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Universiteit Gent (2008)

ASSESSMENT OF POTENTIAL WETLAND DECLINE IN WESTERN CAPE (SOUTH AFRICA) BY CLASSIFICATION OF LANDSAT TM AND ETM MULTISPECTRAL IMAGES

Bayasgalan Gantulga

Titre : ASSESSMENT OF POTENTIAL WETLAND DECLINE IN WESTERN CAPE (SOUTH AFRICA) BY CLASSIFICATION OF LANDSAT TM AND ETM MULTISPECTRAL IMAGES

Auteur : Bayasgalan Gantulga

Université de soutenance : Universiteit Gent

Grade : Master of Science (MS) Physical Land Resources 2008

Résumé
Wetlands in South Africa significantly determine the quality of life of people as well as animals and plants. They perform various important economical, social and environmental roles ; however, they are threatened by human activities, socio-economic development and climate change. This study assesses the status and potential decline of wetlands in Western Cape by means of optical remote sensing. 7 multispectral Landsat TM and ETM+ images and GIS supported software (Idrisi 32 Release Two) were used to successfully classify, delineate and determine wetlands in the region (6916.323 km² of land). Three supervised classification methods (Maximum likelihood, Minimized distance-to-means and Fisher) were used and tested for their accuracy. The method with the highest accuracy was used as a basis for all further analyses. The classified images were analyzed for the following features : number and size of wetlands, occurrence of wetlands, amount of permanent and temporary wetlands, and the distances between wetlands. The results showed that the Maxlike method classified wetlands most accurately (overall accuracies between 99.8% and 99.9%). The number of wetlands varied within years and seasons and showed to increase : during winter 4136 wetlands (June 2002) and 1819 wetlands (October 1990), and in summer ; 504 wetlands (January 1987) and 878 wetlands (February 2001). The size of wetlands in this region ranged from 0.081 ha to more than 20 ha. Most small wetlands were detected once in all images, few wetlands appeared in all images (a period of 19 years). Furthermore, 1421 temporary wetlands and 778 permanent wetlands were observed in the area. The mean distance between wetlands varied from summer to winter : longer distances were observed in summer and shorter in winter. Moreover, an outline of the procedures and methods to classify open water bodies (wetlands) using multispectral image data was developed. It was concluded that remote sensing techniques are a useful tool in characterizing wetlands and that they should be integrated in the study of wetlands. The Maximum likelihood classification method is furthermore very suitable for classification of wetlands using multispectral optical imagery. The potential decline of wetlands in Western Cape should be further investigated using lower resolution images and more consistent (in term of acquisition time) image series. The obtained results can be incorporated in further studies and in implementation of conservation measures

Source : Pedon 20 - Physical Land Resources - Universiteit Gent

Page publiée le 2 janvier 2016, mise à jour le 26 décembre 2019