23 



Design hurricane tides 



32. The model hurricane tide generator vas designed to reproduce 

 hurricane tides of greater amplitude than that of September 1938^ which 

 was the greatest hurricane tide of record in the Narragansett Bay area^ 

 to take care of the possibility that later computations might indicate 

 that tides of greater amplitude are likely to occur in that area. The 

 hurricane of September 19^1^1 was selected for design purposes, and the 

 tides that would have been generated at Newport by this hurricane if it 

 had reached Narragansett Bay at the peak of its intensity were computed 

 for three assumed speeds of movement of the hiirricane center, 20 knots, 

 30 knots, and kO knots. These tides, referred to hereinafter as design 

 tides, were computed by the New England Division and furnished to the 

 Waterways Experiment Station for use in the model tests. 



33 • The model reproductions of the 40-knot and 20-knot design 

 hurricane tides at Netjport are shown on fig. ih. The computed tides do 

 not contain an astronomical tide component as does the 1938 hurricane 

 tide discussed previously, so adjustment of the model hurricane tide 

 generator to reproduce the design tides at Ne-^jport was accomplished with 



TIME IN HOURS AFTER MOONS TRANSIT OVER 71 20' 



DESIGN HURRICANE ADVANCING AT 20 KNOT SPEED DESIGN HURRICANE ADVANCING AT 40 KNOT SPEED 



Fig. 1^1. Verification of design hurricane tides at Neijport 



