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    question 25 identify two examples of natural hazards found in mountains. in each case, give an example of how decisions made by humans have increased or decreased vulnerability to that hazard.


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    This chapter defines natural hazards and their relationship to natural resources (they are negative resources), to environment (they are an aspect of environmental problems), and to development (they are a constraint to development and can be aggravated by it). The chapter demonstrates that the means of reducing the impact of natural hazards is now available. The factors that influence susceptibility to vulnerability reduction-the nature of the hazard, the nature of the study area, and institutional factors-are discussed. The core of the chapter explains how to incorporate natural hazard management into the process of integrated development planning, describing the process used by the OAS-Study Design, Diagnosis, Action Proposals, Implementation-and the hazard management activities associated with each phase. The chapter goes on to show how the impact of natural hazards on selected economic sectors can be reduced using energy, tourism, and agriculture as examples. Finally, the significance of a hazard management program to national and international development institutions is discussed.

    The planning process in development areas does not usually include measures to reduce hazards, and as a consequence, natural disasters cause needless human suffering and economic losses. From the early stages, planners should assess natural hazards as they prepare investment projects and should promote ways of avoiding or mitigating damage caused by floods, earthquakes, volcanic eruptions, and other natural catastrophic events. Adequate planning can minimize damage from these events. It is hoped that familiarizing planners with an approach for incorporating natural hazard management into development planning can improve the planning process in Latin America and the Caribbean and thereby reduce the impact of natural hazards.


    1. How Natural Are Natural Hazards?

    2. Environment, Natural Hazards and Sustainable Development

    3. The Impact of Natural Hazards Can Be Reduced

    A widely accepted definition characterizes natural hazards as "those elements of the physical environment, harmful to man and caused by forces extraneous to him" (Burton, 1978). More specifically, in this document, the term "natural hazard" refers to all atmospheric, hydrologic, geologic (especially seismic and volcanic), and wildfire phenomena that, because of their location, severity, and frequency, have the potential to affect humans, their structures, or their activities adversely. The qualifier "natural" eliminates such exclusively manmade phenomena as war, pollution, and chemical contamination. Hazards to human beings not necessarily related to the physical environment, such as infectious disease, are also excluded from consideration here. Figure 1-1 presents a simplified list of natural hazards, and the boxes on the following pages briefly summarize the nature of geologic hazards, flooding, tsunamis, hurricanes, and hazards in arid and semi-arid areas.

    1. How Natural Are Natural Hazards?

    Not with standing the term "natural," a natural hazard has an element of human involvement. A physical event, such as a volcanic eruption, that does not affect human beings is a natural phenomenon but not a natural hazard. A natural phenomenon that occurs in a populated area is a hazardous event. A hazardous event that causes unacceptably large numbers of fatalities and/or overwhelming property damage is a natural disaster. In areas where there are no human interests, natural phenomena do not constitute hazards nor do they result in disasters. This definition is thus at odds with the perception of natural hazards as unavoidable havoc wreaked by the unrestrained forces of nature. It shifts the burden of cause from purely natural processes to the concurrent presence of human activities and natural events.


    ATMOSPHERIC Hailstorms Hurricanes Lightning Tornadoes Tropical storms SEISMIC Fault ruptures Ground shaking Lateral spreading Liquefaction Tsunamis Seiches


    Debris avalanches Expansive soils Landslides Rock falls Submarine slides Subsidence HYDROLOGIC Coastal flooding Desertification Salinization Drought

    Erosion and sedimentation

    River flooding Storm surges VOLCANIC

    Tephra (ash, cinders, lapilli)

    Gases Lava flows Mudflows

    Projectiles and lateral blasts

    Pyroclastic flows WILDFIRE Brush Forest Grass Savannah

    Although humans can do little or nothing to change the incidence or intensity of most natural phenomena, they have an important role to play in ensuring that natural events are not converted into disasters by their own actions. It is important to understand that human intervention can increase the frequency and severity of natural hazards. For example, when the toe of a landslide is removed to make room for a settlement, the earth can move again and bury the settlement. Human intervention may also cause natural hazards where none existed before. Volcanoes erupt periodically, but it is not until the rich soils formed on their eject are occupied by farms and human settlements that they are considered hazardous. Finally, human intervention reduces the mitigating effect of natural ecosystems. Destruction of coral reefs, which removes the shore's first line of defense against ocean currents and storm surges, is a clear example of an intervention that diminishes the ability of an ecosystem to protect itself. An extreme case of destructive human intervention into an ecosystem is desertification, which, by its very definition, is a human-induced "natural" hazard.

    Source : www.oas.org

    Natural hazards and disaster risk reduction

    Natural hazards are severe and extreme weather and climate events that occur in all parts of the world, although some regions are more vulnerable to certain hazards than others. Natural hazards become disasters when people’s lives and livelihoods are destroyed.

    Natural hazards and disaster risk reduction

    Natural hazards and disaster risk reduction FloodUnited_NationsFlickr.jpg

    Natural hazards and disaster risk reduction

    Tags: Natural hazards Floods Drought

    Natural hazards are severe and extreme weather and climate events. Although they occur in all parts of the world, some regions are more vulnerable to certain hazards than others. Natural hazards become disasters when people’s lives and livelihoods are destroyed.

    The global expected average annual loss in the built environment associated with tropical cyclones (wind and storm surge), earthquakes, tsunamis and floods is now estimated at US$314 billion. This risk presents a real challenge to the global agenda of sustainable development. (...) In absolute terms, global average annual loss is concentrated in large, higher-income, hazard-exposed economies. However, in relation to annual capital investment or social expenditure, many low and middle-income countries, and in particular small island developing states (SIDS), have the highest concentrations of risk. - UNISDR: Global Assessment Report on Disaster Risk Reduction 2015

    Human and material losses caused by such disasters are a major obstacle to sustainable development. By issuing accurate forecasts and warnings in a form that is readily understood and by educating people on how to prepare against such hazards, before they become disasters, lives and property can be protected. Emphasis is on disaster risk reduction: one dollar invested in disaster preparedness can prevent seven dollars’ worth of disaster-related economic losses – a considerable return on investment.

    As signatories to the Sendai Framework for Disaster Risk Reduction 2015–2030, WMO Members have undertaken to prevent new and reduce existing disaster risk through the implementation of  a range of integrated and inclusive measures that prevent and reduce hazard exposure and vulnerability to disaster, increase preparedness for response and recovery and thus strengthen resilience. To support the assessment of global progress in achieving the outcomes and goals of the Sendai Framework, seven global targets have been agreed, most of which have direct implications for WMO and its Members.

    WMO Disaster Risk Reduction activities are integrated and coordinated with other international, regional and national organizations. WMO coordinates the efforts of National Meteorological and Hydrological Services to mitigate human and property losses through improved forecast services and early warnings, as well as risk assessments, and to raise public awareness.

    Natural hazards occur across different time and area scales and each is in some way unique. Tornadoes and flash floods are short-lived, violent events, affecting a relatively small area. Others, such as droughts, develop slowly, but can affect most of a continent and entire countries for months or even years. An extreme weather event can involve multiple hazards at the same time or in quick succession. In addition to high winds and heavy rain, a tropical storm can result in flooding and mudslides. In temperate latitudes, severe thunderstorms can be accompanied by a combination of large, damaging hail stones, tornadoes, strong winds or heavy rain resulting in flash floods. Winter storms with high winds and heavy snow or freezing rain can also contribute to avalanches on some mountain slopes and to high runoff or flooding later on in the melt season.

    Some National Meteorological and Hydrological Services and specialized centres have responsibility for investigating geophysical hazards including volcanic explosions (airborne ash) and tsunamis, and hazardous airborne matter (radionuclides, biological and chemical substances) and acute urban pollution.

    Natural hazards

    Drought Tropical cyclones Air pollution Desert locusts

    Floods and flash floods

    Landslide or mudslide (mudflow)



    Thermal extremes

    Thunderstorms, Lightning, and Tornadoes

    Forest or Wildland Fire

    Heavy rain and snow, Strong winds


    Multi-Hazard Early Warning Systems: A Checklist

    Early warning is a major element of disaster risk reduction. It can prevent loss of life and reduce the economic and material impacts of hazardous events including disasters. To be effective, early warning systems need to actively involve the people and communities at risk from a range of hazards, facilitate public education and awareness of risks, disseminate messages and warnings efficiently and ensure that there is a constant state of preparedness and that early action is enabled.

    Read more

    about Multi-Hazard Early Warning Systems: A Checklist

    Contributing to United Nations Sustainable Development Goals 1 and 9

    Source : public.wmo.int

    Natural Disasters & Assessing Hazards and Risk

    EENS 3050 Natural Disasters Tulane University

    Prof. Stephen A. Nelson

    Natural Disasters & Assessing Hazards and Risk

    This page last updated on 09-Jan-2018

    Natural Hazards and Natural Disasters

    A natural hazard is a threat of a naturally occurring event will have a negative effect on humans.   This negative effect is what we call a natural disaster.  In other words when the hazardous threat actually happens and harms humans, we call the event a natural disaster.

    Natural Hazards (and the resulting disasters) are the result of naturally occurring processes that have operated throughout Earth's history.

    Most hazardous process are also Geologic Processes.

    Geologic processes effect every human on the Earth all of the time, but are most noticeable when they cause loss of life or property. If the process that poses the hazard occurs and destroys human life or property, then a natural disaster has occurred.  Among the natural hazards and possible disasters to be considered are:

    Earthquakes Volcanic Eruptions Tsunami Landslides Subsidence Floods Droughts Hurricanes Tornadoes Asteroid Impacts

    All of these processes have been operating throughout Earth history, but the processes have become hazardous only because they negatively affect us as human beings.  Important Point - There would be no natural disasters if it were not for humans.  Without humans these are only natural events.

    Risk is characteristic of the relationship between humans and geologic processes.   We all take risks everyday. The risk from natural hazards, while it cannot be eliminated, can, in some cases be understood in a such a way that we can minimize the hazard to humans, and thus minimize the risk.  To do this, we need to understand something about the processes that operate, and understand the energy required for the process.  Then, we can develop an action to take to minimize the risk. Such minimization of risk is called hazard mitigation.

    Although humans can sometimes influence natural disasters (for example when poor levee design results in a flood), other disasters that are directly generated by humans, such as oil and toxic material spills, pollution, massive automobile or train wrecks, airplane crashes, and human induced explosions, are considered technological disasters, and will not be considered in this course, except when they occur as a secondary result of a natural disaster.

    Some of the questions we hope to answer for each possible natural disaster are:

    Where is each type of hazard likely to be present and why?

    What scientific principles govern the processes responsible for the disasters?

    How often do these hazards develop into disasters?

    How can each type of disaster be predicted and/or mitigated?

    As discussed before, natural disasters are produced by processes that have been operating since the Earth formed. Such processes are beneficial to us as humans because they are responsible for things that make the Earth a habitable planet for life. For example:

    Throughout Earth history, volcanism has been responsible for producing much of the water present on the Earth's surface, and for producing the atmosphere.

    Earthquakes are one of the processes responsible for the formation of mountain ranges which which direct water to flow downhill to form rivers and lakes.

    Erosional processes, including flooding, landslides, and windstorms replenishes soil and helps sustain life.

    Such processes are only considered hazardous when they adversely affect humans and their activities.Classification of Natural Hazards and Disasters

    Natural Hazards and the natural disasters that result can be divided into several different categories:

    Geologic Hazards - These are the main subject of this course and include:

    Earthquakes Volcanic Eruptions Tsunami Landslides Floods Subsidence

    Impacts with space objects

    Atmospheric Hazards - These are also natural hazards but processes operating in the atmosphere are mainly responsible. They will also be considered in this course, and include:

    Tropical Cyclones Tornadoes Droughts

    Severe Thunderstorms


    Other Natural Hazards - These are hazards that may occur naturally, but don't fall in to either of the categories above. They will not be considered to any great extent in this course, but include:

    Insect infestations Disease epidemics Wildfires

    Natural Hazards can also be divided into , which have devastating consequences to huge numbers of people, or have a worldwide effect, such as impacts with large space objects, huge volcanic eruptions, world-wide disease epidemics, and world-wide droughts. Such catastrophic hazards only have a small chance of occurring, but can have devastating results if they do occur.

    Natural Hazards can also be divided into , such as Volcanic Eruptions, Earthquakes, Flash floods, Landslides, Severe Thunderstorms, Lightening, and wildfires, which develop with little warning and strike rapidly. Slow onset hazards, like drought, insect infestations, and disease epidemics take years to develop.

    Anthropogenic Hazards

    These are hazards that occur as a result of human interaction with the environment. They include , which occur due to exposure to hazardous substances, such as radon, mercury, asbestos fibers, and coal dust. They also include other hazards that have formed only through human interaction, such as acid rain, and contamination of the atmosphere or surface waters with harmful substances, as well as the potential for human destruction of the ozone layer and potential global warming.

    Source : www2.tulane.edu

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