The North Carolina Department of Environmental Quality’s Dam Safety Program recently received the Southeast Regional Award for its work pioneering and implementing internal software programs and studies to monitor dam infrastructure across the state.
The Association of State Dam Safety Officials awarded the program at their annual September conference in Baltimore. The Dam Safety Program is a part of the Department of Environmental Quality’s Energy, Mineral and Land Resources division.
North Carolina’s Dam Safety Program has “initiated several innovative projects to provide for the safety of dams, reduction of risks and benefits for the state,” according to the ASDSO.
State Dam Safety Engineer Josh Colley said taking a risk-based approach to dam safety is relatively new.
“We have been working to start up that process as part of our inspection routine,” Colley said.
One risk-based approach being implemented in the program is the Semi-Quantitative Risk Assessment method. In the next upcoming dam inspection season, items on a tech-based safety checklist will be evaluated and then scored based on their condition.
“There’s an overall score that’s computed for that particular dam,” Colley said. “We can use that as a rough estimate of the potential probability of failure for that dam.”
Colley added that this is a new process still being refined.
Another software being developed and used for internal purposes at the DEQ is Dam Watch. The software uses stream gauges and data from overtopping studies, allowing officials to set a threshold for each dam. When a water basin receives a forecast at this level, an alert is produced.
ASDSO President David Griffin said the Dam Safety Program’s use of tech to monitor and track dams is what set them apart.
“That gives them a way to pinpoint owners that they need to speak with or places they need to go inspect once a storm passes through,” Griffin said.
Alongside innovations in web-based software such as Dam Watch, the state has conducted hydrologic and hydraulic (H&H) studies on overtopping. The studies examined 530 dams in three different river basins in North Carolina.
This data will help determine threshold ranges for specific dams during Probable Maximum Precipitation (PMP) events, such as hurricanes.
Bill Kappel, president of Applied Weather Associates, said PMP is a representation of the theoretical upper limit of the most amount of rainfall that could occur at a given location at a given time of the year over a given area size.
Dam overtopping during these PMP events sometimes results in dam failure.
The state’s H&H studies have provided data that predict under which forecast scenarios overtopping may occur, which is when an increased volume of water cannot flow through the dam and spills over it.
“We can essentially use the forecast data to compare against overtopping studies to identify any dams that we think might be at risk of overtopping,” Colley said.
Colley also said they can then contact dam owners and ask them to start lowering their water level ahead of the hurricane to mitigate overtopping risks.
Alongside these H&H studies, the state secured funding for a new PMP study that will replace outdated maps with meteorological state data and consider the impacts of climate change.
Applied Weather Associates is conducting the study to produce new PMP maps for North Carolina, which will replace Hydrometeorological Report 51, published in 1978, Kappel said.
“That document is more than 50 years out-of-date, which causes some problems,” Kappel said.
An updated PMP map will include recent storms that will model any changes in climate that have occurred since the last PMP map was published. The map’s results will also influence state planning and infrastructure.
Griffin said engineering always looks for the best available data.
“We’re always going to be a little bit behind because we can’t update every study, every time a new piece of data pops up,” Griffin said. “So it’s just a matter of doing something similar to this PMP study to take information.”
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