406
If there is a need for criticism, it must come in two
areas: the relevance of the approaches for a nonAmerican audience, and the lack of treatment of
geological controls on sea-level. The latter point
stems from the stated view that geological controls
operate on too long a timescale to affect global sealevel rise over the next century. In a subject where
the linkages between causes and effect are, as admitted, still poorly known, the dismissal of this fundamental area of study is unfortunate. Still one
cannot cover everything! The other point is underlain by the direction of the book toward the North
American market and other wealthy, technologically advanced countries. Despite the aim to increase appreciation of the global nature of sea-level
rise, no attention is given to the spatial variations in
Problems and remedies that other countries might
experience in reacting to sea-level rise. This may
illustrate a principle that forward planning for environmental hazards is a perogative of the rich!
Case studies from other countries, including from
less developed parts of the world, would have given
a wider audience appeal/impact.
Nevertheless the editors and authors are to be
congratulated on a valuable, and-if literature
citations are anything to go by-an already muchappreciated work.
LITERATURE CITED
MERCER, J.H., 1978. West Antarctic ice sheet and CO.,
greenhouse effect: a threat of disaster. Nature, 271, :\21 ~
:325.
NATIONAL ACADEMY OF SCIENCES, 198:3. Changiru; Climate. Report of the Carbon Dioxide Assessment Committee. National Academy Press, Washington, D.C.
Robert Devoy
University of Cork
Cork, Ireland
Breakwaters: Design and Construction, Institution of Civil Engineers, London: Thomas Telford
Ltd., 1984, 187p., ISBN 0-7277-0190-8. £18.00
(UK), £22.00 (overseas).
The primary function of large breakwaters is to
provide quiet water for the mooring, unloading, and
loading of merchant ships. Such breakwaters are a
necessary element in world trade. Breakwaters at
open ocean sites face severe tests from the sea, and
some haye failed these tests in spectacular instances over the past decade. The most common breakwaters are ru bble mound structures, and this book
is a state-of-the-art review of their design and construction, as presented in papers at the May 1983
conference on breakwaters held in London by the
Institution of Civil Engineers.
In the book, there are three theme papers and 1:3
conference papers arranged in seven sessions. The
seven sessions cover Wave Climate, Construction
Materials, Foundations and Modelling, Armour
Stability, Risk Analysis, Specification and Construction, and Maintenance, in that logical order.
Each session ends with a printed summary of discussion generated by the papers, and these discussions, by cross-referencing the separate papers
and supplying new perspectives, give the book a
unity and coherence not usually achieved in a proceedings volume. Thirteen of the 27 authors are
from Great Britain, and only one paper has American authors. Most of the papers and nearly all the
discussions are oriented toward engineering practice. The focus is on structural design (build it so
that it does not fall down); functional design (build
it so that it serves the intended purpose) is not
covered.
Rubble mound breakwaters have a core of rock
fragments and soil overlain by one or more sloping
layers of large stones, and in some cases, by
specially-designed concrete units. The randomlyplaced surface stones are the armor stones which
resist wave forces and maintain the structural integrity of the breakwater. If space is available to
accommodate them, rubble mound breakwaters
have distinct advantages over monolithic concrete
or fitted-stone breakwaters. Since both rubblemound and monolithic structures must reduce the
incoming wave momentum flux to zero, the longer
distance (and thus longer time) available to do this
in a rubble mound results in a lower force felt by the
armor stone surface than by the monolithic wall. In
addition, rubble mound breakwaters, if they fail,
fail gradually and are less expensive to repair than
monolithic breakwaters.
Construction oflarge rubble mound breakwaters
is an inherently conservative practice. For the first
user, deviation from accepted practice promises
relatively small reward and carries large risk, although competition among contractors as well as
unforeseen construction constraints move the practice gradually toward innovation. Close reading of
the book indicates this slow approach to innovation, offset somewhat by rather elastic interpretations of accepted design procedures.
A major research emphasis today is the attempt
to develop numerical models for design. On the
.lournal of Coastal Research. Vol. :l. No. :\, 1987
407
vidence of the book, such numerical models have a
relatively small part in present construction practice. No construction project, of the many described in the book, is reported to have relied on
numerical models for significant design assistance,
although hydraulic models are almost always used
for large projects on the open coast. The word modelling in the title of Session :l refers to the wet (hydraulic) models rather than the numerical ones.
One of the discussants volunteers the opinion that
in numerical models almost anything is possible,
however unreal (p. 89). This reviewer shares the
cautious approach to using numerical models in
present practice that is evidenced here, although
the applicability of such models is likely to improve
in the coming decade.
One of the major innovations in civil engineering
construction over the past decade has been the
widespread introduction of geotextiles, particularly to prevent washing fine sediments from
the foundation, and to spread concentrated loads
on weak foundations. This innovation originated
with the need for better filters behind coastal revetments, but geotextiles now are much more widely
used in non- coastal construction. On the evidence
of the book, use of geotextiles has only partially
entered breakwater construction practice. Paper 5
on foundation problems does not even mention
geotextiles, although their use is mentioned by discussants and shown in illustrations elsewhere in the
book. In Paper 12 on specifications, the authors
suggest a one- foot minimum thickness of select
stone or gravel as a filter, and add that if a fabric
filter is used, a similar one- foot thickness should be
placed above the geotextile to prevent puncture,
which seems to show a lack of confidence in the
technique. This reviewer believes that the use of
geotextiles for major coastal construction is no longer experimental, although difficulties in underwater installation can inhibit their use in exposed
areas.
To the non-specialist reader, perhaps the most
surprising lesson carried in this book is the extent to
which experience, economics, and contingencies
override the cookbook use of design. The single
most important design decision is selection of the
design wave height, to which the whole breakwater
design is very sensitive. There is repeated demonstration by different authors and discussants
that selection of wave height and the related stability coefficient is highly su bjective. Furthermore,
alternate designs of the underlayer may require
stone weights different by more than a factor of ten,
and still satisfy existing recommended procedures.
Finally, after the design is finished. it may be
further modified in the field, on the evidence of this
book, especially by constraints on rock supply from
available quarries.
Rubble mound breakwaters include mankind's
largest coastal constructions. They are vital to
world trade. For the structural design and construction of rubble mound breakwaters, no other book
contains in one volume an equivalent multi-perspective description of todays practice. For researchers, this book will identify many interesting
applied research problems important to the structural design of rubble mound breakwaters.
.Iournal of Coastal Research. Vol. :l, No. :l. 19/;7
Cyril Galvin
Principal Coastal Engineer
Box G23, Springfield
Virginia 22150 USA