d. Once-the berm on the adjacent unstructured beaches has retreated
landward of the seawalls, there is no significant difference in winter beach
profiles seaward of seawalls or revetments relative to adjacent unprotected
beaches.
e. Increased berm retreat and beach scour occurs up to 500 ft downcoast
from seawalls due to a combination of wave reflection and groin effects.
f. Late spring/summer berm rebuilding takes place in a uniform manner
alongshore with no obvious difference between seawall-backed or adjacent
control beaches.
g. A trough was never observed in front of any walls during the
monitoring period.
h. Longshore troughs oblique to the shoreline often develop in the surf
zone at downcoast ends of seawalls in response to rip current development
during the winter months.
i.
Dean's hypothetical profile (Dean, 1986),. based on the excess sand
removed from in front of a seawall which would have scoured from the area
landward if the seawall had not been constructed, did not occur. Figure 6
shows Dean' hypothetical
profile.
Figure 7 shows mean profiles which
represent all of the mean profiles for an entire season of surveying at the
Aptos Seascape Site, upcoast, at the seawall, and downcoast sites; An area of
localized scour at the seawall area is not present on these profiles.
Normal Rofile
a) Normal ond Storm Profiles on o Natural Shoreline
(without Seawall) .
b) Normol and Storm Profiles on o Seowalled Shoreline
and Comparison with Profiles on a Natural Shoreline
Figure 6.
Dean's Hypothetical Profile predicts additional scour immediately
in front of a seawall due to storms.
6
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