Open a coastal study and you will find a number. Encinitas bluffs: so many centimeters per year. California cliffs: so many tenths of a meter per year. Those figures are useful. They are also easy to misuse. A long-term average is not a promise about the next winter on your specific bluff-top lot, and it is not a yardstick for arguing with a geotech report that looked at your parcel.
This note is about literacy: where the Encinitas numbers come from, what the USGS statewide cliff work actually claims, and how to hold both without false precision. For how the bluffs are stacked, see how Encinitas bluffs are built. For the homeowner overlay conversation, see bluff-top home foundations.
A county table and an Encinitas row
A San Diego County seacliff study archived through CDIP reports long-term erosion rates for nine cliff sites analyzed from aerial photography covering roughly 1932 to 1994. In that table, the Encinitas site is listed near 7.70 centimeters per year with a standard deviation around 2.31 centimeters per year. Neighboring Cardiff and Solana Beach rows in the same table are different. That scatter inside one county is the first lesson: lithology and exposure matter as much as the regional climate story.
The paper’s broader point is that cliff materials strongly influence rates and landforms. Wave energy matters, but the rock and sediment package under the house is not a footnote. When a soils or coastal engineer writes about your lot, they are not required to match a county-average row. They are required to explain your section of bluff.
What the USGS cliff-retreat report is (and is not)
USGS Open-File Report 2007-1133 summarizes historical coastal cliff retreat along California by comparing mid-twentieth-century cliff edges with lidar-derived modern edges. Statewide, the report cites an average retreat rate on the order of a few tenths of a meter per year across many thousands of transects, with Southern California rates often lower where coastal engineering has altered the shoreline. The authors are explicit that the rates describe past conditions over roughly seventy years and are not intended as predictions of future cliff-edge positions.
That disclaimer is the second lesson. Historical end-point rates average quiet decades and storm clusters into one slope. Your next El Niño winter is not obliged to match the average. Neither is a decade of relative calm proof that the long-term story has ended.
Episodic failure hides inside neat averages
Bluff change is often stepwise. A basal notch grows for years. An upper terrace fails in a single season. Sand comes and goes at the toe. Irrigation and drainage on the top of the bluff change pore pressures. A centimeter-per-year line on a chart can describe that history after the fact without telling you which year the next step happens.
Sand replenishment projects can change the nearshore buffer for a time. They do not rewrite geology. Our post on the 2024 sand project and bluff-top homes stays in that lane: temporary beach width is not a permanent redesign of the cliff.
How to read a rate in a geotech packet
When a bluff-top report cites a retreat rate, ask three quiet questions:
- Is the number regional, city-scale, or derived from surveys on this parcel and its immediate neighbors?
- What period and method produced it — aerial end points, lidar, ground survey, or a literature citation?
- How does the report translate the rate into setback, monitoring, or design language for this house?
Those questions keep you from treating a published Encinitas average as if it were a survey of your backyard. The City’s Local Coastal Program, certified in May 1995 with coastal development permit authority assumed that same month, is the planning frame for many bluff-top permits. The Coastal Commission’s appeal information sheet explains which local coastal decisions can be reviewed further. Neither document turns a retreat rate into a lot-specific forecast.
Uncertainty is not the same as knowing nothing
Owners sometimes hear “uncertain” and stop listening. The better reading is narrower: long-term averages orient you; site investigation narrows the range; monitoring watches for change. The California Geological Survey’s San Diego regional geologic map pamphlet is another orientation layer — formation names and map units — not a substitute for borings on your lot.
If you are comparing two studies that disagree by a factor of two, look first at period, method and exact shoreline segment. Disagreement is common when one study averages a wide reach and another resolves a single cove.
What this means for foundation conversations
Retreat literacy belongs next to foundation literacy on a bluff-top lot. Drainage at the top of the bluff, irrigation habits, and the condition of any existing protection at the toe all show up in structural evaluations even when the conversation began with a crack indoors. See bluff stabilization for the structural framing of that work, and coastal permits for foundation repair for the permit vocabulary that often travels with it.
We coordinate with licensed engineers as needed when a bluff-top evaluation has to connect interior symptoms to coastal geotechnical findings. We do not treat a published retreat average as a design value for your parcel, and we do not speak as if any structure erases coastal change.
A practical way to use the numbers
Keep a short folder: the page or table that cited a rate, the date you read it, and any site-specific rate in your soils report. When a new study appears, add it without deleting the old one. Patterns across sources are more honest than a single favorite figure. For a whole-house starting point inland of the bluff edge, a foundation inspection conversation still begins with floors, cracks and drainage — then reaches seaward only as far as the lot requires.
Encinitas owners from Leucadia through Cardiff hear retreat numbers in public meetings and private reports. Reading them calmly is a homeowner skill. When you want that skill paired with an on-site look at your house, ## Holding two numbers without picking a favorite
Homeowners sometimes treat the smaller rate as comforting and the larger rate as alarming. A better habit is to ask which shoreline segment, which years, and which method produced each figure, then to ask the site geotech how either figure was or was not used in the setback discussion for this parcel. Encinitas bluff-top owners from Leucadia through Cardiff can keep both a regional table and a site letter in the same folder without forcing them to agree to the digit.
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