Cyclone Hazard level: High ?

In the area you have selected (Vietnam) cyclone (also known as hurricane or typhoon) hazard is classified as high according to the information that is currently available. This means that there is more than a 20% chance of potentially-damaging wind speeds in your project area in the next 10 years. Based on this information, the impact of cyclones must be considered in all phases of the project, in particular during design and construction. Project planning decisions, project design, and construction methods should take into account the level of cyclone hazard. 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). Look into recent cyclone events and whether it has caused damage to property under construction. Speak with other construction planners to learn if they obtained insurance coverage in advance, and the cost and benefits associated with that coverage.

  • After construction is complete, plan to purchase a long-term hazard policy to protect your investment against cyclone wind damage, especially if it covers other significant hazards in your project area. Keep in mind multiple location policies can be an economical means of covering diverse risks across multiple locations. During financial planning, budget such a policy and prepare for potential premium increases resulting from higher risk levels in the future (for example, under climate change).

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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 - In general, buildings constructed from masonry and reinforced concrete can withstand cyclone winds better than wood frame construction, 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, and often most costly, damage from wind is to the roof of a property. Complex architectural features (e.g., cupolas, lattice work, etc.) add visual interest, but they also tend to increase wind turbulence and the overall vulnerability of the structure. In general, wind pressures are highest at the corners of roofs.

  • An intense cyclone can bring torrential rains and have embedded severe thunderstorms that are accompanied by tornadoes. Buildings damaged by wind often suffer water damage as well. Water driven by hurricane-force wind can enter a building through otherwise sealed openings, and rain entering through a damaged roof can compromise the inside of the building and in some cases expose the building to dangerous mold.

  • Note that strong wind is not the only cause of direct physical damages from tropical cyclones. Wind-borne debris often initiates or enhances damages to a structure. 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 by wind-borne debris.

  Mitigation - Throughout the project from design to construction, consider all available mitigation strategies to reduce your wind risk from cyclones. Balance the cost of mitigation features with the long-term savings via reduced damage and lower cost of repair and replacement.

  • Further detailed information should be obtained to account for the risk from hazards related to tropical cyclones. Be sure to review the ThinkHazard! assessment for related hazards in this region: storm surge (coastal flood), river flood, and landslide.

  • Investigate national building codes for strong winds in your project area. Also determine from your local authorities whether local building codes override national codes, in particular along the coast where winds from cyclones are strongest. Be responsive to national and local building code requirements for wind hazards as following these codes may considerably reduce losses due to cyclone winds.

  • 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.
  • If national structural design guidelines do not exist, wind speeds for safe design should be obtained from other countries with a similar level of cyclone risk or from international guidelines.
  • Contact other national or local organizations that may have supplemental information on wind risk (e.g., meteorological agency, national research council, engineering associations, etc.).

  • Investigate local council and planning commission meeting minutes as they often contain useful information about best practices and emerging mitigation strategies.

  • In terms of replacement cost, roofs can experience high damage and as such are as important as the materials used for walls and connections. Roof design strongly influences a roof’s resilience to strong winds. Roofs with a mid-range slope tend to be more resilient than flat roofs or highly pitched roofs. Hip roofs are resilient to wind damage while gable ends are highly susceptible to damage.

  • Carefully consider roof construction in the design phase and select high quality materials in the construction phase. The most important construction measures to minimize wind damage to a roof include: proper installation of plywood sheathing, bracing of roof trusses, and use of hurricane straps.

  • The use of wind and impact resistant coverings to protect windows, doors, and other openings from breach by wind-borne debris can greatly reduce damage and loss from a tropical cyclone, particularly when a project is near other buildings (especially medium to high-rise construction), trees, and/or other surface obstacles. High-impact resistant glass can greatly reduce glass damage where debris is prevalent. Properly-rated storm shutters can be installed for use over windows and smaller openings. The tops and bottoms of doors can be reinforced using bolt kits. Garage doors and larger openings can be properly reinforced.

  • As a part of comprehensive risk management, consult the International Property Maintenance Code (IPMC) to assure your project has long-term resilience to wind damage. Be sure to plan for proper roof maintenance post-construction.

  • As a part of a long-term maintenance strategy, identify and remove small trees and branches from larger ones that could fall on the building walls or roof, or on nearby power lines. Identify and repair loose or damaged building components such as sheathing, soffit and fascia, shingles and roofing, brickwork, and jutting building features such as chimneys.

  Special Considerations - Consider including a safe room in the design phase of your project. A safe room (wind shelter) provides a space to seek refuge and can provide an additional level of protection. Safe rooms are most effective atop the concrete slab foundation or garage/basement floor. Safe rooms built below grade provide the greatest protection, but must be designed to avoid accumulating water during the heavy rains that often accompany cyclones. A safe room must also be built to withstand flying debris even when the rest of the building is damaged or destroyed.

  • When cyclone warnings are issued by your local or national governmental emergency response agency, there are several steps you can take to prepare. Move breakable items away from windows and doors. Board up doors, windows, and other openings to the exterior. Bring in unsecured outdoor furniture and other property. Secure outdoor fuel tanks (e.g., propane) and shutoff supply of gas to the interior of the building.

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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, thoroughly review the emergency response procedures laid out by your local and national governments and, if necessary, make changes to project design and implementation to account for these procedures. These procedures will have already taken into account the significant hazards inherent to your region, including cyclone wind hazards and other related risks to your project.

  • Adopt your own emergency response procedure leveraging response plans already in place regionally. Your plans should include specific conditions that will activate the plan, a clear chain of command and orders of responsibility, a list of specific emergency functions and who will perform each of them, evacuation procedures, including evacuation routes and emergency exists, and procedures to account for personnel, customers, and visitors as appropriate. Be sure to secure and maintain proper emergency equipment for personnel including medical kits.

  • If your project includes a safe room, clearly post its location and include safe room access and supplies as a part of your overall emergency response plan. Train personnel on emergency response procedures. Prepare for real-time response with unannounced drills and conduct post-mortem to improve personnel preparedness.

  • Remain aware of your government meteorological organization’s watch and warning protocols. When a warning is issued, be aware of the meaning of such a warning and be prepared to clearly communicate its implications to your personnel and visitors. Clearly define the circumstances that would lead to retreat to a safe room, voluntary and mandatory evacuation procedures, operations shutdown, etc.

  • Develop a task checklist for your emergency response plan, and maintain that list at least once per year. The checklist can be customized to each stage of your project or draw attention to tasks more critical in a particular stage (e.g., construction sites will have more potential outdoor airborne debris). A sample checklist is shown below.

  • Board windows or if there’s time install shutters to help protect from flying debris.

  • Clean floor drains, catch basins, and pumps to ensure proper drainage.
  • Anchor temporary structures, trailers, and outdoor storage so they’re less likely to be moved by high winds.
  • If practical, move outdoor storage and unanchored property indoors.
  • Anchor and fill tanks (unless below ground) to capacity with product or water to minimize tipping hazard.
  • Move drums and other portable tanks containing flammables to a properly protected and secure area indoors.
  • Maintain an inventory of flammables and caustic or dangerous materials on site.
  • Secure outdoor cranes in accordance with manufacturer’s instructions.
  • Fill emergency generator fuel tanks.
  • Inspect all fire protection equipment to be sure they’re operational.
  • Move important records and documents to a secure and protected area. If there’s time, duplicate records and move offsite.
  • Shut down any production processes safely and in a timely fashion. Prepare personnel in advance of the shutdown.
  • Shut off supply lines to flammable liquids, combustible liquids and gas at their source.
  • Shut off electrical power at the main building disconnect before the cyclone strikes.

  • Evacuate personnel and, if safe for emergency response teams to remain, ensure that team has the following:

    • Nonperishable food
    • Two-way radios with spare batteries
    • Ample supply of stored drinking water
    • Flashlights and batteries
    • First-aid supplies
    • Vehicles with full gas tanks
    • Gloves, boots, and hard hats
    • Supply of dry clothing

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

  • It’s imperative to plan in advance for all aspects of a catastrophic wind event. Wind debris is inevitable, especially in built up areas, but often unplanned for. In addition to preparing for building damage exacerbated by wind-borne debris, and injuries from flying debris, you should plan for debris clean up especially if it is expected to interfere with operations of the residence or business. Keep in mind debris comes from other areas, buildings, and surfaces, thus you should be aware of surrounding structures especially if hazards (e.g., explosive material) may be contained in nearby structures. The most common debris from cyclone winds include damaged building components or contents, sediments, green waste, and personal property. Other forms of debris are associated with severe rains and flooding that often accompanies cyclones. Debris from flooding can occur many miles from the coast. Debris collection and removal can be extremely costly, and recent experience has shown debris removal is often more costly than direct physical damage to the building itself.

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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, engage with 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

  • Experts can provide significant value to your project since the risk is significant. During the design and construction plan review phases, wind engineers will review the latest available literature and data to confirm that your project is exposed to the dangers of cyclone winds, and propose mitigation measures to protect your assets. Experts can also review recent historical events that have affected your region and how nearby buildings have performed under elevated wind conditions. With this prior knowledge, your project managers can evaluate mitigation and risk transfer options before construction begins.

  • After construction is complete, wind experts can evaluate all scientific literature that has been published since construction began to determine if the risk is even higher than previously suspected and also suggest additional steps to increase resilience. Regardless of whether the risk has changed, experts can propose long-term mitigation strategies, methods of disaster preparedness and response, and the value of insurance given the expected risk levels. In the event wind risk has increased, the expense of hiring the expert will be justified by drawing attention to potential future losses and accounting for those risks before an event produces damage. Experts can also be engaged to evaluate all risk transfer options (including individual insurance policies, pooled risk programs, bonds, etc.) and present them to your finance team to inform the best possible decision for long-term risk management.

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