EAS 201 - 5 - The Science of Natural Disasters Natural...

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The Science of Natural Disasters Natural Disasters , 7th ed., by Patrick L. Abbott (New York: McGraw-Hill, 2009; ISBN-13: 978-0-07-337669-1). Written Assignment 5 – Due Sunday Short Answer Questions Answer the following questions as completely as possible. 1. What is the difference between a flash flood and a regional flood? Are the causes the same? Are the effects the same? [LO5.1] Flash Flood ; are walls of water, set up in a matter of hours by a large convective storm. Many automobile related deaths in a flash flood are in 2 feet of water due to the buoyant lift and current of the water. In 1997, in Antelope Canyon a flash flood took 12 hikers, tumbling them down the canyon as helpless on lookers could only watch. A wall of water builds due to steep topography, channeling the water and striking a particular area in a thunderstorm. In Big Thompson Canyon, Colorado in 1976, a thunderstorm remained stationary in the canyon for four hours. The topography fed the flash floods and carried many hikers and tourist down the canyon to their death. Many survived by fleeing their cars and climbing to safety, seeking shelter along the canyon walls. Those who chose to stay with their cars were swept away in the flood and died. The weight and proximity of the vehicle couldn’t allow them to achieve the safety they required. Regional Flood ; different from flash floods, regional floods inundate an area with rainfall over several weeks, causing fewer deaths and often more damage. Occurring in areas of large river valleys and low topography, these heavy rains
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often result due to cyclonic systems. Their can be many contributing factors as to why a particular river may flood; geological age, riverbed (shape & depth), damming (ice or natural materials), as well as the surrounding landscape. The Hubbard Brook experiment 1 in 1963, illustrates clearing surrounding vegetation of a river valley, doesn’t allow for natural absorption. The excess water then creates floods further up or down the river valleys. Are the causes the same? Are the effects the same? In a sense no, while they are both rainfall cause by low-pressure systems. A regional flood occurs over a prolonged rainfall lasting several days or intense rainfall over a short period of time. A regional flood can be the result of ice or debris jam causing a river or stream to overflow. Melting snow can combine with rain in the winter and early spring, a severe thunderstorm can bring heavy rain or tropical cyclone can bring intense rainfall to the coastal and inland states. Where as a flash flood can occur within six hours of rainfall, after a dam or levee failure,
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This note was uploaded on 09/29/2010 for the course EAS EAS 201 taught by Professor Pearce during the Summer '10 term at Thomas Edison State.

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EAS 201 - 5 - The Science of Natural Disasters Natural...

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