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| Titel |
A global analysis of human habitation on river deltas |
| VerfasserIn |
Douglas Edmonds, Rebecca Caldwell, Sarah Baumgardner, Chris Paola, Samapriya Roy, Amelia Nelson, Jaap Nienhuis |
| Konferenz |
EGU General Assembly 2017
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| Medientyp |
Artikel
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| Sprache |
en
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 19 (2017) |
| Datensatznummer |
250146789
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| Publikation (Nr.) |
 EGU/EGU2017-10832.pdf |
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| Zusammenfassung |
| River deltas are ideal sites for human habitation because of their fertile floodplains, easy
access to the ocean, and abundant land. But anthropogenic and natural processes are causing
deltas to sink, which increases the probability of coastal flooding and human exposure to risk.
The full extent of the risk posed to humans is unclear because the number of people living on
river deltas is unknown. Towards this end we mapped the locations and areas of all deltas in
the world (n= 1813). Using Google Earth we identified all river mouths (≥ 50 m wide) on
marine coastlines that are also connected to an upstream catchment. Rivers that split into two
or more active or relict distributary channels, end in a depositional protrusion from
the shoreline, or do both, are defined as deltas. The depositional protrusion and
distributary channel network define the geomorphic area of each delta. We mark the
position of the delta apex at the first bifurcation, or for a single channel delta at
the intersection of the regional shoreline and the main channel. We mark three
lateral extents, one on either side of the main channel at the maximum displacement
of the depositional protrusion or the distributary network, and one on the most
basinward position of the delta. We define delta area as the convex hull around these
extent points and the delta apex. For each delta area polygon we extract elevation
from the Shuttle Radar Topography Mission dataset and population count in years
2000, 2005, 2010, 2015, and 2020 from Gridded Population of the World, version 4.
In total, deltas cover 0.56% of the total area of the world yet contain 4.1% of the
world’s population. The population on deltas has grown from 237 million in 2000 to
projected values of 322 million in 2020. Deltaic population is growing at 1.59% per
year, which outpaces the world growth rate of 1.11%. Additionally, population
density is increasing with time from 322 people per km2 in year 2000 to projected
values of 422 people per km2 in 2020. Of the 300 million people currently living on
deltas, roughly 69% live below 10 meters elevation in the so-called low elevation
coastal zone that is particularly susceptible to coastal flooding. Interestingly, the
population in the low elevation coastal zone is unevenly distributed. The largest
number of people, approximately 24%, live between 4 and 6 m elevation. This
elevation range is also more densely populated at 580 people per km2, which is
nearly 12 times the global mean of 47 people per km2. We consider these estimates
to be a minimum given that we define delta area from the geomorphic footprint. |
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