before they are dissipated in shoal waters or break on the shore. 

 Driven by hurricane winds, the breaking ;javes will run up on a 

 shelving beach or overtop vertical structures well above the wave 

 heights, so that reports of wave and flood damage from 5 to 2^ 

 feet above water level are not imcominon. Hurricane waves do great 

 damage to shorefront land and buildings and to vessels and snail 

 craft. In the hurricane of 1938, the waves within Narragansett 

 Bay carried a number of lighthouses off foxindations which were 

 well above normal water levels, 



32, TIDAL SURGES 



Although hurricane winds have caused the deaths of thousands, 

 and thousands more have lost their life in ships destroyed at sea, 

 most of the losses of human life and property in hurricanes are due 

 to flooding. Flooding, one of the most devastating effects of a 

 hurricane, results £rom movement of the storm surge, or substantial 

 rise in water levels, onto a shoaling coast and into a bay or inlet. 

 The surge is caused by a combination of hurricane winds and lov: 

 barometric pressure in a storm having a track and speed of forvrard 

 movement synchronized with the normal pattern of tidal movement 

 and oscillations of the sea in the open ocean. 



Usually the rise of the sea is gradiial as the center of the 

 storm approaches but sometimes it comes with great svxiftness. 

 Rising waters accompanying hurricanes have been called "tidal waves", 

 although they are not tides in the ordinary sense. The }iistory of 

 terrible storms reveals me.ny instances of cities and towns flooded, 

 with thousands of lives lost, evidence tliat such rises are not 

 always gradual. 



Usually the level of the storm surge is increased by a rising 

 ocean bed rjid favorable shore contoiirs, factors which similarly 

 affect the astronomical tide in shore locations. The ordinary rise 

 of the tide amounts to only one or tf-xo feet in the open oceans, 

 wliile its ran:^e is often ten to ti-'elve feet at coastal points. 

 In certain bays and channels the rise is 25 to 50 feet above low 

 vrater. The tines of ebb and flow of such tides are, of coxirse, 

 well known, but the storr. surge co^iies so rarely to any one commu- 

 nity that it is seldon onticipated in its frlly developed form, 

 A well-defined storm surge is not developed ujiless the slope of 

 the ocean ^'ed and contour of ti^c coastline are favorable to its 

 rise, in combination :;ith the '-roncr direction of the storm track 

 ana speed of movement. 



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