From the Iowa Flood Center at the University of Iowa:
Stream Stage Sensors
The sensors were developed as a student project to design an affordable, yet effective way to measure stream and river heights. The sensors are solar powered and attached to the side of bridges. A sonar signal is used to measure the distance from the water surface to the sensor and data is transmitted via a cell modem to IFIS where the data is publicly available.
From The Fort Collins Coloradoan (Kevin Duggan):
As Thursday morning’s fog and autumn chill gave way to sunlight and intensely blue skies, Dan Ceynar of the Iowa Flood Center toiled to install a sensor on a pedestrian bridge over the Poudre River near Bellvue.
The sensor is different than conventional gauges along the river that rely on hydraulics to measure the height and flow of the water. This self-contained device uses a sound pulse to measure the distance between the water surface and the bridge.
“It’s basically an ultrasonic range finder,” he said. “We have it pointed at the water level, so what gets reported back is the elevation of the water above sea level. It’s an automated stage gauge.”
Measurements are taken every 15 minutes, day and night. The sensor is powered by a battery charged by a solar panel. It transmits signals using a cellular connection.
Ceynar is a project engineer with the Iowa Flood Center, or IFC, based at the University of Iowa…
About 250 ultrasonic sensors have been installed in Iowa, which Ceynar described as river-rich and flood-prone. The Bellvue monitor is the second to be placed outside the state…
Riverside has modeled maps along that stretch of the river that show where water would go in a flood event, said Sean McFeely, product manager for the company.
Data from the sensor will be used to refine the inundation maps. Coordinating data from the sensor with inundation mapping could have far-reaching ramifications, McFeely said. Project partners included Colorado State University and the University of Kansas.
At roughly $5,000 a piece, the ultrasonic sensor is significantly less expensive to build and maintain than hydraulic gauges, which require time-consuming calibrations to ensure their accuracy.