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August 5, 2021

Mesoscale Hazard modelling of Small Island States

Small Island Developing States (SIDS) are a group of 52 countries and territories, mainly islands, so designated by the United Nations to address collectively their development and sustainability concerns. SIDS are often vulnerable to a vast number of natural hazards, both coastal and land based. The defining physical characteristics (spatial location, geology, local meteorology etc.) of these SIDS make them particularly vulnerable to the impacts of natural hazards. Based on developing future climate projections, there is an ongoing need to assimilate modeling of natural hazards with considerations for sustainable development as well as to evaluate existing government coordinated disaster impact assessments to generate a detailed understanding of those natural hazards. CEAC Solutions has worked across the Caribbean on various hazard, vulnerability and risk assessments for clients in public and private sector, developing climate change resilience for countries through environmental, institutional and socio-economic assessments.

SIDS are especially vulnerable to natural disasters due to a strong exposure to meteorological hazard, future climate conditions (sea level rise), their small size, the high density and concentration of population, and high per capita costs of roads, ports and airport infrastructure. In light of this acknowledged vulnerability, there are relatively few studies which focus on the impacts of natural hazards in these countries.

CEAC has contributed to this research by conducting various mesoscale hazard modeling within the Caribbean. The methodologies typically employed by CEAC in analyzing natural risk and vulnerability includes priority hazards such as wind, landslides, flooding and storm surge while in keeping with good practices and globally recognized approaches.

Wind hazards relate to the potential damage that high velocity winds can generate which are likely to cause damage. Damage is caused by the force exerted directly by wind on the physical structures or is caused by the impact of objects that become projectiles due to the high velocity of the winds. According to the UN International Strategy for Risk Reduction (UNISDR), in the case of a one-in-250-year cyclone, six of the ten countries most at risk are SIDS (UNISDR, 2015). For the Caribbean basin as a whole, climate change contributes an additional US$1.4 billion to expected average annual losses (AAL) associated with wind damage alone (UNFCC, 2015). This will require review of and possible revisions to existing building codes within the SIDS to ensure added resilience to anticipated future cyclone events.

Landslide hazard information serves as one of the many components in an integrated development planning study or determining existing vulnerabilities. A generalized description of landslide is the movement of a mass of soil, rock or debris, down a slope, under the influence of gravity (Hutchinson, 1988). Landslides are expected to increase with increased wind and rainfall or from earthquakes weakening underlying rock support. Landslides within SIDS are mainly driven by lack of/violation of construction codes or building in landslide-prone areas. The resulting impacts are damaged houses and loss of farm and agricultural produce that eventually lead to economic losses and food shortages.

Landslide susceptibility mapping is a useful tool for disaster management and planning development activities in mountainous terrains of tropical and subtropical environments. A landslide susceptibility map was created by CEAC for the island of St. Lucia which identified

vulnerable locations across the country. This map was used to inform the Government of St. Kitts about the vulnerability of three project locations being proposed for development – Bexon, La Croix and La Ressource. The study revealed that two of the three communities were located on ‘high’ susceptible terrain. Our report to the St Kitts government included recommendations for added considerations within the building design criteria.

Many of the countries classified as SIDS are in the process of developing guidelines for the implementation of infrastructure such as roads and drainage. This poses a risk to both lives and assets during a storm or significant rainfall event. It is imperative that studies are done on water courses (rivers, drains etc.) which traverse flood prone areas. CEAC has conducted a flood plain analysis on both South Olivees River and College Street Ghut in St. Kitts. Results of the study revealed that over 1200 buildings (24 per cent of the building stock) in Basseterre, St. Kitts are exposed to the 100-year flood event. Furthermore, climate-related changes could cause an increase to the number of buildings exposed to the one-in-25, 50 and 100-year flood events, by 19.2per cent ,23 per cent, and 26 per cent respectively.

With high percentage of SIDS populations living near the coast, many in low-lying areas, coastal floods, storm surges and inland flooding can cause serious social migration and/or displacement challenges. High sea levels and swells have already resulted in the displacement of people in a number of SIDS including Kiribati, Solomon Islands, the Marshall Islands, and the Federated States of Micronesia (OCHA, 2008). The aforementioned study conducted by CEAC in St. Kitts illustrated that 245 buildings (4.6 per cent of the estimated building stock) in Basseterre are located within the 100-year storm surge catchment. It is essential for public awareness and developing policies and plan that coastal modeling is integrated into

ongoing studies. Research has shown that as many as 29 percent of major resort properties in the CARICOM countries would be partially or fully inundated by a one metre sea-level rise whereas 49 percent are estimated to be damaged or destroyed. Across the Caribbean, Moore et al. (2010) estimate that by 2050 tourist expenditures could decline from US$25 billion to US$15 billion.

By understanding the drivers of risk, a more considered approach to managing risk and developing more resilient small-island economies can be developed. The basis of risk experienced relies greatly on the hazard to which it is exposed. In order to create an effective mitigation plan, the potential hazard and risks must be initially identified where the severity of each is documented. One of the most effective ways is to conduct hazard modeling where adaptation options can be devised to reduce the possible risks associated.

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