Building back towards storm-resilient housing: Lessons from Fiji's Cyclone Winston experience
Introduction
Severe weather disturbances such as tropical cyclones and hurricanes cause massive destruction leading to extensive economic losses [13], [31], [64], injuries and loss of lives [13], [14], [42], [64] damage to structures [14] Among the structures typically damaged are houses, which may lead to massive displacement of people for a single disaster incident [24], [43], [47], [9]. Recent times have also seen an increasing trend in both frequency and magnitude of destructive tropical cyclones [25] as such need arises to learn from previous disasters in order to better prepare for the onset of much bigger hazards.
In February 2016, the island nation of Fiji was severely struck by Cyclone Winston. The cyclone commenced as a tropical disturbance but developed into a Category 5 cyclone, based on the Australian tropical cyclone scale, prior to entering Fiji [43] As it approached Fiji's largest and most populated island, Viti Levu, the cyclone peaked in its intensity packing winds with a 10-min sustained speed of 230 kph (64 m/s) and gusts peaking at 325 kph (90 m/s). The cyclone destroyed 9173 houses, significantly damaged 16,757 houses, partially damaged 29,000 others, and rendered approximately 131,000 Fijians, which is about 15% of the country's population, homeless [43].
Cyclone Winston is, by far, the most intense cyclone to ever impact the island nation of Fiji on record [17]. Fiji has never experienced a Category 5 cyclone before it. The most recent destructive tropical cyclone that affected the island nation before Cyclone Winston was Cyclone Evan in December 2012, a Category 4 on the Australian Scale [11]. Prior to these two events, the strongest cyclone to have made landfall in Fiji was Cyclone Nigel in 1985, which was a Category 3 on the Australian scale. Recent years have seen an increasing trend in storm intensities over the South Pacific basin [32] A study by Holland and Bruyère [28] reveals that the global shift towards stronger (Category 4 and 5) cyclones and hurricanes is brought about by increasing global surface temperatures due to anthropogenic climate change. There is also a corresponding increasing trend in the annual cost of storm disaster damage in the Southern Pacific [25].
In view of the rehabilitation and recovery efforts taking place, it is important to consider the principle of building back better or building back safer, which is among the primary foci of most existing disaster recovery frameworks: the most notable being the Sendai Framework for Disaster Risk Reduction (SFDRR) [42], [64] SFDRR emphasizes the rebuilding of structures, systems and communities to a higher standard; in other words, stronger, safer, and more resilient than what existed before a hazard struck.
One of the facets of building back better is the development of a resilient post-disaster building stock [35], i.e. buildings are reconstructed to a higher structural performance compared to those that existed before the disaster event. In order to achieve this, we must fully understand building performance when exposed to a particular hazard. At the outset of every disaster, there is a plethora of information useful for this purpose; which is why, it is essential to carefully record and analyze data during post-disaster assessments [26], [61], [64]. Systematic post-disaster reconnaissance surveys and building damage assessments capture data necessary for the identification of building behavior, structural vulnerabilities, and failure mechanisms. Much work has already been done in this area in the general sense, [1], [33], [36], [39], [56], and on addressing structural vulnerabilities, [47], [50], [53] It is, however, pertinent to consider nuances in structural design and in construction materials and methodologies, which could be regional in scale or very area-specific, which then could strongly influence structural performances. This highlights the importance of area-specific studies, to complement generalized studies.
Another integral aspect towards developing a resilient building stock is ensuring compliance with building standards and regulations [27], [36], [51], [53], [56]. Among the typical challenges, however, are the steep costs associated with making buildings code-compliant [2], [38], [51], as well as the lack in knowledge and skills among owners and builders [43], [47], [49], [62].
In light of the increasing intensity and the corresponding damages brought about by hazard events, one of the strategies by which building stock resilience is achieved is by institutionalizing building codes or by upgrading existing building standards [36], [41], [56] As such, it is common for a country to revisit their building regulations after a disaster. For example, Hurricane Gilbert elicited the mandatory implementation of the Jamaican Building Code [47]. According to Boughton et al. [9], Cyclone Yasi prompted the review and revision of AS 4055: Wind Loads for Housing [59], AS/NZS 1170.2: Structural Design Actions – Wind Actions [60] AS/NZS 4505: Garage doors and other large access doors [58], and AS/NZS 2050: Installation of Roof Tiles [57]. In the Philippines, cyclone Haiyan in [56] elicited changes in the country's design wind speed zoning [15], [5], [64] Again, this strategy should be balanced against cost and the population's ability to comply.
This paper examines Fiji's Cyclone Winston experience in view of the resilience of housing structures. Specifically, the research aims to evaluate design and construction vulnerabilities, as evidenced by damages caused by the cyclone, and identify other non-structural factors affecting the resilience of housing structures to storms. Such information is pertinent to build back better and establish resilient Fijian settlements. This research contributes to the narrow body of literature concerning severe wind resilience of housing structures in Fiji and the South Pacific. It may also serve as a template for future localized research in relation to the storm resilience of structures.
Section snippets
Research methods
A field study was conducted between the 5–19 June 2016 by a delegation of six researchers from Victoria University of Wellington and the University of Auckland and two personnel from the Fijian National Red Cross.
Ground data were collected from field visits to two villages. The villages were selected based on their proximity to where the cyclone has made its landfall in order to capture the damage brought about by a Category 5 cyclone at its peak. In order to isolate the effect of Cyclone
Damage scoping through aerial photography
Forty-two out of forty-three houses in Naboutolu village were destroyed when Cyclone Winston struck. At the time of the damage survey, four months after the cyclone struck the area, the village was still far from full recovery as can be observed in the aerial view of the village shown in Fig. 3. Village residents still lived in temporary dwellings, in tents provided by non-government organizations (NGOs), in makeshift houses built from corrugated iron sheets and scrap wooden plies and panels,
Conclusion
Overall, Cyclone Winston has brought extensive damage on housing structures in Fiji. The removal of the roof sheathing was a common sight for houses with concrete walls. This could be addressed by using a thicker gaged sheet for the roof sheathing, rust-proofing and maintenance procedures, or the use of screws instead of nails for the connections. For timber houses, their designs could be improved by incorporating an adequate lateral force resisting system that would resist the wind force and
Acknowledgments
Due acknowledgment is given to the team from Victoria University of Wellington whom the author worked with for the data collection. This study was also made possible through the financial support from the University of Auckland and the Philippines’ Department of Science and Technology.
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