EXAMPLE PROBLEM III-2-8

FIND:

Compute the shoreline geometry of a crenulate bay located between two rock headlands for a

shoreline where one dominant wave direction exists.

GIVEN:

The distance between the ends of the headlands is 175 m. The incident wave crests make an angle

of 30 deg with a line drawn between the two headlands.

SOLUTION:

From Figure III-2-27b, the values of the coefficients for the wave angle *β *= 30 deg are

approximately *C*0 = 0.05, *C*1 = 1.14, and *C*2 = -0.19. The location of the shoreline may be predicted

by plotting the distance R, measured from the end of the upwave headland, at angles θ measured from

the line drawn between the headlands. The values R/Ro for various arbitrary angles between the wave

angle, 30 deg, and a maximum angle, 180 deg, are computed from Equation 2-24. The corresponding

dimensional values of R are then computed by multiplying R/Ro by the distance between the headlands

Ro = 175 m. Representative examples are given below:

For θ = 30 deg: R = [ 0.05 + 1.14(30/30) - 0.19(30/30)2 ] ( 175 m ) = 175 m

For θ = 75 deg: R = [ 0.05 + 1.14(30/75) - 0.19(30/75)2 ] ( 175 m ) = 83 m

For θ = 180 deg: R = [ 0.05 + 1.14(30/180) - 0.19(30/180)2 ] ( 175 m ) = 41 m

For *θ *> 180E, the distance *R *may be assumed to be constant and equal to the value of *R *computed at

(2) Le Mhaut and Brebner (1961) discuss solutions for shoreline change at groins, with and without

bypassing of sand, and the effect of sudden dumping of material at a given point. They also present solutions

for the decay of an undulating shoreline, and the equilibrium shape of the shoreline between two headlands.

(3) Bakker and Edelman (1965) modified the longshore sand transport rate equation to allow for an

analytical treatment without linearization. The sand transport rate is divided into two different cases:

III-2-58

Longshore Sediment Transport

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