SELECTED CASE HISTORIES
Untreated Log Bulkhead
Figure 32 is a photograph taken in November 1978 showing a bulkhead constructed in mid-1978
with untreated logs and designed to protect the toe of a high bluff. The logs are substantial and do not
appear susceptible to damage by even severe wave action. In addition, stone toe protection was
provided to prevent problems due to scour. Gravel was placed behind the logs as a filter. On
February14, 1979, a severe storm struck the site with wave heights of perhaps four to five feet (these
were greater than the design conditions). As a result, the gravel filter material was washed through
gaps in the logs and backfill was lost. The toe protection was also displaced, leaving a gap below the
bottom log through which additional backfill passed. Deprived of support afforded by the backfill, the
logs were torn from the vertical posts, where they were held by spikes, and the structure was destroyed
(Figure 33).
The structure could have been improved in several ways. First, coarser gravel could have been
used for filtering. However, because of the relatively large gaps between the logs, and the vibrations
caused by large breaking waves, it probably would have been better to use a filter cloth-. This should not
have been stretched tightly against the back of the structure, but rather, should have been tucked and
folded to fit the contours of the logs. A woven cloth is preferable because of its superior tensile strength.
A second improvement would have been heavier toe protection, coupled with entrenchment of the bottom
logs several feet below the beach surf ace. This would have prevented toe scour and loss of backfill
material through the bottom.
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