By Mike Ekberg, Manager of Water Resources Monitoring and Analysis
Southwest Ohio is getting wetter—and the Miami Conservancy District’s flood protection dams are working harder than ever because of it.
Since their construction nearly 100 years ago, these dams have done exactly what they were designed to do: protect our communities from catastrophic flooding. But with climate change bringing more frequent and intense rain, the question is worth asking—can the system handle it?
The answer, so far, is a resounding yes. And here’s why.
A Wetter Climate Is Our New Normal
Average annual precipitation in the Miami Valley has increased significantly over time. From 1951 to 1980, the 30-year average was about 37 inches per year. Fast forward to the most recent 30-year period (1991–2020), and that number jumps to nearly 42 inches—a 14% increase.
Nearly every month of the year has seen a rise in average rainfall, with October increasing more than 30%. More rain means more runoff, and more runoff means more demand on the dams to store water.
Storage Events Are on the Rise
When river flows reach levels that could cause flooding, MCD dams automatically go into action to hold back water. These instances are called storage events.
MCD tracks each storage event individually for all five dams. So if all five are storing water at the same time, that counts as five separate events. A storage event ends when a dam releases all of the floodwater it was holding back.
Here’s what we’ve seen over the decades:
Before the 1990s, no decade had more than 200 storage events.
In contrast, each of the last three decades has seen more than 200 events, with the 2010s topping 300.
Clearly, the system is working harder—and more often.
Bigger Storms, Bigger Storage
It’s not just the number of storage events that’s increasing. Some of them are huge.
We rank events by the total volume of water held back across all five dams. And the data shows that 32 of the 100 largest events on record have happened in just the last 20 years.
The decades of the 2000s and 2010s each saw 16 events rank in the top 100, rivaled only by the 1950s—which included the largest event ever recorded: January 1959.
Built for Big Water
Here’s the good news: MCD’s flood protection system was designed with extreme events in mind.
It’s built to withstand 40% more runoff than the historic 1913 flood (which equates to 11–14 inches of rain over just three days). Even during the massive 1959 event, the dams stored 44.8 billion gallons of water—just 16% of their total storage capacity.
That means 84% of the capacity remained unused—ready and waiting for the next big one.
Resilience You Can Count On
The climate is changing. Flood risks are increasing. But the MCD flood protection system remains strong, capable, and resilient—thanks to a design that has stood the test of time and the foresight of those who built it.
It’s working more often. It’s handling bigger events. And it’s still protecting the Miami Valley—just as it has for the past century.
Want to learn more about how the flood protection system works? Explore the integrated flood protection system:
