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Gary Moore spent the last three days of 2015 stacking hefty bags of sand in front of a fellow church member’s brick home. With only 1,000 feet between the house and the swelling Mississippi and Meramec Rivers, Moore and other volunteers worked quickly, in frigid temperatures, to assemble a 10-foot high, 1,000-foot-long sandbag wall to ward off floodwaters.

The Vital Nature of Streamgaging

"The sandbag levee did not meet engineering design standards, but it held,” Moore said.

Moore, a program manager at the Metropolitan Sewer District in St. Louis, Missouri, was preparing for a historic flood. Thirteen deaths, hundreds of impassible roads, and over 1,000 power outages across the State were linked to overflowing rivers, which surged through Missouri and surrounding States after a 19-day downpour in December.

“For this particular flood, there were over 225 State roads that were closed,” Paul Rydlund, a supervisory hydrologist with the U.S. Geological Survey (USGS) Missouri Water Science Center, said, “and many of them are major arteries.”

Moore tracked the floods by checking his phone for flood alerts, which are initiated by data from USGS streamgages—metal boxes at the edge of rivers and streams that act as stethoscopes for waterways.

Record Flooding in Missouri
Record flooding on the Meramec River near Eureka, Missouri. This area is close to a USGS streamgage and water-quality monitoring station. Photograph credit: Miya Barr, USGS
Chasing Water

A few days before Moore’s efforts, hydrologic technician Chris Rowden received a text from Rydlund, his supervisor, asking if he would brave the flooded highways and muddy backroads to check nearby streamgages. Rowden said, “yes” and started chasing water.

Rowden and a colleague, easily identified by their bright orange lifevests, ensured that the streamgages were functioning. Into the creek they then deployed a 3½- by 4-foot “tethered boat” with the same vibrant hue as their vests. Mounted inside the boat was an acoustic Doppler current profiler (ADCP), used to take measurements of the speed and depth of the rushing water. As his colleague walked back and forth across a bridge, pulling the boat by a rope, Rowden focused on colorful boxes across his laptop’s screen, which displayed the different datasets collected by the ADCP mounted in the boat.

Streamflow Measurements
USGS scientists Chris Rowden, Larry Buschmann, and Bob Holmes were on the Mississippi River at St. Louis taking streamflow measurements on New Year's Eve. This information is critical to the National Weather Service, the U.S. Army Corps of Engineers, and emergency managers in making flood predictions and response. Photograph credit: Jennifer LaVista, USGS
Flood-Ready for the Future

At the end of every site visit, Rowden reported each site’s location, date, time, and the water level and flow data. The information was entered into the the USGS National Water Information System, which sends alerts, like those Moore received, through USGS WaterAlert.

USGS WaterWatch monitors current river conditions and provides public access to national flood and drought data. The information helps protect vital infrastructure—including water and wastewater treatment plants, dams, and highway bridges—and optimize their design and operation. Information is also used by the National Weather Service to forecast floods and droughts in real time. The USGS operates more than 8,100 streamgages across the Nation.

The 2015 holiday floods inundated the Fenton Wastewater Treatment facility and the nearby Grand Glaize Wastewater Treatment facility.

“Overall, [the Metropolitan Sewer District] spent around $20 million on recovery efforts to restore the two facilities,” Moore said. He also explained that a streamgage closer to the wastewater treatment plants could have let the district anticipate more accurately how high the water was going to rise and use sandbags to ward off the floods.

“In addition to local entities, Federal and State agencies also need accurate flood flow measurements and forecasts so we know what to expect and have the information we need to support our agencies' responses to the threat,” said Chuck Shadie, a retired engineer with the Army Corps of Engineers.

Seventeen people from the USGS Missouri Water Science Center collected data during the floods, with dozens more participating in neighboring States. “When floods happen, stakeholders know we’re going to be boots on the ground,” Rydlund said.

Measuring Streamflow
USGS National Flood Coordinator, Bob Holmes, conducts a live Skype interview with The Weather Channel while measuring streamflow on the Mississippi River at St. Louis on New Year's Eve in 2015. Photograph credit: Jennifer LaVista, USGS
For More Information

For more information, contact Jennifer LaVista, USGS Public Affairs Specialist, at

Read more stories about USGS science in action.

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