The Iowa Flood Center’s stream-stage sensors, mounted on bridges around the state, proved their resilience last week when floodwaters swept through Eastern Iowa. Last Wednesday, at least two of the IFC sensors in the Clear Creek watershed seem to have been overtopped by floodwaters and survived to send more data once the water receded.

The boxes housing the sensors are designed to be submerged in water and still function after the water subsides, says IFC Director Witold Krajewski. “Now we have field proof that the design was successful,” he explains. While the sensors are underwater, they stop sending data. Users of the Iowa Flood Information System (IFIS) will note this absence of data as a white or blank space in the graphic representation of the water levels (see image below).

Gaps in recorded data from this gage over Clear Creek indicated the sensor could have been submerged in floodwaters during heavy rains on April 18, 2013.

Krajewski says that he does not have complete proof that the sensors were submerged, since the sensors do not “see” the distance when water levels are closer than about a foot from the sensing unit. Despite this, he believes the pattern of the reported data strongly suggests that they were in fact underwater.

If you have photos taken during the recent flood event that show the IFC sensors or their bridges actually underwater, please send them to sara-steussy@uiowa.edu.