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

Bolsa Chica Lowlands Restoration Monitoring
2008 Annual Report
several locations from the placement of the ebb bar offshore of the Bolsa Chica entrance. As a result,
the statistical range of closure was re-computed for each historical transect and for the two new
transects based on all available survey data collected between May 1963 and October 2007. The
procedure used to calculate the statistical range of closure for each transect was identical to that
employed for the CCSTWS-OC (USACE, 2002). The results are shown in Table 2-4.
Statistical closure was assumed to occur at the point at which the standard deviation of all measured
elevations ceased to decrease in value. The procedure used to compute the point of statistical closure
at each profile is summarized below:
Statistical closure was assumed to occur at the point at which the standard deviation of all measured
elevations ceased to decrease in value. The procedure used to compute the point of statistical closure
at each profile is summarized below:
• Sea bottom elevations were interpolated at 15.2-m range intervals along all selected profiles.
• The sample standard deviation of the interpolated elevations for all available survey profiles (σ)
was calculated at each 15.2-m interval.
• Statistical closure was assumed to occur at the point at which σ ceased to decrease.
• The maximum depth of all available survey profiles at the point of statistical closure was
recorded as the depth of statistical closure.
• The distance from the transect origin to the point of statistical closure was recorded as the
“range of statistical closure”. This range was adopted as the offshore boundary for the
computation of shorezone volumes.
Table 2-4. Statistical range and depth of closure at Bolsa Chica area transects.
Transect Designation
Range of Closure
(m)
Depth of Closure
(m, NAVD88)
249+30 473 -6.97
311+22 900 -9.29
318+30 793 -8.80
333+30 717 -8.67
350+71 519 -7.70
378+29 381 -6.73
423+89 549 -8.72
The onshore boundary of the control volume for both the shorezone and subaerial volumes was placed
at the landward edge of the beach sand.
Beach Width Measurements
The results of the beach width measurements obtained by Moffatt and Nichol at the seven Bolsa Chica
area transects are presented graphically in Appendix 2-E. The plots include the MSL beach width and
the horizontal distance from the back beach to the berm.
The Corps beach widths, which consist of measurements from a consistent back beach position to the
break-in-slope at the beach berm, are presented graphically in Appendix 2-F.
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