Remnants of Hurricane Ian will test NCDOT’s new flood early-warning system for roads

The remnants of Hurricane Ian are expected to provide the first real test for the state’s new flood early-warning system for roads, bridges and culverts.

The N.C. Department of Transportation and the state Division of Emergency Management have developed systems that use about 400 stream gauges, rainfall data, software and computer models to show where road flooding is likely to happen in advance and to monitor flood waters at key locations in real time.

NCDOT will use the information internally to decide where and when to close roads and to alert first responders and the public, said spokesman Andrew Barksdale.

“It’s just a lot more data at our fingertips so we can make decisions and deploy resources more efficiently and ultimately save lives,” Barksdale said.

NCDOT won’t rely on gauges alone to determine when to close a road, but the system will help the department decide where to send people and equipment. NCDOT will still count on its employees or local authorities to confirm that a road or bridge is flooding before broadcasting it on social media or, the department’s statewide traffic management system.

Still, the data should help NCDOT get closure information out faster, Barksdale said.

NCDOT and Emergency Management put the new system in place last spring but haven’t seen how it works in a big storm yet. Hurricane Ian is expected to slam the Florida Gulf Coast starting Wednesday, then weaken as it moves north through Georgia into the Carolinas.

Forecasters expect the storm will bring potentially flooding rains to North Carolina on Friday into Saturday. The storm’s exact track and intensity remain uncertain, but forecasters say anywhere from 2 to 7 inches of rain are possible in central and eastern North Carolina.

The early-warning system for roads is similar to the Flood Inundation Mapping and Alert Network or FIMAN that the state developed for buildings several years ago. FIMAN-T, as the new system is called, takes data from rain and stream gauges, folds it into models that predict flooding and then shows on maps what’s expected to happen on the state’s streets and highways. The system covers about 3,000 miles of road so far, mostly east of the Triangle, but will grow as more gauges are installed.

NCDOT and Emergency Management also have developed a system that monitors rainfall data generated by National Weather Service radar. The system alerts NCDOT when the volume and intensity of rain reaches levels that historically cause flooding at particular bridges and culverts, helping the department prioritize which ones to monitor and potentially close.

That part of the system allows NCDOT to monitor potential flooding at about 4,000 bridges and culverts statewide, Barksdale said.