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close this bookDisaster Mitigation - 2nd Edition (Department of Humanitarian Affairs/United Nations Disaster Relief Office - Disaster Management Training Programme - United Nations Development Programme , 1994, 64 p.)
View the document(introduction...)
View the documentUnited Nations reorganization and the Disaster Management Training Programme
View the documentIntroduction
close this folderPart 1 - Introduction to mitigation concepts
View the document(introduction...)
View the documentThe sanitary revolution: a paradigm for disaster mitigation
View the documentKnow your enemy: hazards and their effects
View the documentSaving life and reducing economic disruption
View the documentTargeting mitigation where it has most effect
View the documentVulnerability
close this folderSpecific Hazards and Mitigation
View the document(introduction...)
View the documentFloods and water hazards
View the documentEarthquakes
View the documentVolcanic eruption
View the documentLand instabilities
View the documentStrong winds (typhoons, hurricanes, cyclones, tropical storms and tornados)
View the documentTechnological hazards
View the documentDrought and desertification
View the documentSUMMARY
close this folderPart 2 - Actions to reduce risk
View the document(introduction...)
View the documentReducing hazard vs reducing vulnerability
View the documentTools, powers and budgets
View the documentCommunity-based mitigation
View the documentThe menu of mitigation actions
View the documentSUMMARY
close this folderPart 3 - Mitigation strategies
View the document(introduction...)
View the documentAims and methods
View the documentEconomics of mitigation
View the documentPracticalities of mitigation
View the documentOpportunities for mitigation: post-disaster implementation
View the documentEmpowerment and community-based mitigation
View the documentSUMMARY
close this folderPart 4 - Implementing organizations
View the document(introduction...)
View the documentBuilding up skills and institutions
View the documentThe regional context: a problem shared
View the documentInternational exchange of expertise
View the documentSupporting decision-making: external specialists
View the documentKnowledge dissemination
View the documentInternational decade for natural disaster reduction
View the documentDisaster mitigation in UNDP country programming
View the documentInitial phases of the UNDP country programming exercise
View the documentSUMMARY
View the documentAnnex 1: Profile of selected United Nations agencies and their activities in disaster mitigation
View the documentAnnex 2: Acronyms
View the documentAnnex 3: Additional reading
View the documentGlossary
View the documentModule evaluation

Strong winds (typhoons, hurricanes, cyclones, tropical storms and tornados)

Mechanism of destruction

Pressure and suction from wind pressure, buffeting for hours at a time. Strong wind loads imposed on a structure may cause it to collapse, particularly after many cycles of load reversals. More common damage is building and non-structural elements (roof sheets, cladding, chimneys) blown loose. Wind-borne debris causes damage and injury. High winds cause stormy seas that can sink ships and pound shorelines. Many storms bring heavy rains. Extreme low air pressure at the center of a tornado is very destructive and houses may explode on contact.

Parameters of severity

Velocity of wind. Wind scales (e.g. Beaufort) gale severity scale. Local hurricane/typhoon scales.


Winds generated by pressure differences in weather systems. Strongest winds generated in tropics around severe low pressure systems several hundreds of kilometers diameter (cyclones) known as typhoons in the Pacific and as hurricanes in Americas and elsewhere. Extreme low pressure pockets of much narrower diameter generate rapidly twisting winds in tornados.

Hazard assessment and mapping techniques

Meteorological records of wind speeds and direction at weather stations gives probability of high winds in any region. Local factors of topography, vegetation and urbanization may affect microclimate. Past records of cyclone and tornado paths give common patterns of occurrence for damaging wind systems.

Potential for reducing hazard

None. Cloud seeding may dissipate rain content.

Onset and warning

Tornados may strike suddenly but most strong winds build up strength over a number of hours. Low pressure systems and tropical storm development can be detected hours or days before damaging winds affect populations. Satellite tracking can help follow movement of tropical storms and project likely path. The movements of weather systems are however, complex and still difficult to predict with accuracy.

Elements most at risk

Lightweight structures and timber housing. Informal housing sectors and shanty settlements. Roofs and cladding. Loose or poorly attached building elements, sheets and boards. Trees, fences, signs etc. Telegraph poles, pylons and high-level cables. Fishing boats or other maritime industries.

Main mitigation strategies

Engineering of structures to withstand wind forces. Wind load requirements in building codes. Wind safety requirements for non-structural elements. Good construction practices. Micro-climatic siting of key facilities, e.g. in lee of hillsides. Planting of windbreaks, planning of forestry areas upwind of towns. Provision of wind-safety buildings (e.g. strong village halls) for community shelter in vulnerable settlements.

Community participation

Construction of wind-resistant or easily rebuilt houses. Securing fixing of elements that could blow away and cause damage or injury elsewhere, e.g. metal sheeting, fences, signs. Preparedness for storm action. Taking shelter in strong, wind-resistant buildings. Protection measures for boats, building contents or other possessions at risk.