At one point during last month’s Hurricane Florence, a storm surge completely cut off the city of Wilmington, North Carolina, and its nearly 120,000 residents from the outside world. People desperate to return to their homes via Interstate 40 – the main highway leading into Wilmington – were confronted by an ocean that seemed to stretch to the horizon.

Estimating the scope of the flood was impossible from the ground, and helicopters were tied up with search-and-rescue missions. But officials at the state’s Department of Transportation had a new tool to assess the damage and reopen thoroughfares into the city: drones.

Surveillance videos captured by drones revealed that four miles of highway was submerged, making it impossible to reopen until floodwaters receded. DOT officials used that intelligence to set up an alternative route through Jacksonville, reuniting victims with their homes and loved ones more quickly.

Florence was one of the biggest tests yet of drone technology as a disaster recovery aid. In the aftermath of Florence, the North Carolina DOT flew 253 drone missions, capturing 2,600 photos and videos of flooding and infrastructure damage across the southeastern part of the state. Although it’s impossible to say if lives were saved, there’s no question that the quad-copters improved the efficiency of recovery operations, got people home sooner and gave residents and a worldwide audience a first-hand view of the devastation.

“We didn’t realize how big an impact they’d make,” said Basil Yap, program manager in the Unmanned Aerial Systems division of the North Carolina DOT.

The state had started preparing for post-disaster drone deployment after Hurricane Matthew slammed into the southeast coast two years ago. North Carolina is one of 10 states selected for participation in the FAA’s Integration Pilot Program, which seeks to find safe and effective ways to integrate drones into low altitude flight operations. Matthew made it apparent that disaster recovery would be a prime use case.

The equipment the department acquired from Raleigh-based PrecisionHawk Inc. is nothing like the plastic toys people play with in their back yards. The untethered 55-pound birds can fly for 40 minutes in winds of up to 40 miles per hour. Onboard cameras deliver live streaming video (pictured, bottom), which turned out to useful for both field diagnostics and public relations.

Dashboard software from AirMap Inc. provided visual airspace and flight information to keep emergency responders aware of traffic in managed airspace. Visuals captured with drones were also posted to social media so locals could see how their neighborhoods were affected.

Tricky operation

Sending a fleet of more than 30 drones into the skies amid the tumult of post-hurricane cleanup is no simple matter. Even at the 200-foot altitude permitted under FAA rules, there’s a risk of collision with the low-flying helicopters that were plucking people from the roofs of their houses. That’s one reason the state limited the drone deployment to infrastructure monitoring and left search-and-rescue to the copters. “We knew if a helicopter operator saw a drone he’d get very nervous, and we didn’t want that,” Yap said.

More stunning #drone images of #FlorenceNC flooding, these are of Chinquapin & N.C. 41.
📸: @ncaviation pic.twitter.com/5ZE0nKh236

— NCDOT Southern Coast (@NCDOT_Scoast) September 21, 2018

Officials said their eyes in the sky had value beyond identifying blocked intersections and washed-out roads. Post-storm damage assessment can expose first responders to peril as they venture into flooded areas. “Although on the surface these waters look calm, there can be unknown drops where vehicles can be swept away,” said Glady Singh, vice president of enterprise services at PrecisionHawk and the company’s project lead with the North Carolina DOT. Athough drone operators still have to travel into the field, they can set up in a safe spot and let their flying companions do most of the hard work.

One of the areas of greatest impact was managing traffic on detour routes, Yap said. The drones helped officials guide supply trucks and first responders to safe routes and quickly set up detours if conditions deteriorated. Officials could also see if traffic was building up on a detour route and adjust light cycles or position state troopers to direct traffic. “In 15 minutes we could assess the situation and make decisions to get traffic moving more quickly,” Yap said. “That was repeated again and again.”

Airborne images posted on the Division of Aviation Twitter stream also became a magnet for local residents trying to gauge the situation in their area. That probably saved lives. People who can see the extent of flooding ahead of them are less likely to drive around road stops and get themselves in trouble, which is a common risk in flood situations, Yap said. Social media images “helped alleviate some of the complaints and questions we usually get about why people couldn’t get around,” he said.

In this case, drones were basically used as flying cameras, but new technology is coming that will enable more sophisticated diagnosis, Singh said. For example, LiDAR-equipped drones can enable volumetric analysis of debris and heat signature detectors can indicate locations where people may be trapped.

Still, drones aren’t appropriate for every scenario, Yap noted. Current models can’t operate in gale-force winds and untethered drones must return frequently to base for fresh batteries. The units the DOT chose are weather-resistant, but they aren’t fully waterproof. “We’d like to have weatherproof drones that get into the storm quicker,” he said.

Nevertheless, drones are destined to become a staple of the state’s disaster-recovery arsenal — if one that officials hope they seldom have to use.

Photo: North Carolina Department of Transportation