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 City of Solana Beach
Section 3
Shoreline and Coastal Bluff Management Strategies Draft MEIR
Environmental Impact Analyses
2.
Reduction of sediment contribution. Seawalls and other shoreline structures prevent
natural erosion processes of coastal bluffs. Therefore, the bluff will not naturally erode
and cannot contribute to sediment on the beach in front of it. However, the amount of
sediment that is denied from eroding is generally not significant in Solana Beach. The
estimated rate of sand contribution from bluff erosion alone specific to Solana Beach is
1 to 6 cubic yards per yard per year, or less than 15,000 cubic yards of sand per year;
1 percent of gross longshore transport for all of Solana Beach (Flick, 2001). Therefore,
the reduction in sediment contribution due to bluff protection structures is not considered a
significant impact because it will not result in long-term degradation of recreational
opportunities.
3.
Beach encroachment/placement loss. This refers to when a seawall or shoreline structure
is constructed seaward of the base of the seacliff, there is a reduction in the average
beach width. The boundary of the beach is moved toward the ocean, therefore reducing
the amount of beach. Therefore, this effect has significant impacts to recreation. Seacave
and notch fills are different in that they are backfill and do not extend the natural bluff
boundary seaward.
4.
Wave reflection. A seawall or protective structure such as seacave and notch fills may
induce the seaward transport of sand, due to increased reflection of wave energy. This
could result in a reduction of mean beach width over the long term and is therefore
potentially significant to recreation.
5.
Erosion of tidal terrace. If bluff retreat is fixed by a seawall or protective structure such as
a seacave and notch fills, new tidal terrace is not formed. Implications of this effect on
recreation and public access would be a loss of level beach and increased sand loss.
Therefore, impacts would be significant.
Based on the findings above, under the No Project Alternative, impacts from seawalls to
recreation and lateral beach access would be more significant as compared to seacave and
notch fills. Seawalls could fix the landward boundary of the beach, reduce the amount of beach,
increase the reflection of wave energy, and the erosion of tidal terrace. Seacave and notch fills,
in contrast, could fix the landward boundary of the beach, increase the reflection of wave
energy, and the erosion of the tidal terrace, but would not reduce the amount of beach as would
occur with seawalls. Impacts to access structures, such as stairways, would be less than
significant.
To mitigate the potential effects of shoreline protection structures, as stated above, the following
mitigation measures were developed (also described in Section 3.1):
Project No. 323530000
Page 3-54
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