ABSTRACT

In the design of earth work constructions along rivers and lakes, it is important to know the relationships which exist between wind and the waves. Such observations are a first stage in a complete investigation of wave effects on beaches and earth structures of different shapes and materials. The generally used form of these relationships deals with deep-water conditions, where the fetch is unlimited. Such relationships cannot be applied to small lakes and protected bays.

The earliest work in this field was that of Johnson on Clear Lake, California. He concluded that wind duration but not fetch was the controlling factor in any kind of a change in wave characteristics. Later, on the basis of the study of Abbots Lagoon, California, Johnson showed that the dimensionless term gF U² is useful in estimating wave conditions within certain limits. Burling compared the wave data from Staines reservoir with the data of Johnson, Bretschneider and Sverdrup and Munk. Whereas the curves are of the same form, there is a great amount of discrepancy. Burling's line is 15-25% below the other lines. Data from Lake Okeechobee, Florida, indicate that there is a transitional region between deep water and shallow water, where the wave height is affected by combinations of wavelength and depth of water.

The data from Lake Okeechobee align closely with Burling's results. However, Burling's observations were from a reservoir where the maximum fetch was around one km. In Okeechobee the fetch ranges up to 60 kms. The Okeechobee study reveals that the proper method to define shallow water waves should include fetch and wind velocities as well as the depth of water. The wave heights are lower than expected for lower wind velocities and higher than expected for higher wind velocities in shallow water, with limited fetch.

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