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 />
abandoned. Of these, 174 total chicks were produced in <strong>2008</strong> and a minimum of 57 and a maximum of<br />
109 (32.8 to 62.6%) chicks survived to fledge. The minimum fledgling estimate per nest (0.85<br />
fledglings/nest) is slightly below the average (0.95 fledglings/nest) of the study years. The maximum<br />
estimate of fledglings per nest (1.62 fledglings/nest) would exceed the previous high of 1.47 in 2005.<br />
Avian monitoring recommendations include continuing the Belding’s Savannah sparrow monitoring<br />
program to include a minimum of 2 surveys per breeding season and implementation of the<br />
management recommendations detailed in the snowy plover report (Appendix 1-F).<br />
INLET FLOOD SHOAL<br />
The rate and distribution of sand accretion in the FTB inlet was assessed by bathymetric survey in<br />
January and June 2007, and in January, July, and December <strong>2008</strong>. The volume and distribution of<br />
accumulated sand was compared to the pre-basin opening conditions of August 2006. A small shoal<br />
had formed in the inlet by January 2007 and continued to expand through 2007 and <strong>2008</strong>. The net<br />
volume of sediment (composed entirely of littoral sand) accreted within the assessment polygon was<br />
compared to the pre-opening conditions and had reached 204,923 m 3 by December <strong>2008</strong>. This can be<br />
expressed as a total rate of volume change from the basin opening through December <strong>2008</strong>, roughly 28<br />
months later, of approximately 240 m 3 /day. It is important to note, however, that this average rate<br />
does not represent the actual accretion per day, as deposition and erosion occurred throughout the<br />
period at an uneven rate.<br />
To examine this variable rate, the contour plots of each survey were compared to each other to quantify<br />
areas of erosion and accretion between surveys. As anticipated, there was a large input of sand<br />
between the basin opening on August 24, 2006 and the first survey on January 19, 2007, with an<br />
average of 402 m 3 /day. The influx rate then decreased between subsequent surveys, to an average of<br />
230 m 3 /day in 2007 and 134 m 3 /day in <strong>2008</strong>.<br />
The flood shoal volume, area of shoaling, and shoaling rate have occurred similarly to processes<br />
predicted during the project design. The variable seasonal influx of sand, and added complication of<br />
provision of local source sand in the pre-filled ebb bar and beach around the mouth, is expected to<br />
have played a role in the high early infill rates. Further, early infill would have also added sand to the<br />
oversized entrance channel, thus decreasing the observed rate of shoaling from the true rate since the<br />
flood shoal survey assessment area does not extend out fully into the entrance channel. Subsequent<br />
reduced rates of infill may indicate more rapid achievement of relative stability following the initial<br />
system loading.<br />
Future monitoring of the flood shoal will occur in January and June of 2009 and 2010.<br />
TIDAL MONITORING<br />
Accretion of sand within the flood shoal of the FTB is the most important factor causing tidal lag and<br />
muting. Tidal monitoring provides a means of tracking the lag and muting and providing information<br />
necessary to determine the need for maintenance dredging to ensure proper physical and ecological<br />
system functioning.<br />
Tidal monitoring began in the FTB in December 2006 and was continuous throughout <strong>2008</strong>.<br />
Comparison of the lower low tide data for each day showed that the FTB did not completely drain to<br />
local oceanic sea levels (as measured at Los Angeles Outer Harbor [LAOH]) during lower low spring<br />
Merkel & Associates, Inc. 6