Study uses lasers to prevent flooding along Texas' South Llano River

AUSTIN (KXAN) — A recent study conducted by the Texas Water Development Board could help the state prevent flooding along the South Llano River, according to hydrologists with the board. This study involved Topobathymetric Lidar, essentially a laser, to scan the landscape and river bed of the South Llano River.

"For Texas, I think it's kind of a new day of being able to understand our rivers and monitor them and use that information for the benefit of the state," said Dr. Mark Wentzel, a hydrologist with the Texas Water Development Board.

Wentzel said the data obtained by the scan is foundational and can be used for a wide variety of projects, including flood prevention.

"This data can be important for large floods, it's even more important for smaller floods," Wentzel said

What is Topobathymetric Lidar?

"Lidar is a remote sensing technique that utilizes pulsed light particles," said Joey Thomas with the Texas Natural Resource Information System, a division of the Texas Water Development Board, was tasked with interpreting the study.

Thomas says the lidar works by having a plane fly over an area, in this case the South Llano River, shooting light particles at the landscape. The particles then bounce off of whatever they hit.

Thomas and his team then measure the height that the particle bounced off of to create a 3D map of the landscape.

The Texas Water Development Board has done this before with traditional lidar, but it is unable to accurately scan the river bed.

This is also the first time the Board has commissioned a study using a commercial-grade lidar system. Before now, they've used research-grade lidar, which is more expensive.

The advantages of using Lidar over traditional studies

Why use lidar? Speed and efficiency. Wentzel says that a traditional study like this would involve a three-person team heading out to the river and measuring it by hand. It could take 1-2 months to collect the data, but a lidar study can gather the same data in 1-2 days.

"The efficiency is so much more than a three person team out there collecting data for two months," Wentzel said.

Traditional lidar can only scan the surface of the river and the land around it, but Topobathymetric Lidar uses a slightly different laser to scan the riverbed.

Wentzel says that this is what will help with flood prevention. "What the bottom of the channel looks like, is really foundational data for all kinds of activities."

Wentzel says the data can help them know the height of waves and even which bridges will be overrun when flooding does occur.

The South Llano River has been responsible for devasting flooding in the past. In 2018, multiple people died when it flooded near the town of Junction.

That flooding can impact us in Austin, too. The South Llano River is upstream of the Highland Lakes.