related sedimentation. There would be no significant indirect sedimentation impact at the Cardiff receiver
site.
The evaluation below describes briefly the potential indirect sedimentation impacts at these six locations
were sedimentation risk (depth and duration) is predicted. A more detailed analysis of each location is
provided in Appendix D.
Potential Indirect Sedimentation Near South Oceanside. As shown in Figure 4.4-1, a model-
predicted persistent sediment deposition area would be located offshore the southern end of the receiver
site in a location where commercial fisherman had identified scattered rocks. That area was later mapped
during the side-scan sonar and dive effort and found to contain hard substrate. Two hard substrate areas
in this location (-15 to -25 feet MLLW) have scattered occurrences of sea fans but the heights of the reef
would be above the maximum persistent sedimentation depths and no significant impacts would occur.
Other hard substrates within the area include cobble and rock relief with opportunistic coralline algal turf.
Scattered rocks to the north of Oceanside Boulevard are not considered to be at risk of substantial
sedimentation because model-predicted increases in sand levels are within the historical average resulting
from seasonal variation in sand.
Results of the model predictions exhibit similarity to empirical profile data collected before and after 1983
and 1988 beach replenishment projects. For both of those projects, sedimentation mainly occurred out
from 1,100 to 1,300 feet from the backbeach, and sedimentation was not obvious past 1475 feet from the
backbeach. Similarly, model predictions for this project indicate little sedimentation beyond 1,200 feet
from the backbeach.
Potential Indirect Sedimentation South ofNorth Carlsbad. Worst-case sedimentation transport from
the North Carlsbad receiver site would be toward the south, and some sedimentation risk is predicted by
the modelimmediately south of the site (between Oak and Chestnut Avenues), south of Tamarack Avenue,
and south of the discharge jetty for Agua Hedionda Lagoon. Figure 4.4-2 illustrates the biological
resources offshore and just south of the receiver site and Figure 4.4-18 illustrates the resources in those
areas surveyed near the lagoon. Intertidal hard substrate that supports surfgrass is located off Juniper
Avenue (Figure 4.4-2) and south of Cannon Road (Terra Mar) (Figure 4.4-18). Nearshore reef with
various sensitive resources occurs southof the receiver site near Agua Hedionda Lagoon. Historically, kelp
has occurred offshore and further south at depths generally greater than 20 feet MLLW, which is typically
Regional Beach Sand Project EIR/EA
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