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

Bolsa Chica Lowlands Restoration Monitoring
2008 Annual Report
Bolsa Chica Monitoring Period Shoreline Changes (2005 to 2008): Beach width changes between
October 2005 and October 2008 are shown in Figure 2-13. During the three-year period encompassing
the construction of the Bolsa Chica Lowlands Restoration Project, the shoreline advanced at the three
transects located north of the entrance channel (249+30, 311+22, and 318+30). The greatest gain, 24
m, occurred at Transect 311+22. Shoreline retreat predominated at the survey sites located south of the
entrance channel. Beach widths changes ranged from a gain of 1 m at Transect 333+30 to a loss of 14
m at Transect 423+89. Similarly, investigation of the time series plots in Appendix 2-C indicates
trends of shoreline advance north of the entrance channel and shoreline retreat south of the entrance
channel during the Bolsa Chica Monitoring Period.
Figure 2-13. Bolsa Chica monitoring period shoreline changes, October 2005 to October 2008
Sediment Volume Changes
Long-Term Subaerial Volume Changes (1963 to 2008): The long-term subaerial volume trends
(Appendix 2-D) were similar to the long-term shoreline changes. Volume gains occurred at six of the
seven Bolsa Chica area transects during the 45-year period between 1963 and 2008. In keeping with
the shoreline change trends, the exception was Transect 378+29, where subaerial volumes were
relatively stable during this period with no apparent trend. Figure 2-14, which shows the net longterm
subaerial volume changes between May 1963 and May 2008, bears a striking resemblance to
Figure 2-12 (showing shoreline changes for the same period).
Merkel & Associates, Inc. 126