’A disaster expert explains why the Texas floods were so devastating’

By the Columbia Climate School with Andrew Kruczkiewicz

This is an edited version of an interview earlier this week on the Columbia Climate School’s State of the Planet news site. Andrew Kruczkiewicz is a meteorologist and senior researcher at the school’s National Center for Disaster Preparedness, and a technical adviser for the Climate Centre. His research focuses on flash floods and the use of climate and weather data and forecasting to reduce disaster risk and facilitate humanitarian action.

Q What caused these floods in Texas and why were they so catastrophic?

AK There are many factors at play when we’re talking about flash floods: meteorological, climate-related, geophysical, and those related to the built environment.

On the meteorological front, the moisture associated with the remnants of Tropical Storm Barry interacted with a mesoscale convective vortex (MCV) over central Texas. The MCV interaction allowed for new, intense and rainfall-rich thunderstorms to form.

In addition, these storms were both very slow-moving. Underlying drier-than-average conditions on the ground were also a contributing climatological factor when determining why the impact of the floods on lives and livelihoods was so great.

One of the fingerprints of climate change is that warmer atmospheres lead to wetter tropical systems. But flash floods have been happening in this area for a very long time. Did climate change make this worse? We should be asking that question.

Other factors at play include socioeconomic shifts, and changes in land cover and use. We must consider all of this when trying to assess increased levels of risk, broadly speaking, in order to develop revised policy and disaster preparedness, warning and anticipation.

“Flash Flood Alley” is not a well-defined term, and more work should be done to define and map the various types of flash flood alleys, as they are areas that experience elevated risk, and require more specific approaches, including communication of baseline levels of risk and warnings for when there are elevated relative levels of risk – especially for the most vulnerable communities.

‘There are very few parts of the world at zero risk of flash flood – risk communication must be different compared to other hazards’

Q Would better communication around the risk of flash floods have helped save lives?

AK There are very few parts of the world that are at zero risk of flash floods, and because of this we need different types of risk communication that is tailored to the perception of baseline levels of risk, and what deviation from those levels mean for different people.

In areas where flash floods are common, they are likely to be perceived as something locals can deal with – it might wash away your car or your cow – and while that leads to economic stress, which disproportionately impacts lower-income populations, it’s very different from a 30-foot wall of water.

I think something we’re learning is that the binary of “no flash flood warning” versus “flash flood warning” is not sufficient. The “flash flood emergency” is a relatively new mechanism. It was meant to address the issue of different intensities of flash floods. So I think we need more sensitivity in the way we issue these different types of messages, and ensure the most vulnerable and underserved communities are central in the messaging and actions the messages are tied to.

Also, many of the people who died in Texas weren’t living in this area. They were there for recreational purposes. Who has the responsibility to communicate risk and raise their awareness – to tell them they’re entering a zone where the baseline risk is low but not zero?

What seasons or months will the baseline risk be elevated? And what does an enhanced risk of flash floods mean in an area where the baseline level of risk is already higher than surrounding areas?

As flash floods increase in intensity, we are at a critical moment to review and revise our approaches to flash flood risk mitigation, early warning and anticipatory action – and these questions will support moving toward more comprehensive systems.

Q What tools or technology might have helped warn people to evacuate?

AK This is an opportunity for us to better integrate new technology with traditional technologies such as a siren system, or what we call NOAA weather radios, which use a VHF frequency.

People don’t use these radios much anymore because they think their phone will do the trick. They assume that if risk suddenly increases, they’ll get an automatic push notification. But sometimes those notifications don’t come.

VHF is much more reliable – weather radios don’t need to be charged. You put some batteries in, and they last for a very long time.

‘This is an opportunity to integrate new with traditional technology such as a sirens or what we call NOAA weather radios on VHF’

Could new technology such as AI have helped here?

AK In many locations we are learning that AI-driven forecasting is better than numerical weather prediction when we’re talking about average or moderate amounts of rainfall. That’s because we have a lot of training data representing those types of events.

However, when we’re talking about events that are so far outside the norm, we don’t have the historical data to train the AI modelling infrastructure, and so we don’t have evidence that AI-driven products are doing much better at forecasting disasters in a given geographic area.

Q How can we better prepare for such extreme events?

AK At the very least, everyone should have some sense of the potential for extreme weather in the place where they’re going to be sleeping on a given night.

When we have periods without disasters, social science shows that we become comfortable. In the back of our minds, we’re aware there is a risk of a flash flood, but we don’t like to think about it, especially when we are trying to enjoy a vacation.

Q Who should be responsible for communicating risk?

AK The primary question to ask is, what type of communication motivates people to take meaningful action at the right time? Up until recently, one approach was based on frequent and consistent messaging by trusted and authoritative sources. However, the “trusted” element is key here.

To what extent are sources trusted by everyone in a certain community or county? Do people at the highest level of risk trust the same sources as those at moderate risk? If you are travelling in a new area, for work or tourism, for example, is your perception of “trusted source” the same as those who live in that area?

Data shows that, particularly for flash floods, residents at the highest risk levels are more likely to be economically under-served. Even if they receive a warning, they may not be able to evacuate or can only evacuate into an area that is at even higher risk. For this event, how many people received the warning and couldn’t leave for various reasons?

This is a good opportunity to ask these questions and see if they can inform policy for people living in areas at all levels of risk for flash floods, in addition to developing approaches to communicate risk and warning messages for people moving into such areas for work, vacation or other reasons.

The American Red Cross is supporting several emergency shelters, providing food, relief supplies, and financial and family travel assistance to people affected by the Texas flash flood (pictured). There are also two reunification centres open to reconnect loved ones, and the Red Cross is distributing emergency supplies to community sites run by its partners in six counties, including clean-up items such as shovels, cleaning products, trash bags and more. (Photo: US Coast Guard via social media)