2008 Annual Monitoring Report (pdf 10.9MB) - Bolsa Chica ...

Bolsa Chica Lowlands Restoration Monitoring
2008 Annual Report
In response to the loss of private and public property caused by erosion, the U.S. Army Corps of
Engineers, in concert with the State of California and the County of Orange, has undertaken periodic
beach nourishment operations in the Huntington Beach cell since 1964. The majority of the sand
nourishment has been placed at Surfside-Sunset Beach, immediately upcoast of the Bolsa Chica study
area. Table 2-3 summarizes the beach nourishment history at Surfside-Sunset Beach. The next
nourishment episode (Stage 12) is planned for winter/spring 2009.
The beaches along the Bolsa Chica study area benefited as the downdrift recipient of the Surfside-
Sunset nourishment material. During the 34-year period between 1963 and 1997, the beaches
advanced at four of the five historical transects included in the Bolsa Chica monitoring program.
Mean sea level (MSL) shoreline advance ranged from 14 m at Transect 423+89 to 71 m at Transect
350+71. The only occurrence of shoreline retreat during the 34-yr period was a loss of 18 m at
Transect 378+28, located at Huntington Cliffs. The volume of sand above MSL increased in parallel
to the beach width changes during the period. The shorezone volumes in the study area, which
incorporate the sediment changes further offshore, increased at all of the sites. The greatest gains
typically occurred prior to 1978 (USACE, 2002).
Table 2-3. Beach nourishment history.
Date Placement Site Borrow Site Volume (m 3 )
1964 Surfside/Sunset (Stage 1) Naval Weapons Station 3,058,000
1971 Surfside/Sunset (Stage 4) Naval Weapons Station 1,728,000
1979 Surfside/Sunset (Stage 7) Nearshore Borrow Pit 1,257,000
1983 Surfside/Sunset (Stage 8) Naval Weapons Station 382,000
1984 Surfside/Sunset (Stage 8) Nearshore Borrow Pits 1,147,000
1984 Surfside/Sunset (Stage 8) Naval Weapons Station 497,000
1988 Surfside/Sunset Naval Weapons Station 138,000
1990 Surfside/Sunset (Stage 9) Nearshore Borrow Pits 1,393,000
1997 Surfside/Sunset (Stage 10) Nearshore Borrow Pit 1,223,000
2002 Surfside/Sunset (Stage 11) Nearshore Borrow Pit 1,707,000
Source: USACE, 2002; Mesa, 2008a
Historical Shoreline Data
Historical shoreline data were used to provide context for the results of the current Bolsa Chica
monitoring program. The available beach profile and beach width measurement data are summarized
below.
Historical Beach Profile Data
As indicated above, five of the beach profile transects used in the Bolsa Chica monitoring program
were included in the CCSTWS-OC. The study incorporated data from 18 beach profile surveys
conducted between 1963 and 1997. The U.S. Army Corps of Engineers conducted an additional beach
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