You may not be able to predict when it’s going to flood in Raleigh, but you probably have a pretty good idea where it will flood.
Call them the usual suspects, those low-lying areas, usually near Crabtree and Walnut creeks, that reliably get inundated when rain comes down hard.
Now the city Stormwater Management Division is trying to keep a better eye on those places, using sensors tied to warning signs and remote cameras. The new system lets the department monitor flood-prone areas from a single computer and notify the police and fire departments when they’re needed to reroute traffic or help people who are stranded.
“These cameras are real time,” said Wayne Miles, the city’s stormwater program manager. “We can look at what’s happening right now.”
The idea for using cameras to monitor flooding came up last year during Hurricane Florence. As city officials gathered in the emergency operations center, members of the stormwater division noticed the city had dozens of cameras trained on intersections to monitor the flow of traffic.
As stream gauges showed Crabtree Creek rising, Miles said his team asked the transportation department if they had a camera they could point to where the creek passes under Wake Forest Road. It did, though the camera was more than a block away.
Now the Stormwater Management Division has access to 108 traffic cameras plus 16 new ones installed over flood-prone streets, including one near the Wake Forest Road bridge over Crabtree Creek. The cameras can be moved remotely, so the city can zoom in on the creek or tilt and pan to look for signs of flooding in all directions.
The cameras are meant to augment the network of gauges along Walnut and Crabtree creeks that the city and the National Weather Service use to monitor flooding. There’s a lag time of up to 15 minutes in the readings those gauges provide, Miles said, and not all flooding in the city comes from streams spilling over their banks.
The cameras have already been used twice this month, says Kelly Daniel, who calls the images up on his computer when the city gets a heavy rain. In both cases, it wasn’t a stream that was flooding, but rather overwhelmed ditches and storm drains. Daniel saved images from Glenwood Avenue at Ebenezer Church Road on Aug. 5 and on Creedmoor Road next to Crabtree Valley Mall on Aug. 16.
“We wouldn’t know about this by monitoring a stream gauge,” he said. “The only way we would know about this is having a camera or a person physically out there.”
While Daniel can save a screen shot from the cameras, the system isn’t recording video, Miles said.
“The video isn’t going into a database we can go back and get for any reason,” he said. “Like if a crime happened, we wouldn’t be able to go back and look at them.”
Automatic warning signs
In addition to the cameras, the stormwater program is installing 10 “High Water” warning signs that will light up when nearby sensors detect rising water. The sensors will also notify the city when the signs have been lit, so staff members can send police or firefighters if needed.
The city has also hired a contractor to develop a computer model using historic rainfall and flooding data that can be used to predict future flooding based on the forecast.
Before Hurricane Florence, the city called and emailed every household living in a flood plain to warn them about potential flooding. Miles said the computer model might allow the city to pinpoint where to send those warnings.
Miles said just about every time a road floods in Raleigh, someone drives into the water and gets stuck. The cameras and warning signs should make that less likely, he said, but that’s up to the drivers.
“We’re doing our best to keep people safe by educating them, by notifying them, by putting up all these warnings,” he said. “But ultimately the decision to stay safe is up to them. They need to respond to the warnings.”