Next Wave of Stream-Stage Sensors

by Shianne Gruss

IFC stream-stage sensors have proven they're tough enough to withstand being inundated by floodwaters.

IFC stream-stage sensors have proven they’re tough enough to withstand being inundated by floodwaters.

For Iowa City residents and University of Iowa students, it’s impossible to forget the floods of 2008 – not with more than a dozen different flood mitigation and recovery projects underway across campus.

Luckily, the Iowa Flood Center (IFC) continues to work hand in hand with the Iowa Department of Natural Resources to better inform citizens of Iowa City, and countless other communities across the state, of potential flooding.

The IFC stream-stage sensors, an idea pioneered by both UI engineering students and faculty back in 2010, have been an “overwhelming success,” says Dan Ceynar, an IFC engineer.

Of the 100 sensors funded by the DNR, the first 50 sensors installed have been revisited just once or twice for minor updates. The majority of the more recent sites, however, have never required a follow-up visit.

“When the IIHR approached the DNR about the stream-stage sensors that they developed, we felt it would be a great way to see if the information provided by the stage-sensors would fill in some of the information gaps, especially for local emergency managers and having time to respond to a potential flood event,” says Lori McDaniel, supervisor of the DNR’s Division of Flood Plain Management, Dam Safety, & Water Quality Standards.

Several stream-stage sensors await submersion in a wet tank in the IIHR Hydraulics Wind Tunnel Annex to be tested for leaks.

Several stream-stage sensors await submersion in a wet tank in the IIHR Hydraulics Wind Tunnel Annex to be tested for leaks.

The sensors, priced at $3,500 apiece, are a system of electronics, modems, and antennas encased by weather-resistant aluminum and installed on the downstream side of bridges. Each sensor emits an electronic pulse to measure the distance to the water below and sends that data via cell modem to a central database every 15 minutes.

Earlier this spring, about 15 sensors sat submerged in a wet tank, being tested for leaks, in the IIHR Hydraulics Wind Tunnel Annex. With more than 50 more in progress, Ceynar estimates the IFC has built a total of 250 sensors, most of which are the new and improved models.

These second-generation sensors measure distances of roughly 44 feet, 10 feet more than the first batch. The improvement was necessary for bridges more than 20 feet in height. The newer sensors have also shed their radio-like communication capability — a feature Ceynar says went virtually unused.

While the majority of the sensors were installed at request of the DNR, many Iowa municipalities, counties, colleges, and universities have asked the IFC to install sensors of their own — and the list keeps growing. Even state and federal agencies, such as the Iowa Department of Transportation and the National Weather Service, have had sensors installed at various locations.

“I use gauges as one of my agency’s tools to prepare for and predict rising water levels, which in turn causes a list of various actions to take place,” says Larry Hurst, director of Mills County Homeland Security & Emergency Management Agency. “[I] would actually like several more units installed in my county.”

Although the IFC is the only academic flood center in the nation, it functions as a non-profit and must approach partnerships with caution, says Ceynar.

“The IFC bridge sensors receive quite a bit of interest from other states, as well as from other agencies and engineering companies as far away as Australia,” says IFC Director Witold Krajewski. “While currently we have no plans to create a for-profit company that would market the sensors, we feel that our impact would be greatest through some kind of a national or regional flood research center. We are exploring different avenues toward this.”

Citizens are encouraged to use the Iowa Flood Information System (IFIS), an online maps-based application, to view the stream-stage information for their area.