2008 Annual Monitoring Report (pdf 10.9MB) - Bolsa Chica ...
2008 Annual Monitoring Report (pdf 10.9MB) - Bolsa Chica ...
2008 Annual Monitoring Report (pdf 10.9MB) - Bolsa Chica ...
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<strong>Bolsa</strong> <strong>Chica</strong> Lowlands Restoration <strong>Monitoring</strong><br />
<strong>2008</strong> <strong>Annual</strong> <strong>Report</strong><br />
120<br />
12-Month Rolling Average Berm Width (m)<br />
100<br />
80<br />
60<br />
40<br />
20<br />
long-term mean = 52.4 m<br />
minumum permitable beach width<br />
+-2 Standard Deviations<br />
from Long-Term Mean<br />
0<br />
2005 2006 2007 <strong>2008</strong> 2009 2010<br />
Year<br />
Figure 2-19. Twelve-Month average berm width at Corps Station 424+44<br />
Influence of Entrance Channel<br />
Shoreline Changes Adjacent to Entrance Channel: Between October 2005 and October <strong>2008</strong>, the<br />
beaches upcoast (north) of the new entrance channel accreted, while those downcoast (south) of the<br />
channel tended to erode (Figure 2-13). Figure 2-20 compares the shoreline changes immediately north<br />
of the channel (Transect 318+30) with the changes for the remaining upcoast monitoring sites<br />
(Transects 249+30 and 311+12). The shoreline at the three upcoast transects responded similarly<br />
between October 2005 and January 2007. Following the opening of the new channel (January 2007 to<br />
October 2007), the shoreline at Transect 318+30 retreated slightly, while the beaches at the other<br />
upcoast sites advanced. Between October 2007 and October <strong>2008</strong>, the shoreline advanced at Transect<br />
318+30, stabilized at Transect 311+12, and retreated at Transect 249+30.<br />
A time series of the shoreline changes at the four transects located downcoast (south) of the entrance<br />
channel is shown in Figure 2-21. The shoreline changes at Transect 333+30 (immediately downdrift of<br />
the channel) were nearly identical to those at Transects 350+71 and 423+89, and indicate a trend of<br />
shoreline retreat between October 2005 and October 2007. The shoreline changes at Transect 378+29<br />
differed only modestly. During the most recent one-year period (October 2007 to October <strong>2008</strong>),<br />
modest shoreline advance occurred at the two transects nearest the entrance channel (333+30 and<br />
350+71). In contrast, the shoreline retreated at the remaining sites.<br />
Volume Changes Adjacent to Entrance Channel: The subaerial volume changes upcoast of the<br />
entrance channel (Figure 2-22) responded similarly to the shoreline changes. The subaerial volume<br />
increased during the three-year period at each of the sites, with the most pronounced gains occurring at<br />
Transects 311+22 and 318+30.<br />
Merkel & Associates, Inc. 132