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 Solana Beach Coastal Preservation Association
August 20, 1998
Project No. 1831
Page 16
3.2
Short-Term Sea-Level Change
The effect of waves on the coast is highly dependent on the sea level during the wave
episode. Large waves at low sea level cause limited erosion, since they break well offshore.
When episodes of large waves combine with short-term high sea level from tides and other
factors, rapid retreat may occur along vulnerable coastlines.
3.2.1 Tides
Tides are caused by the gravitational pull of astronomical bodies; primarily the
moon, sun, and planets. Tides along the San Diego coast have a semi-diurnal
inequality. On an annual average basis, the lowest tide is about -1.6 feet (MLLW
datum) and the highest tide is about 7.1 feet, MLLW datum.
The National Oceanic and Atmospheric Administration (NOAA) collected 18 years
of measurements at La Jolla in establishing tidal datums of the 1960 to 1978 tidal
epoch (NOAA, 1978). Tidal characteristics at the La Jolla Tidal Station are shown
in the following table. The highest recorded sea level at the La Jolla Pier Gauge was
7.81 feet, MLLW, on August 8, 1993.
San Diego Tidal Characteristics at La Jolla
(elevation in feet referenced to mean lower low water, MLLW)
Highest observed water level (Aug. 8, 1983)
7.81
Mean Higher High Water (MHHW)
5.37
Mean High Water (MHW)
1.32
Mean Sea Level (MSL)
2.75
Mean Tide Level (MTL)
2.77
National Geodetic Datum - 1929 (NGVD)
2.56
Mean Low Water (MLW)
0.93
Mean Lower Low Water (MLLW)
0.00
Lowest observed water level (Dec. 17, 1933)
-2.6
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