That’s due to an average increase of nearly 5 inches in annual rain and snow, a 14% increase, said Mike Ekberg, water monitoring and analysis manager at the Miami Conservancy District.
Raw data aside: “It just seems like we have way more high-water events than people who have been around a while remember,” Ekberg said.
That increase in rain and snow matches up with more than a century of statewide data and is a sign of climate change.
“This falls in line with what we would expect in a warming world,” Ekberg said.
Built after the Great Flood of 1913, the system now protects roughly 1 million people and more than 47,000 properties in Butler, Hamilton, Miami, Montgomery and Warren counties.
Of the top 100 storage events, almost a third occurred in the past 20 years.
“As we compile all the numbers and look at trends, we see it’s really increasing,” Ekberg said.
The decades of the 2000s and 2010s each had 16 storage events that ranked in the top 100. Only the 1950s, with 14 storage events, comes close.
In January 1959, 5.6 inches of rain ran off frozen ground — and despite the dams — caused widespread flooding, which forced evacuations, closed schools, destroyed property and took at least two area lives, according to Dayton Daily News reporting.
But due to the dams, Dayton was spared widespread devastation like that from the 1913 flood, which covered parts of downtown with up to 20 feet of water and took 360 lives.
The conservancy district has not modeled how the more recent large events would affect the region without the flood control system, but Ekberg said Dayton and other communities would probably not have emerged unscathed.
“The January 1959 event and some of the more recent storage events such as January 2005 and December 2013 likely would have resulted in some level of flooding in downtown Dayton and other communities along the Great Miami River,” he said.
Warmer, wetter
MCD currently collects precipitation data from 42 observer stations throughout the basin, some of the readings going back nearly 100 years.
“Every day, every month, we have years and years and years of it,” Ekberg said.
Warming temperatures and an increase in precipitation is seen not only in the Miami Valley, but across the state, said Aaron Wilson, an atmospheric scientist with the State Climate Office of Ohio with a joint appointment with the Ohio State University Extension.
Statewide, eight of the top 10 warmest years have occurred since 1990, as well as 80% of the wettest years, including 2017, 2018 and 2019, Wilson said of data dating back to 1895.
A changing climate impacts differing geographic regions in divergent ways, Wilson said.
“It looks different depending on where you are in the world,” he said. “Wildfires and droughts out West; we know that our strongest hurricanes are increasing in intensity; … here in the Midwest and the Northeast, one side is the extreme precipitation.”
The effects of climate change aren’t smooth or gentle, said Shuang-ye Wu, an associate professor at the University of Dayton and chair of the Department of Geology and Environmental Geosciences.
“Instead, a warmer climate means there’s more energy in the climate system and what we’re going to get is much more erratic climate patterns — both with temperature and precipitation,” she said.
And all precipitation is not equal, Wu said.
“We’re going to see less light rain, but we’re going to see a lot more increase in heavy precipitation,” she said. “We have already seen a dramatic increase in extreme precipitation.”
While average precipitation for Midwestern states has increased roughly 5-10% since 1950, extreme precipitation events are up 30-40%, according to Wu’s research.
“That’s a big difference,” she said.
More precipitation falling as heavy rain in the winter and spring when the ground might be already saturated by melting snow is a recipe for flooding and why major floods tend to happen in February and March, Wu said.
But the same changes fueling more precipitation in some months are making others drier, Wilson said.
“We’ve intensified not only the heavier precipitation, but we’ve intensified the droughts as well — the drying side. And now we can dry out very rapidly at the height of the summer because of warmer temperatures,” he said.
The conservancy district’s records show August is the only month precipitation declined over the study period.
“That’s not an anomaly in what we’re seeing,” Wilson said. “If you look across the state, there are areas actually seeing declines in precipitation during July and August.”
From an agricultural standpoint, farmers are experiencing wetter planting seasons and wetter harvests, Wilson said, while the growing season is plagued by water shortages.
The risks extend to urban and suburban areas, Wilson said.
Ohio’s major cities could more frequently become “heat islands.” More homeowners’ gutters will overflow and basements flood while municipal storm systems are overburdened, Wilson said.
“It impacts every single sector of our economy, agriculture, engineering, construction, insurance, there’s just so many different aspects of what we’re seeing. And the impacts are right here locally in the Miami Valley,” he said.
Built to withstand challenge
A community effort after the 1913 flood led to the formation of the Miami Conservancy District in 1915. The engineer Arthur Morgan designed the system built between 1918 and 1922 that included the five dry dams and 43 miles of levees and channel improvements.
The system protects towns up and down the region’s drainage basin including Piqua, Troy, Tipp City, Dayton, West Carrollton, Miamisburg, Franklin, Middletown and Hamilton.
The flood control system has never been taxed to its limit. Despite the severity of the 1959 event, just 16 percent of the five dams’ total storage capacity was used, according to Miami Conservancy District records.
“The good news is that our flood protection system is probably in a pretty good position to deal with the challenges that climate change brings our way,” Ekberg said.
But that doesn’t mean climate change isn’t having an impact on the district’s infrastructure and operations.
More high-water events put more stress on the dams and concrete armoring on levees, Ekberg said.
Though it’s difficult to determine just how much wear and tear can be attributed to an increase in high-water events, “a concern would be that there is an added cost over the long run,” he said.
Since most of the high-water events occur in winter and early spring, recreational paddlers brought out during warmer months have been little-impacted. Year-round runners, bicyclists and walkers, however, are finding lower trails underwater more frequently.
Once water recedes, the lower trails are typically covered with mud and debris, Ekberg said.
“It just means that there’s more work, more labor to keep the trails open,” he said. “There’s going to be a cost involved in that.”
The region, though, is prepared to weather the most serious consequence of increased precipitation caused by climate change, Wu said.
“We have this really splendid flood control system that has protected us and is likely going to continue to protect us in the future,” she said. “But other places and other people may be less fortunate.”
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