4.1 Geology and Soils
GEOLOGY AND SOILS
4.1
The following analysis of coastal geology and littoral processes related to beach replenishment is based on
studies performed in Shoreline Morphology Study, San Diego Regional Beach Sand Project (Moffatt
& Nichol 2000a) and the previous EAs prepared by the U.S. Navy (Department of the Navy 1997a,
1997b).
4.1.1
Significance Criteria
The protection of unique geologic coastal features and the minimization of erosion are considered when
evaluating potential impacts of a proposed action. For this analysis, an impact to geologic resources would
be significant if it would:
destroy, permanently cover, or modify any unique geologic or physical features;
increase erosion of soils, either on or offsite; or
cause erosion of beach sand.
Beach replenishment using dredged sediments is generally considered beneficial in areas where beach
erosion is a problem as material provides recreational beach area and shoreline protection, including
stabilizing fragile bluffs. However, placement of the sand can also create a temporary change in the
shoreline. Over a period of time, the sand would be moved and redistributed from the placement location
alongshore and cross-shore through natural littoral transport creating an equilibrium beach profile. The
equilibrium beach profile would have a similar shape as the pre-fill beach profiles, but may extend further
seaward. The longshore spread of the beach fill would temporarily widen the beaches upcoast and
downcoast of the receiver sites, until natural littoral transport redistributed the sand through the littoral cell.
Regional Beach Sand Project EIR/EA
Page 4.1-3
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