Speakers at the CSULB College of Engineering Distinguished Lecture Series Thursday agreed that a strong El Nino is brewing, and Southern California should be braced for higher-than-average rainfall this winter and spring. Although engineers and planners have learned much from past El Nino events, large-scale infrastructure improvements are still needed to prevent severe damage from future storms.
El Nino events are classified as weak, moderate, or strong, and usually peak in February. This year’s is strong, said Mark Jackson, meteorologist in charge of the Oxnard National Weather Service office, although it remains to be seen how many inches of rain it will deliver. “I’m not going to give my exact forecast for how many inches of rain we’re going to get. There are too many microphones and cameras here,” he said.
El Nino is actually an oscillation, called the El Nino Southern Oscillation (ENSO) in meteorological terms, accompanied by warming waters. “The oceans in the atmosphere are constantly trying to balance the heat budget. That’s why we have weather,” Jackson said.
What’s been termed “the blob,” the reddish patch of warm water that appears on meteorological maps, will eventually break down. But in the meantime, its effect is being felt in the remnants of hurricanes that brought rain to Southern California in July, and the recent deluge that delivered several inches of rain per hour, closing the Grapevine and causing hundreds of cars to be trapped in mud in the Antelope Valley. “Without question it was able to feed off the warm water over the Pacific. It had a very dramatic impact as well,” Jackson said.
El Nino is also causing very discernible changes in the ocean habitat. “The surfers are complaining their wetsuits aren’t thick enough. We’re getting sea snakes. We’re getting hammerhead sharks. All of this is because of this very warm water,” Jackson said.
Northrop Grumman Engineering Fellow Pamela Emch, an expert on satellite imagery, shared how important satellites are for weather prediction. “A lot of countries don’t have satellites. In the long term, the challenge is that although weather is critical to everyone and impacts transportation, it’s not necessarily a national priority. It comes down to budget.”
There have been six El Ninos since forecasters began tracking them in 1950. The two most powerful for Southern California took place in 1982-83, when powerful waves ripped the end off the Santa Monica pier, and in 1996-97, when homes in Malibu’s Broad Beach slipped into the ocean.
Russell Boudreau, VP of Coastal Engineering at Moffatt & Nichol, said “significant wave heights” of nearly 24 feet were recorded during the 1982-83 El Nino, meaning that the largest wave was about 50 feet high. A 25 percent increase in wave height results in a doubling in the force of the wave. And during El Nino storms, the wave period is longer, allowing them to build up even more force before crashing into the shore.
Boudreau showed news footage from the two previous El Ninos. He theorized that the 1996-97 El Nino caused less damage because weak structures were winnowed out and some piers weren’t rebuilt. But it’s not only loss of structures that we need to worry about, but loss of sand that provides a buffer. “I’m a little bit concerned because beaches are a little narrower now than they were before. If we get high waves and tides combined, it can be a recipe for problems,” he said.
Kevin Bryan, Senior Principal Geologist with Leighton Consulting, said new stormwater management systems are needed to replace existing infrastructure, most of which was built in the 1940s. Designers then were most concerned with quickly routing storm water to the ocean, he said, rather than saving it in reservoirs. He added that when stormwater flows into the ocean, it carries with it a toxic mix of chemicals, plastic, disposable cups, and other debris.
“The infrastructure put in 40, 50, 60 years ago was not designed for the expanded development we have now,” he said.
As most Southern Californians know, hills denuded by wildfires are another El Nino threat, capable of creating mudslides and deadly debris flows. And Bryan pointed out that it takes at least five years for burn areas to recover after a fire.
Bryan said engineers have a responsibility to help drive policy. “As a geologist, I tend to look much more long term. Large infrastructure projects for stormwater are decades long.”
Jackson stressed that one El Nino won’t end four years of drought, both because of the size of the rain deficit and the fact that most stormwater washes into the ocean. “What we need is multiple seasons of rain rebuilding that snowpack and helping refill those reservoirs,” he said.