By Gregg Hennigan
CEDAR RAPIDS, Iowa – It was anxious times for some Butler County residents last week.
The Shell Rock River – which had a history of minor flooding before it “ran wild” in 2008, according to Mitch Nordmeyer, the county’s emergency management coordinator – was above flood stage.
Nordmeyer was able to use a new tool at his disposal to get a better look at the 30 miles of the river running through his county and ease those concerns.
Sensors developed by the Iowa Flood Center that show the water level have been placed on three bridges along the Shell Rock in Butler County, north of Waterloo. Additional ones are in other communities farther upstream.
They were among 50 sensors installed statewide last fall as part of a joint project between the Iowa Flood Center and the Iowa Department of Natural Resources. The hope is to install many more to allow for better, and more affordable, real-time monitoring of flood conditions.
The sensors use sonar to measure the distance to the water’s surface, thus showing how high the water is, and send reports every 15 minutes to a database at the center’s headquarters on the University of Iowa campus.
That information, in turn, is available on a map on the center’s website. Local officials have to go and physically look at spots where sensors or gauges are absent.
Nordmeyer had to do that for the Shell Rock River in the past, but last week he used the website and assured people the river was dropping. Some people, pointing to the river’s height, remained skeptical.
“I said, ‘Trust me, the sensors are reading the river and it’s actually starting to drop,’” Nordmeyer said. “So it was able to give people a sense of comfort.”
The river was soon back below flood stage.
The floods of 2008 showed there was a need for a more comprehensive network of river and stream gauges, said Larry Weber, director of the UI’s IIHR-Hydroscience & Engineering.
Iowa has about 150 gauges overseen by the U.S. Geological Survey, but these are mostly on rivers and larger streams. They also are expensive, costing about $15,000 to install and another $15,000 a year in maintenance, said Chuck Corell, the DNR’s water quality bureau chief.
The flood center’s sensors cost $3,500 each and require little maintenance. The DNR paid for the first 50 at a cost of $175,000. It would like to buy more, Corell said, but is waiting to see what its budget will be next fiscal year.
The sensors are about 12 inches by 18 inches and are bolted to the side of a bridge. They’re powered by a solar panel and a 12-volt battery, said Jim Niemeier, an electrical engineer doing postdoctoral work at the UI who helped develop the sensors.
They have a small microprocessor in them that gathers the information, bundles it and transfers it using a cell modem to a database at the flood center, he said.
The relatively inexpensive cost makes it more realistic to put the sensors on smaller streams near smaller communities, Corell said. As people learned in 2008, streams and creeks can cause a lot of flooding, too.
The cheaper price tag also allows the sensors to be used to create a network. Like on the Shell Rock River, there can be a series of sensors, which lets officials watch the water move downstream and better forecast when flooding may hit an area.
“That’s the real value of these stage sensors, is that you get real-time information on what’s happening upstream on that smaller stream where you don’t have that information otherwise,” said Corell.
The USGS gauges supply a lot more data, including the water flow and volume. But during a flood, water height is paramount, said Witold Krajewski, director of the Iowa Flood Center and one of the principal developers of the sensors.
“What you care about is the water is rising,” he said.
Officials believe the sensors and the website will be of great value during flooding. The website incorporates a weather radar to capture a storm in progress and has an easily understandable graphic showing what’s happening at the location of each sensor.
Krajewski said no forecast is perfect, but imagine if in June 2008 people in Cedar Rapids could have received real-time data from a network of sensors that showed floodwater would arrive in three days.
“We couldn’t stop the water, but certainly we could lessen the damage,” he said.
Weber said the sensors also are providing data that will help the center calibrate its flood models. Krajewski said the National Weather Service recently inquired about getting access to the database.
The DNR contacted county officials throughout Iowa to see who was interested in the initial 50 sensors. Corell said some balked because the county would have to pay for a cellphone plan for each sensor, which use a cell modem to transmit the data
The flood center is picking up the cost of that for now at about $30 each a month, but next year local governments may be asked to contribute, Krajewski said.
Corell hopes that once other communities see the benefit of the sensors, they’ll want them. Butler County’s Nordmeyer would provide a testimonial.
“I think it’s one of the best things the flood center and the DNR have ever done,” he said.