L’exposition des populations des atolls de Rangiroa et de Tikehau (Polynésie française) au risque de submersion marine

• Main Authors: Alexandre K. Magnan, Marien Ranché, Virginie K.E. Duvat, Adrien Prenveille, Fanny Rubia
• Format: Article
• Language: fra
• Published: Éditions en environnement VertigO 2018-12-01
• Series: VertigO
• Subjects: Atolls; exposure; coastal risks; marine submersion; French Polynesia
• Online Access: http://journals.openedition.org/vertigo/23607

This paper characterizes the current exposure of people leaving on the low-lying atoll reef islands to the risk of marine inundation induced by various sea-related hazards (i.e. cyclones, distant swells and local storms). It offers one of the rare scientific studies that go beyond the general assertion on atoll populations’ exposure to sea-related hazards, by bringing empirically based and detailed evidence on real exposure today. The paper builds on case studies in the Tuamotu Archipelago in French Polynesia, and combines two main types of data, i.e. the inundation levels of past events, and the management practices implemented by both inhabitants and public authorities (type of housing and coastal protection devices). The total sample is composed of 106 interviews and 931 studied houses. The results show first, that more than 61% of houses are located in an area that experienced at least one substantial marine inundation event since the 1980s. Second, that when inhabitants implement options to face coastal risks, they rather target coastal erosion (seawalls, rip-raps, vegetation plantation, etc.) than marine inundation. They only address the risk of marine inundation through housing standard, i.e. buildings’ elevation. This option however remains limited as 52% and 23% of houses have floor elevations less than 50 cm and 20 cm high, respectively. As a result, the population exhibits a high level of exposure to marine flooding. Exploring the root causes of such a situation, the paper emphasises the contributions of both the population growth that occurred over the past three decades and the constraining land tenure system to the increase in houses and public buildings density in flood-prone areas. Then the paper discusses pragmatic and realistic ways to decrease population exposure in the near future.