Freeboard is an important safety parameter in the design of earthfill dams, where thernprevailing wind direction, wind speed, and over-water fetch distances are used to establish thernwave height for design. The maximum wind speeds used for freeboard design have generallyrnranged from a 100 mile per hour wind speed to unspecified probable maximum wind speedsrnwith the reservoir at normal maximum water surface elevation. In combination with the peakrnwater surface elevation for the inflow design flood, standard references generally recommendrnlesser or average winds that could be expected to occur during extreme floods. But whatrnabout coastal areas where hurricanes can provide the most extreme wind speeds and rainfallrnin the same storm? Hurricane storm rainfall depths are among the greatest on record. Thernassociated hurricane wind speeds vary widely based on overland distance from the coast andrnhave been recorded at over 175 mph. The wind direction varies as the storm passes and canrnoccur at essentially any compass direction. Existing detailed freeboard design criteria forrnreservoirs located in coastal areas prone to hurricane events are very limited.rnThis paper will explore the development of wind speeds for design, wind directionrnrelated to hurricane storms, adjustments to wind speed from various data sets to valuesrnrequired for design, and suggested design criteria for wind and precipitation events forrnfreeboard design will be provided. A case study showing the effects of alternative freeboardrncriteria will be presented.
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