An unsuspecting room in one of the fort Pitt Bridge's support beams, that residences the modern technology that procedures the river stage by the Point.

Pittsburgh is well-known for that is rivers. But many residents, like 90.5 listener Judith Hoover, aren"t certain where the bottom of each of the three lie.

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Hoover has actually a see of the Allegheny flow from her North next home, and also during job of heavy flooding this previous year, she and her husband watched the water level rise.

"And so that was due to the fact that of the flooding that we wondered how deep the water is, for all the rivers," Hoover said.

Wayne Grgurich, a listener native Lawrenceville and also an avid paddler, keeps an eye on the newspaper"s consistent listings of flow stages before he goes out on the water.

"I"m curious who actions them and also how they"re measured," that asked.

Experts who research bodies that water say "depth" isn"t exactly the exactly term, because the bottom that the flow is fixed but the level have the right to fluctuate. Instead, they usage the terms "river stage" and also "gauge height." Matthew Kramar, a meteorologist with the nationwide Weather Service, claimed to calculate the flow stage, it"s crucial to understand the volume at any type of given stretch.

"The lot of water that a segment of the river can hold is dependence on the width, height and length the the flow segment," Kramar said.

Imagine a four-lane highway. When it merges down to two lanes, website traffic will earlier up and slow down, since the same number of cars are trying to fit right into a smaller sized space. The river works the very same way. Together it narrows, water flow at the exact same speed will ago up and also the river stage will increase.

The various other measurement term, gauge height, needs to do through two permanent tools affixed come the fort Pitt Brige.


Credit catalent J. Davis / 90.5
The 2 gauges running down the support beam that the ft Pitt Bridge.
Jamie McCoy, a hydrologic surveilance regime chief v the U.S. Geological Survey, claimed the first gauge is dubbed the bubbler system. It"s a rusty pipe the runs under the next of a support beam right into the water, and also sits around a foot turn off the flow bottom. It forces compressed air down the pipe, and also released about 60 bubbles per minute.

"The sensor in there can tell the greater the pressure on the end of that orifice line, we recognize the press going up and also the river is going up," McCoy said. "If that pressure starts to decrease, the river is walking down."

McCoy stated this device is usually very accurate, within 2 hundredths the a foot. However, there"s a backup plan in instance the bubbler fails referred to as a non-contact sensor.

"And what that does is use a radar pulse," McCoy said. "Every 15 minutes it shoot a pulse, bounces turn off the river and also back, and also sends the elevation to a computer inside."

This is component of our great Question! series where we investigate what you've always wondered around Pittsburgh, that is people and also its culture.

The river stage in Pittsburgh is on average in between 16 and 17 feet, follow to McCoy, and also that level stays constant from the Point, to several miles ~ above both the Allegheny and Monongahela rivers, and also down the Ohio come the Emsworth Locks and also Dams in ~ Neville Island.

When the phase rises to 18 feet, the Mon kai parking lot of downtown starts to flood. At 22 feet, the 10th Street Bypass top top the Allegheny floods. In ~ 25 feet, the Parkway eastern that hugs the Mon wharf fills v water, earning the the nickname "the bathtub."


Credit kathleen J. Davis / 90.5
The gauge height reads at 17.21 feet on the bubbler system.
There room controls to keep the flow stage continual most of the time. It"s preserved most days in between 16 and also 17 feet many thanks to a device of locks and dams, which exists to help boats navigate the rivers.

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On the USGS website,river stage data is updated around every 15 minutes for both gauges. There"s a little windowless room in among the fort Pitt Bridge assistance beams that residences the tech and computers the ping the gauge height data.

McCoy said the USGS will certainly probably have actually real-time river phase data obtainable online in ~ the next few years. That way riverside residents, avid kayakers and curious Pittsburghers can examine on the condition of the rivers that make Pittsburgh the city of rivers.