5.11 Recommendations for Current Influence Estimation
251
As shown above, the effective fetch in a fair current is less than that
without any current. The ratio (5.154) shows that the wave heights of small
probability are decreased and those of large probability are increased. The ratio of effective fetches is inverse in a countercurrent. The wave heights of small
probability are increased. But, starting from some definite or greater probability, they are decreased compared to the situation of the absence of current.
This phenomenon of the wave height distribution function corresponds qualitatively to available observations. In particular, the greatest extreme waves
are observed in a countercurrent wind. A similar transformation of the wave
height distribution function under the influence of a current is revealed in
the Karakumy Channel (Mass et al., 1988; Rzhanitsyn et al., 1988). Since
the greatest changes occur with wave heights of small probability, this transformation should be taken into account to determine the wave elements in
designing hydrotechnical construction.