Tsunami Hazard level: Low ?

In the area you have selected (Sierra Leone) tsunami hazard is classified as low according to the information that is currently available. This means that there is more than a 2% chance of a potentially-damaging tsunami occurring in the next 50 years. Based on this information, the impact of tsunami may be considered in different phases of the project for any activities located near the coast. Project planning decisions, project design, and construction methods may want to take into account the level of tsunami hazard. Further detailed information should be obtained to adequately account for the level of hazard.

Climate change impact: The areas at risk of tsunami will increase as global mean sea level rises. According to the IPCC (2013), global mean sea level rise depends on a variety of factors, and estimates for 2100 range from ~20 cm to nearly 1 m. However, regional changes in sea level are difficult to predict. Projects in low-lying coastal areas such as deltas, or in island states should be designed to be robust to projected increases in global sea level.

Recommendations

• REGULATIONS: Check with local authorities to identify any local regulations concerning tsunami hazard and impacts. Ensure that the project conforms to existing tsunami avoidance zone land use planning regulations, flood regulations and any existing plans for warning and evacuation. More information
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  CONTEXT:

  • Around the world there is increasing recognition that avoiding development in the most frequently tsunami (or river flood or storm surge) inundated areas is one of the most effective means of managing future losses to natural hazards. Therefore, the planning for new developments should include consideration of already-existing national or regional regulations and guidelines
  • Many countries have some form of formal legislation, regulation or guidance for tsunami risk mitigation. These may broadly cover such aspects as:
  • Land-use planning, controlling the location of development for all or some types of building or project
  • Warning, through natural signs (earthquake, ocean disturbance), local initiatives and/or Tsunami Warning Centres
  • Response planning, usually focussed on life safety, evacuation routes, signage and safe locations
  • Public alerting mechanisms such as mobile phone apps, sirens, radio etc.
  • Hard defence options
  • Vertical evacuation options
  • Risk assessment

  MITIGATION:

  • Note that avoidance of a natural hazard such as tsunami is the most effective form of risk mitigation, but this should be a decision made based on the informed understanding of social, economic and political risk.
  • Comply with laws and regulations including land-use planning and flood management. Design the project to best integrate the regulations.
  • Comply with all Health and Safety obligations appropriate to the hazard level.
  • If the location of the project conflicts with land-use planning regulations, or cannot comply with warning and evacuation regulations consider relocation of the project.

  Links:

  International Tsunami Information Centre http://itic.ioc-unesco.org/index.php

  Pacific Tsunami Warning Centre: http://ptwc.weather.gov/

  Indian Ocean Tsunami Warning and Mitigation System (ICG/IOTWMS), more information at: http://www.ioc-tsunami.org/index.php?option=com_content&view=article&id=8&Itemid=58&lang=en

  North-Eastern Atlantic, Mediterranean and connected seas: Tsunami Information Centre. http://neamtic.ioc-unesco.org/

  Examples:

  NZ tsunami warning plan – http://www.civildefence.govt.nz/cdem-sector/cdem-framework/guidelines/national-tsunami-advisory-and-warning-plan/

  NZ tsunami evacuation mapping guideline – < http://www.civildefence.govt.nz/assets/Uploads/publications/dgl-08-08-tsunami-evacuation-zones.pdf>

  NZ public notification options assessments - http://www.civildefence.govt.nz/cdem-sector/cdem-framework/guidelines/public-alerting-options-assessment/

  Integrating tsunami inundation modelling into land use planning http://www.eqc.govt.nz/sites/public_files/1604-tsunami-inundation-modelling-into-land-use-planning_0.pdf

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• UTILITIES AND ACCESS: Consider the impact of tsunami inundation on the availability and function of: transport, communications, water, sanitation and energy infrastructure, and public health for continued operation of the project. More information
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  CONTEXT:

  • A project may be situated far from the coast but still be sensitive to loss of services.
  • Failure to function or lack of availability of these essential services may compromise the building of the project, the functionality, or the financial viability of the completed project.
  • Public administration and services such as governance, banking and health may be disrupted due to either direct damage or diversion of resources.
  • Transport routes are regularly disrupted in tsunami, due to the coastal location and orientation of roads, train lines, bridges and airports.
  • Ports are regularly damaged by tsunami.
  • Communications, communication cables and energy networks often follow the roads and may cross waterways on bridges that are vulnerable to tsunami impact.
  • Energy supply, refining, and storage facilities are often in coastal locations. Near-shore and off-shore oil and gas supply platforms, bores and pipes are vulnerable. Shipping of energy (gas and oil tankers, etc.) relies on ports. Refineries often exploit low coastal plains. Power cables across oceans and small waterways may come ashore in areas at risk of tsunami.
  • Fuel is often stored in coastal tank farms, which can be heavily damaged by tsunami. The tanks and fuel are often floating and possibly present as a direct hazard to the project. Tsunami and associated earthquakes can cause rupture of gas supplies and spillage of flammable materials. Fires may subsequently occur and spread on the water surface.
  • Water and sanitation pipes and treatment plants are often in coastal areas and can be damaged by tsunami.
  • Public health is often compromised following a tsunami due to damaged sanitation services, loss of refrigeration, water-borne disease and lack of availability of health services and food.
  • Food distribution loss through transport, refrigeration, and storage, along with loss of supply from agricultural, fisheries and tourism impacts, is a common consequence of tsunami inundation.

  MITIGATION:

  • Consider which services are essential to maintain social and economic function of the project and the region during the months to years of post-event recovery. For these services:
  • Discuss possible redundancy of services with the relevant infrastructure operators. For example, electricity and road networks that do not run parallel or close to the coastline.
  • Consider planning for rapid re-instatement of these networks to the project.
  • Consider on-site back-up supply of essential services. For example, backup power generation, and long term fuel supply availability. Independent wireless communication such as VHF radio could also be considered.
  • Services may be made more resilient by incorporating higher engineering specifications designed for tsunami scour, lateral pressure, buoyancy, debris impact and fire.
  • If the critical service dependencies are not able to be duplicated or hardened, then consider relocating the project to a location with more resilient services, even if the project location itself is not vulnerable to tsunami.

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• CRITICAL INFRASTRUCTURE CONSIDERATIONS: If the project is involves the development of critical infrastructure (e.g., a hospital, fire station, or power transmission line), investigate the cascading effect of vulnerable network dependencies of the project (e.g. power supply and computer and communication networks) that may impact the project, even if the project itself is not inundated. More information
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  CONTEXT:

  • For projects that are critical infrastructure (such as a hospital, a power station, or a key communications facility) there is a greater need and expectation that they will function post-event to maintain essential services or are a pivotal part of response and recovery efforts.
  • Most projects rely upon incoming services such as electricity, water supply, workforce, etc., (‘upstream dependencies’) and provide services or products that are important to the local, regional or national economy and social wellbeing (‘downstream dependencies’). Thus, even when the project itself is damaged by the tsunami, it may not function.
  • Thus, even if the project itself is not inundated or damaged by the tsunami it may not be able to fulfil its required role in the wider economy. If the project has supply guarantee deliverables, then the wider dependencies need to be robust to tsunami damage.
  • Most common dependencies include energy supply (especially electric) and communications. These services are often supplied along the road corridor which runs parallel to the coast and is often supported by bridges. Coastal locations and bridges are highly vulnerable to tsunami, so it is likely these services will be damaged and unavailable following a tsunami.

  MITIGATION:

  • Consider which dependencies are vulnerable to tsunami. Consider backup or redundant systems where possible, in conjunction with service providers. For example, are there service corridors that do not run parallel to the coastline.
  • Consider planning for rapid re-instatement of these services to the project.
  • Consider on-site back-up supply. For example, backup power generation with long term fuel supply could be considered. Independent wireless communication, such as VHF radio may be vital at a time of crisis.
  • If roads are in themselves important to the project, either for staff access or for post-event functionality (e.g. as an emergency service) consider alternative routing.
  • If service failure cannot be avoided, consider relocation of the project.

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• EARLY WARNING SYSTEMS: Early warning may be required to enable successful evacuation and to enable temporary shut-down of the project if this could reduce consequential and compounding damage. Consider the requirements for successful evacuation of the project location in case of a warning (e.g., adequate transportation, evacuation routes, and safe refuges by undertakeing evacuation planning and exercises. More information
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  CONTEXT:

  • Some tsunami impacts can be mitigated through warning and evacuation.
  • If people can be evacuated outside of the hazard zone it would greatly reduce the likelihood of death and injuries.
  • If equipment and materials can be shut down, moved or secured, some impacts may be reduced. For example, the rapid evacuation of toxic or flammable materials, evacuation of ships, shutdown of nuclear power plants.
  • The project must adhere to workforce health and safety regulations. Often, this places constraints on the design, construction, and operation of the project, and may require protocols to be developed to maintain staff safety during a tsunami. In cases of high hazard, there may be an obligation to develop or gain access to early warnings of impending tsunami arrival and to have evacuation plans in place to satisfy health and safety obligations.

  MITIGATION:

  • Early warning is possible for most tsunami, but be aware that substantial and sustained investment is needed for early warnings to be effective, timely and reliable.
  • Regional warning agencies are noted in the Links section.
  • Plans should be made including evacuation routes, safe locations and capacity/welfare/communication at those locations for evacuation in response to all warnings.
  • Regular exercises are essential to test plans (at least annually, or more frequent to match staff turnover cycles) exercises are essential to test plans. Exercises also act as some of the most effective education, causing staff to rapidly learn the plan ahead of the exercise, and reinforce it with action.
  • If shaking from an earthquake continues for longer than a minute or if people find it hard to stand up (not necessarily both) evacuate immediately. D and do not wait for any official warning – it is unlikely to come in time.
  • For tsunami coming from further away, particularly the other side of the Pacific or Indian Oceans, there may be many hours of warning via the respective Tsunami Warning Systems.
  • Both the Pacific Tsunami Warning Centre (PTWC) and Indian Ocean systems connect to formal government warning agencies, and the country’s government should be consulted for a link to receive warnings. The Pacific and Indian Ocean Tsunami Warning Systems are independent of one-another.
  • As a fall-back, informal monitoring of the PTWC website can provide non-secure, non-guaranteed, delivery of warnings which may provide a basis for response.
  • In areas where the travel time to high ground is prohibitive compared to the tsunami arrival time, consider planning for vertical evacuation to levels above tsunami flow depths in reinforced concrete buildings with deep foundations (those with reinforcing and foundations typical of Japan/California/New Zealand earthquake building codes).

  LINKS:

  Pacific Tsunami Warning Centre: http://ptwc.weather.gov/

  Indian Ocean Tsunami Warning and Mitigation System (ICG/IOTWMS), more information at http://www.ioc-tsunami.org/index.php?option=com_content&view=article&id=8&Itemid=58&lang=en

  North-Eastern Atlantic, Mediterranean, and connected seas: Tsunami Information Centre. http://neamtic.ioc-unesco.org/

  Tsunami evacuation: lessons from the Great East Japan earthquake and tsunami of March 11th, 2011 http://shop.gns.cri.nz/sr_2012-017-pdf/

  Guidelines for Design of Structures for Vertical Evacuation from Tsunamis https://www.fema.gov/media-library-data/1426211456953-f02dffee4679d659f62f414639afa806/FEMAP-646_508.pdf

  Designing for tsunamis (including vertical evacuation buildings) http://www.preventionweb.net/files/1505_DesigningforTsunamis.pdf

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• SEEK INFORMATION: Investigate the tsunami risk in the area in more detail (see additional information). Consider whether local site conditions (nearshore bathymetry and topography) could amplify tsunami hazard.