Rain Drain: Choosing a Surf Site After a Storm
by Lori Lambertson

What’s more exciting for a surfer than having your boss ask you to surf as part of your job? That's the situation I found myself in as the Exploratorium geared up to add information about science and surfing to its Web site. I needed to coordinate my surf date with a photographer, producer, and videographer. As we got our calendars out to plan, I realized that setting a date to surf isn’t always straightforward.

Before heading out, Lori considers recent, as well as current weather. Runoff from storms can leave pollutants in ocean water.

Seemingly, all I had to do was pick a day that worked for everyone, but it was more complicated than that. Of course I had to consider tides, waves, and weather. But I also had to consider what the weather had been like in previous days.

Planning for the tide was simple: I was looking for low tide, as the surf area we had picked for our shoot usually breaks better on a low tide (for more on how tides work and why they’re important for surfers, check out our Dance of the Tides article). I consulted my Tidelog (a book that shows the height of the tide, graphically, for every day of the year) to find a low tide in the middle of the day at our chosen beach near Santa Cruz (you can also find on-line tidal information for anywhere in the United States at the Saltwater Tides Web site ).

Finding a date with good weather and waves was a little trickier. Surfers use a variety of resources to predict what days will bring the best conditions. From the tide perspective, Wednesday looked like a good bet. But weather reports from NOAA (National Oceanic and Atmospheric Administration) indicated that a storm would arrive that day.

We could see from our surf forecast that we would likely find decent waves on Sunday, but by Tuesday, the fun would probably be over. With no swell on Tuesday and rain predicted for Wednesday, we decided to change the date to Friday, with the caveat that we might have to cancel if it continued to rain on Thursday. If we’re planning to surf Friday, why should we care if it rains on Thursday? A look at what happens to ocean water during a storm might shed some light.

The Drain from Rain Falls Mainly into the Nearby Ocean

In urban and suburban communities, rain runs off impervious surfaces (which include rooftops, sidewalks, driveways, parking lots, playgrounds, streets, and highways). As runoff moves toward storm drains, it picks up oil, garden and household chemicals, animal waste, bird waste, litter, settled particulate matter, and other pollutants. More densely populated areas usually have more impervious surfaces, which results in more runoff.

Rainwater and the pollutants it collects enter drains like this one on city streets...

In some communities, runoff in storm drains is partially cleaned up at water-treatment facilities, but often, it isn’t treated at all, to some extent because these facilities have limited capacity (it is also simpler and cheaper to just let the storm-drain water flow into the local watershed). So during and after a rainstorm, the runoff entering storm drains may be diverted directly into the ocean. When you see a storm drain with a sign that says, "Do not dump, flows to ocean" stenciled on it, it’s a pretty good bet that the water won’t be treated. This untreated runoff is the most common type of non-point source pollution (pollution that originates from many different sources rather than one specific, identifiable source) in our bays and oceans, and it presents a worldwide coastal-pollution problem.

Non-point source pollution from motor vehicles and roadways may be the greatest threat to the San Francisco Bay Area’s water quality. Copper from brake pads, cadmium from tires, oil and grease from engines, and other fine particulates enter Bay Area streams, the San Francisco Bay, and the ocean via surface-water runoff. Paved surfaces that prevent rainwater and other runoff from filtering through the ground increase the amount of urban pollutants entering watersheds and waterways. To find out more about the non-point source pollution, see the Surfrider Foundation's Environmental index .

...and eventually dumps into the ocean through drainpipes like this one, on a surfing beach.

Waiting for a Healthy Wave

What does all this mean to surfers? Many have become sick after surfing in polluted water. Common illnesses include eye, ear, nose, and throat infections, stomach problems, and skin rashes. To be safe, lots of surfers stay out of the water for several days after a storm. Over time, the concentration of pollutants in the surf zone decreases, as tides, waves, and currents disperse the pollutants.

How do you know if the water is safe at your beach? The Surfrider Foundation is dedicated to the protection and enjoyment of the world’s oceans, waves, and beaches. Local chapters of the Surfrider Foundation post regularly updated water-quality data on their Web sites. The Surfrider Foundation recommends avoiding water contact for two to three days after the end of a rain event.

It rained on Wednesday. It was cloudy on Thursday. By Friday, the pollutants in the surf zone had had some time to dissipate, and we decided to go ahead with our plans because the weather, wave, and water conditions were okay. You can view the photos and videos from our surf session here. Do I have the best job or what?