Chapter 15
Coastal engineering
15.1 Introduction
Coastal engineering encompasses a variety of problems of practical
importance, e.g. provision of harbours and their protection against sedi-
mentation, provision for discharge of effluents into the sea, design and
construction of works to protect coastal areas from flooding, defence
against erosion, etc. A coastal structure should not only satisfy the func-
tions it is intended for but also structurally withstand the hostile environ-
ment. Most coastal problems are difficult to tackle owing to the complexity
of the processes involved. A solution to one problem may very well cause
others, and so particular attention should be given to the interaction
between the various elements that determine the coastal régime. Over the
years coastal processes have been better understood and designs have
been rationalized with the aid of laboratory studies, theoretical methods
and field observations. For extensive treatment of the subject of coastal
engineering the reader is referred to Ippen (1966), Muir Wood and
Fleming (1969), Silvester (1974), Horikawa (1978), Fredsoe and Deigaard
(1992), Herbich (2000), Kamphuis (2000) and Reeve et al. (2004).
Waves play the most dominant role in the coastal processes causing
erosion, movement of sediments, development of beach profile, overtop-
ping of coastal defence structures, harbour resonance, etc. The properties
of wind-generated waves of short period and their refraction, diffraction
and breaking are treated in Chapter 14.
The very slow rise and fall of water level is due to the astronomical
tides produced by the gravitational field in the presence of rotating Earth,
Moon and Sun. The timescale of tidal oscillations is very much larger than
that of the wind-generated waves. Water level variation due to astronomi-
cal tides is generated by the interaction of the gravitational fields of the
rotating Earth, Moon and Sun during their orbital motions. These motions
cause periodic forces on water on the surface of the Earth introducing a