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

Bolsa Chica Lowlands Restoration Monitoring
2008 Annual Report
Figure 2-16. Long-Term shorezone volume changes, May 1963 to October 2008
Bolsa Chica Monitoring Period Shorezone Volume Changes (2005 to 2008): It is not possible to
quantify the shorezone volume changes for the Bolsa Chica Monitoring Period because the October
2005 profile does not extend below the waterline. However, investigation of the time series plots in
Appendix 2-D indicates that a trend of shorezone volume loss has prevailed at each transect between
January 2007 and October 2008. This may be attributable dispersal of the ebb bar and natural
shoreline erosion between Surfside-Sunset nourishment intervals.
Beach Width Measurement
Time series plots for the beach width measurements obtained at the seven Bolsa Chica area transects
by Moffatt and Nichol and at three nearby locations by the U.S. Army Corps of Engineers are
presented in Appendices 2-E and 2-F, respectively.
The results of the beach width measurements obtained at the seven Bolsa Chica area transects are
summarized in Table 2-5. During the two-year period between the January 2007 and December 2008
observations, the MSL beach width decreased at three of the seven sites, increased at three locations,
and was essentially unchanged (3 m or less) at the remaining site. In general, the shoreline tended to
advance north of the entrance channel and retreat to the south. The greatest shoreline advance was
14 m, and occurred north of the entrance channel at Transects 311+22 and 318+30. The greatest
shoreline retreat, 22 m, occurred immediately south of the entrance channel at Transect 333+30, and at
the north end of the study area at Transect 249+30. Shoreline change rates during the two-year period
ranged from -10.9 m/yr at Transect 249+30 to 8.0 m/yr at Transect 318+30.
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