Predict the Rip

Researchers use the information gathered from tracking buoys in the surf to create computer models that will not only better predict rip currents but also teach swimmers how to avoid them.

MOREHEAD CITY — On any given day along North Carolina’s beaches you’ll find crashing waves, noisy seagulls, gentle breezes, and lots of people soaking in the sun and enjoying the surf.

Rip CurrentsMost of the folks walking along the beach or lying in the sand will eventually jump in the Atlantic Ocean for at least a few minutes. And it’s likely when they do hit the water, they won’t think at all about the number one hazard for beachgoers: rip currents. 

A rip current is essentially a strong current that moves away from shore. The currents are found in the ocean everyday and on most days, rip currents are so weak a swimmer barely notices them. But on four or five days per year, rip currents reach such dangerous velocities there is a risk of drowning.

The National Weather Service reports seven rip current-related fatalities along the North Carolina coast in 2013. The U.S. Lifesaving Association says almost 80% of all rescues are related to rip currents.

That’s why researchers are diving into a new effort to better understand rip currents, and teach swimmers how to avoid them.

“The results of these studies have huge implications about what we should be telling people if they get caught in a rip and what should they do,” says Spencer Rogers, Coastal Construction and Erosion Specialist with North Carolina Sea Grant. “There’s no one perfect answer to the issue of rip currents because the ocean is constantly changing and the people who interact with the ocean on the beach are all different. Ultimately it comes back to education and prevention.”

The new study involves launching rip current drifters into the surf. The data-logging drifters are deployed at several points along the coast to document the velocity, circulation and ejection frequency of the currents. Each device has a GPS device inside that records its position every second. That will allow the drifters to show the direction the rip current is flowing, the current’s velocity, the distance from shore and how far along the coast the current stays strong before it weakens and changes.

The long-term hope is to create a computer model to better predict when and where rip currents will occur. Even then, the ultimate answer to saving lives is educating the swimmer.

Starting from the shore, recirculating rip currents flow out towards where the waves are breaking. The current essentially bounces off of the wave and goes back towards the shallow areas before heading back out to sea. Think of it as a merry-go-round of water circulation.

Exiting rip currents are also known as ejecting rip currents. These rip currents usually start when multiple waves break together. The force of the water pushes the current out from the shore and it breaks through the waves before heading parallel to the coastline.

In some ways, North Carolina’s rip currents are similar to those found in Australia, which are easily predictable because they are found in channels, between sand bars. That’s one of the reasons Rob Brander is joining the research team. Brander is a coastal geomorphologist with the University of New South Wales. He’s known as 'Mr. Rip' in the Land Down Under and is an expert in rip currents.

‘While many of the rip currents here are what we call fixed rips, meaning they are found in the same location consistently, not all of them are because the coastline is so varied,” explains Brander. “That makes this research even more fascinating because we need to understand the differences in rip currents. It also makes the focus on education even more important because not all rip currents can be easily forecast.”

Researchers believe the rip currents along North Carolina’s coast are smaller and shorter in duration, and difficult to predict because the coast is so varied. The slope of the surf zone changes along with the sandbars and the height and direction of the waves. There are also plenty of man-made features that affect the surf.

Along with the research into predicting rip currents, the study is also surveying beachgoers to measure the effectiveness of rip current safety campaigns.

“The public can provide a wealth of information about rip currents because we’re asking people how often they go to the beach, if they know what rip currents are, and what were the weather conditions when you got caught in a rip current,” adds Brander. “We also want to know what it felt like when you got caught in the current, your physical and emotional response when it happened and how you got out of the current.”

Preliminary findings from the research show that almost 10% of the rip currents along North Carolina’s coast are exiting, or ejecting rip currents, which carry water straight out from shore. That’s a much higher percentage than first thought. The discovery means more emphasis needs to be placed on teaching beachgoers to relax and swim parallel to shore to escape a rip current. That’s because rip currents are not very wide.

County governments, visitor’s bureaus and the National Park Service plan to continue rip current education campaigns. The Park Service and several other organizations will also maintain funding for lifeguards at three positions along the Cape Hatteras National Seashore.

In addition, the National Weather Service office in Newport/Morehead City will continue testing a Beach Hazards Statement, which is an online service that alerts beachgoers to dangers in the surf zone, including rip currents and dangerous shore breaks.

Related Resources: