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OKI Wanna Know: What's in that shaft on the Roebling Suspension Bridge?

A view of the Roebling Suspension Bridge from the northwest, including the concrete shaft. A ferry is docked beneath it, waiting to take on passengers on a sunny day.
Bill Rinehart
The concrete shaft starts under the water level, and rises to meet the pedestrian walkway on the Roebling Suspension Bridge.

Our feature OKI Wanna Know seeks to satisfy your curiosity about our area. We try to answer the questions you're not sure who to ask. This week, we look at one of the regions most iconic landmarks.

The Roebling Suspension Bridge has been featured in corporate logos, postcards and loads of videos. It has sandstone towers, blue cables and a necklace of lights.

There's one feature that has Tom Blumena confused. On the west side of the northern tower, there's a concrete shaft from the water reaching up to the pedestrian walkway. He wants to know, what's in there?

If you're hoping the shaft contains a ladder down to a secret underwater fortress, you're going to be disappointed.

Jeff Woods is a supervisory hydrologist with the U.S. Geological Survey. He says the shaft houses equipment used to measure the height of the Ohio River. A float and a counterweight are attached by steel tape to a pulley wheel. The wheel's movement clockwise, or counterclockwise, determines if the river is rising or falling.

"It's a relatively empty room. What's going to be inside is a small electronic box that collects the data from the instrument itself which is measuring the water level."

Woods says the shaft and the measuring equipment were installed in 1946. They were added to the north tower because it's farther from the mouth of the Licking River.

"If you're having multiple contributing rivers coming together, there's going to be a lot of eddys, maybe turbulence, it's going to cause fluctuations in data that are not otherwise maybe not representatives of the larger body of water itself," he says.

The data is transmitted via satellite to a server in North Dakota, which puts the information on the world wide web. The data is also sent to the National Weather Service office in Wilmington, Ohio.

That's where hydrologists like Julie Dian-Reed study the numbers, using them to make predictions about river levels, flooding and more.

"We monitor the river levels and we also include future rainfall, so we have different models — hydrologic and hydraulic models — that we use in putting the future rainfall, using the current river levels that are expected, both the river height as well as the volume of water."

Dian-Reed says predicting river flow requires math, some physics and a lot of data points.

"We take into account how much rain has fallen, and we utilize radar-estimated rainfall, as well as automated and manually read rain gauges," she says. "So anybody who has an interest in providing rainfall data, we will take it. We estimate the volume of that rainfall and estimate what it will do to the Ohio River and other rivers in the area."

The estimate includes what's coming from the Monongahela and Allegheny rivers in Pittsburgh. It adds the flows from the Scioto and Licking rivers, and other tributaries. There are hundreds of flood gauges, along the Ohio River, its tributaries, and in small streams that feed into those. Dian-Reed says the hydrologists also have to pay attention to what the Army Corps of Engineers is doing.

"They have certain what they call flood control reservoirs — think of things like East Fork Lake, Caesar Creek Lake," she says. "Their primary purpose is flood mitigation."

The Army Corps uses those reservoirs to hold water back when the Ohio River is already running high.

Dian-Reed says the water level predictions help entities like the Metropolitan Sewer District get out ahead of flooding.

"Historically with flooding along the Ohio River in the Cincinnati area, thinking back to the floods of 1913, the floods of 1937, the greater damage actually occurred not necessarily on the riverfront itself, but up on the Mill Creek."

A high flow prediction means the Metropolitan Sewer District can stop water from backing up into the Mill Creek and damaging its facility in Lower Price Hill.

"They worked with the U.S. Army Corps of Engineers and built the Mill Creek Barrier Dam and channelized the lower area of Mill Creek to prevent that backwater flooding from happening."

The predictions also mean Covington and Newport know when to close their floodgates ahead of high water.

Woods with the U.S. Geological Survey says even without flooding, commerce needs to know how high the water is. "The barges and river traffic are going to want to know when it's too high to actually clear the bridge."

If you have a question about the area that no one else has an answer for, ask OKI Wanna Know by filling out the form below.

Bill Rinehart started his radio career as a disc jockey in 1990. In 1994, he made the jump into journalism and has been reporting and delivering news on the radio ever since.