When rivers rise: warning you before the next flood

Published: Feb. 1, 2017 at 6:53 PM EST|Updated: Feb. 7, 2017 at 1:29 PM EST
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The USGS has a wire weight gage (left) and a radar sensor attached to this bridge along Highway...
The USGS has a wire weight gage (left) and a radar sensor attached to this bridge along Highway 130 in Columbus County. The devices help gather data on the Waccamaw River below. (Source: WECT)
USGS Hydrologic Technician Bryce McClenney uses a tethered boat to gather data in the Waccamaw...
USGS Hydrologic Technician Bryce McClenney uses a tethered boat to gather data in the Waccamaw River in Columbus County. (Source: WECT)
A closer look at the tethered boat used by USGS technicians to gather data on streamflow....
A closer look at the tethered boat used by USGS technicians to gather data on streamflow. (Source: WECT)

COLUMBUS COUNTY, NC (WECT) - A bright, sunny 70 degree January day means Bryce McClenney's work outside the office is enjoyable. He is spending time walking back and forth on a Department of Transportation bridge along Highway 130 near Freeland, guiding a tethered boat across the Waccamaw River with a rope in one hand and computer in the other.

As a Hydrologic Technician with the United States Geological Survey, McClenney is gathering data to measure how much water is flowing at this spot on the river, where the USGS also has a gage to monitor the river's level.  McClenney will note today's level, which is 11.64 feet, along with his data on streamflow.

The agency records and updates that information in rivers, streams, swamps and other bodies of water across North Carolina and the United States. Forecasters use McClenney's information to help protect families and properties during hurricanes and other weather events.

"Knowing the volume of water, and how fast that water is moving past a given point, is what's important," said Jeanne Robbins, the Assistant Director for Data at the USGS South Atlantic Water Science Center. "It's that information the National Weather Service uses to actually develop river forecasts and flood forecasts. We have to be out here during an event like (Hurricane) Matthew, making those streamflow measurements."

Simply put, if the Waccamaw River is rising at this site in Columbus County, forecasters can use streamflow data to project when levels will rise at other locations along the river in North and South Carolina.

"They are able to forecast what the discharge (water flow) and the elevation is downstream," said McClenney. "They can assess when they need to issue a flash flood warning or flood warning, to know when to evacuate and know to what extent they need to evacuate downstream."

The USGS operates 260 gages across North Carolina like the one at the Waccamaw River site.  Inside the stainless steel or aluminum boxes are instruments that measure the water level, and then send the information by satellite to the USGS office in Raleigh.  The gage is connected by a conduit to a radar sensor, one of two devices mounted to the side of the bridge, that measures the river level every fifteen minutes. The data is available to weather forecasters, scientists, government agencies or any member of the public interested in receiving the information. The agency has agreements with cities, towns, agencies, even companies, to install and maintain these gages.

"With flood forecasting you're concerned about those really high (stream)flows," said McClenney. "But, there might also be a cooperator interested in low flow, for water quality or water supply for a user that pulls water from the river downstream."

This interactive MAP shows the location of gages the USGS operates across North Carolina. In addition to the gage near Freeland, there is a second gage in Columbus County near Boardman, monitoring the Lumber River level near the Robeson County line. There is a gage in Bladen County, monitoring the level of the Cape Fear River at Lock and Dam #1 near Kelly. Another gage watches the Northeast Cape Fear River near Burgaw, along Highway 50 in the Six Forks area.

There are no USGS gages installed in either Brunswick County or New Hanover County.  The National Oceanic and Atmospheric Administration has two gages, one in Wrightsville Beach and the other along the Cape Fear River across from downtown Wilmington, which measure water levels. According to David Herlong of North Carolina Emergency Management, the NOAA gages are used more for tidal data and not to measure the flow of water past the site.

Brunswick County Emergency Services is currently working on mitigation projects to determine whether funding is available after Hurricane Matthew to help pay for installing a gage. County leaders have worked with the USGS to identify nearly a dozen potential locations. The list includes Highway 904 along the Waccamaw River downstream from the gage at Highway 130, the Caw Caw Swamp area in Carolina Shores which flooded heavily in October of 2015, and locations along the Shallotte and Cape Fear Rivers.

"Everything we get is based on hydrological data that the National Weather Service and state Emergency Management teams put together, based on historical data, and what things are doing further out on other gages," said Scott Garner, Deputy Director of Brunswick County Emergency Services. "It is one of the priorities of the mitigation program that is going on after Hurricane Matthew. It was already one of the things in meetings we were already putting as one of our top priorities. We know it is a priority for some of the agencies that manage the funds. Hopefully, it will be something that come to fruition."

Pender County has money in the budget to buy a USGS gage and have it installed on the bridge along Highway 210 over the Black River. Tom Collins, the Director of Pender County Emergency Management, asked the USGS to move a temporary gage there from Surf City in the days after Hurricane Matthew passed through the county. A gage along the Black River in Duplin County had already recorded higher levels by that time. Once crews installed the gage on the Highway 210 bridge, Collins knew from the rapidly rising levels he saw, it was time to act.

"It put us in a response mode, that we actually moved resources forward here (near Currie), had a staging area at Blueberry Road and had assets in place to start getting people out," Collins said. "For us, it was an early warning. It gave us time, very little time, because by the time we got assets in place and started getting people out, they were already dealing with flood waters."

In the days that followed, crews used helicopters to rescue 22 people from the flooding associated with the Black River in Pender County. Collins says the county is now budgeting to buy one new gage per year. The cost is approximately $15,000. The county splits (with NOAA) the cost of maintaining the gage that monitors the Northeast Cape Fear River near Burgaw. Those maintenance costs run about $6,500 a year, according to Collins. But he considers it money well spent.

"Let's put it this way, it's very cheap insurance," Collins said. "Fifteen thousand dollars in the scheme of our county budget, and county budgets in this region, is a very low cost considering what we're doing."

McClenney realizes the importance of the data he gathers, that it can be used in keeping families safe when the weather conditions worsen.

"When we do have these big flood events, it becomes pretty clear to us pretty quickly that what we're doing has a real purpose," McClenney said during a break in entering the data into his computer. "It really truly is helping people, and with forecasters and meteorologists in knowing where people's lives are in danger."

The USGS has systems available for the public to get text or email alerts when water levels reach a certain threshold at one of the gage sites. The Water Alert System also provides threshold-specific and current information regarding conditions.

You can click here to learn more about the Water Alert System.  Another system, called WaterNow, allows the public to get current conditions at one of the USGS sites sent immediately to a mobile phone or email address.

You can click here to learn more about using the WaterNow application. The public can also monitor the current conditions at any of the USGS gage sites by clicking on this link to the interactive map on the agency's website.

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