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 City of Solana Beach
Section 1
Shoreline and Coastal Bluff Management Strategies Draft MEIR
Introduction
above the mean sea level to the larger portion of the beach offshore covered by seawater.
These combined seasonal processes, including both winter and summer sand shifts, comprise a
complete sedimentation cycle.
A coastal segment that contains a complete sedimentation cycle is defined as a littoral cell. It is
the dynamic interface between the ocean and land. Along the San Diego region's coast, there
are three littoral cells that cycle sand on and off the beaches (Figure 1-3). Bounded on one side
by the landward limit of the beach and extending seaward beyond the area of breaking waves, a
littoral cell is the region where wave energy dissipates.
Littoral cells are physically
interconnected; occurrences in one part of a littoral cell will ultimately have an impact on other
parts. The three littoral zones off of the San Diego region include the southern half of the
Oceanside Littoral Cell, the Mission Bay Littoral Cell, and the Silver Strand Littoral Cell.
Solana Beach is an isolated beach within the southern half of the Oceanside Littoral Cell. It
does not have any major river, stream, or cliff resources that continually provide sufficient sand
supply to the beach. Thus, the City's beaches are experiencing a net loss of sand. The reach
from southern Oceanside to northern Del Mar is dependent on longshore transport of sand from
the north and south. Longshore sand transport is driven by waves breaking at an angle to the
shoreline. Transport is generally southward in winter and northward in summer. Estimates of
long-term transport potential average about 750,000 cubic yards of sand per year to the south,
and 550,000 cubic yards per year to the north. This means that a total of 1,300,000 cubic yards
of gross sand transport per year are capable of being mobilized, with a net southward rate of
200,000 cubic yards per year.
Sand also moves onshore and offshore. Typically, between 10 and 35 cubic yards per yard of
beach move back and forth between winter and summer. In big storm events, up to 100 or
more cubic yards per yard may be lost offshore. Under the present conditions of sand
starvation, the small contribution from cliff erosion in Solana Beach gets immediately swept
away.
Seacliff erosion is a natural process occurring throughout San Diego County generally and in
Solana Beach specifically, which in the last several decades has been greatly accelerated by
the lack of sand replenishment due to the damming of, and mining in, coastal rivers that
formerly carried to the ocean much greater amounts of sediment than are currently being
delivered. Current approximate rates of erosion are estimated at an average of 0.4 feet per
year, equating to a range of approximately 27 to 40 feet per 100 years. However, depending on
multiple factors, such as wave action, winter storms, and upper bluff irrigation runoff, which
contribute to cliff erosion in a given year, rates will vary. Seacliff erosion becomes an inevitable
threat to unprotected housing atop the upper bluffs. Even if all of the existing seawall and
shoreline protection structures were removed, Solana Beach would still experience a sand
shortage. For instance, even at a high rate of 6 cubic yards per yard per year of cliff sand
contribution, the entire 1.7 miles (2,500 yards) of Solana Beach Coastline would contribute less
than 15,000 cubic yards of sand per year. This is the primary reason why shoreline protection
management is and has been a critical issue in Solana Beach.
Project No. 323530000
Page 1-4
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