| Tweet |
Custom Search
|
|
|
||
 Solana Beach Coastal Preservation Association
August 20, 1998
Project No. 1831
Page 39
followed by the bluff at a typical slope angle of 37" degrees to elevation 63 to 68 feet.
Existing sea caves extend 30" feet into the cliff, which consists of Del Mar Formation north
of 629 Pacific Avenue and interbedded Del Mar and Torrey Sandstone to the south. The
Del Mar Formation introduces clayey layers that are more susceptible to erosion than the
enclosing sandstone. The clay layers usually form the roofs and floors of the sea caves,
while faults and joints control the sides.
Comparison of the 1990 and 1998 topographic profiles in Cross Section 1 suggests 10"
feet of retreat of the sea cliff in the last eight years. Accelerated subaerial erosion affects
the lower bluff below 629 and 633 Circle Drive. The two slope failures affecting the top of
the bluff at 617 Circle Drive were reportedly caused by excess irrigation saturating the
upper marine terrace deposits. The larger, northern slope failure caused loss of
approximately 8 feet of the upper bluff and deposited a debris cone on the beach that
extends above the bedrock contact. At the north side of the slope failure is an active over-
bluff drainage.
A seawall protects the sea cliff at 645 Circle Drive. Recent cliff retreat at the south end has
caused exposure of several feet of the south abutment of the wall.
6.2
Reach 2 - 529 to 517 Pacific Avenue
Reach 2 is characterized by small coves and headlands, limited beaches consisting
primarily of shingle, limited mitigation of wave energy only from the northwest, numerous
sea caves, all of which have been filled, and the northernmost limit of partially cemented
beach ridge deposits. The reach is shown in Map and Photo 3, and represented by Cross
Section 2 at 529 Pacific Avenue, Figure 14.
The beach varies from 0 to 20 feet in width, extending up to elevation 5 feet at the base of
the sea cliff in the coves. Offshore, the shore platform is underlain by exposed bedrock.
The near-vertical sea cliff rises to elevation 18 feet, followed by the bluff at a typical slope
angle of 41" degrees to elevation 63 to 80 feet. Numerous sea caves extend up to 30" feet
into the cliff, which consists of interbedded Del Mar and Torrey Sandstone. The Del Mar
Formation introduces clayey layers that a more susceptible to erosion than the enclosing
|
 
|
|
|
||
