Agenda - 05-06-2010 - 4m - Laserfiche WebLink

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Since there is no recorded history of earthquakes impacting Orange County and its' municipalities, and it is highly unlikely that a earthquake would impact Orange County, this natural hazard was not analyzed for potential impact on Orange County, including the Town of Carrboro and Town of Hillsborough. Tsunamis Tsunami (pronounced tsoo-nah-mee)is a wave train, or series of waves, generated in a body of water by a disturbance that vertically displaces the water column. Earthquakes, landslides, volcanic eruptions, explosions, and even the impact of cosmic bodies, such as meteorites,can generate tsunamis. Tsunamis can savagely attack coastlines, causing devastating property damage and loss of life. Tsunamis are unlike hurricane or wind generated waves in that they are characterized as shallow-water waves, with long periods and wave lengths. A wind-generated swell that rhythmically rolls in,one wave after another, might have a period of about 10 seconds and a wave length of 150 meters. A tsunami, on the other hand, cari have a wavelength in excess of 100 kilometers and last on the order of one hour. The character of a tsunami transforms as it leaves the deep water of the open ocean and travels into the shallower water near the coast. A tsunami travels at a speed that is related to the water depth-hence, as the water depth decreases, the tsunami slows. But the energy flux of a tsunami, which is dependent on both wave speed and wave height,remains nearly constant. Consequently, as the speed of the tsunami diminishes as it travels into shallower water, the height of the tsunami grows. A tsunami may be imperceptible at sea but grow to be several meters or more in height near the coast. When the tsunami finally reaches the coast it may appear as a rapidly rising or falling tide or a series of breaking waves. Just like other water waves, tsunamis begin to lose energy as they rush onshore-part of the wave energy is reflected offshore, while the shoreward-propagating wave energy is dissipated through bottom friction and turbulence. Despite these losses, tsunamis still reach the coast with tremendous amounts of energy that strips beaches of sand and undermines trees and other coastal vegetation. Capable of inundating or flooding hundreds of ineters inland past the typical high-water level, a tsunami can crush homes and other coastal structures. Tsunamis may reach a maximum vertical"runup"height onshore above sea level of 10, 20, and even 30 meters. History of Tsunamis in Orange County Since there is no recorded history of tsunamis impacting North Cazolina, and it is highly unlikely that a tsunami would impact Orange County,this natural hazard was not analyzed for potential impact on Orange County. 24