| Tweet |
Custom Search
|
|
|
||
 Solana Beach Coastal Preservation Association
August 20, 1998
Project No. 1831
Page 42
also been aggravated by the formation of edge waves traveling along the face of the infill,
impacting upon and eroding the sidewalls of this relatively large sea cave. Sea cave and/or
notch infills extend from 265 to 309 Pacific Avenue and 367 to 407 Pacific Avenue. These
infills appear to have been successful, except below 269 Pacific Avenue, where an active
block fall is in progress. Installations intended to mitigate subaerial erosion of the upper
bluff include gunite at 235 Pacific Avenue, Jute matting at 245 and 327 Pacific Avenue,
plastic sheeting at 301 Pacific Avenue, and post and board soil retainers at 325 Pacific
Avenue.
6.5
Reach 5 - 231 to 139 Pacific Avenue
Reach 5 is characterized by a bedrock shore platform having no sand or shingle cover.
Although block falls have not yet occurred, the sea cliff is severely undermined by notches
and sea caves. The undermined areas are subject to failure at any time. The reach is
shown in Map and Photo 6 and 7, and represented by Cross Section 11 at 211 Pacific
Avenue, Figure 23. Photo 14 shows the extent of notching in this area in April 1998, prior
to the removal of the emergency riprap and subsequent infill with the summer beach.
Throughout the majority of this reach, no beach exists. However, locally, below the lot at
231 Pacific Avenue, where past faulting has resulted in a step in the coastline, a 20-foot-
wide beach currently exists. Small areas of shingle beach exist along the base of the cliff
up to elevation 5 feet. Offshore, the bedrock shore platform is exposed. The near-vertical
sea cliff rises to elevation 26 feet. The bluff rises at a typical slope angle of 44" degrees to
an elevation of 84 to 89 feet. Sea caves extend up to 18 feet into the cliff, which consists of
Torrey Sandstone. Deep notches and overhangs affect this reach (Table 3).
Comparison of the 1990 and 1998 topographic profiles in Cross Section 11 suggests the
westerly-most limit of the sea cliff has not yet retreated along most of this reach.
Accelerated subaerial erosion and active over-bluff drainage is absent from the upper bluff.
A sea-cave infill below 201 Pacific Avenue has been flanked by deepening of the notch on
both the north and south. The deep notches and overhangs could collapse at any time,
producing high vertical scarps in the overlying marine terrace deposits, thus creating severe
conditions like those at Reach 4.
|
 
|
|
|
||
