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Solana Beach Coastal Preservation Association
August 20, 1998
Project No. 1831
Page 11
been evident since the early 1980s, and has been noted in Solana Beach for the last few
years.
2.6
Bathymetry
Nearshore bathymetry published by NOAA (1980) and Continental Data Systems (1971)
suggests a relatively uniform offshore bathymetry out to the 10-fathom contour, with the
single exception of the surf break at Tabletop Reef. Average offshore slopes are on the
order of 60:1 to 70:1. The Corps of Engineers (Los Angeles District) has profiled one
survey range within Solana Beach just north of Fletcher Cove (Range SD600) on an
intermittent basis. This range was also reportedly surveyed by the U.S. Coast and Geodetic
Survey in April 1894, with essentially no variation in the profile in 60 years (USCOE, 1960).
SD600 has most recently been surveyed by the Corps as part of a sand thickness survey
report (USCOE, 1988), with the results reported on Figure 5. The results of the 1957
Corps survey have been superimposed upon the 1988 Corps survey; however, it should be
noted that we have assumed a backshore width of 100 feet, recognizing that this value was
not reported in the 1960 Corps survey. It should be noted, however, that within the 1960
Corps study, backshores were often noted throughout much of the North County coastline.
The sand thickness reported in the 1988 Corps study was determined by a jet probe, with
the acknowledgment that the onshore measured sand thickness may not accurately reflect
the total thickness above the shore platform, acknowledging the presence of an extensive
shingle beach below the active sand beach.
Group Delta Consultants (GDC) also surveyed one profile to a depth of 40 feet, extending
offshore from 367 Pacific Avenue, with both horizontal and vertical control provided by a
Total Station Survey instrument (the same technique as used in the 1988 Corps study).
The GDC profile is also shown on Figure 5, and as with the 1988 Corps study, a shingle
beach was encountered that we could not penetrate, along with an offshore bar, the
approximate extent of which is shown on Figure 5. Both onshore and offshore sand
measurements in the GDC study utilized a steel probe, with the tactile feel of the underlying
shore platform clearly discernible from the overlying transient sand surface and the
underlying shingle beach.



 


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