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

Bolsa Chica Lowlands Restoration Monitoring
2008 Annual Report
Table 2-5. Beach width measurement program summary statistics, Jan. 2007 to Dec. 2008.
Transect
Range
(m))
Distance to Berm (m)
Ave
(m)
Change
(m)
Trend
(m/yr)
Range
(m))
MSL Beach Width (m)
Ave
(m)
Change
(m)
Trend
(m/yr)
249+30 57-86 67 -12 -11.7 73-104 85 -22 -10.9
311+22 50-67 59 7 4.0 65-87 75 14 4.5
318+30 56-77 65 9 6.7 69-99 82 14 8.0
333+30 24-46 32 -22 -10.3 38-72 56 -22 -5.7
350+71 22-37 28 -2 -5.9 34-53 47 -3 -2.7
378+29 0-14 3 2 -2.8 6-33 18 6 -2.4
423+89 78-99 85 -3 -0.2 95-110 102 -5 1.4
The Bolsa Chica Monitoring Plan (USFWS, 2001b) defined beach nourishment triggers based on the
monthly beach width observations at the Corps measurement sites within the study area. The
minimum permitable beach width based on two consecutive monthly measurements was stipulated to
be 15.2 m (50 ft). A second condition indicated that the 12-month rolling average beach width could
not deviate from the long-term mean beach width (based on the period January 1980 to January 2000)
by more than two standard deviations. Table 2-6 shows the beach width statistics for the three Corps
measurement sites within the study that were provided in the monitoring plan.
Table 2-6. Range and depth of closure at Bolsa Chica area transects.
Station
Berm Width (m)
Range Mean Std. Deviation
247+88 48 - 105 64.0 7.6
307+88 12 - 59 33.2 7.3
424+44 18 - 81 52.4 10.4
Figures 2-17, 2-18, and 2-19 show the long-term rolling average berm width from October 2006 (preproject)
to December 2008 at each of the three Corps measurement sites within the study area. The
time series plots also show the minimum stipulated berm width (15.2 m), the long-term mean berm
width, and a shaded area encompassing two standard deviations above and below the long-term mean
berm width.
The 12-month rolling average berm width remained above the minimum stipulated berm width
(15.2 m) throughout the period at each of the sites. At 307+88 and 424+44, the 12-month rolling
average berm width exceeded two standard deviations above the long-term mean. At no location,
however, was the 12-month rolling average berm width less than two standard deviations below the
long-term mean.
Merkel & Associates, Inc. 130