When a large sinkhole opened in Land O’ Lakes last month and swallowed a pair of homes, Dr. Lori Collins first heard about it not on the news, but in text messages from her family.
“I grew up in a house about two streets down, right around the corner literally from this," Collins said. "We were one of the first houses to be built in Lake Padgett when we first moved down to Florida, and I remember riding my dirt bike all through what used to be this place where no homes were, it was just a lake back in there.”
But beyond the ties to her past, Collins had another reason to be concerned by what was unfolding. As co-director of the University of South Florida Library's Digital Heritage and Humanities Collections, her team of researchers were among the first called by Pasco County officials.
“Dr. Travis Doering and myself are also affiliated with (the USF School of) Geosciences and we work a lot with the faculty there. Dr. Sarah Kruse, who we work with collaboratively on a sinkhole project that she’s already doing, immediately said, ‘Hey, we need to get out there,’” Collins said.
Collections’ co-director Dr. Travis Doering said they used 3D scanners, which basically operate like sonar, to map the sinkhole.
“It’s accurate to a little under two millimeters, so we have a complete documentation of the surface and the sidewalls and the subsidence.”
Doering walked as close as he could to the edge of the abyss, estimated to be 225 feet in diameter and 50 feet deep.
“It’s a really emotional setting for the families who lost their homes because basically their lives are floating on the surface of the sinkhole,” he said.
Researchers also used aerial drones, flying as high as 30 feet above the surface to collect video as well as still photos. Collins says all those images are fed into a computer program to create a 3D reconstruction of the area.
“The 3D model is really useful because we can see depths, we can see surface delineations, we can make measurements, we can compare data sets," she said. "So we have drone imagery that was flown on different days and now we can compare those datasets and we can look at the change that’s occurring.”
Collins adds that they’ve also been studying the history of the site. On her computer, she first pulls up a survey map of the area around Lake Padgett and Lake Saxon from 1847 and then maps from various times along the following 150 years that indicate how neighborhoods popped up.
“What happened in here was also some modification of the shoreline area probably to increase the number of waterfront properties that were available in this development,” she says, pointing at a new land mass from a 1974 map, around the time construction began on Lake Padgett Estates.
Finally, she hits a button and the last map from 1999 is laid on top of the first map from 1847. The shapes of the two lakes have been altered, mainly by construction, and the homes where the sinkhole occurred appear to have been built on what once was a lakebed.
"By today’s standards, I think this development would have happened a lot differently," Collins said. "So this is something that Pasco will need to consider and look at because essentially, what it’s telling me, is that this lake is trying to go back to what it once was."
For the past few years, USF’s School of Geosciences and the Library have been amassing historic sinkhole data for much of the state and making it available on the web.
For example, Collins pulled up another map and, much like you’d see on Google Earth, zoomed in much closer to the Lake Padgett neighborhood, where an image of the sinkhole-damaged homes is projected over their previous state. But what draws attention is a handful of red dots just to the east of that scene.
“Those red dots indicate areas where there’s been reports of subsidence activity, which is really important when you’re looking at sinkhole formation processes," Collins said, pointing to the screen. "You can see what’s going on in the whole Pasco County area, but you can also go into that neighborhood and know that there were three little subsidence areas that occurred in close proximity to where we had the sinkhole develop.”
Since it’s summer, many USF Geoscience researchers are out of state, working at other dig sites. Collins said this gave graduate students the chance to take the lead in Pasco County.
“They’re really getting a lot of lessons in project management and response," she said. "A lot of these students may never see an event like this if they’re working even for a professional geologic firm or something.”
USF researchers will continue to visit Land O’ Lakes over the coming weeks and months to update their findings – but Collins says they will not draw any conclusions from their work – they’re taking the opportunity to observe and record a natural disaster that occurred just 13 miles from campus.
"This is a really kind of important teaching and learning thing as well because this is from the beginning of an event like this sinkhole formation – we can actually track the entire thing," she said. "So that offers a lot of really important, significant data and we don’t have to travel around the world to get to it, it’s right in our backyard."
Dean of Libraries Todd Chavez says USF will then take the research and make it available to people around the world who want to learn more about sinkholes.
"Much like publishers produce books and journals, magazines and so forth, Lori and Travis and their work, they are creating data that will get transformed eventually into information and that information will be the basis for future research," he said.