Brody, Director of Center for Texas Beaches and Shores at Texas A&M University at Galveston and a Kinder Fellow, says that dealing with the issue of urban flooding has become a nationally resonant conversation. And with good reason. Their new report, The Growing Threat of Urban Flooding: A National Challenge, captures the scale of the problem along with a list of recommendations to improve flood mitigation, planning and response.

In addition to life-threatening potential of flood events, the report found that urban flooding is "a growing source of significant economic loss, social disruption and housing inequality." After a presentation of the report's findings to Congress, Brody said, "It seems like there's a lot of interest in addressing what is called urban flooding, which is really flooding where there's development."

Up next is a two-year project that seeks to make Texas the case study for implementing some of the report's recommendations and put it at the forefront of flood mitigation and resiliency. The Urban Edge talked with Brody about the study's finding and which cities are getting it right. This interview has been edited and condensed for clarity and length.

Let’s start with getting a scale of urban flooding? Certainly, after Hurricane Harvey, the stories of urban flooding took on a new dimension for us here in Houston, but it did also seem that we're starting to see more of these stories and not just around coastal, hurricane-related flooding. How big of an issue is this and why do you think it’s getting more urgent to address?

To me urban flooding is flooding that is either entirely created or exacerbated by the built environment. It's really rapid development in urban areas combined with changing patterns of rainfall, that combination is what's making this problem significantly worse over time.

And it's not a new problem but because it's getting worse and then you’ve got sea-level rise, changing climate particularly around intense rainfall episodes as we continue to put homes and roads and rooftops in these vulnerable areas and fragment the natural drainage patterns, it's creating a lot of flooding that is disconnected from a stream channel and disconnected from a FEMA-defined floodplain. We can see over time how more and more flood impacts are occurring in those areas outside the traditional flood risk zones and that’s an indication of the way the human built environment is changing the landscape and creating these unintended consequences.

Harvey was this catastrophic event that, to me, just really highlighted what was already happening. Everyone said, "It’s a once in a generation storm, too bad. We'll recover." Well, it was just the exclamation point at the end of a series of chronic and acute events that’s been building up in Houston. A key report [on flooding] before was out of Chicago. But also Miami and now Washington, D.C and Baltimore and, of course, New Orleans has always been a mainstay of flooding. New York has a lot of issues. And so, the problem is just going to get worse and it's bound up in infrastructure and planning and future development and communicating risk.

It’s an issue of national significance that plays out at the local level. It’s a national issue, it’s a local responsibility. My hope is to use Texas as a case study and test bed for understanding and addressing the issue on the long-term and national scale.

The report mentions issues with data that pretty quickly emerge around flooding. What don’t we know? And are any cities taking the lead here to get better data and transparency?

That directly speaks to our new project that’s coming out of what we don’t know. The data on risk is hydraulic data, centered around the channel and the FEMA floodplains. Well, why do we have so much impact outside of those areas? That’s one thing we need to better understand.

The second thing is the impact of these large events largely focuses on either windshield surveys or flood insurance claims but that’s only a fraction of the picture. People who don’t have insurance are not part of that picture. I'm part of that problem. I've been floating around with these hot spot maps and NFIP claims but on average those are wealthier people who can afford insurance or people who are mandated to have insurance and those are people in the floodplain. We need to better understand non-insured losses, losses outside the floodplains and disconnected from a channel and to do that we’re going to have to collect new data and bring new data sets that are not traditionally used in this arena. That’s what this new project is about, it's about mapping and articulating at the local level.

I hear people talk about the problem across the country. I think it has to start at the federal level. The existing data sets are federal. That is changing. It's taking time but there are initiatives to better coordinate federal data and synthesize and share it. During Harvey, that was a huge obstacle; getting the data that already exists and then using federal data to then marry that with local and regional datasets. We really need to work that out.

You think data is a minor issue but if we don’t know where the impacts are and who's being impacted we're not going to be able to mitigate the impacts over the long term. Just thinking off the top of my head, there's a whole ground swell movement around 311 data. We’re using that as well, that’s part of our new project, using that sort of crowdsourcing-type data. Again, people calling tend to have more time and acumen and resources to call, so you're never going to get the complete picture but we can do a lot better [than we have been doing]. We’re going to use crowdsourcing data, surveys, and actually go and talk to humans with maps and say, "Tell us why this wrong, how do we improve it," and use that local knowledge to then recalibrate.

That’s the vision. It's time consuming and expensive. If we can systemically incorporate local knowledge into our risk models, I think that will go a long way toward addressing the problem.

The report highlights some of the factors contributing to and complicating urban flooding: intensifying storms, aging infrastructure and unclear jurisdictions. What should those various levels of government be doing about this from federal down to cities?

From a mitigation standpoint, it has to be at the local level where the decisions are made about infrastructure and about current and future development standards and communicating to neighborhoods and residents. The data may start at the federal level but all of the mitigation activity is a local level proposition. That means counties working with cities and cities working with neighborhoods and building departments working with emergency response departments. You see that happen during a crisis pretty well. It's maintaining that in times of non-crisis that can be difficult.

I think part of getting there is thinking about watersheds and watershed collaboration. That’s something that Texas can start doing better in the future. Once you think about watersheds instead of jurisdictions, it becomes clear who needs to talk to who and how upstream development affects downstream development.

There’s this issue of equity brought up in the report, how does urban flooding connect to existing inequity and where are the major gaps right now in terms of mitigation and recovery response in regard to equity?

I think [one gap is] identifying communities that are experiencing chronic and acute flooding but don’t show up on the impact maps because the impact isn’t dollar-wise as great because the average structural value is much lower, but the impact and disruption is even greater. If you're in a socially vulnerable community, flooding has a greater impact than if you're living in River Oaks. It's identifying those communities better, putting them in the forefront of the policy and mitigation agenda and going into those communities and working with them to give them a voice and give them ownership over the decisions that are made.

There are a lot of options. We’re not just seeing that in Houston being problematic, we’re seeing that all over the country in places like Baltimore and Chicago. I got into this and realized the shortcomings of my own work and how I can do better. With Gerry's help, we realized there are so many forgotten communities that are suffering but don’t have the resources, the voice and don’t show up in the dollar impact bottom line but the problem is as bad if not worse.

There are a number of recommendations, but thinking locally here, how would you characterize or even rate Houston’s response thus far?

I see a lot of positive examples and work being done and I see a lot of areas that we can improve when the next storm comes.

That's a diplomatic answer. Are there certain cities really doing it right right now?

I'm really impressed with Sugar Land, from the modeling they're doing all the way up to the community engagement and communication and understanding they're part of a larger ecological system. They want to genuinely work with other entities in that system and take a more holistic approach. I was really encouraged by all the stuff they're doing. It’s a smaller community obviously but in terms of vulnerability to flooding they're among the top. They're really taking a different approach.

Charlotte and Mecklenburg County for buyouts. Their mapping and their data and ranking of every structure, they have the full package. Milwaukee for buyouts is top notch and thinking about natural drainage and green infrastructure.

Read the full report here.

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