From the infamous Malibu to the quirky Venice, the beaches near Los Angeles (LA) bring out surfers come rain or shine. But surfers entering the waters during and after rainstorms expose themselves to more than just epic swells. Excessive bacteria in water, including fecal coliforms such as E. coli. and Enterococci, are associated with more than 600,000 gastrointestinal illnesses a year. A local environmental organization called Heal the Bay (HTB) monitors these beaches. They found that surfers are 20 percent more likely to get sick in the region’s wet winters compared to its dry summers.
Stormwater runoff is a major source of ocean pollution in LA and Southern California. The Southern California Bight (SCB), a curved coastline from Point Conception to San Diego, is home to nearly 25 percent of the coastal population in the United States. “We have millions of people surrounded by mountains,” said Benjamin Holt, a researcher at NASA's Jet Propulsion Laboratory (JPL) in Pasadena, California. “Anything you can think of that happens to be on the streets, enters the ocean—untreated.”
Holt has been keeping an eye on the ocean from high above. The native Californian has collected over two decades worth of satellite images of stormwater runoff into San Pedro and Santa Monica Bays to see how satellites could guide in situ water quality data collection and beach monitoring.
Assessing the impacts of stormwater runoff in coastal oceans commonly relies on sparse beach sampling and from onboard research vessels, but boat operations are costly and rain is sporadic. “Monitoring programs could do a lot more with respect to remote sensing,” said Michelle Gierach, another JPL researcher and coauthor of the study. By combining two different satellite sensors that image the ocean differently, Holt and his team hope to focus in situ sampling to the most polluted areas along the SCB coast.