Above is an Encinitas, CA (northern coastal city in San Diego, my home) subdivision map from 1883, overlaid with surveys up to 1980. What it shows is that the cliffs near Cottonwood Creek eroded more than 600 feet from 1883 to 1891, or in only 8 years. This was during a particularly epic wet period in California between 1884 and 1891. At one point the rain over a 2 week period in Oceanside was 13 inches, which was more the previous YEAR'S total. San Diego's "normal" rainfall is around 9 inches a year. The cause was likely weather changes after the eruption of Krakatoa, which sent up volcanic dust into the atmosphere as niduses for rain droplet formation. On the map you can clearly see that it wiped out several blocks of seaside property, and even temporarily caused land parcels inland to go up in value.
20 years prior to this period, in 1862, there was an even more epic rainy season on the entire West Coast! The rain "began in December 1861 and continued until the summer of 1862." Sacramento was so flooded the state capitol was temporarily moved to San Francisco. "The great Sacramento and San Joaquin valleys of California were turned into a lake about 300 miles long and 20-60 miles wide." and "approximately one-quarter of the taxable real estate was destroyed", causing the State of California to go bankrupt.
This history is from a delightful book published in 1984 by SIO scientists Gerald Kuhn and Francis Shepard titled "Sea Cliffs Beaches and Coastal Valleys of San Diego County: Some Amazing Histories and Some Horrifying Implications." , complete with multiple photos of bluff failures. There are many complicating factors in bluff erosion, but one of those currently is excessive runoff from landscape watering and resulting over-saturation of soils- one of the things we can actually control. I believe this book should be required reading for any city's climate change or Global Warming committee.
Perhaps things may have turned out differently for the Self-Realization Fellowship in Encinitas, who built a temple 30 feet back from the bluffs in 1938, only to watch it crumble into the waves 3 years later. History, History, History...!
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