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FIJI Post-Disaster Needs Assessment Annex 5: Supplementary Material for the Housing Sector Methodology Used for Determining TC Winston Housing Sector Damage and Losses The process for estimating the effects of TC Winston on the residential housing stock has two steps: one, estimation of the baseline housing stock and its economic value; and, two, estimation of the effects on the housing stock following TC Winston. The analysis for the housing sector was carried out at the Tikina level (equivalent to the provincial level), later aggregated up to the divisional level. Estimated Breakdown of the Baseline Building Stock by Building Type The baseline building stock was estimated through use of 2007 Census data, which shows the breakdown of the number of households living in six different building typologies. This information was overlaid on the exposure data available from the PCRAFI data compiled in 2010 for estimating the total number of buildings. Population growth rates were derived for each Tikina using population census growth rates between 1996 and 2007. This growth rate was applied to the 2007 census household data to estimate the 2010 average household numbers per building type per Tikina, from which the number of housing units per building type per Tikina were derived. This established the housing stock baseline for 2010, which was then projected to 2014 using the population growth rate between 1996–2007 per Tikina. Table 102 shows the pre-event housing building stock as estimated using the method described above. Table 102: Estimated Pre-Event Building Stock by Province Province Concrete Wood Tiniron Bure Makeshift Other Total Ba 21,796 7,503 17109 675 282 168 47,533 Bua 158 841 1611 127 28 30 2,795 Cakaudrove 1,128 4,182 2,105 278 109 56 7,858 Kadavu 621 845 644 44 5 2 2,161 Lau 1,051 2,920 1,823 68 16 18 5,896 Lomaiviti 861 802 774 43 19 19 2,518 Macuata 1,278 2,099 1,967 134 55 101 5,634 Nadroga 4,034 1,163 3,532 349 90 83 9,251 Naitasiri 11,681 4,900 8,141 277 119 122 25,240 Namosi 256 311 678 103 46 25 1,419 Ra 1,441 934 3,019 385 90 77 5,946 Rewa 9,609 3,125 3,555 69 58 10 16,426 Rotuma 368 124 92 52 3 1 640 Serua 864 783 904 35 8 3 2,597 Tailevu 2,682 2,983 4,398 188 58 69 10,378 Total 57,828 33,515 50,352 2,828 986 784 146,292 Source: Estimations by Assessment Team. Estimated Damage to the Housing Stock by Building Type Data on damage to the housing stock collected in the field and compiled by the NDMO was made available for the PDNA and was the main source of information for damage estimation. Information on damage is available for the four divisions in <strong>Fiji</strong>. The data from NDMO reports damage to residential buildings using two classes: destroyed and damaged. The challenge was to disaggregate this information by building type to be able to estimate the economic impact on the housing sector, and to further separate the buildings reported as damaged into major damage and minor damage. Considering 144 Tropical Cyclone Winston, February 20, 2016
FIJI Post-Disaster Needs Assessment the damage observed in the field characteristically caused by strong winds, major damage was defined as major damage to the roof (blown off), whereas minor damage was defined as partial damage to the roof and/or some claddings or other non-structural building elements. For the disaggregation of these reported buildings into building types, information on the vulnerability of typical building types in the Pacific was used. Vulnerability was assessed at various intensity levels—in this case wind speed of the cyclone—using information available from the scientific literature. To further disaggregate into major damage and minor damage, all buildings in the damaged category reported by NDMO were simply split 50:50, using expert judgement and reflecting the field reports, which described the observed proportion of the damaged buildings in the field to be 60:40 in the high-intensity (=high wind speed) areas. The assumption was that the further away from the center of the hurricane track, the lower the damage. Using this logic, in low intensity areas the nominal split between major and minor damage was assumed to be 40:60, meaning that the average of the split across the country would be 50:50. With the information available, coming up with a more realistic ratio between the two damage levels was not possible, unless an extensive field survey was carried out. After splitting the number of NDMO reported damaged category buildings into 50:50 for major and minor damage, the breakdown of the number of buildings in each damage class by building type was estimated again using the information about the vulnerabilities of the building types in the literature. The entire country was divided into three intensity areas (based on wind speed), using 80-160 kph (intensity 1), 160-240 kph (intensity 2) and 240-320 kph (intensity 3). Cyclone wind speed maps were used to allocate an intensity level to each province, assuming a homogeneous wind speed within a province. Figure 37 shows the provinces colored according to the intensity level assigned for this exercise. Figure 37: Provinces Color Coded According to Wind Speed Intensity Levels Source: Estimations by Assessment Team. The final estimated breakdown of the number of housing units 136 by building type, damage class and Tikina. Table 103 shows results aggregated at the province level. 136 An assumption was made that, in <strong>Fiji</strong>, most housing units are single dwellings. Tropical Cyclone Winston, February 20, 2016 145
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