UC Irvine researchers are preparing to monitor the effects of El Niño conditions, which are gathering strength in the tropical Pacific Ocean. Expected impacts for Southern California include high surf and tides at regional beaches, alongside heavy precipitation that could cause landslides and flooding in inland areas.
Among the investigators is Connor Broaddus, a Ph.D. candidate in the Department of Civil and Environmental Engineering at UC Irvine. Broaddus, who is set to become a postdoctoral scholar in January, will be in the field observing how runoff-swollen rivers and creeks transport sediment to the coast. This process is a natural mechanism for beach replenishment.
Broaddus is currently a PhD student in the Efi Foufoula Lab at UC Irvine and will defend his dissertation in December. Following this, he will begin his postdoctoral work in the lab of Dr. Brett Sanders. His work contributes to the broader goal of UC Irvine researchers to use observations and collected data to better inform future responses to events like El Niño.
El Niño effectively warms sea surface temperatures in the tropical Pacific, which can lead to increased storm activity along the California coast. These storms bring both heavy rains, capable of causing flooding and erosion, and large waves, which contribute to coastal erosion. While not all impacts are guaranteed, researchers are utilizing this opportunity to study these potential effects.
Already this year, Southern California has experienced heavy wave activity on its coastline, leading to significant erosion events. Areas including Dana Point, Laguna Beach, and Long Beach have reportedly been hit hard. Preliminary data from these events suggests they are "outside the range of observations" seen previously, reflecting the strength of this El Niño event even in the late summer.
Tropical cyclone impacts from Hurricane Marie and other Pacific storms earlier this year have also left beaches in a more vulnerable state. These tropical systems produce waves from directions not commonly seen, which can have an outsized impact on local beaches.
Beyond coastal concerns, El Niño conditions are expected to affect inland areas. Significant rain events could lead to flooding hazards, often accompanied by erosional hazards such as landslides, a concern for residents this winter.
To study these dynamics, the Sanders lab has received funding to investigate the possibility of moving sand along river corridors to replenish coastal sediment. This predicted wet winter provides an opportunity to study how both water and sediments move through these systems.
Monitoring efforts are focused on the Santa Ana River and San Juan Creek in South Orange County. Researchers will use bridges to access the full width of the rivers, lowering sampling devices into the current to collect water samples. These samples will then be analyzed to measure the amount, type, and size of sediment present. This data will help scientists understand how sediment is transported and enable them to parameterize and calibrate models representing sediment movement.
