Hydraulic Structures: Fourth Edition

WORKED EXAMPLES 663

(MAFF, 1995): to study the coastal processes in a cell defined by the phys-
ical features and sediment transport, to predict the likely shape of the
coasts in the future, to identify all the resources within the area covered by
the plan, to assess various coastal defence options including ‘doing
nothing’, to carry out regional and site-specific research and monitoring, to
facilitate consultation between interested parties and to develop future
objectives for shoreline management.

Worked Example 15.1

A storm in deep water generates waves which travel towards the shore,
impinging on a breakwater. The breakwater is a vertical wall erected on a
rubble mound (Fig. 15.9b). The fetch-limited storm has a wind speed of
10 m s^1 and a fetch of 100 km. The base of the vertical wall and the sea bed
are respectively 3 m and 8 m below HWL.
Find the maximum force on the vertical wall and the bending
moment about A using Sainflou’s method.

Solution

As given below, fetch100 km and wind speed10 m s^1.

JONSWAP spectrum(SEE SECTION 14.9.2)

fm3.5 

0.33

0.165 Hz;

Ts0.777/fm4.7 s;

0.076

0.22

0.01;

Hs 0

 .0 

1

 2.01 m;

L 0 34.5 m.

For d/L 0 8/34.50.23, H/H 0 0.93 and L/L 0 0.93 (Fig. 14.8), H
0.932.011.87 m and L0.9334.532 m,

9.814.7^2



2 π

0.5529.81



π^2 0.165^2

9.81 100  103



102

9.81 100  103



102

9.81



10