Guest Posts / Science and Communication / Uncategorized

Rip Currents: What everyone needs to know

Have you ever noticed a rip current at the beach? If you or someone you know was caught in a rip current, would you know what to do? If you’ve been paying attention to the coastal news along North Carolina recently, you may have noticed recent stories about rip currents and rip current safety.

Dr. Greg Dusek, a UNC Chapel Hill Marine Sciences Alumni, works for the NOAA National Ocean Service and is one of the leading experts on rip current research. Check out this Q&A session with him to learn everything you need to know about rip currents.

rip_currents_dye

One of the projects from Dr. Greg Dusek where green dye was used to help show why rip currents form. (Source: NOAA Ocean Today)

What’s your academic background? What types of things are you currently working on? What is the path that you took to get to your current position?

I am a coastal physical oceanographer and a senior scientist with the NOAA National Ocean Service. I am also a Tar Heel! I completed my PhD at UNC in 2011, and my dissertation work focused on better understanding what physical mechanisms contribute to hazardous rip currents and how to statistically predict rip current occurrence. I was lucky enough to have a GREAT adviser (Harvey Seim) and some absolutely superb committee members (including Rick Luettich and Tony Rodriguez). Much of my field work was in Kill Devil Hills, NC and had an incredible amount of support from Mike Muglia and others at CSI. I have continued to have opportunities to stay connected to North Carolina through continuing working on rips, and my NOAA office even collaborated with Mike recently to deploy an ADCP (Acoustic Doppler Current Profiler) in the Gulf Stream.

In my present position I serve as the Chief Scientist for the Center for Operational Oceanographic Products and Services (CO-OPS). We are the tides and currents office at NOAA, and among other things, we operate the over 200 real-time tide gauges across the U.S. We use our water level, currents and other data to develop and deliver operational oceanographic products to users. As Chief Scientist my time is largely split between operational oceanography, mentoring and training our workforce, and applied research. We are presently in the decade-long process of transitioning our tide gauges from acoustic to microwave technology. This has been keeping me busy, as it turns out it’s quite difficult to change sensor types when every mm of error is important.

On the research side of things I have been working with my colleagues on high tide flooding. We have made a lot of progress on assessing and projecting tidal flooding at our gauges and working on annual and seasonal flooding outlooks. One of my favorite projects is our High Tide Bulletin, in which we simply use tide predictions and seasonal sea level change to tell people when and where tidal flooding is most likely. And of course, I continue to work with the National Weather Service on rip currents including social science, communications and forecasting.

Can you explain how rip currents form, how we can notice them, and what we can do to help someone who is caught in a rip current?

Rip currents can form on any beach with breaking waves, even in the Great Lakes.  There are a number of types of rips (this science overview we wrote provides a good starting point), but the primary driving factor in most cases is that rip currents occur due to variations in breaking wave height alongshore. This is common in places where you have a sand bar with a deeper channel. There is greater wave breaking over the shallow bar than over the deeper channel, which drives corresponding changes in water level alongshore and results in flow from regions of high water level to lower water level. This video I made demonstrates this pretty well.

First off, the best way to see a rip is to be at an elevated position like a beach access or dune line. You’ll want to look for gaps in the lines of breaking waves, or where waves AREN’T breaking. This usually indicates the presence of a deeper rip channel. You can also look for sediment or foam in the water being transported offshore.

We have been focusing a lot on what to do if you see someone caught in a rip, because there have been A TON of drownings of people going in to attempt a rescue. If you see someone caught in a rip, don’t just rush in after them, there are three things to think about:

  1. Go get a lifeguard
  2. Call 911
  3. Try to throw them something that floats and guide them out of the current

If you feel like you have to go in after them – always, always, always bring something that floats with you (whether a boogie board, a float, anything). I can’t stress that enough.

There seems to be a lot of news this summer about dangerous rip currents. Is this normal for the summer months or above average? 

The short answer is that we don’t really know if there are more hazardous rip currents this summer than in past summers. Since rip drownings or rescues are dependent on both the physical conditions AND the beach population’s exposure to those conditions, it is hard to parse out contributing factors without some intense observing programs. The number of drownings nationwide have been similar to past years, so I don’t think it’s substantially different than other summers. But, it seems that every year rip currents get more and more media coverage – so potentially this makes it seem worse. I think the increased media coverage is a good sign that people are starting to take rips more seriously and want to know more about them.

Are there particular locations where rip currents occur the most? What causes these rip currents to occur more frequent in some locations?

Probably the best examples of rip current “hot spots” are at hard structures like jetties, groins and piers. Structures can cause variations in breaking wave heights (like I described above) and lead to rips. They can also cause a longshore current to deflect creating a rip. So, rips can occur near structures over a broad range of wave and tide conditions – and so those areas should always be assumed hazardous places to swim. We are actually collaborating with a whole host of NC partners (USACE, NCSG, CSI, Dare County, NPS, and more) on trying to collect dye footage of a structural rip. Hopefully by this fall if conditions cooperate.

Is it possible to predict (forecast) if a rip current is going to occur? If so, how?

Yes! We use a statistical forecast model, which was a big part of my dissertation work, to forecast rips. The statistical model relies on wave height and direction, water level, and a previous wave condition proxy for the surf zone bathymetry and outputs the likelihood of hazardous rip current occurrence from 0-100% (kind of like say a precipitation forecast). We use a nearshore numerical wave and water level model to force the statistical model every ~ km or so along shore, for an hourly forecast out to 6 days. You can see an experimental version of this here. We are in the process of validating and implementing the model at NOAA and are hoping to have it operational soon.

Do human modifications to the beach such as nourishment projects and hardening structures have an impact on rip currents? If so, how?

Structures definitely do (see above). Beach nourishment is still a question mark. Certainly the surf zone bathymetry is critically important to rips, and nourishment undoubtedly alters that bathymetry – so nourishment is likely important to consider. We just don’t have a good sense for how it might change rip formation on short-term (immediately after nourishment) or long-term (over the months – years following nourishment) scales yet. This is something I am hoping to be able to research in the future.

How is the risk of rip currents communicated to the public, and what are the challenges associated with communicating this risk?

Communicating both the rip current hazard and rip current forecast information to the public is a huge challenge, but something that we are making a lot of strides in. We have done some recent social science research to try to evaluate both our general safety messaging and how we communicate our forecast information. We used some of the results of this and other research to improve our communication products. For example, we recently made a new series of NOAA rip current safety videos, and the rip current survival guide has had over 20 million views!!! So I think we are making an impact.

Right now, rip current forecast information is communicated via individual Weather Forecast Offices, and it’s largely limited to a once or twice a day update. With the new model we will be able to provide much more location and time specific information, and while powerful, this also makes how we communicate it even more vital. Especially with things like communicating probabilities and uncertainty – this is a challenge with all types of forecasts and rips are no different. We are presently evaluating this, but likely have more social science research to do.

What do you wish everyone knew about rip currents?

Well, there is a lot I wish people knew, but if I had to narrow it down I would say two things:

  1. Know how to spot a rip current. Or, at least know what general things to look for and to take the time to observe the ocean conditions BEFORE going in the water.
  2. The weather doesn’t have to be bad, and the waves don’t have to be huge for strong rip currents to occur. Rip currents can be hazardous on nice sunny days, and with waves of only 2 to 3 feet.

Our research suggests a lot of people now know what to do if caught in a rip, but many fewer people know what a rip looks like or what conditions might be hazardous. There are a lot of un-guarded beaches, and so being able to self-evaluate the ocean is really important.

Do you have any tips or recommendations for graduate students interested in jobs and careers outside of academia? 

I started at NOAA in 2011 in my present office as an oceanographer on our coastal and estuarine currents team. When I finished up school, I was looking for a position that focused on applying my oceanographic expertise to something that would have societal impact. I thought that the federal government and NOAA specifically would be a good place for that sort of thing and I applied for a few positions. I also participated in the Presidential Management Fellow (PMF) program, which is an excellent way to get into the federal government if you can get accepted. The PMF program is typically more for policy type positions (and not science positions), but it helped me get my foot in the door. My advice to those looking at careers outside of academia would be to be proactive! Talk to people, ask questions and don’t be afraid to cold-email or cold-call people at places you might want to work. People tend to be really willing to talk about their organization and can help you know what opportunities might exist. I also know from being on the hiring end of things that having a face (or voice) to go with a name can go a long way. And of course if you are interested in NOAA you can shoot me an email or give me a call – I’d be happy to chat.

My email is gregory.dusek@noaa.gov and you can also follow me on twitter at @DrGregDusek

Anything else you would like to add?

Just to say thanks for having me on your blog! I have enjoyed telling you all about what I do and about rip currents. I hope you find it interesting!

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