“The more we know where there are flood risks, and the more often those flood risks occur, that gives us indications that we do have a problem here,” said George Remias, manager of stormwater strategic support at the Northeast Ohio Regional Sewer District (NEORSD). “And as we look at those solutions, the more that we can reduce that risk, the more value that project is, and it helps us prioritize those projects across the board.”
The sewer district, which serves 57 member communities across about 374 square miles — and multiple watersheds — includes a population of about 1 million people. It uses a network of technologies to measure, monitor and analyze rain events to distill an improved understanding of their impacts.
In August 2024, Tropical Storm Debby impacted only a small percentage of the NEORSD service area. However, in that area, the impact amounted to a 1,000-year-level rain event.
“Most of the rest of our area received almost nothing. It was like a light drizzle. So being able to have such a widespread understanding of where the rainfall is really helps tell the picture,” Remias said.
NEORSD uses technology from AEM, an environmental technology company that has developed a technique using both rain gauges and radar, called Gauge Adjusted Radar Rainfall (GARR), to understand rainfall throughout its coverage area. The sewer district has 40 rain gauges positioned across the service area, which report not only how much rain as fallen on an area, but how quickly. NEORSD also has a number of flood monitors, officials say, which can generate alerts in real time.
“GARR takes advantage of the accurate at-a-point measurement of rain gauges and the spatial variability of radar to produce an accurate rainfall measurement across an entire region,” James Logan, AEM water sector and professional services leader, said in an email. “It effectively creates the equivalent of a 1-kilometer by 1-kilometer grid of rainfall data across the region.”
This technology not only covers NEORSD’s 374-square-mile service area, but also the watersheds of which it is part, making the coverage 1,300 square miles at a 1-kilometer-square scale, Remias said.
“So it gives you a much more granular understanding of where some of these storm events may have occurred. And it really helps us understand some of those storms we may have not captured with our rain gauges because the rain can travel and not necessarily hit those rain gauges,” he added.
This detailed and layered understanding of rainfall across the region is shared with member communities, allowing them to send alerts — often in real time — to residents and businesses, giving them actionable data. The sewer district also shares data with the National Weather Service, boosting its already formidable forecasting muscle.
“We’ve kind of formed this Northeast Ohio storm event collaborative, which is really local, regional, state and federal folks that respond to storm events,” Remias said of the culture of data sharing that has taken root. “With the whole goal of having free-flowing data sharing in the event of a storm. Because everyone has their own little ‘hundred acre woods,’ you can say. And you want to be able to make sure that they have access to whatever information could benefit them.”
As extreme weather events grow in frequency and strength, emergency operations officials and others will require improved data and analytics to plan for and mitigate the impacts of flooding, industry experts say.
“The more accurate rainfall data produced by GARR allows engineers to correctly design, model and optimize stormwater, sewer, flood forecasts, water resource management, agriculture systems,” Logan said. “The resulting systems save lives, save money, and make us more resilient during extreme events.”
