To Save Lives, Researchers Are Creating An Online Library Of Potential Flood Maps

By Editor On Sep 15, 2021

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Imagine it is 2 a.m. and you are one of the first responders at the scene of a flood.

Your vehicle is approaching water on the road. Trying to cross them could wash you away. So you stop and watch your headlights cut through the rain.

You can see that there is water around some houses nearby, but it’s dark and you don’t know how far it goes or how deep it is. What you do next could save life – and put your own at risk.

This situation is not hypothetical for Harry Evans. He says it could describe many of the floods he worked with the Austin Fire Department during his 30 years.

At best, Evans says, first responders would immediately understand the magnitude of the flood approaching them, including the amount of watered soil and the depth of that water. But it can be difficult at night.

The challenge, he says, is often how bad it is. “How badly are we flooded?”

Since leaving the department in 2015, Evans has been part of a research team at UT Austin working on a new way to find answers to these questions. They say the tool they developed, an app and an online database called Pin2Flood, could do the job. The project recently received a $ 1.6 million grant to continue its development over the next two years.

In the situation described by Evans, rescue workers feel in the dark, but they have one useful piece of information: they know where the flood has arrived.

Now that single data point can be enough to draw a picture of the tide in its entirety, thanks to a mapping technology called Lidar (short for Light Detection and Ranging). Lidar is a relatively new method of measuring the surface of the earth using lasers shot from airplanes. It enables people to create a detailed relief map of the earth’s terrain with a level of detail never before achieved on a widely used scale.

“This information is usually [down to] one meter, ”says Paola Passalacqua, professor of building architecture and environmental technology, who helped develop the app. “That means you have an elevation point for every 1 meter by 1 meter square.”

By knowing how high the water is and understanding the contours of the surrounding landscape and the water flow, one can extrapolate where else the water is.

It just takes a lot of computer modeling.

“We filter the data. We calculate various attributes of the terrain, then we track them [water] Canals, ”says Passalacqua. “Once we have that, we take that logical prediction and then convert it to a depth and get a flood map.”

However, to get this flood map, the app needs to know how high the water is. This is where the “Pin” in Pin2Flood comes into play.

First aiders open the app and place a virtual “pin” on the water’s edge. The app takes this data and calls up a pre-generated flood map that shows where the flood events are otherwise in the vicinity and takes the water flow into account.

The desired result? A relatively accurate map of the local flooding was delivered to her phone within minutes.

“It’s a pretty simple thing,” says David Maidment, a professor at the university’s Center for Water and Environment.

“The biggest challenge is that you have to put everything on the web,” he says, “so that when you get to a certain place and say the water is here, you can immediately go to a map library.”

But there are other obstacles.

For one thing, Passalacqua points out that the lidar maps she uses to model floods can lose accuracy over time. If the landscape changes after the terrain has been surveyed (often due to flooding), the model may be less useful.

“In a dream world, every time you get one [flood] Event, you would fly [a surveying plane] one more time and then you see how the landscape has changed as a function of that event, ”she says.

Passalacqua says she is working on adding water depth information to the app’s flood maps.

“As a modeler, my original goal is always to make things more efficient and accurate and to somehow move things forward,” she says. “But when you talk to Harry … [Evans], he will tell you that anything is better than nothing. ”

Rescue workers are already testing Pin2Flood in the field. Researchers say accuracy should improve as the tests progress. The team is also working with the National Weather Service to compare their flood maps with NWS forecasts to refine the product.

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