CHAPTER IV Risk Assessment and Vulnerability Assessment 68 Territory of American Samoa Multi-Hazard Mitigation Plan Assessing risks is the second step in the four-step mitigation plan process. The risk assessment step has four parts: identify hazards, profile hazard events, inventory assets and estimate losses (Figure 1). Conducting a risk assessment is a way of asking and answering “what if…” questions. For instance, what if the Territory receives several days of heavy rain? The risk assessment answers questions regarding history, probability and impact. These answers are then used in the third step of mitigation planning, developing a mitigation plan. They provide essential data to determine mitigation strategies and to define specific prioritized mitigation projects. The development of a comprehensive natural hazard risk and vulnerability assessment is necessary to gain an understanding of the risks of natural disasters to the people of American Samoa. The Project Team, in collaboration with American Samoa Government (ASG) representatives, examined the vulnerability of current and future populations and structures (including critical facilities and infrastructure) to various natural hazards. The risk assessment provides a compilation of information and available data sets to American Samoa government officials for comprehensive planning purposes to save lives and reduce property losses in future disasters. Step 1 Step 2 Step 3 Step 4 Identify Profile Inventory Estimate Hazards Hazards Assets Losses Figure 1 Risk Assessment Process The risk assessment is formatted to meet the Federal Emergency Management Agency’s state-level hazard mitigation planning regulations as found in C.F.R. 44 201. FEMA requires American Samoa to profile each possible natural hazard event, to assess vulnerability and estimate potential losses by jurisdiction. Using data compiled on historical natural hazard events between approximately 1960 and 2014, the risk assessment discusses thirteen main natural hazards as follows: climate change (including sea level rise), coastal erosion, drought, earthquake, flood, high surf, landslide, lightning, soil hazards (including sinkholes, subsidence and expansion) tropical cyclones (including storm surge and high wind storms), tsunamis, volcano (including vog), wildfire and one man-made hazard, hazardous materials. Storm surge is treated as an associated hazard to tropical cyclones. New hazards for the 2015 update are coastal erosion, high surf, lightning strike, and soil hazards. Hazards profiles, including a description of the hazard, historical occurrences, extent (or magnitude), location and vulnerability, beginning on page 64 with the climate change hazard. Hazard profiles are presented in alphabetical order. Extensive information regarding the history, economy, population and islands that make up American Samoa can be found in Chapter 2. Major areas of population include the villages of Tafuna, Nu’uuli, Pago Pago, Iliili, and Pavaiai. It is advisable to review Chapter 2 prior to reading the Risk Assessment to best understand the layout and villages of the Territory. DRAFT April 2015 69 GIS Date for Buildings Data was requested and collected through American Samoa agencies, federal agencies, state sources, non-profits, and Internet sources. Baseline building and critical data is as follows: • Tutuila/Aunu’u Buildings: 2010 dataset. This dataset incudes includes 16,351 structures. There is no associated building value information. However, 94 of these structures were listed as demolished or destroyed as a result of the tsunami. These structures were not included in the hazard zones estimates. o Tutuila/Aunu’u Critical Facilities: 2007 dataset. The 2007 dataset includes type, name, and value estimation. New critical facility information was requested. Although a new critical facility layer was not available, new information was added to the list through the planning process. This included 2 fire stations, a hospital in eastern Tutuila, and the new court building. However, values were not provided for the new facilities. This brings the total up to 240 critical facility structures. In addition, several additional holdings were mentioned and also included separated including ASTCA infrastructure, tsunami sirens, and safe zones. In appendix D, the complete list of critical facilities is available included which critical facilities are new for the 2015 plan update. • Ta’u Buildings: 2003 data set. Limited information on type was provided and no building values were provided. o Ta’u Critical Facilities: 2003 dataset. Name and type was provided. No building values were provided. However, some of the new critical facility data (primarily tsunami sirens) are available for the Manu’a Islands. • Ofu-Olosega Buildings: 2011 dataset. No information on type, name or building value was provided. o Ofu-Olosega Critical Facilities: no data provided. However, some of the new data (primarily tsunami sirens) are available for the Manu’a Islands. • Swains Island: No information was provided on buildings. Only 17 people live on the island according to the 2010 U.S. Census. • Rose Atoll: Uninhabited Hazard Identification Hazard identification is the process of identifying the kinds of natural hazards that can affect the mitigation plan study area – in this instance the Territory of American Samoa. For the purpose of this plan, five hazards were added to the list from 2011. These are sea level rise (combined with climate change), lightning strike, coastal erosion, high surf and soil hazards (expansion, subsidence and sinkhole). In all, fourteen hazards were studied: they are climate change (including sea level rise), coastal erosion, drought, earthquake, flood, hazardous materials, high surf, landslides, lightning strike, soil hazards (including expansion, subsidence and sinkholes), tropical cyclones, tsunami, volcano and wildfire. Table 1 indicates each hazard studied and the justification for inclusion in the mitigation plan. 70 Territory of American Samoa Multi-Hazard Mitigation Plan 12 Hazard Justification for Inclusion Table 1 Hazards Climate Change Climate Change directly impacts American Samoa by increasing the impacts of hazard Included in the Plan (sea level rise) events such as flooding, drought and tsunamis. In addition, climate change may be a possible cause of sea level rise. Sea level rise will threaten areas further inland with flooding. Coastal Erosion Much of the development is located in the relatively narrow coastal plain making this a hazard of major concern. The reef flat, which extends up to 200 feet on the south shore of Tutuila, provides some shoreline protection, although steep volcanic cliffs generally characterize the north shore coasts. Shoreline analysis identified about 10 percent of critical facilities within critical erosion areas, potentially many of these structures at risk to future erosion. 1 Drought Drought occurs in American Samoa and has resulted in economic impacts and water shortages. There is evidence that severe drought events may follow a strong El Niño period. Drought can result in water shortage and impact economic activities on the island. Earthquake The primary earthquake source for American Samoa is the northernmost section of the Tonga Trench (or Tonga-Kermadec Trench), more than 100 miles southwest of the Samoan island chain. The Tonga Trench is a seafloor geographic and tectonic feature created by the collision of the Pacific Plate that subducts westward beneath the Australian Plate. The Pacific-Australian subduction zone is considered an area of high seismic activity, and the collision of these two plates is a source of large but distant earthquakes felt in American Samoa. Earthquakes over 7.0M have been recorded. Further, earthquakes can be a precursor for a tsunami. Flood Flooding is a regular occurrence in American Samoa due to rainfall, thunderstorm rain, tropical cyclones, and tsunami. Several disaster declarations resulted from flood impacts. Flood has resulted in substantial damages and often is a precursor for landslides. Hazardous American Samoa stores extensive hazardous materials on island. Further, many Materials extremely dangerous (and illegal) hazardous materials, such as fertilizer, are being imported. Often times, the most dangerous hazardous materials are being abandoned or not stored properly, creating a safety and health issue to nearby dwellings and to the environment.2 High Surf This hazard has resulted in road damage and debris, and it may impact economic activity. Landslides Previous landslides have resulted in substantial damage and even death on island. Given the natural topography and history of landslides on Tutuila, future landslides are a certain occurrence. Landslides are less frequent on the Manu’a islands but still possible given the steep slope in some areas. Lightning Lightning strikes are not frequent occurrences but have reportedly caused a death, an Strike injury and electronic damage in American Samoa. Future events can result in death, injury, power outage, wildfire or structure fires. 1 Section 309 Assessment and Strategy for the American Samoa Coastal Management Program. (2011). American Sa- moa Coastal Management Program. Retrieved August 8, 2014 from http://coastalmanagement.noaa.gov/mystate/docs/ as3092011.pdf, p. 20 2 Only natural hazards are required in the hazard mitigation plan. However, given the concern and potential impact by a natural hazard, hazardous materials on the island are discussed. DRAFT April 2015 71 Hazard Justification