Hydraulic Structures: Fourth Edition

WORKED EXAMPLES 619

Hs(m) 000.5 001.0 01.5 02.0 02.5 03.0 03.5 04.0 4.5 5.0 5.4
Number
of waves
(Hs) 340128847348371815621

Estimate the significant wave height for a return period of 20 years.

Solution

1. P(H) ,Hs2.5 m.

H/Hs 00.1 00.2 00.3 00.4 00.5 00.6 00.7 00.8 00.9 01.0 1.1 1.2 1.3 1.4
Number
of waves
exceeding
H 97 90 83 76 64 53 43 35 26 13 6 4 1 0
P(H)(%) 96 89 82 75 63 52 43 35 26 13 6 4 1

P(H) versus H/Hsis plotted on probability paper for the Rayleigh

distribution, which fits the data reasonably well (Fig. 14.25).

number of waves exceeding H



N 1

Fig. 14.25 Probability distribution (Worked example 14.1, part 1)

Hs(m) 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.4
P(Hs) 0.93 0.35 0.23 0.2 0.13 0.1 0.05 0.04 0.016 0.005 0.003