The raging Logan River this spring was both a novelty and a potential hazard, but it was also an opportunity.
Ian Gowing, AggieAir Service Center manager at the Utah Water Research Laboratory, collaborated with Logan and Nibley cities to get an overall view of this year’s high river flows. AggieAir’s unmanned aerial vehicles, or UAVs, offer a safe, quick and very high-resolution option for mapping the river’s high flows and assessing both the extent of the flooding and the success of flood mitigation efforts. The imagery they collected can also be used to help verify that current flood models accurately predict future flooding events.
“We knew the river was going to be high,” Gowing said. “Ultimately, the goal was to show the extent of the flooding.”
On May 24, with flood estimate maps provided by the City of Logan in hand, Gowing waited for the clouds to clear and launched the AggieAir drone above the river. The city had placed sandbags along the bank all the way down to the Logan River Golf Course, and from there, the extent of the flooding broadened out.
Gowing and his pilot, Austin Washke, first collected high-resolution visual and thermal imagery of the entire river from downstream of First Dam to the Logan River Observatory gaging station located on Mendon Road, and then they flew the drone four more times over specific areas to help the cities to assess the extent of the flooding.
“From here [at the water lab] down to the golf course, I could only see one or two spots where it came out of the bank,” Gowing said.
In other words, Logan city’s flood prevention efforts were successful for the volume of water coming down the river system.
As seen in the imagery, the area downstream of the Logan River Golf Course experienced significant flooding. Darren Farar, an engineer for the City of Logan, explained that the Logan River peaked this spring at over 1,700 cubic feet per second. This was the largest flow in the river since 1986, nearly 40 years ago, but the river was still not as high as what might be expected for a 100-year flood. While flooding did occur in some areas, the peak flows were not as high as they might have been if the cool spring temperatures hadn’t kept that record snowpack from melting too quickly, and Farar was happy with how the river system performed as a whole.
“There will be some cleanup work to do, but with the river still flowing at higher levels we don’t know just yet the full extent of what flooding impacts will be,” Farar said. “City staff are already making plans and talking to state agencies regarding funding opportunities to help take care of the things we can.”
According to UWRL hydraulics engineer Brian Crookston, having these UAV images will aid in future flood management as well. The cities can use the data to improve models to better estimate potential future flows and plan for adequate prevention measures.
“You can help manage your risk by employing UAVs during floods,” Crookston said. “The more that we can characterize the water and how it’s moving, the better we can predict actual flooding potential on the river through modeling.”
These models can then become the basis of decision-making for zoning, municipalities, bridges, roads and more.
Crookston and a Ph.D. student are working to model hypothetical flooding situations and climate change scenarios. Crookston is hoping to continue collaborations with both cities to try to maximize the usefulness of their research efforts.
Logan also sent out a team of engineers and interns to survey the flooding limits on the same day AggieAir took to the sky. The combination of these two data sets will enable the city to more accurately calibrate their flood model.
“Ian and the AggieAir team were fantastic to work with,” Farar said. “This calibration will help us verify that we aren’t asking too much or too little of properties that are located in our floodplains. It will take some time to process everything, but it’s a step in a positive direction.”
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