Natural Hazards: Causes and Effects - Disaster Management Center ...

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the Pacific between the years 1900 and 1970. (See Fig. 3.2.) Of these, 35 caused casualties and damage near the source only, whereas nine spread destruction throughout the Pacific. Natural Preconditions for Disasters Tsunamis are believed to originate as vertically displaced columns of ocean water. Seismic or volcanic action on the ocean floor may cause tsunamis by creating a pulse or force on a wall of water equal to the depth of the ocean at the point of the movement. Tsunamis spread outwards in all directions from the point of origin, traveling at a speed proportional to the square root of the depth of water and reaching 1,000 kilometers per hour (600 miles per hour) in the deep ocean. The distance between successive wave crests may be as much as 500 kilometers (310 miles). As the waves reach coastal areas, this speed decreases, though the interval of time between the passage of successive waves remains unchanged (usually between 20 and 40 minutes). A single tsunami may comprise up to 12 large wave crests. The destructive power of tsunamis derives from the fact that the amplitude of the waves, which is usually less than one meter (three feet) in the deep ocean, increases sharply as the waves reach shallow water near the coast, and may be further enhanced by funnelling or resonance effects on bays and estuaries. In extreme cases, wave heights may reach as much as 20 or 30 meters (65 or 100 feet). In such cases, waves may sweep a considerable distance inland. 3 Approximate Epicenters of Tsunami Generating Earthquakes 1900 – 1969 Figure 3.2
Impact on Natural and Built Environment The effects of these waves on the coastal areas of the Pacific are characterized by maximum destructive force at the water’s edge. Damage further inland is potentially high, even though the force of the wave has diminished, because of the floating debris, which batters the inland installations. Ships moored in harbors often are swamped and sunk or are left battered and stranded high on the shore. Breakwaters and piers collapse, sometimes because of scouring actions that sweep away their foundation material and sometimes because of the sheer impact of the waves. 4 Recovery/Reconstruction Problems and Strategies As indicated by Table 3.1 a tsunami can seriously disrupt major elements of a community. The responses required are typical of those required by sudden onset disaster. They are summarized below. Initial response by local authorities: • Receive and implement warning and evacuation procedures • Perform search and rescue in the disaster area • Provide medical assistance • Conduct disaster assessment and epidemiological surveillance • Provide short term food, water, shelter Initial response by foreign intervenors: • Provide cash • Assistance in re-establishing infrastructure, lifelines, and communications • Conduct disaster assessment Secondary response by local authorities: • Repair/reconstruction of infrastructure, housing, public buildings • Generate or reestablish employment • Provide assistance for agricultural areas Secondary response by foreign intervenors: • Repair/reconstruction of housing • Create employment opportunities • Provide credit • Provide technical assistance to agricultural recovery and to coastal industries 5 A particular problem created by a tsunami is that the land struck by the disaster may have a radically altered condition. Industries, businesses and some agricultural owners may decide that the land is too high risk to rebuild or reestablish the pre-disaster operation. This would produce falling land values and dislocation of these enterprises. Or the owners may bring political pressure on the government to provide protective measures that they feel (or hope) will enable them to rebuild and continue their activities with safety and economic security.
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Natural Hazards: Causes and Effects
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This publication was prepared by th
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Introduction How to Get Started Thi
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eruption may be the saturation of a
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Course Objectives Lesson 1 Introduc
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Lesson 1 - Introduction to Natural
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_____ 9. The transitional period an
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Lesson 2 - Self-Assessment Test Mul
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Lesson 3 - Tsunamis Study Guide Ove
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Lesson 4 - Volcanoes Study Guide Ov
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a) frequency of tremors b) upward m
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Lesson 5 - Self-Assessment Test Mul
Page 25 and 26: ) two secondary responses handled b
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Page 29 and 30: Lesson 7 - Drought Study Guide Over
Page 31 and 32: ) often easier than implementing th
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Page 35 and 36: Lesson 9 - Deforestation Study Guid
Page 37 and 38: 10. One method holding great promis
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Page 41 and 42: Contents List of Figures List of Ta
Page 43 and 44: Chapter 1 Introduction to Natural H
Page 45 and 46: Type of Event Number of People Kill
Page 47 and 48: Low-income Economy Afghanistan Bang
Page 49 and 50: Phases of a Disaster Disaster speci
Page 51 and 52: Effects of Disasters Each type of d
Page 53 and 54: take steps to prevent the disaster,
Page 55 and 56: Chapter 2 Earthquakes Introduction
Page 57 and 58: Himalayan zone. Most earthquakes ap
Page 59 and 60: The different rates of travel betwe
Page 61 and 62: Modified Mercalli Intensity Scale o
Page 63 and 64: Frequency of Earthquakes More than
Page 65 and 66: How an earthquake damages a house F
Page 67 and 68: Rupture Zones and Epicenters in Cen
Page 69 and 70: of population from rural to urban a
Page 71 and 72: In all emergency activities it is o
Page 73 and 74: Notes 1 Rita Funaro-Curtis, Natural
Page 75: foundations by the water buoyancy.
Page 79 and 80: Disaster Mitigation The most system
Page 81 and 82: - for tsunamis of local origin, pot
Page 83 and 84: Chapter 4 Volcanoes Introduction Ov
Page 85 and 86: production of sugar and cattle. Bec
Page 87 and 88: lava is a thin fluid (not viscous),
Page 89 and 90: then cool as thin, gently dipping s
Page 91 and 92: drains, causing flooding during sub
Page 93 and 94: then recognized, but today an incre
Page 95 and 96: Volcanic Zoning and Risk Mapping Wi
Page 97 and 98: 1. Environmental Effects Volcano Di
Page 99 and 100: Altogether the combined disaster of
Page 101 and 102: force caused by the earth’s rotat
Page 103 and 104: An atmosphere disturbance forces wa
Page 105 and 106: The Saffir / Simpson Hurricane Scal
Page 107 and 108: measures as have to be devised and
Page 109 and 110: Storm Surge Source: Cuny, Disasters
Page 111 and 112: a set of activities in anticipation
Page 113 and 114: and buildings will affect the veloc
Page 115 and 116: How High Winds Damage Buildings Win
Page 117 and 118: • developing an effective forecas
Page 119 and 120: Notes 1 INTERTECT, The Potential Co
Page 121 and 122: 1. Environmental Effects Tropical C
Page 123 and 124: also by human changes to the surfac
Page 125 and 126: The most noted floods are associate
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Magmatic Water ATMOSPHERE The Hydro
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Seasonality —Inundation of land d
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• Since Landsat images are taken
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The second step in vulnerability re
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100-year flood, since this frequenc
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• Publish a master plan report wi
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• Blankets can be useful, but if
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Initial Response By Local Authoriti
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Notes 1 INTERTECT, The Potential Co
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Chapter 7 Drought Introduction Drou
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In addition to the droughts in the
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The Drought Cycle Normal Hydrologic
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• priority be given to developing
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land aware of the issues. Planning
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The importance of responding to the
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Chapter 8 Desertification Introduct
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Region Estimates of Populations and
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1960; 500,000 in 1973. In 1975, in
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Adaptation of the Hydrological Cycl
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eluctance to cut back on stock numb
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effect. Finer materials are lifted
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such measures involve the disruptio
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Slash-and-Burn Agriculture. This me
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Issues in Reconstruction Peculiar t
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Chapter 9 Deforestation Introductio
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uncontrolled deforestation is a sym
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Related Disasters Description of Ph
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exploitable timber available per pe
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implementation. But essential as th
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Analogue modeling — the applicati
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Crater — a bowl-shaped depression
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organizations (public and private),
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Fault — a planar or gently curved
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Hurricane — in the Western Hemisp
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Malnutrition — the condition of s
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Precipitation — in meteorology, w
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— S — Sand dune stabilization
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Telemetry — the use of communicat
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Vulnerability — the extent to whi
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International Society on Disaster M
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University of Colorado Natural Haza
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Disaster Management Center Universi
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