Environmental Engineering Reference
In-Depth Information
Chapter 1
Introduction
Abstract
This chapter provides an introduction to concepts and sets the context
for the topic of beach renourishment. Issues with definitions and terminology are
discussed and a number of technical manuals and guides introduced.
Beaches can be defined as accumulations of generally loose, unconsolidated
sediment on the shore. Some beaches are long and almost straight or gently
curved; others are shorter, and include sharply curved 'pocket beaches' in bays
or coves between rocky headlands. Beaches fringe about 40 % of the world's
coastline, the remainder being partly rocky, partly marshy or muddy, and partly
artificial (Bird
2008
). Many are exposed to the ocean or stormy seas, but others
are sheltered in bays or behind islands or reefs. Beach systems deal with the
interactions between beaches and the processes (wind, wave, tides and currents)
that work on them. Most beaches consist of sand (sediment particles with grain
size between 0.2 and 2.0 mm), but some contain particles with larger diame-
ters, such as granules (2-4 mm), pebbles (4-64 mm) and cobbles (64-256 mm).
Beaches consisting entirely of sediment coarser than sand are termed gravel or
shingle beaches.
During the past century many of the world's beaches have been depleted by
erosion (Bird
1985
). Where beaches are eroding, this is likely to continue and even
increase due to the predicted global sea level rise and an increase in storm fre-
quency and intensity associated with global climate alterations (Zhang et al.
2004
;
IPCC
2013
). Some beaches, particularly in the United States, Western Europe and
Australia, have been restored by dumping sand or gravel on the shore. Sand or
gravel, brought from inland, alongshore or offshore sources, has been deposited
mechanically or hydraulically to form a beach that is built higher and wider than
the depleted beach (US Army Corps of Engineers
1984
), the aim being to restore
and maintain a beach that will protect the coast from erosion by storm damage
(hurricanes, typhoons or tropical cyclones), and also prevent flooding of the hin-
terland while providing an improved area for seaside recreation and habitat for
