Southern California Sea Level Rise and Flood Risks

SC Coastal Sea Level Rise, Flood Heights, and Population at Risk

We use the web site Surging Seas Risk Finder to find projected sea level and flood heights for the Southern California Beach Cities south of Long Beach.

We start with flood risks. For Laguna Beach, the tidal heights use the tidal gauge at La Jolla. There is a 100% risk of a flood over 3 feet between now and 2050. There is a 50% risk to 2040, but only a few percent to 2030. This is with the medium scenario for sea level rise.

Now for sea level rise in the medium scenario. The rise above the 1992 high tide level is: 3.5 ft in 2100; 2.5 ft in 2080; 1.6 ft in 2060; and 0.9 ft at 2040.

A “mild flood” is one that happens once a year. A “moderate flood” is one that is 2.1 feet above the 1992 high tide. We show the table of mild and moderate flood heights in the future.

Year…..Mild Flood….Moderate flood heights:

2020……….2.2 ft………2.1 ft
2040……….2.7 ft………2.6 ft
2060……….3.4 ft………3.0 ft
2080……….4.3 ft………3.8 ft
2100………..5.3 ft………5.7 ft

From the Risk Zone Maps, at 6 feet rise, there is no damage to downtown Laguna Beach. At 7 feet, coast highway is flooded next to main beach. At 8 feet, Ocean and Broadway are flooded a half of the way up to Glen Eyre. At 9 feet, they are flooded two thirds up to Glen Eyre. At 10 feet, downtown is flooded up to Glen Eyre.

For the population at risk who live less than 3 feet above high tide level, we start with Orange County and the 2010 census. There are 6,500 people in Newport Beach, 3,100 in Huntington Beach, and 400 in Sunset Beach. These are people not protected by sea walls.

We start with the 48th Congressional District represented by Republican Dana Rorabacher. It runs along the coast from Seal Beach through Huntington Beach, Newport Beach, and Laguna Beach to Laguna Niguel. The 48th has 10,000 people living below 3 feet, essentially those listed above for Orange County.

The 47th Congressional District covers Long Beach to Westminster and is represented by Democrat Alan Lowenthal. It has 6,000 people living below 3 feet.

The 49th Congressional District runs from San Clemente through Del Mar, stopping at La Jolla. It has only 93 people below 3 feet. It is represented by Republican Darrell Issa.

The 14th Congressional District covers San Mateo and borders the SF Bay and the Pacific Coast. It is represented by Democrat Jackie Speier. It has 73,000 people below 3 feet.

The 2nd Congressional District covers the coast from Marin County to the Northern border. It has 23,400 people below 3 feet. It is represented by Democrat Jared Huffman.

The 9th Congressional District is centered around Stockton and is East of the SF Bay. It is represented by Democrat Jerry McNerney. It has 10,900 living below 3 feet.

These Districts of the State of California have 123,000 people living below three feet above high tide level. We summarize their districts: 14th at 73,000; 2nd at 23,400; 9th at 10,900; the 48th at 10,000; and the 47th at 6,000.

On the other hand, their are 55,000 Stockton residents and 22,800 in Sacramento living less than one feet above high tide, but protected by levees that will be overrun at 3 feet above high tide. This is in the Sacramento-San Joaquin River Delta, and includes the 9th Congressional district. Below 3 feet in this area is $7.5 billion of property, 254 miles of roads, 25 schools, and 33 contaminated sites.


About Dennis SILVERMAN

I am a retired Professor of Physics and Astronomy at U C Irvine. For a decade I have been active in learning about energy and the environment, and in lecturing and attending classes at the Osher Lifelong Learning Institute (OLLI) at UC Irvine.
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