July 25, 2006
Charlotte NC—Charlotte-Mecklenburg Storm Water Services has fixed problems with its automated Flood Information & Notification System (FINS). Both the primary and backup systems are now working as designed.
The system is designed to notify fire departments, first responders and other emergency personnel to the possibility of flooding at ten specific flood-prone locations. But several technical problems and human errors prevented the FINS system from working during heavy rain on Saturday, July 22.
Mitch Combs, Associate Engineer with Storm Water Services, says a lightning strike occurred the morning of July 22 at the U.S. Geological Survey offices in Charlotte. That strike knocked out DSL lines used to transmit data to USGS from more than 100 rain gauges and stream gauges around Charlotte-Mecklenburg. The service interruption automatically prompted the FINS system to revert to its backup mode which relays the data through an antenna on top of a downtown building. However, that antenna had been hit by lightning about three weeks ago and was not working.
The lightning strike that damaged the antenna also damaged two computers used by Storm Water Services. Data had been loaded into new computers, but the data contained an error that prevented the computer from notifying Storm Water Services staff that data was not being transmitted either by the primary system (USGS' DSL line) or the backup system (antenna).
Storm Water Services spent Monday assessing the reasons the notification system didn't work and finding solutions. The damaged antenna has been replaced. A lightning protection device and additional battery backups have been added. Data errors in the new computers have been corrected. USGS has also agreed to telephone Storm Water Services whenever there is a data interruption, rather than rely on automated technology.
"We sincerely regret the property losses and difficulties experienced by residents along sections of Stewart Creek," says Combs. "However, it's important to remember that, even if the notification system had been working at 100%, it would not have informed emergency responders of problems at the headwaters of Stewart Creek."
The automated warning sensor closest to the flooding was several miles downstream, at Stewart Creek and Freedom Drive. Combs says water did not reach flood stage at that location. Even if fire crews had responded to the Freedom Drive sensor and inspected the immediate area, they would not have known to go several miles upstream where flooding was forcing people from their apartments.
"The FINS system only has ten automated warning sensors throughout the County. They are in areas previously identified as most vulnerable to flooding. Those ten sensors can't track potential flooding in every part of Charlotte-Mecklenburg. Because of that, residents who see streams rising rapidly or see street flooding need to call 911."
Combs says the automated system to notify emergency responders is now stronger than it was. That's because Storm Water Services has corrected problems and vulnerabilities discovered over the weekend. Rain gauge and stream gauge data from the weekend downpours will be analyzed in detail to help determine priority locations for future automated warning sensors.