EM 1110-2-1100 (Part V)
31 Jul 2003
a. Barrier island migration at geologic time scales
Figure V-3-9. Time scales for shoreline movements (Continued)
(d) Natural erosion processes (wave-induced, sediment imbalances) plus anthropogenic induced erosion
produce larger erosion rates than sea level rise (Komar et al. 1991). These are herein labeled as those at
engineering time scales. The degree to which coastal armoring affects the adjacent beach has been the focus
of some research effort.
(2) Literature review.
(a) Common concerns. Dean (1987) critically examined nine commonly expressed concerns about
seawalls and adjacent beaches as summarized in Table V-3-3. Use was made of conservation of sediment
mass, laboratory and field data, and the theory of sediment transport. Conclusions from this analysis were
(numbers coincide with Table V-3-4) as follows:
Concerns Probably False (or Unknown)
profile steepening (6)
delayed beach recovery after storms (5)
increased longshore transport (8)
Shore Protection Projects
V-3-29
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