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

Bolsa Chica Lowlands Restoration Monitoring
2008 Annual Report
As a result of the shoal-associated muting and its controlling influence on the functioning of the MTBs
and Freeman Creek, along with other variables (shoal volume and area of low intertidal habitat lost),
maintenance dredging was warranted in 2008 and first scheduled to occur in the fall of 2008.
In the “Statements of Interest for the Environmental and Beach Profile Monitoring of the Bolsa Chica
Lowlands Restoration Project”, a dredging trigger was proposed as follows: “a tidal muting of the
average low tide elevations (Mean Low Water) on the order of 0.5 feet would indicate that the flood
shoal maintenance dredging was warranted”. This should be revised since the Mean Low Water in the
FTB is unlikely to ever be muted prior to failing of the required MTB and Freeman Creek drain-out
conditions. The spring low tide would be a more appropriate parameter to gauge the muting in the
FTB.
While water quality conditions and habitat function within the FTB remained high during all periods of
2007 and 2008, the operational restrictions within the west MTB and increasing base water levels in
the MTB affect vegetation condition and distribution, as well as tidal circulation. Both of these have
the potential to significantly affect habitat functions. As a result, an appropriate maintenance dredging
trigger related to impacts to tidal drainage from the MTBs should be included to optimize overall
system functioning. This is addressed in Section 3.
2.3. BEACH MONITORING
Introduction
The objective of the beach monitoring program is to develop a quantitative understanding of changes
in the condition of the beaches adjacent to the newly constructed Full Tidal Basin (FTB) entrance
channel. The study area includes portions of the Bolsa Chica and Huntington Cliffs shorelines. The
monitoring program, which commenced in January 2007, is comprised of semi-annual beach profile
surveys and monthly beach width measurements at seven sites located along a 5.3 km section of
coastline between Bolsa Chica State Beach and 17 th Street in Huntington Beach. Coastal Frontiers
Corporation conducted the beach profile surveys, while Moffatt and Nichol performed the beach width
measurements. The historical research and collected data analysis was conducted by Coastal Frontiers
Corporation.
Figure 2-8 shows the locations of the beach profile transects used in the monitoring program. Two of
these were established specifically for the monitoring program and were first surveyed in January
2007. Five of the transects had been established previously and were included in the Coast of
California Storm and Tidal Waves Study for the Orange County Region (CCSTWS-OC) conducted by
the U.S. Army Corps of Engineers (USACE 2002).
Transect establishment/recovery activities were conducted prior to the commencement of the initial
beach profile survey. The initial beach profile survey for the Bolsa Chica Lowlands Restoration
Project was conducted in January 2007. Additional surveys have been performed during each of the
subsequent May and October time periods in 2007 and 2008 (Appendix 1-A). The monthly beach
width measurements commenced in January 2007. The monitoring activities were detailed previously
by Coastal Frontiers (2007a, 2007b, 2008a, 2008b, 2009) and are discussed under the methodology
section below.
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