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indicates that the model produces useful and valid predictions of the waves and currents in
the nearshore region in the presence of obstructions such as groins and breakwaters. The
predictions obtained through use of the computer model herein reported are not intended
to be the sole resource for the engineer. A good engineer or planner will seek answers from
multiple sources and cross check them, recognizing the limitations of each method used to
obtain the answer.
Predictions of waves and currents can be obtained for different cases analytically,
through experiments or by numerical solutions. Analytical solutions are obtained only
for simple cases involving idealized beaches using simplified assumptions which are not al
ways satisfied in nature. Longuet-Higgins and Stewart (1963) give an analytic solution for
wave set-up for steady state conditions on a plane beach with straight and parallel con
tours, assuming linear waves approaching the beach normally, and spilling breakers where
the wave height shoreward of the breaker line is a constant times the total depth of the
water column. Longuet-Higgins (1970a) gives a cross shore profile of the longshore current
for a plane beach with straight and parallel contours, for linear waves approaching the beach
at an angle, spilling breakers, and linearized bottom friction, while neglecting the influence
wave set-up has upon the total depth of the water column. In a companion paper, Longuet-
Higgins (1970b) extended the solution to include lateral diffusion of the current momentum.
There are other analytical solutions for waves and currents but all are limited to very simple
cases.
The literature is replete with laboratory investigations of waves and currents. Physical
models have advantages and disadvantages. The advantages of experimentation are that
results can be obtained for complex situations where there is uncertainty about the exact
form of the governing equations or about the precise form of any of the component terms
of the equation. Any reasonable amount of detail can be included. Visualization of the
physical processes provides an opportunity to identify problems which otherwise might not
be evident.