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Prologue

Is there anyone who can watch without fascination the struggle for supremacy between sea and land?

The sea attacks relentlessly, marshaling the force of its powerful waves against the land’s strongest points. It collects the energy of distant winds and transports it across thousands of miles of open ocean as quietly rolling swell. On nearing shore this calm disguise is suddenly cast off, and the waves rise up as angry breakers, hurling themselves against the land in a final furious assault. Turbulent water, green and white, is flung against sea cliffs and forced into the cracks between the rocks to dislodge them. When the pieces fall, the churning water grinds them against each other to form sand; the sand already on the beach melts away before the onslaught.

But the land defends itself with such subtle skill that often it will gain ground in the face of the attack. Sometimes it will trade a narrow zone of high cliff for a whole low beach. Or it may use some of its beach material in a flanking maneuver to seal off arms of the sea that have recklessly reached between the headlands. The land constantly straightens its front to present the least possible shoreline to the sea’s onslaught.

When the great storm waves come, the beach will temporarily retreat, slyly deploying part of its material in a sandy underwater bar that forces the waves to break prematurely and spend their energies in futile foam and turbulence before they reach the main coast. When the storm subsides, the small waves that follow contritely return the sand to widen the beach again. Rarely can either of the antagonists claim a permanent victory.

This shifting battleground is the surf zone and the beach face. The two combatants continue their engagement in a coastal world that exists at the whim of a grander empire; now swept with the winds of climate change. The land will retreat before the rising sea levels with elusive transfers of sediments not seen for millennia. This is their story in the twenty-first century.

UNITS AND VARIABLES USED IN THIS EDITION

Units of measurement are fundamental to quantify anything. Here is an attempt to provide an understanding of the jumble of maritime-related units and variables found later in this book that may be difficult for some readers. The focus is to communicate concept, relative size, and magnitude. Today all scientific publications use the International System of Units (SI from the French Système International). In the maritime world, another unit system is inescapable: Imperial units, once used across the British Empire, is still used in the United States. Many international engineering efforts, such as the ill-fated Mars Orbiter, have stumbled upon remnants of these units. In this edition, Imperial units are used first, followed by SI units in parentheses. Whenever possible the conversion between units is approximated without diminishing significance.

As an example, the unit ton has multiple usages, but all are referred to in this book simply as “ton.” There is a cornucopia of meanings for this unit. Ton can be used for weight (2,000 pounds, 1,000 kilograms, or 2,240 pounds for a “long ton”) or volume such as freight (40 cubic feet), ship volume (100 cubic feet per registered ton), petroleum products (about 7 barrels of oil), and sand (0.6 cubic meters or 0.7 cubic yards). Understand the concept first, then read on, and if necessary, bypass a confusing jumble of units.

Units and conversions
ft	foot—Unit of distance, (0.3048 meters), there are 3 feet per yard (0.91 meters).
lb	pound—Unit of weight (0.45 kilograms, abbreviated kg).
kt	knot—Unit of speed (1.15 mph), (1.85 kilometers per hour, abbreviated km/h), (0.514 meters per second, abbreviated m/s), (514 centimeters per second, abbreviated cm/s).
cubic yard	Unit of volume 9 cubic feet, (0.76 cubic meters, also written m3).
t	ton—Unit of weight 2,000 pounds (metric ton is 1,000 kg) or volume (40 cubic feet) or (7 barrels of oil).
psi	pressure—Pounds per square inch, force per unit of area, 14.5 psi is equal to 1 bar.
J	Joule—Unit of work equal to a force times distance, also 1 Watt for 1 second.
W	Watt—Unit of power, equal to 1 Joule per second, also 1,000 Watts is equal to 1 kW.
kWh	kilowatt-hour—Unit of energy, power in kilowatts times the number of hours.
hp	horsepower—Unit of power (approximately 750 Watts).
F	degrees—Unit of temperature; to convert Fahrenheit to Celsius subtract 32 and multiple by 0.5555.

Variables
L	Wave length or distance between two points.
d	Water depth in units of distance (length).
H	Wave height measured from trough to crest (peak).
f	Frequency measured in cycles per unit time (same as 1/T), one cycle per second is 1 Hertz (Hz).
g	Force of gravity, approximately 32.2 ft/sec2 (9.8 m/sec2).
π	(Greek letter “pi”) approximated by 3.14 (ratio of a circle’s circumference to its diameter).
T	A period of time, usually in seconds.
α	(Greek letter “alpha”) a measure of angle in degrees.
C	Velocity expressed as a distance per unit time, (from the word “celerity” also written lowercase c).
cos	Cosine, trigonometric function.
tanh	Hyperbolic tangent, trigonometric function.
ρ	(Greek letter “rho”) the density of a material in mass per unit volume.
K	A coefficient, typically used as a constant with an assigned value.
energy	In units of Joules, also in kilotons of TNT, which is equal to 4.184 terajoules.
power	Energy expended per unit time.