be provided next to a wharf.
Bulkheads are frequently used along channels
and marina-type developments to separate, and hold the land from the deeper
water channels and berths.
FUNCTIONAL LIMITATIONS: A bulkhead, by itself, may not provide stability to
a bank. If a bulkhead is placed at the toe of a bank that has been steepened
by erosion to the point of incipient failure, the bank above the bulkhead may
slide, burying the structure or carrying it seaward.
To insure the struc-
ture's success, the bulkhead may have to be placed seaward of the bank's toe
and/or the bluff be graded to a flatter, more stable slope. Bulkheads are
limited to protecting only the land Immediately behind them, offering no
protection to adjacent areas up- or downcoast or to the beach fronting the
bulkhead.
On an eroding shore, recession of the surrounding shoreline will
continue and may be accelerated by wave reflection effects in the vicinity
If nearby beaches are being supplied with sand by the
of the bulkhead.
erosion of the area protected by a new bulkhead, these beaches will be
s t a r v e d and will experience increased erosion. If a beach is to be retained
adjacent to a bulkhead, additional structures will be required.
Because bulkheads are normally constructed with a vertical face for con-
structibility and cost efficiency, wave reflection is maximized, increasing
in turn the height of waves at the bulkhead and overtopping potential, and
Since such scour can be a serious problem
scour in front of the bulkhead.
with bulkheads, toe protection may be necessary to insure their stability.
Bulkheads are highly vulnerable to flanking; therefore, it is essential for
their ends to be extended landward an adequate distance into the retained
area to prevent flanking.
STRUCTURAL ASPECTS: There are three main types of bulkhead structures:
Each type differs in the way
cantilever, anchored or braced, and gravity.
Cantilever bulkheads are the
it withstands the lateral earth pressures.
simplest and consist of a wall of sheet-piling, which derives its lateral
support solely by ground penetration (see Figure 1). Anchored or braced
bulkheads are similar to cantilever structures, but gain additional support
against seaward deflection from anchors set sufficiently far back in the
bank, as shown in Figures 2 and 3; or from battered structural piling on
the seaward side of the bulkheads as shown in Figure 3. Gravity bulkheads
include rock-filled cribs and sheet-pile cells, as shown in Figures 4 and 5,
2
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