How are floods predicted in Horry County? These gauges play a big role.

When predicting the severity of flooding in Horry County, forecasters rely on data from a “river stage gauge” along river banks that calculate the depth of the water at any given moment.

The gauges, which collect information on water conditions at various points along the river, are under threat as waters rise in the aftermath of Hurricane Florence.

The U.S. Department of the Interior has crews moving the gauges to higher ground to prevent vital information from being lost.

John Erbland, with the U.S. Geological Survey, was part of a crew working to move the gauges to safer locations.

“We will take the equipment out and move it to higher ground to hopefully continue collecting stage data,” he said.

The data is useful for predicting future river conditions. Flood levels are predicted by measuring how much water is further up in the stream using gauges that determine the water height. Boxes further upstream report how much water is in the river and how quickly it is flowing downstream. Forecasters can then take this data and use it to create predictive models of what might happen.

Tom Blowe and Keith Cobb, members of a United States Geological Survey team, move sensitive sensor equipment on the bridge over the Waccamaw in Conway to protect it from rising flood waters. The radar which sends flow and water level readings to the National Weather Service will remain functional by sending data to a receiver at the top of the bridge span. September 19, 2018. Jason Lee jlee@thesunnews.com

“The National Weather Service uses the data to predict the severity of the flood and to issue the warnings to the different areas and communities,” Erbland said.

Other conditions contribute to forecasting models, but these gauges provide key information to knowing what the immediate future will look like. Erbland said his job is to be a non-biased data collector for the federal government; other people use the information to create the forecasts.

In Conway, these monitors are usually under the U.S 501 Business bridge exiting Conway, right in the middle of the river’s flow. On Wednesday evening, geological surveyors loaded into a jon boat to save the equipment. They moved the monitors up to the top of the bridge, well above where the flooding is expected to be.

During Hurricane Matthew in 2016, a box in Bucksport was swept away by the flood waters, creating a gap in the data available to forecasters.

Floods from Hurricane Florence are expected to exceed those of previous storms by at least three feet. So the geological surveyors are making sure their equipment is safe so government agencies can continue to have accurate numbers on flood levels as waters continue to rise.

The data from these gauges can be found online at the Geological Survey’s website.

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