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 City of Solana Beach
Section 3
Shoreline and Coastal Bluff Management Strategies Draft MEIR
Environmental Impact Analyses
track. The estimated 50-year and 100-year top-of-bluff setback lines are shown in Figures 2-1
through 2-7.
Summary
The Planned Coastal Retreat alternative would allow natural erosion processes to occur. If
permitted by state law, this alternative would most likely trigger the removal of existing beach
protective devices (seacave in-fillings, seawalls, revetments, tie-backs, etc.) so that areas with
protective devices would not erode differentially with respect to unprotected areas and cause
headland areas, arches, seacaves, etc., which would cause nonuniform erosion and/or a safety
hazard. As such, removal of these devices would cause erosion of the cliff base, and an
increased potential for landsliding and erosion. As increased erosion of the base of the bluff
progressed, the block falls of the Torrey Sandstone would become more likely and large-scale
landsliding of the terrace deposits would follow. As the stability of the overall bluff slope would
decrease from erosion at the bluff toe, the reduction of irrigation associated with removal of the
bluff top residences would slightly increase the overall and surficial stability of the upper bluff
area.
In general, planned bluff retreat would not be affected by geohazards such as ground rupture or
liquefaction. However, earthquake-induced ground shaking, flooding, and tsunamis would have
a significant (negative) effect on the bluff toe area and bluff face if current protective structures
were removed and wave action were allowed to erode the base of the bluff. This alternative
would increase the potential for erosion, large-scale landsliding, and soil failure. Warning signs
or buffer zones would have to be established near the base of the bluff to reduce the potential
for injury to the public by eroding soil or block falls. Even with these protections in place,
lifeguard and public safety issues would be increased and would result in a significant public
safety impact with this alternative. As bluffs crumbled or otherwise gave way to the forces of
coastal erosion, people along the beach would be exposed to the risk of injury or possibly even
death.
To mitigate differential erosion along the beach, existing protective devices (seawalls, riprap,
seacave in-fills, notch in-fills, etc.) would be removed and natural erosion allowed to occur. As
these devices are removed, blockfalls, landslides, and/or areas of accelerated erosion may
occur. Safe buffer zones would be established at the base of the seacliff for public safety.
Additional signage and lifeguard patrol services may be necessary to warn the public and
monitor these safe buffer zones respectively. Additionally, the coastal bluff stability should be
evaluated and mitigative measures implemented to increase static and dynamic slope stability, if
necessary. These measures could include "flattening" or decreasing the slope inclination
(angle) of the upper and lower bluff to make the slope more stable. Structures and utilities at
and for a distance landward from the top of the bluff should be removed so that bluff retreat
would not cause a safety hazard when the bluff (and the improvements supported by the bluffs)
fail.
Project No. 323530000
Page 3-31
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