Tropical cyclone Hazard level: Low ?

Tropical cyclones are intense rotating storm systems that form over warm tropical oceans, characterized by strong winds, heavy rainfall, and storm surges. These systems derive energy from warm ocean waters and can cause damage through multiple mechanisms: high-speed winds, torrential precipitation leading to flooding, and coastal inundation from storm surge. The severity depends on the cyclone's intensity, size, forward speed, track, and the vulnerability of affected areas.

In the area you have selected (French Polynesia) cyclone (also known as hurricane or typhoon) hazard is classified as low according to the information that is currently available. This means that there is approximately 0.1% chance per year of potentially-damaging wind speeds in your project area (about 1% chance in the next 10 years). Based on this information, the impact of cyclones should be considered in the project, in particular during design and construction. Risk studies, project planning decisions, project design, and construction methods should take into account the level of cyclone hazards. Note that damages can not only occur due to wind but also cyclone induced heavy rainfall and subsequent flooding as well as coastal floods in coastal areas. Further detailed information should be obtained to adequately account for the level of hazard.

Climate change impact: Global average tropical cyclone wind speed and rainfall is likely to increase in the future, and the global average frequency of tropical cyclones is likely to decrease or remain unchanged. It is possible that the frequency of the most intense tropical cyclones will increase substantially in some ocean regions (IPCC, 2013). The present hazard level in areas currently affected by tropical cyclones may increase in the long-term. Projects located in such areas should be robust to future increases in cyclone hazard.

Recommendations

• INSURANCE: For cyclone wind risks that cannot be mitigated, consider insurance products specifically aimed at alleviating the financial costs associated with wind risk. More information
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  • During the design and construction phases, carefully consider purchasing a ‘builders risk’ insurance policy for your project. In particular, ensure that the policy can cover aggregate weather hazards including those related to cyclones (such as extreme rainfall).

  • After construction is complete, carefully consider a long-term hazard policy to protect your investment, especially if it covers other significant hazards to the project. Keep in mind multiple location policies can be an economical means of covering diverse risks across multiple locations.

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• INTERACTING HAZARDS: Project planning, design, and construction practices should account for strong wind from potential cyclones in your project area. More information
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  Context - Throughout the project from design to construction, you should understand the level of wind hazard in your project area. Keep in mind that in a changing climate, windstorms may be experienced in regions where they have been historically rare. Also be mindful that other short-term wind events (such as severe thunderstorms) may be highly localized and still cause significant wind damage.

  • During design and construction, account for national and local building codes for wind hazards. Start by consulting with widely accepted building code organizations such as the ICC (International Code Council) to access commercial and residential code (ICC/IRC) standards pertaining to your project. Next, determine if your region has adopted international codes or has modified them locally. Consult your jurisdictional planning division for the most up-to-date information on building codes. Be mindful of recent code changes as they are often developed in response to recent adverse natural events that have caused loss to similar projects. Contact other organizations that may have supplemental information on wind risk (e.g., meteorological agency, national research council, engineering associations, etc.).

  • In general, buildings constructed using masonry and reinforced concrete perform better than wood frame construction when subjected to marginally damaging wind speeds, although it is important to consider building design for cyclone wind alongside other hazards that might be present in the project area.

  • The most common damage from wind is to the roof of a property, so carefully consider roof construction in the design phase and select high quality materials in the construction phase.

  • Note that strong wind and flying debris are not the only cause of direct physical damages from tropical cyclones. Extensive damage can also be induced by heavy rainfall and subsequent inland flooding and, in coastal areas, by coastal floods and beach erosion, especially after the roof and/or windows or other openings are compromised.

  Mitigation - While the wind hazard level for your project location is LOW, well-constructed buildings will reduce the risk of other hazards that may be present in your project area. For example, properly constructed roofs and building connections that do well in high winds also withstand strong ‘gravity loads’ from heavy snow and ice. Properly formed and sealed foundations may reduce impacts during flooding.

  • Consider wind along with other related hazards (e.g., precipitation, inland and coastal flooding, landslides) in the overall mitigation strategy for your project.

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• EMERGENCY RESPONSE PLANS: Identify the regional and national government’s emergency response policy and protocols to cyclones (including coastal and inland flooding and wind hazard) in your project area and incorporate as necessary. More information
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  • During the design and construction phases, reserve time to review the emergency response procedures laid out by the local and national governments in your project area. These procedures will take into account the hazards inherent to your region, including cyclone wind hazards.

  • After construction is complete, remain mindful of emergency response procedures and if they change with regard to the hazards of strong winds, and consider increasing your resilience via improved building mitigation and/or new or additional insurance coverage.

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• CRITICAL INFRASTRUCTURE: If the project involves the development of critical infrastructure (e.g., a hospital, fire station, or power transmission line), or will support critical infrastructure, you should consider how your project can be affected by wind that occurs outside of the specific project location. More information
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  CONTEXT: - For projects that relate directly to critical infrastructure (such as a hospital project, utility expansion, or communications facility), there is a need for the assets to function post-event either to maintain essential services or to provide emergency response and recovery efforts.

  • Most projects (even unrelated to infrastructure) rely upon public services such as electricity, water, communications, etc. and provide services or products that are important to the local, regional or national economy and commerce. Thus, even when the project itself is not damaged by cyclone winds, it may not remain functional due to disruptions in critical infrastructure. The chain of supply of these critical services should be considered and contingency plans developed for each service (e.g. water, electricity, transportation networks). In particular, if the project is for infrastructure development (e.g., a new electrical sub-station), its connection to the wider service network should be planned carefully.

  • Damage and disruption to the local transportation network may not disrupt the functioning of a facility, but it can prohibit personnel from reaching critical infrastructure or an emergency facility.

  MITIGATION: - Consider all dependencies on your project that are vulnerable to wind. Consider redundant (backup) systems whenever possible, in conjunction with service providers. For example, in the event of a power outage does the budget support housing backup generators and, if not, what would be the most likely electrical service available? If power were lost for 1 day, 1 week, etc. what would be the financial impact? Are there insurance products that can protect the project from such an interruption (see insurance section)?

  • Play out disaster scenarios (scenario planning) to stress such conditions on your project and to plan how to respond.

  • Conduct cost/benefit analysis to determine if on-site backup power generation is an option within the budget. Independent wireless communication (e.g., VHF) radio may be a cost-efficient option for communications redundancy and prove vital in a time of crisis.

  • If roads and transportation access are important to the project, either for on-site staff or for post-event operations (e.g., ambulance service) consider alternative routing, or if the risks are high an alternative site for the project.

  • Dependencies to infrastructure are often difficult to manage. If the dependencies are high and the cost of mitigation and redundancy are over budget, consider an alternative site for the project.

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• TECHNICAL EXPERTISE: Consult with an expert familiar with cyclone wind hazard and risk-related construction practices in your local area. Such consulting professionals include structural engineers, civil engineers, and atmospheric scientists. Incorporate local and subject matter expertise in the design, construction, and maintenance phases of your project. More information
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  • To learn more about the risks, consider hiring qualified meteorological and engineering experts with the goals of: 1. Understanding the frequency and intensity of cyclones and related natural risks to the project 2. Determining how local site conditions may increase or decrease such risks to the project 3. Learning about recent and/or nearby events that can provide real-life context to the risks and impacts 4. Supervising design, construction and maintenance from a wind risk perspective 5. Understanding and adapting proper mitigation strategies based on the current state-of-science 6. Conducting cost/benefit studies to evaluate and prioritize mitigation, insurance, and resilience 7. Interviewing local staff and residents having local experience with any aspect of risks to your project

  • During the design and construction plan review phases, wind engineers can review the latest available literature and data to ensure that your project is not highly exposed to the impacts of cyclone winds.

  • After construction is complete, wind experts can evaluate all the latest scientific literature that has been published since construction began to ensure the risk remains LOW and is not significantly higher than previously suspected. In the event wind risk has increased, the expense of hiring such an expert is financially justified by drawing attention to potential future losses and accounting for those risks before an event produces damage. Consult with nearby construction managers to determine if an expert has assisted in their project.

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