EVALUATING THE SPATIAL AND TEMPORAL EXTENT OF INUNDATION DUE TO SEA LEVEL RISE ON LAND, BUILDINGS, AND PEOPLE IN MO’OREA, FRENCH POLYNESIA
Abstract
Driven by a combination of ice sheet loss, ocean thermal expansion, and changes in
land water storage, sea levels are expected to rise, though local rates of change
vary considerably. Historically, small island nations have been understudied despite
disproportionate impacts relative to their emissions contributions. This paper presents
a case study of Mo’orea, a small South Pacific island in French Polynesia. Using LIDAR
data collected in 2015 and IPCC regional sea level rise models, we evaluate how local
sea level rise will inundate land, buildings, and displace people. LIDAR data was
used to create a Digital Elevation Model (DEM) with a 5 m resolution, giving us the
ability to resolve the scale of the built environment. The IPCC 4.5 and 8.5 sea level
rise models were applied to the DEM at decadal intervals using an 8 point model. If
decadal sea level rise was greater than the elevation of that pixel and the pixel
boundary touched the ocean or an adjacent inundated pixel, the pixel was classified
as inundated. In order to classify buildings as inundated, each building was sampled
through the inundation datasets and buildings were classified as inundated if the
center of the structure intersected with the inundation layer. Human displacement
was modeled using publicly available census data from 2017. The census data was divided
into each of the five watersheds of the island: Afareaitu, Haapiti, Papetoai, Paopao,
and Teavaro. The average number of people in each watershed was averaged by the number
of pixels in the watershed that were classified as residential buildings. Human displacement
was calculated by summing of the pixels classified as both residential and inundated
in a given decade. By 2100, our models show that 462 ha of land will be inundated
by 2100 under RCP 8.5 and 248 ha under RCP 4.5. While this inundation represents less
than 4% of the island, the island is mountainous, with the majority of the island
having more than 20 m of elevation. In contrast, 95% of all infrastructure is located
in areas below 20 m elevation, bordering the coastline. The inundation will mostly
be constrained to the northern and eastern portions of the island, and is modeled
to inundate homes, public infrastructure, professional buildings, and farmland. Professional
buildings include the ferry, airport, and hotels, infrastructure intrinsic to the
island’s economy. Of the different building classifications, housing will be the most
impacted at over 7% under RCP 4.5 and 20% under RCP 8.5. Energy and water treatment
plants will be the least impacted, with no infrastructure in this category projected
to be inundated by the end of the century. Under RCP 4.5, nearly 8% of the island’s
inhabitants are projected to be displaced while under RCP 8.5 over 20% are projected
to be displaced. There are two distinct dominant patterns of inundation that will
occur throughout the island: beginning through low lying points and seeping inland
to low lying areas not directly on the coast or moving inland from the coast. Understanding
where each of these patterns occurs is important when planning for the future. Our
results can be used by stakeholders to better plan for future sea level rise and mitigate
some of the predicted impacts.
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https://hdl.handle.net/10161/18404Citation
Bensadoun, Raquel; & Bubb, Ilan (2019). EVALUATING THE SPATIAL AND TEMPORAL EXTENT OF INUNDATION DUE TO SEA LEVEL RISE ON
LAND, BUILDINGS, AND PEOPLE IN MO’OREA, FRENCH POLYNESIA. Master's project, Duke University. Retrieved from https://hdl.handle.net/10161/18404.Collections
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