EXAMPLE PROBLEM II-2-2

FIND:

The appropriate 100-year wind speed for a basin with a fetch length of 10 km.

GIVEN:

A 100-year wind speed of 19.9 m/s, derived from 3-hr synoptic charts.

SOLUTION:

Figure II-2-3 requires knowledge of both wind speed and fetch distance; however, reasonable

accuracy is gained by simply using the original wind speed and the appropriate fetch. In this case from

Figure II-2-3, the appropriate wind-averaging interval is approximately 90 min. Using information from

Figure II-2-1, the ratio of the highest 90-min wind speed to the highest 3-hr wind speed is given by the

relationship

U5400/U10800 = [-0.15 log10 (5400)+1.5334]/[-0.15 log10(10800)+1.5334] = 0.9735/0.9284 = 1.048

Thus, the appropriate wind speed should be 1.048 times 19.9 m/sec, or 20.8 m/sec.

II-2-6

Meteorology and Wave Climate

Integrated Publishing, Inc. |