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| Titel |
Geoinformatics in mangrove monitoring: damage and recovery after the 2004 Indian Ocean tsunami in Phang Nga, Thailand |
| VerfasserIn |
D. Kamthonkiat, C. Rodfai, A. Saiwanrungkul, S. Koshimura, M. Matsuoka |
| 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 Science ; 11, no. 7 ; Nr. 11, no. 7 (2011-07-06), S.1851-1862 |
| Datensatznummer |
250009556
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| Publikation (Nr.) |
 copernicus.org/nhess-11-1851-2011.pdf |
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| Zusammenfassung |
| In the aftermath of the 2004 Indian Ocean Tsunami, it has been proven that
mangrove ecosystems provide protection against coastal disasters by acting
as bioshields. Satellite data have been effectively used to detect, assess,
and monitor the changes in mangroves during the pre- and post- tsunami
periods. However, not much information regarding mangrove restoration or
reforestation is available. Rather than undertaking time-consuming
fieldwork, this study proposed using geoinformatic technologies such as
Remote Sensing (RS), Geographic Information System (GIS), and Global
Positioning System (GPS) to monitor the mangrove recovery. The analysis
focused only on the tsunami-impacted mangrove areas along the western coast
of the Tai Muang, Takuapa and Khuraburi Districts of Phang Nga Province,
southern region of Thailand. The results consisted of 2 parts, first: the
supervised classification of main land uses, namely forest, mangrove,
agricultural land, built-up area, bare soil, water body, and miscellaneous
covers in ASTER images, was conducted using the maximum likelihood method
with higher than 75 % for overall accuracy. Once the confusion between
classes was improved in post-processing, the accuracy of mangrove class
was greater than 85 % for all dates. The results showed that the mangrove
area in 2005 was reduced by approximately 5 % (1054.5 ha) from 2003 due
to the impact of the 2004 Indian Ocean Tsunami. Although the recovery
program (replacing the same species of dead mangrove trees, mainly the Rhizophora apiculata Bl and
Rhizophora mucronata Poir, in situ) had started by mid-2005, the areas gradually
decreased to approximately 7–8 % in 2006 and 2010 compared with the
reference year of 2003. Second, the recovery trend was observed in the
Normalized Difference Vegetation Index (NDVI) fluctuation curve and the
supporting field survey data. The recovery patterns were summarized into 2
categories: (i) gradually recovery, and (ii) fluctuating recovery. The
gradually recovery category that implied the homogeneous pattern or uniform
reforestation was observed in the seriously damaged area where most of the
mangrove trees were swept away during the tsunami. This pattern covered
approximately 50.35 % of the total reforested area. The NDVI time series
of the uniform or homogeneous reforested mangrove at the sampled plots has
gradually increased after 2005. The fluctuating recovery category that implied the
heterogeneous pattern or non-uniform reforestation was observed in partially
damaged areas where some of the mangrove trees were swept away and broken
but still some trees were remained in the area. The heterogeneous patterns
covered approximately 49.65 % of the total reforested area. |
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