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Solana Beach Coastal Preservation Association
August 20, 1998
Project No. 1831
Page 8
resistant formation, compared to subaerial erosion of the upper bluff, produces a
characteristic profile.  Rapid marine erosion compared to subaerial erosion
produces a steep overall bluff, whereas slower marine erosion produces a more
gently-sloping upper bluff. The letter A(c)@ indicates that the long-term rate of
subaerial erosion is approximately equal to that of marine erosion. Where the
upper-bluff terrace deposits are undergoing active subaerial erosion, the slope face
is slightly concave. Where subaerial erosion is less active, it is slightly convex.
Local geologic variations within the study area create a derivative of the Type AC(c)@
bluff. The geologic sections along the Solana Beach coast show a partially-
cemented cap of beach ridge sediments. In these areas, where the cap erodes
more slowly and protects the underlying uncemented sediments, the upper bluff will
retreat more in accordance with the Type AB(c)@ bluffs in the Emery and Kuhn
classification, maintaining a steeper profile.
2.4
Shoreline Processes
Littoral currents (currents running parallel to the beach) are one of the dynamic factors
affecting the entire North County coastline. Littoral current is set in motion by waves
moving toward the beach at an angle. Such waves have perpendicular and parallel
components relative to the beach. Under such conditions, sand grains that are lifted by the
surf are moved at right angles to the beach, and at the same time, they are transported
down the beach with the littoral current.
Solana Beach is located within the southern portion of the Oceanside Littoral Cell (Figure
4). A littoral cell is a coastal segment that contains a complete sedimentation cycle,
including sources, transport paths and sinks. The Oceanside Cell extends from the Dana
Point headland southerly to La Jolla Submarine Canyon, a distance of approximately 52
miles. Under natural conditions, a littoral cell is supplied with sediment by rivers and
streams that empty into the ocean within its limits. The sandy material brought to the
coast by fluvial action is then incorporated into the beach sands and transported along the
coast by wave action. This longshore transport of sand is ultimately intercepted by a
submarine canyon or other sink, where it is diverted offshore and lost to the nearshore
environment.






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