How USGS tracked the Mississippi flowing … backward

There are certain things you can count on in life. The sun will rise. Nobody lives forever. And rivers flow to the sea. Except new technology deployed by the U.S. Geological Survey proves that the last one isn’t always true. Even the mighty Mississippi can reverse its flow when faced with adverse conditions.

The USGS has developed a system to track the patterns of and damage caused by hurricanes with a distributed sensor network that is deployed ahead of storms. The USGS hopes that data from its networks can lead to better storm predictions, smarter building codes and a deeper understanding of what exactly causes damage during violent weather.

The sensors are deployed in sealed metal tubes that are lashed to dock pilings, telephone poles and other sturdy structures prior to a major hurricane’s landfall. For a major storm, about 70 sensors are deployed 50 miles to the left and 100 miles to the right of a projected landfall. The network can be setup quickly by between six and 10 two-person teams.

The devices are 18-inches tall and are open at the bottom to allow for water to enter. Every 30 seconds, the sensor records water levels and barometric pressure. They generally can run for up to three days on their own.

The information they collect could be considered sparse data, but isn’t actually transmitted anywhere. Instead, after the storm, teams from the USGS collect the sensors and compile all the data into 3D computer models. These new sensors, combined with a network of permanent stream flow gauges, have led to some interesting discoveries.

When Hurricane Isaac came ashore on Aug. 28, the Mississippi River, pushed by winds and a strong storm surge, actually flowed backwards for about 24 hours. The average flow of the river near its terminus is 125,000 cubic feet per second. But for the 24 hours surrounding Isaac, the flow was as much as 182,000 cubic feet/sec back upstream.

"This reversal of flow of the mighty Mississippi is but one measure of the extreme force of Isaac," USGS Director Marcia McNutt said. "While such events are ephemeral, they are yet another reminder of why we need to respect hurricane warnings."

Data from both the permanent stream flow sensors and the new deployable devices is used by other agencies as well, including the National Ocean and Atmospheric Administration, the National Weather Service, the National Hurricane Center, the U.S. Army Engineer Research and Development Center and state and local emergency management officials.

All stream flow data is also accessible online.

About the Author

John Breeden II is a freelance technology writer for GCN.


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