Pacifica California: Icon of Coastal Erosion & Natural Climate Change
Pacifica, California’s Natural Coastal Erosion and the Lust for Climate Catastrophes
For 25 years I’ve lived in the beautiful town of Pacifica, California situated about 15 miles south of San Francisco. It was a wonderful place to raise a family. Its great expanse of green space is a delight for an ecologist. My daily hikes vary from coastal bluffs to watch feeding Humpback Whales or migrating Gray Whales, to inland mountain trails with abundant deer, coyotes and bobcats. Oddly this past week I received emails from friends around the country asking if I was “all right”, thinking my little slice of heaven was falling into the sea. Not to disrespect their concern, I had to belly laugh. The news of a few houses, foolishly built on fragile land too near the sea bluffs’ edge, were indeed falling into the ocean and were now providing great photo-ops for news outlets around the world. See a video here. It is fascinating how such an isolated event covering 0.5% of the town of Pacifica would suggest to friends that the whole town was endangered.
But it was more bizarre that this dot on the map could be extrapolated into an icon of CO2 climate change. I could only laugh as ridiculous CO2 alarmists who metamorphosed a local disaster, brought about by ignorance of natural coastal changes, into a global warming “crystal ball”. NBC news reported the Pacifica event as “a brief window into what the future holds as sea levels rise from global warming, a sort of a crystal ball for climate change.” The SF Chronicle suggested “increased global warming and rising sea levels due to climate change would double the frequency of those severe weather events across the Pacific basin.” The result would be “more occurrences of devastating weather events and more frequent swings of opposite extremes from one year to the next, with profound socio-economic consequences.”
Such apocryphal stories fueled a menagerie of bizarre blogging alarmists. I was recently interviewed by James Corbett, which incurred the wrath of a few internet snipers trying to denigrate my scientific background. Not knowing I also live in Pacifica, bd6951, a skeptic?bashing poster, linked to a video of threatened apartments in Pacifica and commented, “What we are observing is run away climate change/planetary warming. This is just a guess but, the architecture of these apartment buildings suggest they are at least 20 years old. That means the people who built these units had determined the site was suitable for construction. They clearly were not thinking that an increasingly warming Pacific Ocean would cause their buildings to crash into the ocean 50 or more feet below. Oops. So I want to hear how the climate change denier crowd is going to explain this phenomenon.”
But like so many other alarmists, bd6951 blindly believes every unusual event must be due to rising CO2. Because the media rarely tries to educate the public about natural changes, paranoids like bd6951 perceive every weather event as supporting evidence for their doomsday beliefs, despite a mountain of evidence that it is all natural. Sadly when you try to educate them about documented natural change, paranoids feel you are “disarming them and exposing them to even greater dangers of rising CO2. But anyone familiar with Pacifica’s history understands this coastal erosion hotspot has nothing to do with global warming, and everything to do with the local geology and the natural El Nino oscillation.
So let’s put California’s eroding coastline into both a long term and recent framework. About 72% of California’s coastline consists of steep mountains slopes or raised marine terraces that are being relentlessly chipped away by Pacific Ocean waves. However the geology of the coast is complex due to varied depositional events, colliding plate tectonics and earthquake faults. At one extreme are erosion-resistant metamorphosed submarine basalts, greenstones, formed over 100 million years ago during the age of dinosaurs, and often forming headlands that defy the battering waves. Similarly the granites of the Monterrey Peninsula endure with very little erosion.
On the other extreme are unconsolidated sandstones that were deposited during the past 12,000 years of the Holocene. Due to vastly different resistances to erosion, California presents a majestically steep and undulating coastline. The Pacifica locale has eroded more rapidly because the sea cliffs consist mostly of weakly or moderately cemented marine sediments from the more recent Pleistocene and Holocene. And because Pacifica has long been known as a hot spot of coastal erosion, it has been studied for over 100 years. For a more detailed geology read a 2007 USGS report Processes of coastal bluff erosion in weakly lithified sands, Pacifica, California, USA . As always, before we can blame catastrophic CO2 climate change, we must understand the local setting and the effects of natural change.
Since the end of the Last Glacial Maximum sea levels have risen about 120 meters. During the past 18,000 years most of California’s coast retreated 10 to 20 kilometers eastward at rates of 50 to 150 centimeters per year. The San Francisco/Pacifica region was much more susceptible to erosion and retreated about 50 km. After the Holocene Optimum ended about 5,000 years ago and sea level rise slowed, California’s current rate of coastal erosion decreased to about 10 to 30 cm/year. Undoubtedly rising sea levels have driven coastal erosion. But based on San Francisco Bay Area’s sea level change posted at the PSMSL, since the end of the Little Ice Age this region has undergone a steady rise in sea level of about 2 mm/year and counter-intuitively, the rate of sea level rise has slowed the past few decades as seen in the graph. Sea level rise varies most between El Nino and La Nina events.
Assuming a 150-year rate of local coastal erosion of 30 cm/year, any structure built within 20 meters of the sea bluffs’ edge in 1950, was doomed to fall into the ocean by 2015. But homebuyers that were new to the region were typically naïve about the natural geology and climate. Fortunately when I was shopping for Pacifica homes in 1982, my background allowed me to recognize that developers had ignored all the signs of natural climate change. They unwisely built homes too near the cliffs’ edge to ensure a spectacular view, or they had built in the flood plains and filled tidal marshes.
Awareness of the power of El Niño’s is critical. Sea cliffs crumble and flood plains flood during El Nino events. Indeed during the 1982 El Nino, Pacifica’s Linda Mar lowlands flooded as heavy precipitation filled the banks of San Pedro Creek and high tides resisted the creek’s flow to the ocean. Inspecting Linda Mar’s homes, we could still smell the dampness in every house located in those lowlands. Along the bluffs of Esplanade Drive we likewise saw evidence of coastal retreat during the 1982 El Nino, but not enough to undermine homes and apartments. That did not happen until the El Nino of 1997/98. Wisely we bought our home further inland on a solid ridge. As seen in the picture below from a USGS report, homes in the Esplanade area still had backyards until the 1997/98 El Nino struck. Residents were well aware of the imminent threat as revealed by the boulders, or riprap, placed at the base of the crumbling cliffs to discourage erosion, but those remedies were no match for the ensuing El Nino storm surge.
Unfortunately scientific measurements of coastal erosion did not begin until the 1960s led by Scripps Institute of Oceanography. So early developers had to guess how far back to set their homes from the bluffs’ edge. Due to recent research we now know that those cliffs had “retreated episodically at an average rate of 0.5 to 0.6 meter (1.5 to 2 feet) per year over the past 146 years.” But lacking geologic backgrounds and unaware of natural weather cycles, developers’ ability to estimate a “safe distance” was hampered by the episodic nature of coastal erosion that could lull people into believing erosion was minimal.
Minimal erosion may happen for decades when La Ninas divert the storm tracks northward, during which time naïve homebuyers and builders are not alerted to inevitable future threats. Those mild periods are soon followed by rapid losses during El Nino events. Thus ill informed in 1949, developers constructed several homes at the top of a 20-meter sea cliff along Esplanade Drive in the city of Pacifica. During the heavy winter storms of the 1997/1998 El Niño, 10 meters of local coastline were rapidly eroded, eliminating the last vestiges of the backyards that had survived the 1982 El Nino (see pre-1997 photograph below). In 1997/98, seven homes were undermined and three others threatened. All ten homes were eventually condemned and demolished.
Nonetheless early developers should have been more cautious and alerted by past catastrophes. Early entrepreneurs in California were eager to develop its vast potential. The Ocean Shore Railroad was built, hoping to link San Francisco to Santa Cruz and entice more immigration into the area, as well as to transport lumber and agricultural products. Where the terrain was too daunting to go up and over, they chiseled out ledges that circumscribed the coastal cliffs. Scheduled to open in 1907, the 1906 San Francisco earthquake disrupted those plans. Pacifica lies just south of the San Andreas Fault, and its movement dropped a length of 4000+ feet of right-of-way along Pacifica’s fragile sea cliffs into the sea along with all their railroad building equipment. The surviving railroad ledges can still be seen today.
If you spend enough time walking along Pacifica’s beaches, you would recognize an annual pattern of beach erosion. Heavy winter storms carry the smaller grains of sand offshore restructuring a sandy beach into a bed of rocky cobble. The gentler waves during the summer return the sands to the beach and bury the cobble. The currents will also carry some displaced sand down the coast, while those same currents also carry sands from further upstream. When not enough sand is delivered to replenish a beach, it undergoes rapid erosion. So in addition to natural changes, the damming of rivers that halt the seaward supply of sediments can starve a beach and promote erosion.
Likewise when naturally eroding cliffs are armored at their base by boulders, the lack of local erosion can starve adjacent beaches of needed replenishing sediments. Because of that possible impact on neighbors, the California Coastal Commission now requires a permitting process before any seawall can be built. Finally jetties that are built to protect harbors often block the transport sand along the coast, starving beaches down stream from the jetty and causing amplified erosion. In many locations, governments dredge regions of sediment build-up, and dump those sediments where beaches are now starving, such as being done by San Francisco just north of Pacifica.
This region’s coastal erosion is episodic for well-understood reasons. When a cliff face collapses it leaves a pile of rubble at the cliff’s base, sometimes called the “toe”, which raises the beach and acts to naturally buffer the cliff face from further erosion. After several years, waves and currents carry the buffering toe away, and eventually exposes the cliff to another “bite” from the ocean.
Furthermore the Pacific Decadal Oscillation is expressed as a 20 to 30 year negative phase with more frequent La Nina’s alternating with a positive phase with more frequent El Nino’s. The relatively stationary high-pressure systems prominent during La Nina’s, forces storm tracks to the north of California. Fewer storms mean less coastal erosion, but also result in more California droughts. The current return of El Nino now allows storm tracks to attack the California coast. Snow is currently above average in the Sierra Nevada and reservoirs are filling, but simultaneously coastlines are more heavily eroded.
In addition, the effect of higher rates of precipitation associated with El Nino also cause greater slippage between geologic layers that differ in their ability to handle subsurface water flows. Heavier precipitation caused episodic collapses of coastal Highway 1 at Devil’s Side at the south end of Pacifica. A tunnel was just built to re-route the highway away from that geologically unstable area.
For millennia El Nino cycles have caused these natural extreme swings that alternate between droughts and floods and episodic coastal erosion. Changing your carbon footprint will never stop the process. But knowledge of these natural processes will keep people out of harms way. One of the greatest sins of the politics of the climate wars is that people are not being educated about natural climate change. They are not being taught how to be wary of natural danger zones.
Instead every flood and every drought, every heat wave or snowstorm is now being hyped as a function of global warming. After every catastrophic natural weather event, yellow journalists like the Washington Post’s Chris Mooney or APs Seth Bornstein, seek out CO2 alarmist scientists like Kevin Trenberth or Michael Mann, to make totally unsubstantiated pronouncements that the event was 50% or so due to global warming. After centuries of scientific progress, Trenberth and his ilk have devolved climate science to the pre-Copernican days so that humans are once again at the center of the universe, and our carbon sins are responsible for every problem caused by an ever-changing natural world.
You can recognize those misleading journalists and scientists who are either totally ignorant of natural climate change, or who are politically wedded to a belief in catastrophic CO2 warming, when they falsely argue, as NBC news did, that “frequent swings of opposite extremes” are due to global warming. El Nino’s naturally bring these extremes every 3 to 7 years, as well as the 20 to 30 years swings of the Pacific Decadal Oscillation. These swings have occurred for centuries and millennia! The same storms that bring much needed rains will also batter the coast and increase episodic erosion.
But by ignoring natural change, climate fear mongers delude the public into believing La Nina-caused droughts of the past few years were due to CO2 warming. And now as El Nino returns the rains to California, those same climate fear mongers want us to believe CO2 warming is causing an abrupt swing to heavy rains and coastal erosion. One needs only look at the historical records to find Pacifica’s coastal erosion was much greater around the 1900’s, and that El Ninos have caused natural extreme swings for millennia.
Honest science, useful science, must educate people about our natural hazards and natural climate oscillations; so that people do not build too close to fragile cliff edges or build in the middle of a flood plain. It is not just the coast of California that is eroding. The politicization of climate change is eroding the very integrity of environmental sciences. Reducing your carbon footprint will never save foolishly placed buildings in Pacifica or stop the extreme swings in weather induced by El Nino’s and La Nina’s. It was the end of the Ice Age that initiated dramatic coastal erosion and only a return to those frozen years will stop it. Pacifica’ eroding bluffs are simply evidence that most of California has still not reached an equilibrium with the changes that began 18,000 years ago. Pacifica is truly an icon of natural climate change.
But the ranks of climate alarmists are filled with legions of scientific ignoranti who blindly see such coastal erosion as another “proof” of impending CO2-caused climate hell. This group lusts for climate catastrophes to prove they are not blindly paranoid. Other self-loathing CO2 alarmists simply lust for climate catastrophes that will deal humans their final “come-uppance.” So they too lust for climate catastrophes. Only a solid of understanding of natural climate change can prevent this climate insanity and pave the way to truly scientifically based adaptive measures.
For those who visit or reside in Pacifica, take a walk along the Devil's Slide trail or hike the bluffs near Mori Point. With luck on a clear day you will be able to see the Farallon Islands that lie 48 kilometers west of the Golden Gate. Eighteen thousand years ago, at the end of the Last Glacial Maximum, the Farallons were the tops of the coastal bluffs that delineated California's coastline. Below is a photograph of the Farallons posted by summitpost.org to the internet.
January 30, 2016