The king tides are coming and bringing with them a peek at how rising sea levels will likely impact our coastline by 2100.
The highest tides of the year, known as king tides, are a naturally occurring phenomenon that take place when a new or full moon coincides with the moon reaching its closest point to earth in its elliptical orbit. The combined result is a much stronger than usual gravitational pull that causes abnormally high tides.
King tides are also a close mirror of a very unnatural phenomenon — climate change induced sea level rise.
The extreme tides will take place on Dec. 4 and 5 reaching a high tide level of 7.2 feet at 8:18 a.m. on Saturday and 7.1 feet at 9:01 a.m. on Sunday.
“The expected height of the king tides is between two and three feet higher than normal high tide, so it’s giving us exactly a snapshot picture of what we’re likely to see on a daily basis by the end of the century,” said Annelisa Moe, water quality scientist at Heal the Bay.
According to the 2021 Intergovernmental Panel on Climate Change Report, sea level is predicted to rise by at least two feet by 2021, even if efforts continue to lower greenhouse gas emissions. If no mitigation measures are taken and pollution continues at a business-as-usual rate, sea level could increase by as much as seven feet by 2021.
Even small amounts of sea level rise will have significant impacts on coastal communities.
Flooding will increase causing damage to houses and infrastructure and contaminating groundwater resources with salt water. Beaches will erode and become shorter, while intertidal, coastal and wetland habitats will be threatened.
“Even if we only see two feet of elevation of sea level rise in the next 100 years, it’s actually still going to have a huge impact on the Santa Monica Bay and particularly on the ports of LA,” said Moe. “That area will flood pretty significantly even with just two feet of elevation.”
Although the beaches in Santa Monica are very deep, increasing tide levels accelerate erosion and lead to the loss of sand. According to Moe, this means that about half of the beach depth in the Santa Monica Bay could be lost by 2100.
The king tides can be observed at any beach, but their effect will be particularly pronounced in Malibu where beaches are already very narrow at high tide. Heal the Bay points to Paradise Cove, Westward Beach, Broad Beach, El Pescador State Beach, and Leo Carrillo State Beach as nearby beaches that will see the strongest impacts.
Viewing the king tides in person, especially in areas where local beaches will practically disappear, can be a very impactful experience for residents.
“So much of the science around climate change is predictions of the future and a lot of those don’t necessarily feel tangible to folks,” said Moe. “But this is an opportunity for people to go out and see for themselves what some of the impacts are going to be.”
Heal the Bay encourages residents to go see the king tides, not only to get a personal picture, but also to capture those images for the use of scientists and policy makers.
This is part of a broader initiative led by the California Coastal Commission called the California King Tides Project. The project began in 2018 and is an annual effort to photograph king tides across the California coastline in order to predict how sea level rise will impact communities and habitat areas.
“It’s incredibly helpful for the scientific community to have photographs and be able to use that as sort of a digital storytelling of what sea level rise is going to look like to not only help with creating models, but to communicate that story out to decision makers and to the public,” said Moe.
Even though two feet of extra tide might not sound like a big deal, it is enough to generate significant flooding. Large portions of Marina del Rey are only two feet above sea level as are areas around the Venice Canals. When king tides, or future regular high tides, are combined with storm surges the flooding impacts will be compounded.
“I think that a big part that’s often lost in the conversation about sea level rise is not just the steady increase in it, but the frequency at which we’ll be experiencing king tide like flooding,” said Tom Ford, Director of the Bay Foundation. “We could start to see big storm surges that will invade large areas of our coastline, causing some public safety concerns, certainly putting private and public infrastructure directly in harm’s way.”
Locally there are worries about sea level rise causing saltwater intrusion into groundwater. Groundwater accumulates in underground aquifers as rain and runoff filters through soil and rock particles. Groundwater is Santa Monica’s primary source of water and an incredibly valuable community resource.
An additional area of concern is the Ballona Wetlands, an ecological preserve and center of coastal biodiversity.
“If the sea level rises and goes over into that wetland it will become more like an estuary, so the water will be more saline than then it would normally be,” said Moe. “If that happens too quickly, then the species that live there will have a difficult time moving or adapting to that change.”
Fortunately, the news is not all dire on sea level rise and beach erosion. The Bay Foundation is working on a nature based solution called the Los Angeles Living Shoreline Project.
This initiative helps restore natural dune habitat to beaches by planting indigenous beach vegetation. Native plants build dunes by accumulating sand blown by the wind and then growing out of these sand piles. As the dunes grow in size they create barriers against sea level rise and help hold sand in place, which in turn fights erosion.
The program was first piloted in Santa Monica and successfully restored three acres of coastal wildlife habitat. It has since been expanded to Zuma and Point Dume beaches in Malibu as well as Dockweiler Beach in El Segundo.
“Folks in Santa Monica, go down and check out the project that we helped lead off of the Annenberg Beach House and see what a natural set of dunes looks like off of our coast,” said Ford. “That site has grown almost a meter, roughly three feet in height, since we established it in 2016.”
Ford said those interested in learning more about living shorelines should visit www.santamonicabay.org, while those interested in photographing king tides should visit www.coastal.ca.gov/kingtides.
Clara@smdp.com
