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Hurricane Impacts Total Storm Inundation Total storm inundation is the combined impact of high tides,storm surge,and large breaking waves caused directly by a tropical cyclone. In Hawaii,high tides generally fall between 2 and 3 feet above mean sea level. Storm surge can be thought of as the surface of the sea being elevated due to the force of the hurricane's winds,in addition to a slight rise in sea level under the storm due to its lower pressure. Advanced computer modeling from the University of Hawaii Ocean and Resources Engineering Department suggests a category four hurricane making landfall in Hawaii will produce a 3 to 5 foot storm surge in some locations. These values are consistent with the storm surge of 4 to 5 feet observed when Hurricane Iniki made landfall on Kauai. If the storm surge arrives at high tide,the total water height will be even greater. While Hawaii coastlines are impacted by high surf throughout the year,large breaking waves will encroach considerably further inland during a hurricane as the waves are on top of an already elevated water level. As an example,as a hurricane moves ashore,a 5 foot storm surge added to a 2 foot high tide produces a water level 7 feet above mean sea level. This mass of water,topped by large breaking waves,may produce a total storm inundation as high as around 25 feet above mean sea level. This means areas along affected coastlines which are below 25 feet in elevation could experience damaging impacts from waves and saltwater intrusion. The large waves will also carry floating debris,increasing the damage potential. i r `L _ r Hurricane Iniki Inundation on Kauai- 6