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| Titel |
Detailed quantification of delta subsidence, compaction and interaction with man-made structures: the case of the NCA airport, France |
| VerfasserIn |
O. Cavalie, A. Sladen, M. Kelner |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1561-8633
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| Digitales Dokument |
URL |
| Erschienen |
In: Natural Hazards and Earth System Sciences ; 15, no. 9 ; Nr. 15, no. 9 (2015-09-08), S.1973-1984 |
| Datensatznummer |
250119676
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| Publikation (Nr.) |
 copernicus.org/nhess-15-1973-2015.pdf |
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| Zusammenfassung |
| River deltas are dynamic coastal systems and their evolutions are closely
monitored as it often concentrates vital natural resources for the
surrounding areas. Many deltas worldwide experience subsidence due to
geological processes (sediment loading and compaction) or human activities
(groundwater or hydrocarbon extraction, land reclamation). This causes
shoreline erosion or wetland loss which represent serious issues for the
population. In this study we investigate the dynamic of the Var delta
(France) where reclaimed lands over sea have been built to host the Nice
côte d'Azur airport (NCA). Actually, the stability of this infrastructure
is a permanent concern since, in 1979, a newly built extension of the runway
platform collapsed in the sea, causing important damages. The project of land
extension stopped, but the present airport platform is still located on
reclaimed land. Factors that can trigger such catastrophic landslide are
thought to be linked to the delta activity and the artificial airport
platform load. We used, therefore, Envisat InSAR data to measure accurately
the ground deformation of the area that includes the Var delta and NCA
airport. Combining data from ascending and descending orbits, we estimated
the east–west and vertical components of the deformation and obtained very
accurate displacement rate (with a 1σ error of
0.25 mm yr−1). We found that nearly all the deformation is
vertical and impacts the whole Var delta. The Var valley subsides at a very
low rate (0.5–1 mm yr−1) but downstream the subsidence rate
increases and a clear jump is observed at the transition with the reclaimed
lands (1–2 mm yr−1). On average, the reclaimed lands subside at
3 mm yr−1. Since the subsidence rate increases in correlation
with the sediment thickness, we interpret it as the compaction of the delta
quaternary sedimentary wedge. In addition, three areas subside faster
(between 5 and 10 mm yr−1), with one calling for more attention
as it is the largest and overlooks the steep Var canyon. The progressive
increase of subsidence rates toward the sea also suggests that the underwater
parts of the margins could subside at rates well above 10 mm yr−1. |
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